Recreational water exposures and illness outcomes at a freshwater beach in Toronto, Canada: A prospective cohort pilot study

Ian Young; J Johanna Sanchez; Binyam Negussie Desta; Cole Heasley; Jordan Tustin

doi:10.1371/journal.pone.0286584

. 2023 Jun 2;18(6):e0286584. doi: 10.1371/journal.pone.0286584

Recreational water exposures and illness outcomes at a freshwater beach in Toronto, Canada: A prospective cohort pilot study

Ian Young ^1,^*, J Johanna Sanchez ¹, Binyam Negussie Desta ¹, Cole Heasley ¹, Jordan Tustin ¹

Editor: Timothy J Wade²

PMCID: PMC10237503 PMID: 37267237

Abstract

Background

Swimming and other recreational water activities in surface waters are popular in Canada during the summer. However, these activities can also increase the risk of recreational water illness. While routine monitoring of beach water quality is conducted by local authorities each summer, little research is available in Canada about beach exposures and illness risks.

Methods

We conducted a pilot of a prospective cohort study at a popular beach in Toronto, Ontario, Canada, in 2022 to determine characteristics of beachgoers, common water and sand exposures, the incidence of recreational water illness, and the feasibility for a larger, national cohort study. We enrolled beachgoers on-site and surveyed about their exposures at the beach and conducted a follow-up survey 7 days following their beach visit to ascertain acute gastrointestinal, respiratory, skin, ear, and eye illness outcomes. We descriptively tabulated and summarized the collected data.

Results

We enrolled 649 households, consisting of 831 beachgoers. Water contact activities were reported by 56% of beachgoers, with swimming being the most common activity (44% of participants). Similarly, 56% of beachgoers reported digging in the sand or burying themselves in the sand. Children (≤14 years) and teenagers (15–19 years) were most likely to report engaging in water contact activities and swallowing water, while children were most likely to report sand contact activities and getting sand in their mouth. Boys and men were more likely than women and girls to report swallowing water (15.2% vs. 9.4%). Water and sand exposures also differed by household education level and participant ethno-racial identity. E. coli levels in beach water were consistently low (median = 20 CFU/100 mL, range = 10–58). The incidence of illness outcomes was very low (0.3–2.8%) among the 287 participants that completed the follow-up survey.

Conclusions

The identified beach exposure patterns can inform future risk assessments and communication strategies. Excellent water quality was observed at the studied beach, likely contributing to the low incidence of illnesses. A larger, national cohort study is needed in Canada to examine risks of illness at beaches at higher risk of fecal contamination.

Background

Recreational water activities in surface waters are popular among Canadians during summer months. Such activities include swimming, wading, kayaking, canoeing, boating, and other water sports (e.g., surfing, jet skiing). A national survey in 2015 found that nearly 30% of Canadians reported engaging in recreational water activities in any water source in the prior 7-day period during the summer, with children aged 0–9 years more than four times as likely as adults to engage in these activities [1]. Further, approximately one-fifth of Canadians reported canoeing, kayaking, boating, or jet skiing at least once in the past 12 months in 2018 [2]. These activities can lead to exposure to various enteric and other pathogens that can cause recreational water illnesses (RWI) [3–5]. RWI has a significant health and economic burden on society. Although data are not available for Canada, approximately 90 million cases of RWI are estimated to occur each year in the United States (U.S.) due to exposures in surface waters, resulting in annual costs of US$2.2–3.7 billion [6]. Additionally, 140 RWI outbreaks due to exposure to natural surface waters were reported in the U.S. from 2000–2014, causing nearly 5,000 illnesses and two deaths [3], while 742 RWI outbreaks were reported from 1991–2007 in the Netherlands, resulting in >5,600 illnesses [7].

Globally, there is strong and consistent evidence that swimming and other high-contact recreational water activities (e.g., surfing) in surface waters increase the risk of acquiring acute gastrointestinal illness (AGI) and other RWI outcomes among beachgoers [6, 8–10]. For example, a systematic review and meta-analysis found that swimming was associated with a 2.19 times higher risk (95% CI: 1.82, 2.63) of AGI, and a 1.78 times higher risk of respiratory illness (95% CI: 1.38, 2.29), compared to those who go to the beach but do not swim [9]. In the U.S., swimming at beaches is estimated to cause 9.2 excess episodes of AGI, 8.6 excess episodes of diarrhea, and 4.9 excess days of missed work or activities per 1,000 beachgoers (representing 15%, 21%, and 9% of all such episodes, respectively) [10]. Further, beach sand contact activities (e.g., digging in the sand) have also been associated with increased risks of AGI among beachgoers [11, 12]. These risks are higher among children, as they tend to spend the most time in the water and sand, are prone to swallowing water when swimming, and have developing immune and digestive systems [10, 13–15].

While risks of RWI from different recreational water activities have been investigated in the U.S. and other countries via prospective studies [9, 10, 13, 16–18], no such studies have been conducted in Canada since 1980 [19]. In Canada, national guidelines for recreational water quality in natural water bodies are set by Health Canada, which are then adopted by local and provincial health and/or environmental authorities who conduct routine beach water surveillance [20, 21]. The guidelines set beach action values for E. coli and enterococci as indicators of fecal contamination and RWI risks [20]. These beach action values are based on U.S. data, given the lack of burden of illness data from Canada [20]. However, RWI risks can be affected by diverse and varying local pollution sources, environmental and weather patterns, and beachgoer activities [9, 22–24]. Therefore, Canadian data are needed on recreational water activities and associated risks of RWI. We conducted a prospective pilot cohort study of beachgoers at a popular urban, freshwater beach in Toronto, Ontario. The study objectives were to determine characteristics of beachgoers, common water and sand exposures, the incidence of RWI, and the feasibility for a larger, national cohort study.

Materials and methods

Study design and setting

We conducted this study at Woodbine Beach in Toronto, Ontario, from June 4 to August 31, 2022. The study design and data collection tools were guided by the U.S. National Epidemiological and Environmental Assessment of Recreational water (NEEAR) study and the Chicago Health, Environmental Exposure, and Recreation Study (CHEERS) [13, 16–18]. We reported this manuscript in accordance with the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) guidelines (see checklist in S1 File) [25]. The Toronto Metropolitan University Research Ethics Board (REB# 2022–046) reviewed and approved this study. All participants provided informed consent via completion of a digital consent form, with parents or guardians providing informed consent for those younger than 16 years of age in their household. In addition, a digital assent form was completed for all children and youth in consultation with their parents or guardians.

Toronto is Canada’s most populous city with approximately 3 million inhabitants and 6.3 million people living in the broader Toronto region. Woodbine beach is one of 11 public beaches in the city [26], located on Lake Ontario, east of Toronto’s downtown core and ~1 km from the city’s Ashbridges Bay Wastewater Treatment Plant [27]. We selected Woodbine beach for this pilot study because it is one of the most popular beaches in the city, with a large beachgoer population sufficient to assess cohort study recruitment feasibility. It received the Blue Flag designation in 2022 as well as prior years, an international certification program that assesses water quality and other environmental and safety criteria [28]. However, elevated E. coli levels occasionally occur throughout the summer season leading to swimming advisories [28, 29], suggesting one or more recurring sources of fecal contamination.

Participation eligibility and enrollment

Our study population was all beachgoers that visited Woodbine Beach during the summer of 2022. To be eligible for participation, at least one household member aged 16 years or older needed to be present to conduct the survey in English, the household home address was required to be in Canada or the U.S., and individuals must not have already participated in the prior 21-day period. Re-enrolment was allowed after 21 days given the acute and self-limiting nature of RWI. Two data collectors attended the beach each enrollment day and approached as many beachgoers as possible. One of our aims was to determine how many beachgoers could be feasibly recruited each day to support power analysis calculations for a larger study. Household members were enrolled and surveyed together, with separate answers provided for each individual participant. We approached and enrolled potentially eligible beachgoers 2–4 days per week during the study timeframe (38 days total). Enrollment was conducted between 11AM and 5PM each day. We enrolled most Fridays, at least one weekend day, and one to two additional days per week.

Data collection surveys

We originally planned to conduct two on-site interviews with beachgoers; an entrance survey to ask about eligibility, sociodemographic characteristics, and baseline health status, and an exit survey as participants were leaving the beach to ascertain their exposures (e.g., water and sand contact activities). However, piloting on the first two data collection days indicated a very low proportion of households were returning to complete the exit survey (<10%). Therefore, we subsequently modified the on-site beach surveys to be completed at one point in time. Trained data collectors asked participants if they had recently arrived or if their exposure status planned to change, and if so, returned to survey those households at a later time on the same day. We conducted a follow-up survey by email or telephone (participant preference) 7 days after the beach visit to determine any RWI outcomes experienced by participants. A random draw prize ($50 gift cards) was offered as an incentive to 1% of participating households.

We adapted survey questionnaires from those used in the prior U.S. NEEAR study [18]. Additionally, we pre-tested the adapted versions with 10 individuals using a cognitive interviewing approach [30]. We used this process to refine the questions, their clarity, and layout. Participants completed on-site beach surveys via our tablet devices. The questionnaires were hosted on the web-based SimpleSurvey platform (OutSideSoft Solutions Inc., Quebec, Canada). We sent up to five reminders (emails or phone calls) to participants that did not complete the follow-up survey for 3–5 days following the initial contact. Copies of the questionnaires are available in S2 File.

Exposures and outcomes of interest

We collected data on two different beach exposures of interest: water contact activities and sand contact activities. Specifically, we asked participants to indicate if they swam, waded below their waist, or engaged in various other recreational activities (e.g., paddle-boarding, kiteboarding, boating). We also asked participants whether they submerged their face in the water and if they swallowed any water. For sand activities, we asked participants to indicate if they dug or buried themselves in the sand or got sand in their mouth.

We collected household-level information on province or state of residence, income, and the highest educational attainment level within the household. We then collected the following additional sociodemographic information for each individual participant: age group, sex at birth, current gender, and ethno-racial identity. We also collected self-reported information about baseline health outcomes, chronic health condition status, and other beach exposures (e.g., food consumption, sunscreen application). Sociodemographic questions were optional, so resulted in different rates of missing values for those questions, while all other questions on the survey were mandatory and completed by all participants.

The follow-up survey asked participants indicate if they or any other household members experienced any of the following RWI outcomes of interest within 7 days of their beach visit: AGI, respiratory, skin, ear, and eye infections. We selected this length of follow-up as it corresponds with incubation periods of the primary viral and bacterial enteric pathogens of concern for RWI [31, 32]. We defined AGI as: (a) diarrhea (≥3 loose stools in 24 hrs); (b) vomiting; (c) nausea with stomach cramps; or (d) nausea or stomach cramps that interfere with regular daily activities (e.g., missed work or school) [10, 13, 16, 17, 33]. We defined other RWI outcomes as follows: respiratory illness (fever with sore throat, fever with nasal congestion, or cough with phlegm); skin infection (rash or itchy skin); ear infection or earache; and eye infection or irritation [13, 16, 17, 33, 34].

We obtained data on beach water E. coli levels during our enrollment dates from the local public health authority (City of Toronto Open Data Portal). The City of Toronto conducts routine sampling for E. coli once per day during the summer season at all beaches, including Woodbine [21, 26]. Water samples are collected in sterile bottles at a depth of 1–1.5 m, approximately 15–30 cm below the surface, at five points along the beach [21]. Samples are shipped to the provincial laboratory network within 24 hr and are tested using a standard, culture-based membrane filtration method [35]. The geometric mean of the five samples is used as a indicator of water quality, with the city using a locally adopted threshold of ≤100 CFU/100 mL to determine whether to issue a swimming advisory [26].

Data analysis

We downloaded data from SimpleSurvey and imported it into RStudio (version 2022.07.1 running R 4.2.1) for formatting, preparation, and analysis [36, 37]. Given the low incidence of illness outcomes reported in this study and low completion rate for the follow-up survey, we focused on descriptively summarizing the survey results instead of modelling exposure-illness associations. We calculated descriptive tabulations and summary measures for all exposure, sociodemographic, and outcome variables. Participants who had any of the RWI outcomes at baseline were excluded from our summary of those outcomes. We conducted cross-tabulations to compare water and sand exposures by age group, gender identity, highest education level in the household, and ethno-racial identity. Further, we compared sociodemographic characteristics of those who completed and did not complete the follow-up survey to evaluate possible biases from loss to follow-up. The deidentified dataset and R script files are available at the following Github page: https://github.com/iany33/beachcohortpilot2022.

Results

Participant characteristics

Throughout the enrollment period we approached 1,007 households, of which 649 (64.4%) agreed to participate. Among the 348 (35.6%) who did not participate, primary reasons for not participating included: not interested in the study (N = 151, 42.2%), did not want to be bothered or interrupted at the beach (N = 128, 35.8%), did not speak English (N = 25, 7.0%), did not have time (N = 22, 6.1%), not eligible (N = 18, 5.1%), and wanted to remain anonymous (N = 14, 3.9%). Of participating households, 831 individual participants completed the beach survey and 287 completed the follow-up survey, for a follow-up rate of 34.5%. Most participants requested the email follow-up option (78.7%), which had a slightly higher completion rate than telephone follow-ups (35.3% vs. 32.1%). Only two participants completed the survey more than once. The average time of completion of the beach and follow-up surveys was 4 min 56 sec and 1 min 57 sec, respectively.

The characteristics of participants that completed the beach survey, stratified by enrollment month, are shown in Table 1. Most participants were aged 20–39 (56.7%) and identified as woman or girls (65.2%). Most participants (60.2%) chose not to answer the question about household income. Nearly all participants (93.0%) resided in Ontario, and most participants (57.4%) identified as white. The most prevalent baseline illness was respiratory illness (1.9%). Over 40% of participants reported engaging in other recreational water contact within the prior 2-week period. Fewer children, households in the lowest income categories, and households with post-graduate degrees were enrolled in July and August compared to June. Fewer illness outcomes were also identified in July and August compared to June.

Table 1. Characteristics of 831 beachgoers surveyed at Woodbine Beach, Toronto, 2022, stratified by enrollment month.

AGI = acute gastrointestinal illness.

	N (%)
Characteristic	June	July	August	Total
Age group:
0–14	55 (20.5)	25 (9.5)	23 (7.9)	103 (12.5)
15–19	31 (11.6)	50 (18.9)	57 (19.7)	138 (16.8)
20–39	142 (53.0)	155 (58.7)	169 (58.3)	466 (56.7)
40+	40 (14.9)	34 (12.9)	41 (14.1)	115 (14.0)
Missing	3	1	5	9
Gender identity:
Woman/girl	174 (64.7)	154 (59.7)	205 (70.4)	533 (65.2)
Man/boy	89 (33.1)	99 (38.4)	82 (28.2)	270 (33.0)
Gender fluid, non-binary, or transgender	6 (2.2)	5 (1.9)	4 (1.4)	15 (1.8)
Missing	2	7	4	13
Household income (CAD$):
<$40,000	44 (21.2)	17 (16.8)	1 (4.5)	62 (18.7)
$40,000–79,999	39 (18.8)	37 (36.6)	6 (27.3)	82 (24.8)
$80,000–149,999	72 (34.6)	32 (31.7)	12 (54.5)	116 (35.0)
$150,000+	53 (25.5)	15 (14.9)	3 (13.6)	71 (21.5)
Missing	63	164	273	500
Highest education completed in household:
High school or less	58 (22.6)	58 (36.0)	70 (41.2)	186 (31.6)
College, trades, or apprenticeship	49 (19.1)	27 (16.8)	43 (25.3)	119 (20.2)
Bachelor’s degree	64 (24.9)	32 (19.9)	57 (33.5)	153 (26.0)
Post-graduate degree	86 (33.5)	44 (27.3)	0 (0.0)	130 (22.1)
Missing	14	104	125	243
Location of residence:
Ontario	249 (91.9)	241 (90.9)	283 (95.9)	773 (93.0)
U.S.	14 (5.2)	12 (4.5)	7 (2.4)	33 (4.0)
Quebec	5 (1.8)	9 (3.4)	2 (0.7)	16 (1.9)
Other Canadian provinces^a	3 (1.2)	3 (1.1)	3 (1.0)	9 (1.1)
Ethno-racial identity:
White	130 (52.2)	135 (60.5)	146 (59.8)	411 (57.4)
South Asian	18 (7.2)	22 (9.9)	21 (8.6)	61 (8.5)
Southeast Asian	9 (3.6)	15 (6.7)	24 (9.8)	48 (6.7)
Arab or Middle Eastern	15 (6.0)	14 (6.3)	18 (7.4)	47 (6.6)
East Asian	19 (7.6)	11 (4.9)	11 (4.5)	41 (5.7)
Latin	20 (8.0)	9 (4.0)	5 (2.0)	34 (4.7)
Black	13 (5.2)	7 (3.1)	13 (5.3)	33 (4.6)
Multiple ethnicities	16 (6.4)	9 (4.0)	6 (2.5)	31 (4.3)
Indigenous	9 (3.6)	1 (0.4)	0 (0.0)	10 (1.4)
Missing	22	42	51	115
Baseline illness status^b:
Respiratory illness	8 (3.0)	7 (2.6)	1 (0.3)	16 (1.9)
AGI	5 (1.8)	1 (0.4)	1 (0.3)	7 (0.8)
Skin infection	4 (1.5)	1 (0.4)	1 (0.3)	6 (0.7)
Ear infection	1 (0.4)	0 (0.0)	0 (0.0)	1 (0.1)
Eye infection	0 (0.0)	1 (0.4)	0 (0.0)	1 (0.1)
Baseline health conditions^b:
Allergies	16 (5.9)	25 (9.4)	30 (10.2)	71 (8.5)
Chronic respiratory condition	7 (2.6)	8 (3.0)	12 (4.1)	27 (3.2)
Chronic gastrointestinal condition	8 (3.0)	6 (2.3)	1 (0.3)	15 (1.8)
Immune-compromised	3 (1.1)	5 (1.9)	2 (0.7)	10 (1.2)
Engaged in other recreational water activities within the past 2 weeks	85 (31.4)	122 (46.0)	141 (47.8)	348 (41.9)

Open in a new tab

^a Other provinces included Alberta (N = 5), Nova Scotia (N = 2), and British Columbia and Newfoundland and Labrador (N = 1 each).

^b Multiple selections were possible for these variables.

Beach exposures

A summary of the water and sand contact exposures and activities reported by participants is shown in Table 2, stratified by enrollment month. Swimming and wading were both lowest in June, with swimming increasing in July (46.0%) and highest in August (61.0%). The number of participants reporting wading was similar in July and August (31–32%). Similarly, the prevalence of face contact with water and swallowing water also increased monthly, with highest levels in August (Table 2). In contrast, digging in the sand (58.7%) and getting sand in one’s mouth (29.2%) were most commonly reported in June, while burying oneself in the sand was most common in July (29.1%). In addition to these exposures, 37.5% (N = 312) of participants reported having contact with seaweed, 73.8% (N = 613) reported applying sunscreen, and 69.4% (N = 577) reported consuming food at the beach.

Table 2. Water and sand exposures reported among beachgoers, stratified by study enrollment month, at Woodbine Beach, Toronto, 2022.

Exposure	N (%)
Exposure	June	July	August	Total
Water contact	106 (39.1)	152 (57.4)	209 (70.8)	467 (56.2)
Swimming	65 (24.0)	122 (46.0)	180 (61.0)	367 (44.2)
Wading (below one’s waist)	43 (15.9)	85 (32.1)	92 (31.2)	220 (26.5)
Paddleboarding	6 (2.2)	5 (1.9)	2 (0.7)	13 (1.6)
Other water sports^a	4 (1.5)	1 (0.4)	2 (0.7)	7 (0.8)
Other minimal contact activities^b	6 (2.2)	3 (1.1)	2 (0.7)	11 (1.3)
Face contact with water	28 (10.3)	68 (25.7)	90 (30.5)	186 (22.4)
Swallowing water	15 (5.5)	29 (10.9)	50 (16.9)	94 (11.3)
Sand contact^c	168 (62.0)	171 (64.5)	127 (43.1)	466 (56.1)
Digging in the sand	159 (58.7)	125 (47.2)	122 (41.4)	406 (48.9)
Burying oneself in the sand	45 (16.6)	77 (29.1)	13 (4.4)	135 (16.2)
Sand in mouth	52 (29.2)	30 (16.8)	25 (19.7)	107 (22.1)

Open in a new tab

^a Other water sports included kitesurfing (N = 3), diving (N = 2), surfing (N = 1), and waterskiing (N = 1).

^b Other minimal contact activities included kayaking (N = 4), boating (N = 3), fishing (N = 2), sailing and canoeing (N = 1 each).

^c We defined sand contact as digging in the sand or burying oneself in the sand.

Tables 3–6 show differences in the most common beach exposures by participant sociodemographic characteristics. Children (0–14) and teenagers (15–19) were most likely to have any water contact, while teenagers swam more than other age groups (Table 3). Children and teenagers were also most likely to have face contact with water and swallow water. Almost all children reported sand contact (91.3%); they were the most likely age group to engage in sand contact activities and to get sand in their mouth (Table 3).

Table 3. Water and sand exposures reported among beachgoers, stratified by age group, Woodbine Beach, Toronto, 2022.

Exposure	N (%)
Exposure	0–14 years (N = 103)	15–19 years (N = 138)	20–39 years (N = 466)	40+ years (N = 115)
Water contact	71 (68.9)	89 (64.5)	236 (50.6)	67 (58.3)
Swimming	46 (44.7)	84 (60.9)	182 (39.1)	52 (45.2)
Wading (below one’s waist)	38 (36.9)	29 (21.0)	112 (24.0)	38 (33.0)
Face contact with water	33 (32.0)	48 (34.8)	79 (17.0)	25 (21.7)
Swallowing water	17 (16.5)	21 (15.2)	46 (9.9)	9 (7.8)
Sand contact^a	94 (91.3)	79 (57.2)	230 (49.4)	60 (52.2)
Digging in the sand	90 (87.4)	67 (48.6)	197 (42.3)	49 (42.6)
Burying oneself in the sand	34 (33.0)	21 (15.2)	59 (12.7)	20 (17.4)
Sand in mouth	45 (47.9)	14 (17.5)	36 (14.6)	11 (18.0)

Open in a new tab

^a We defined sand contact as digging in the sand or burying oneself in the sand.

Table 6. Water and sand exposures reported among beachgoers, stratified by ethno-racial identity, Woodbine Beach, Toronto, 2022.

Exposure	N (%)
Exposure	Arab (N = 47)	Black (N = 33)	East Asian (N = 41)	Indigenous (N = 10)	Latin (N = 34)	Multiple ethnicities (N = 31)	South Asian (N = 61)	Southeast Asian (N = 48)	White (N = 411)
Water contact	31 (66.0)	14 (42.4)	17 (41.5)	3 (30.0)	14 (41.2)	23 (74.2)	33 (54.1)	22 (45.8)	238 (57.9)
Swimming	26 (55.3)	12 (36.4)	11 (26.8)	3 (30.0)	13 (38.2)	12 (38.7)	23 (37.7)	21 (43.8)	191 (46.5)
Wading (below one’s waist)	13 (27.7)	5 (15.2)	7 (17.1)	1 (10.0)	3 (8.8)	12 (38.7)	23 (37.7)	12 (25.0)	120 (29.2)
Face contact with water	14 (29.8)	6 (18.2)	6 (14.6)	0 (0.0)	5 (14.7)	7 (22.6)	12 (19.7)	5 (10.4)	99 (24.1)
Swallowing water	6 (12.8)	4 (12.1)	5 (12.2)	0 (0.0)	4 (11.8)	2 (6.5)	12 (19.7)	4 (8.3)	49 (11.9)
Sand contact^a	26 (55.3)	17 (51.5)	26 (63.4)	6 (60.0)	22 (64.7)	23 (74.2)	31 (50.8)	26 (54.2)	227 (55.2)
Digging in the sand	18 (38.3)	16 (48.5)	23 (56.1)	6 (60.0)	20 (58.8)	20 (64.5)	26 (42.6)	21 (43.8)	195 (47.4)
Burying oneself in the sand	12 (25.5)	1 (3.0)	7 (17.1)	2 (20.0)	8 (23.5)	5 (16.1)	11 (18.0)	7 (14.6)	75 (18.2)
Sand in mouth	5 (19.2)	1 (5.9)	4 (14.8)	1 (16.7)	7 (31.8)	9 (39.1)	7 (21.2)	7 (25.0)	58 (24.3)

Open in a new tab

^a We defined sand contact as digging in the sand or burying oneself in the sand.

Boys and men engaged in similar water contact activities as woman and girls, but they were more likely to have their faces touch the water and report swallowing water (Table 4). Boys and men were also more likely to report digging in the sand, but there were no differences in the likelihood of getting sand in one’s mouth. Participants from households where the highest level of education completed was a post-graduate degree were less likely than those in other households to report water contact activities and exposures, and they were also more likely to report sand contact exposures (Table 5).

Table 4. Water and sand exposures reported among beachgoers, stratified by gender identity, Woodbine Beach, Toronto, 2022.

Exposure	N (%)
Exposure	Woman/girl (N = 533)	Man/boy (N = 270)	Fluid/non-binary/trans (N = 15)
Water contact	290 (54.4)	159 (58.9)	8 (53.3)
Swimming	223 (41.8)	127 (47.0)	8 (53.3)
Wading (below one’s waist)	137 (25.7)	77 (28.5)	2 (13.3)
Face contact with water	96 (18.0)	78 (28.9)	5 (33.3)
Swallowing water	50 (9.4)	41 (15.2)	0 (0.0)
Sand contact^a	286 (53.7)	163 (60.4)	9 (60.0)
Digging in the sand	246 (46.2)	145 (53.7)	8 (53.3)
Burying oneself in the sand	86 (16.1)	44 (16.3)	1 (6.7)
Sand in mouth	65 (21.9)	33 (19.4)	3 (33.3)

Open in a new tab

^a We defined sand contact as digging in the sand or burying oneself in the sand.

Table 5. Water and sand exposures reported among beachgoers, stratified by highest education completed in the household, Woodbine Beach, Toronto, 2022.

Exposure	N (%)
Exposure	High school or less (N = 186)	College/trades/ apprenticeship (N = 119)	Bachelor’s degree (N = 153)	Post-graduate (N = 130)
Water contact	104 (55.9)	74 (62.2)	83 (54.2)	50 (38.5)
Swimming	85 (45.7)	55 (46.2)	60 (39.2)	33 (25.4)
Wading (below one’s waist)	44 (23.7)	27 (22.7)	29 (19.0)	20 (15.4)
Face contact with water	43 (23.1)	30 (25.2)	31 (20.3)	14 (10.8)
Swallowing water	21 (11.3)	11 (9.2)	16 (10.5)	4 (3.1)
Sand contact^a	96 (51.6)	62 (52.1)	71 (46.4)	80 (61.5)
Digging in the sand	84 (45.2)	59 (49.6)	67 (43.8)	76 (58.5)
Burying oneself in the sand	22 (11.8)	15 (12.6)	11 (7.2)	19 (14.6)
Sand in mouth	23 (22.8)	11 (17.2)	14 (17.7)	17 (20.5)

Open in a new tab

^a We defined sand contact as digging in the sand or burying oneself in the sand.

Differences in exposures by ethno-racial identity are shown in Table 6. Although there are small numbers in most categories, some trends are noted. Arab and Middle Eastern participants reported the highest prevalence of swimming and face contact with water, while East Asian participants were least likely to report swimming (Table 6). Participants that identified as multiple ethnicities, Latin, and East Asian were most likely to report engaging in sand contact activities (Table 6).

Across the study enrollment period, the beach water geometric mean E. coli levels were consistently low and never exceeded the local health threshold level (median = 20, IQR = 21, range = 10–58). Fig 1 shows the distribution of E. coli level exposures by participant.

Illness outcomes

Table 7 shows the incidence of each of the five illness outcomes of interest among those who completed the follow-up survey, stratified by water and sand contact exposure status. The most common outcome was skin infection (2.8%), which was more frequently reported among those who had sand contact exposures. Similarly, all five cases of respiratory illness reported sand contact exposures. Only three cases of AGI were identified, and one each of ear and eye infections. Severity outcomes were collected for the AGI cases only: one reported missing work due to illness, all three reported taking over-the-counter drugs to treat illness, and none reported seeking medical attention.

Table 7. Incidence of RWI outcomes among beachgoers, stratified by water and sand contact status, at Woodbine Beach, Toronto, 2022^a.

AGI = acute gastrointestinal illness.

Outcome	N (%)
Outcome	Water contact (N = 180)	No water contact (N = 107)	Sand contact (N = 155)	No sand contact (N = 132)	Total (N = 287)
AGI	2 (1.1)	1 (0.9)	2 (1.3)	1 (0.8)	3 (1.0)
Respiratory illness	2 (1.1)	3 (2.8)	5 (3.2)	0 (0)	5 (1.7)
Skin infection	3 (1.7)	5 (4.7)	6 (3.9)	2 (1.5)	8 (2.8)
Ear infection	1 (0.6)	0 (0)	1 (0.6)	0 (0)	1 (0.3)
Eye infection	0 (0)	1 (0.9)	0 (0)	1 (0.8)	1 (0.3)

Open in a new tab

^a Incidence values exclude those who had the same outcome at baseline.

A comparison of sociodemographic and baseline characteristics of those who completed the follow-up survey vs. those who did not are shown in S1 Table. Notably, fewer children and more older adults, those with higher incomes, and those with a bachelor’s vs. high school or less education were more likely to complete the follow-up survey (S1 Table). Those who completed the follow-up survey also were more likely to report water contact (62.7% vs. 52.8%), and less likely to report burying themselves in the sand (10.8% vs. 19.1%) and getting sand in their mouth (14.1% vs. 26.2%).

Discussion

We conducted a prospective cohort pilot study at a popular, urban beach in Toronto, Canada, to determine beachgoer characteristics, reported types of water and sand exposures, the incidence of RWI, and the feasibility for a national cohort study. The findings of this study provide insights into beach exposure patterns and illness outcomes at a freshwater beach with very low levels of identified fecal pollution. In addition, we provided a detailed examination of differences in water and sand exposures by beachgoer characteristics, which can inform future studies and risk communication efforts. Our sample was approximately two-thirds women and girls, and it is not clear whether this reflected the wider beachgoer population or if women and girls were more likely to participate in the study. Previous U.S. cohort studies also had more female than male participants [13, 18, 38, 39]. Based on the most recently available Census data (2021), our sample had more participants with a post-graduate degree than with high school or less education and contained more individuals that identified as white vs. other ethno-racial backgrounds compared to the average for Toronto [40]. Future research should investigate ways to enroll more diverse samples in beach cohort studies, particularly from historically underrepresented population groups.

We identified much lower levels of water contact and swimming, and higher levels of sand contact activities, compared to prior cohort studies in the U.S. [14, 22]. Water and sand contact activities in August more closely matched prior studies, suggesting that the colder lake water temperatures in Toronto result in different exposure patterns for beachgoers than in other locations. Earlier in the beach season in Toronto (June and July), sand exposures appear to be the most important risk of encountering possible pathogens among beachgoers, especially children. Sand exposures have been previously associated with increased risks of AGI among beachgoers [11, 12]. However, there is no routine monitoring for fecal indicator organisms in beach sand in Toronto or other jurisdictions in Ontario, nor are there any guidelines for such monitoring in Canada [20]. Instead, Health Canada recommends that authorities primarily manage possible sand contamination through control measures such as beach grooming and access restrictions [41]. In their 2021 recreational water guidelines, the World Health Organization suggested a provisional health threshold level of <60 CFU/g of intestinal enterococci for beach sand [42]. However, they also noted that additional research is needed to determine acceptable levels of fecal contamination in sand and to assess possible RWI risks from exposure [42]. In addition to enteric pathogens, both beach water and sand can also contain antimicrobial-resistant (AMR) bacteria (e.g., methicillin-resistant Staphylococcus aureus) and opportunistic fungi that can also present different risks of illness to beachgoers [43–45]. Neither beach water nor sand are monitored for these microbial hazards in Canada. Additional research is needed on beach sand contamination, possible risks to beachgoers from sand exposures, and contamination levels and risks from non-fecal microbial hazards in sand and water.

We found that children and teenagers were most likely to report any water contact activities and swallowing water, while nearly all children engaged in sand contact activities and nearly half reported getting sand in their mouth. These exposure trends are similar to prior U.S. studies [14, 22], though our study found a much higher incidence of sand contact activities and getting sand in one’s mouth, further highlighting the need for additional investigation of the microbial quality of beach sand. We found no gender-related differences in water contact activities but found that boys and men were more likely to report having their faces touch water, swallow water, and dig in the sand. This finding corresponds with prior research in the U.S. that found that boys tend to swallow a greater volume of water and spend more time in the water than girls [14]. Additional research to investigate gender-related differences in beach exposures is warranted to guide risk communication efforts.

We found that participants from higher education households were less likely to report water contact activities and more likely to report sand contact activities. This finding could be related to a greater understanding of or attention to beach water quality risks among beachgoers with higher levels of household education [46, 47], but further research is needed in this area. Similarly, we found some difference in beach activities and exposures depending on participants reported ethno-racial identity, which could indicate possible cultural differences in beach behaviours. Additional research into these differences is necessary to inform targeted beach water quality education and outreach needs and gaps among equity-deserving population groups.

E. coli levels were consistently very low during the study period, with none of our participants exposed to levels exceeding local or federal beach action values [20, 26]. It was not surprising, therefore, that we identified very few cases of AGI among respondents that completed the follow-up survey. This finding suggests that there was no increased risk of enteric illness among beachgoers at this urban beach, given the excellent water quality levels observed during the study period. However, we identified very low numbers of all RWI outcomes at baseline and in the follow-up survey, indicating more research is needed to examine possible relationships between water and sand exposures and RWI outcomes among beachgoers in Canada. It is possible that the lower RWI rates may also be due to enrollment of fewer children than in prior studies, especially during July and August, given that children are at a much higher risk of contracting AGI and other RWI outcomes [10, 48]. Some of the illness outcomes (e.g., eye infections) were observed at higher levels in the non-exposed groups, which could have been due to the low sample size, potential misclassification bias, or confounding factors. Future cohort studies should include beach sites that have a history of more fluctuations in water quality, including numerous days with high fecal contamination levels, and sites with known sources of human sewage contamination (e.g., sewage outfalls) to assess the relationship between water quality levels and RWI. Additionally, in this study we relied on culture-based E. coli levels as an indicator of fecal contamination, as this is the indicator routinely used by public health authorities in Ontario [35]. Future studies should aim to incorporate rapidly-measured indicators, such as qPCR-based enterococci, and microbial source tracking genetic markers that can determine specific sources of fecal contamination [49, 50].

Fewer children completed our follow-up survey than expected, which likely explains the other identified differences in reported exposure levels found between those who completed the follow-up compared to those who did not. This is likely at least in part due to parents and guardians of children being too busy to complete the follow-up survey, as well as completing the online survey for themselves only and not including or forgetting to include the names and outcomes for their children. For example, our data collectors anecdotally noted that parents and caregivers were often reluctant to take time to participate and complete surveys on the beach given their childcare duties, contributing to the responses of ‘not wanting to be bothered’ and ‘not having time’ to participate among 41.9% of non-participants. Future beach cohort studies should incorporate more comprehensive methods to enroll and boost retention of families with children. Targeted prompts and personalized follow-ups and requests for additional information from such participants might help to address such data gaps [51]. Further, as this was a pilot study with limited funding, we were only able to offer a chance at a draw prize for participating households. Providing direct monetary incentives at the beach to all participating households in future studies would also likely enhance enrollment and follow-up retention among all participants, including families with children [52, 53].

There are several limitations of this study. While we had a relatively high participation rate among approached households in this study (64%), the follow-up survey completion rate was lower than prior cohort studies conducted in the U.S. which ranged widely from ~45–95% [16, 17, 33, 38, 39]. This limits conclusions that can be drawn from the illness outcome data. Combining the beach entrance and exit survey was also not ideal, but we determined was necessary after the first two enrollment days given that most participants were not returning to complete the exit survey. Woodbine Beach has no defined entrance and exit points, with beachgoers arriving and leaving from a boardwalk along a wide beach area, which likely contributed to this issue. Therefore, our modified strategy ensured that we collected all beach-level data from participants as they were finishing up or nearing the end of their beach visit. Although additional misclassification errors were possible, we also asked participants to report if their exposure status changed after completing the survey, and very few (~5%) reported any changes. We intended to capture a range of different water exposures, but nearly all reported activities were swimming or wading. More targeted efforts may be needed in future studies to enroll beachgoers engaging in other water sport and minimal contact activities.

Conclusion

This pilot cohort study identified and categorized water and sand contact exposures among beachgoers at a popular urban beach in Toronto, Canada. Sand contact activities were much more common than water activities compared to prior studies, especially earlier in the bathing season (June and July). Future research is warranted to investigate the microbial quality and risks of illness from sand exposures. Differences in exposure patterns were noted by age group, gender identity, education, and ethno-racial identity, and those results can be used to guide targeted risk communication and outreach initiatives as well as quantitative microbial risk assessments of beach water quality risks. While follow-up data were also collected on RWI, a high attrition rate and low baseline levels limits the utility of these outcomes. The beach examined in this study had excellent water quality as indicated by E. coli monitoring data and its Blue Flag certification status, and any health risks to bathers were likely minimal. A larger, national cohort study is needed in Canada to examine relationships between water and sand contact exposures, water quality indicators, and RWI outcomes in beaches at high risk of fecal pollution.

Supporting information

S1 File. STROBE checklist for cohort studies.

(DOCX)

Click here for additional data file.^{(33KB, docx)}

S2 File. Beach cohort study questionnaires, Woodbine Beach, Toronto, 2022.

(DOCX)

Click here for additional data file.^{(34.9KB, docx)}

S1 Table. Comparison of participants who completed the follow-up survey vs. those who did not complete the follow-up survey, Woodbine Beach, Toronto, 2022.

(DOCX)

Click here for additional data file.^{(22.1KB, docx)}

Acknowledgments

The authors thank all of the beachgoers who offered their time in completing questionnaires for this study. We also thank Tannis Bubeloff and Zacharia Ramdayal for their efforts conducting participant enrollment, administering surveys, and coordinating follow-ups.

Data Availability

The deidentified dataset and R script files for this study can be obtained at the following publicly available Github repository: https://github.com/iany33/beachcohortpilot2022.

Funding Statement

Funding for this study has been made possible through a contribution from the Public Health Agency of Canada (principal investigators: IY and JT; grant number 2021-HQ-000017; website: https://www.canada.ca/en/public-health/services/funding-opportunities/infectious-diseases-climate-change-fund.html). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

References

1.Janicki R, Thomas KM, Pintar K, Fleury M, Nesbitt A. Drinking and recreational water exposures among Canadians: Foodbook study 2014–2015. J Water Health. 2018;16: 197–211. doi: 10.2166/wh.2018.261 [DOI] [PubMed] [Google Scholar]
2.Statistics Canada. Participation in outdoor activities in the past 12 months by age group, sex, current employment status, and perceived health, Canada, provinces and regions. 2020. https://www150.statcan.gc.ca/t1/tbl1/en/tv.action?pid=4510003001
3.Graciaa DS, Cope JR, Roberts VA, Cikesh BL, Kahler AM, Vigar M, et al. Outbreaks associated with untreated recreational water—United States, 2000–2014. MMWR Morb Mortal Wkly Rep. 2018;67: 701–706. doi: 10.15585/mmwr.mm6725a1 [DOI] [PMC free article] [PubMed] [Google Scholar]
4.Soller JA, Bartrand T, Ashbolt NJ, Ravenscroft J, Wade TJ. Estimating the primary etiologic agents in recreational freshwaters impacted by human sources of faecal contamination. Water Res. 2010;44: 4736–4747. doi: 10.1016/j.watres.2010.07.064 [DOI] [PubMed] [Google Scholar]
5.Schoen ME, Ashbolt NJ. Assessing pathogen risk to swimmers at non-sewage impacted recreational beaches. Environ Sci Tech. 2010;44: 2286–2291. doi: 10.1021/es903523q [DOI] [PubMed] [Google Scholar]
6.DeFlorio-Barker S, Wing C, Jones RM, Dorevitch S. Estimate of incidence and cost of recreational waterborne illness on United States surface waters. Environ Health. 2018;17: 3. doi: 10.1186/s12940-017-0347-9 [DOI] [PMC free article] [PubMed] [Google Scholar]
7.Schets FM, Husman AMDR, Havelaar AH. Disease outbreaks associated with untreated recreational water use. Epidemiol Infect. 2011;139: 1114–1125. doi: 10.1017/S0950268810002347 [DOI] [PubMed] [Google Scholar]
8.Leonard AF, Singer A, Ukoumunne OC, Gaze WH, Garside R, AFC L, et al. Is it safe to go back into the water? A systematic review and meta-analysis of the risk of acquiring infections from recreational exposure to seawater. Int J Epidemiol. 2018;47: 572–586. doi: 10.1093/ije/dyx281 [DOI] [PMC free article] [PubMed] [Google Scholar]
9.Russo GS, Eftim SE, Goldstone AE, Dufour AP, Nappier SP, Wade TJ. Evaluating health risks associated with exposure to ambient surface waters during recreational activities: a systematic review and meta-analysis. Water Res. 2020;176: 115729. doi: 10.1016/j.watres.2020.115729 [DOI] [PMC free article] [PubMed] [Google Scholar]
10.Arnold BF, Wade TJ, Benjamin-Chung J, Schiff KC, Griffith JF, Dufour AP, et al. Acute gastroenteritis and recreational water: highest burden among young US children. Am J Public Health. 2016;106: 1690–1697. doi: 10.2105/AJPH.2016.303279 [DOI] [PMC free article] [PubMed] [Google Scholar]
11.Heaney CD, Sams E, Wing S, Marshall S, Brenner K, Dufour AP, et al. Contact with beach sand among beachgoers and risk of illness. Am J Epidemiol. 2009;170: 164–72. doi: 10.1093/aje/kwp152 [DOI] [PubMed] [Google Scholar]
12.Heaney CD, Sams E, Dufour AP, Brenner KP, Haugland RA, Chern E, et al. Fecal indicators in sand, sand contact, and risk of enteric illness among beachgoers. Epidemiol. 2012;23: 95–106. doi: 10.1097/EDE.0b013e31823b504c [DOI] [PMC free article] [PubMed] [Google Scholar]
13.Wade TJ, Calderon RL, Brenner KP, Sams E, Beach M, Haugland R, et al. High sensitivity of children to swimming-associated gastrointestinal illness: results using a rapid assay of recreational water quality. Epidemiol. 2008;19: 375–383. doi: 10.1097/EDE.0b013e318169cc87 [DOI] [PubMed] [Google Scholar]
14.Deflorio-Barker S, Arnold BF, Sams EA, Dufour AP, Colford JM, Weisberg SB, et al. Child environmental exposures to water and sand at the beach: findings from studies of over 68,000 subjects at 12 beaches. J Expo Sci Environ Epidemiol. 2018;28: 93–100. doi: 10.1038/jes.2017.23 [DOI] [PMC free article] [PubMed] [Google Scholar]
15.Dufour AP, Behymer TD, Cantú R, Magnuson M, Wymer LJ. Ingestion of swimming pool water by recreational swimmers. J Water Health. 2017;15: 429–437. doi: 10.2166/wh.2017.255 [DOI] [PubMed] [Google Scholar]
16.Wade TJ, Calderon RL, Sams E, Beach M, Brenner KP, Williams AH, et al. Rapidly measured indicators of recreational water quality are predictive of swimming-associated gastrointestinal illness. Env Health Perspect. 2006;114: 24–28. doi: 10.1289/ehp.8273 [DOI] [PMC free article] [PubMed] [Google Scholar]
17.Dorevitch S, Pratap P, Wroblewski M, Hryhorczuk DO, Li H, Liu LC, et al. Health risks of limited-contact water recreation. Env Health Perspect. 2012;120: 192–197. doi: 10.1289/ehp.1103934 [DOI] [PMC free article] [PubMed] [Google Scholar]
18.Wade TJ, Sams EA, Haugland RA, Brenner KP, Li Q, Wymer L, et al. Report on 2009 national epidemiologic and environmental assessment of recreational water epidemiology studies. Washington, DC; 2010. https://www.epa.gov/sites/default/files/2019-03/documents/report-2009-national-epidemiologic-studies.pdf
19.Seyfried PL, Tobin RS, Brown NE, Ness PF. A prospective study of swimming-related illness I. Swimming-associated health risk. Am J Public Health. 1985;75: 1068–1070. doi: 10.2105/AJPH.75.9.1068 [DOI] [PMC free article] [PubMed] [Google Scholar]
20.Health Canada. Guidelines for Canadian recreational water quality: indicators of fecal contamination. 2021. https://www.canada.ca/en/health-canada/programs/consultation-guidelines-recreational-water-quality-fecal-contamination/document.html
21.Ontario Ministry of Health and Long-Term Care. Operational approaches for recreational water guideline. 2018. https://www.health.gov.on.ca/en/pro/programs/publichealth/oph_standards/docs/protocols_guidelines/Operational_Approaches_to_Rec_Water_Guideline_2018_en.pdf
22.Collier SA, Wade TJ, Sams EA, Hlavsa MC, Dufour AP, Beach MJ. Swimming in the USA: beachgoer characteristics and health outcomes at US marine and freshwater beaches. J Water Health. 2015;13: 531–543. doi: 10.2166/wh.2014.095 [DOI] [PMC free article] [PubMed] [Google Scholar]
23.Nevers MB, Whitman RL. Efficacy of monitoring and empirical predictive modeling at improving public health protection at Chicago beaches. Water Res. 2011;45: 1659–1668. doi: 10.1016/j.watres.2010.12.010 [DOI] [PubMed] [Google Scholar]
24.Francy DS, Stelzer EA, Duris JW, Brady AMG, Harrison JH, Johnson HE, et al. Predictive models for Escherichia coli concentrations at inland lake beaches and relationship of model variables to pathogen detection. Appl Environ Microbiol. 2013;79: 1676–88. doi: 10.1128/AEM.02995-12 [DOI] [PMC free article] [PubMed] [Google Scholar]
25.von Elm E, Altman DG, Egger M, Pocock SJ, Gøtzsche PC, Vandenbroucke JP. The Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) statement: guidelines for reporting observational studies. J Clin Epidemiol. 2008;61: 344–349. doi: 10.1016/j.jclinepi.2007.11.008 [DOI] [PubMed] [Google Scholar]
26.City of Toronto. About beach water quality. 2023. https://www.toronto.ca/community-people/health-wellness-care/health-inspections-monitoring/swimsafe/beach-water-quality/about-beach-water-quality/
27.Toronto and Region Conservation Authority. Ashbridges Bay landform project. 2021. https://trca.ca/conservation/green-infrastructure/ashbridges-bay-erosion-sediment-control-project/
28.Swim Drink Fish. Woodbine beach. 2023. https://www.theswimguide.org/beach/83
29.Sanchez J, Tustin J, Heasley C, Patel M, Kelly J, Habjan A, et al. Region-specific associations between environmental factors and Escherichia coli in freshwater beaches in Toronto and Niagara region, Canada. Int J Environ Res Public Health. 2021;18: 12841. doi: 10.3390/IJERPH182312841 [DOI] [PMC free article] [PubMed] [Google Scholar]
30.Peterson CH, Peterson NA, Powell KG. Cognitive interviewing for item development: validity evidence based on content and response processes. Meas Eval Couns Dev. 2017;50: 217–223. doi: 10.1080/07481756.2017.1339564 [DOI] [Google Scholar]
31.Lee RM, Lessler J, Lee RA, Rudolph KE, Reich NG, Perl TM, et al. Incubation periods of viral gastroenteritis: a systematic review. BMC Infect Dis. 2013;13: 1–11. doi: 10.1186/1471-2334-13-446 [DOI] [PMC free article] [PubMed] [Google Scholar]
32.Chai SJ, Gu W, O’Connor KA, Richardson LC, Tauxe RV. Incubation periods of enteric illnesses in foodborne outbreaks, United States, 1998–2013. Epidemiol Infect. 2019;147: e285. doi: 10.1017/S0950268819001651 [DOI] [PMC free article] [PubMed] [Google Scholar]
33.Wade TJ, Sams E, Brenner KP, Haugland R, Chern E, Beach M, et al. Rapidly measured indicators of recreational water quality and swimming-associated illness at marine beaches: a prospective cohort study. Environ Health. 2010;9: 66. doi: 10.1186/1476-069X-9-66 [DOI] [PMC free article] [PubMed] [Google Scholar]
34.Colford JM, Wade TJ, Schiff KC, Wright CC, Griffith JF, Sandhu SK, et al. Water quality indicators and the risk of illness at beaches with nonpoint sources of fecal contamination. Epidemiol. 2007;18: 27–35. doi: 10.1097/01.ede.0000249425.32990.b9 [DOI] [PubMed] [Google Scholar]
35.Public Health Ontario. Public health inspector’s guide to environmental microbiology laboratory testing. 2021. https://www.publichealthontario.ca/-/media/documents/lab/phi-guide.pdf?la=en
36.R Core Team. R: a language and environment for statistical computing. Vienna, Austria: R Foundation for Statistical Computing; 2022.
37.Posit Team. RStudio: integrated development for R. Boston, MA: Posit Software, PBC; 2023.
38.Marion JW, Lee J, Lemeshow S, Buckley TJ. Association of gastrointestinal illness and recreational water exposure at an inland U.S. beach. Water Res. 2010;44: 4796–4804. doi: 10.1016/j.watres.2010.07.065 [DOI] [PubMed] [Google Scholar]
39.Arnold BF, Schiff KC, Griffith JF, Gruber JS, Yau V, Wright CC, et al. Swimmer illness associated with marine water exposure and water quality indicators: impact of widely used assumptions. Epidemiol. 2013;24: 845–853. doi: 10.1097/01.ede.0000434431.06765.4a [DOI] [PubMed] [Google Scholar]
40.Statistics Canada. Census profile. 2021 census of population. 2023. https://www12.statcan.gc.ca/census-recensement/2021/dp-pd/prof/index.cfm?Lang=E
41.Health Canada. Guidelines for Canadian recreational water quality: understanding and managing risks in recreational waters. 2023. https://www.canada.ca/en/health-canada/services/publications/healthy-living/guidelines-understanding-managing-risks-recreational-waters.html
42.World Health Organization. Guidelines on recreational water quality: volume 1 coastal and fresh waters. 2021. https://www.who.int/publications/i/item/9789240031302 [PubMed]
43.Brandão J, Gangneux JP, Arikan-Akdagli S, Barac A, Bostanaru AC, Brito S, et al. Mycosands: Fungal diversity and abundance in beach sand and recreational waters—Relevance to human health. Sci Total Environ. 2021;781: 146598. doi: 10.1016/j.scitotenv.2021.146598 [DOI] [PubMed] [Google Scholar]
44.Thapaliya D, Hellwig EJ, Kadariya J, Grenier D, Jefferson AJ, Dalman M, et al. Prevalence and characterization of Staphylococcus aureus and methicillin-resistant Staphylococcus aureus on public recreational beaches in northeast Ohio. Geohealth. 2017;1: 320–332. doi: 10.1002/2017GH000106 [DOI] [PMC free article] [PubMed] [Google Scholar]
45.Fogarty LR, Haack SK, Johnson HE, Brennan AK, Isaacs NM, Spencer C. Staphylococcus aureus and methicillin-resistant S. aureus (MRSA) at ambient freshwater beaches. J Water Health. 2015;13: 680–692. doi: 10.2166/wh.2014.278 [DOI] [PubMed] [Google Scholar]
46.Quilliam RS, Taylor J, Oliver DM. The disparity between regulatory measurements of E. coli in public bathing waters and the public expectation of bathing water quality. J Environ Manag. 2019;232: 868–874. doi: 10.1016/j.jenvman.2018.11.138 [DOI] [PubMed] [Google Scholar]
47.Pratap PL, Redman S, Fagen MC, Dorevitch S. Improving water quality communications at beaches: input from stakeholders. J Water Health. 2013;11: 647–658. doi: 10.2166/wh.2013.077 [DOI] [PubMed] [Google Scholar]
48.Wade TJ, Arnold BF, Schiff K, Colford JM, Weisberg SB, Griffith JF, et al. Health risks to children from exposure to fecally-contaminated recreational water. PLoS One. 2022;17: e0266749. doi: 10.1371/journal.pone.0266749 [DOI] [PMC free article] [PubMed] [Google Scholar]
49.Shrestha A, Dorevitch S. Slow adoption of rapid testing: beach monitoring and notification using qPCR. J Microbiol Methods. 2020;174: 105947. doi: 10.1016/j.mimet.2020.105947 [DOI] [PubMed] [Google Scholar]
50.Harwood VJ, Staley C, Badgley BD, Borges K, Korajkic A. Microbial source tracking markers for detection of fecal contamination in environmental waters: relationships between pathogens and human health outcomes. FEMS Microbiol Rev. 2014;38: 1–40. doi: 10.1111/1574-6976.12031 [DOI] [PubMed] [Google Scholar]
51.Teague S, Youssef GJ, Macdonald JA, Sciberras E, Shatte A, Fuller-Tyszkiewicz M, et al. Retention strategies in longitudinal cohort studies: a systematic review and meta-analysis. BMC Med Res Methodol. 2018;18: 1–22. doi: 10.1186/S12874-018-0586-7 [DOI] [PMC free article] [PubMed] [Google Scholar]
52.Abdelazeem B, Abbas KS, Amin MA, El-Shahat NA, Malik B, Kalantary A, et al. The effectiveness of incentives for research participation: a systematic review and meta-analysis of randomized controlled trials. PLoS One. 2022;17: e0267534. doi: 10.1371/journal.pone.0267534 [DOI] [PMC free article] [PubMed] [Google Scholar]
53.Gillies K, Kearney A, Keenan C, Treweek S, Hudson J, Brueton V, et al. Strategies to improve retention in randomised trials. Cochrane Database Syst Rev. 2021. doi: 10.1002/14651858.MR000032.pub3 [DOI] [PMC free article] [PubMed] [Google Scholar]

PLoS One. doi: 10.1371/journal.pone.0286584.r001

Decision Letter 0

Zakir Abdu

10 Feb 2023

PONE-D-22-34376Recreational water exposures and illness outcomes at a freshwater beach in Toronto, Canada: a prospective pilot cohort studyPLOS ONE

Dear Dr. Young,

Please submit your revised manuscript by Mar 27 2023 11:59PM. If you will need more time than this to complete your revisions, please reply to this message or contact the journal office at plosone@plos.org. When you're ready to submit your revision, log on to https://www.editorialmanager.com/pone/ and select the 'Submissions Needing Revision' folder to locate your manuscript file.

Please include the following items when submitting your revised manuscript:

A rebuttal letter that responds to each point raised by the academic editor and reviewer(s). You should upload this letter as a separate file labeled 'Response to Reviewers'.
A marked-up copy of your manuscript that highlights changes made to the original version. You should upload this as a separate file labeled 'Revised Manuscript with Track Changes'.
An unmarked version of your revised paper without tracked changes. You should upload this as a separate file labeled 'Manuscript'.

If you would like to make changes to your financial disclosure, please include your updated statement in your cover letter. Guidelines for resubmitting your figure files are available below the reviewer comments at the end of this letter.

If applicable, we recommend that you deposit your laboratory protocols in protocols.io to enhance the reproducibility of your results. Protocols.io assigns your protocol its own identifier (DOI) so that it can be cited independently in the future. For instructions see: https://journals.plos.org/plosone/s/submission-guidelines#loc-laboratory-protocols. Additionally, PLOS ONE offers an option for publishing peer-reviewed Lab Protocol articles, which describe protocols hosted on protocols.io. Read more information on sharing protocols at https://plos.org/protocols?utm_medium=editorial-email&utm_source=authorletters&utm_campaign=protocols.

We look forward to receiving your revised manuscript.

Kind regards,

Zakir Abdu

Academic Editor

PLOS ONE

Journal Requirements:

When submitting your revision, we need you to address these additional requirements.

1. Please ensure that your manuscript meets PLOS ONE's style requirements, including those for file naming. The PLOS ONE style templates can be found at

https://journals.plos.org/plosone/s/file?id=wjVg/PLOSOne_formatting_sample_main_body.pdf and

https://journals.plos.org/plosone/s/file?id=ba62/PLOSOne_formatting_sample_title_authors_affiliations.pdf

2. Please provide additional details regarding participant consent. In the ethics statement in the Methods and online submission information, please ensure that you have specified what type you obtained (for instance, written or verbal, and if verbal, how it was documented and witnessed). If your study included minors, state whether you obtained consent from parents or guardians. If the need for consent was waived by the ethics committee, please include this information.

3. In your Data Availability statement, you have not specified where the minimal data set underlying the results described in your manuscript can be found. PLOS defines a study's minimal data set as the underlying data used to reach the conclusions drawn in the manuscript and any additional data required to replicate the reported study findings in their entirety. All PLOS journals require that the minimal data set be made fully available. For more information about our data policy, please see http://journals.plos.org/plosone/s/data-availability.

Upon re-submitting your revised manuscript, please upload your study’s minimal underlying data set as either Supporting Information files or to a stable, public repository and include the relevant URLs, DOIs, or accession numbers within your revised cover letter. For a list of acceptable repositories, please see http://journals.plos.org/plosone/s/data-availability#loc-recommended-repositories. Any potentially identifying patient information must be fully anonymized.

Important: If there are ethical or legal restrictions to sharing your data publicly, please explain these restrictions in detail. Please see our guidelines for more information on what we consider unacceptable restrictions to publicly sharing data: http://journals.plos.org/plosone/s/data-availability#loc-unacceptable-data-access-restrictions. Note that it is not acceptable for the authors to be the sole named individuals responsible for ensuring data access.

We will update your Data Availability statement to reflect the information you provide in your cover letter.

4. Please include captions for your Supporting Information files at the end of your manuscript, and update any in-text citations to match accordingly. Please see our Supporting Information guidelines for more information: http://journals.plos.org/plosone/s/supporting-information.

Additional Editor Comments:

Dear Author (s),

Thank you for submitting an important and scientific piece of work in the field of SRH Recreational water exposures and illness outcomes at a freshwater beach in PLOS ONE journal. With due reverence to our reviewers and valuable comments, the following points are additional ones found to be addressed, the manuscript writing and its flow are praiseworthy though :

Clarify the methodology part. Who was your study population? Source population? And what is your study unit? How did you select one (Woodbine beach) from the popular 11? (is popularity is a criteria? I did not think so). Please justify? What is the others beach?
While collecting data, what do think about more than 1 participants present in household?
Clearly describe the sample size calculation with rationale
Another of my concern is that about confidentiality (while emailing or calling the participants for the issue of get information)
Did you found a participant with illness? What did you do for them?

[Note: HTML markup is below. Please do not edit.]

Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #1: Yes

Reviewer #2: Yes

**********

2. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: Yes

Reviewer #2: Yes

**********

3. Have the authors made all data underlying the findings in their manuscript fully available?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #1: Yes

Reviewer #2: Yes

**********

4. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #1: Yes

Reviewer #2: Yes

**********

5. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #1: Thank you for inviting me to review this paper which describes a survey of water and sand exposures among visitors to one freshwater beach in Canada. It’s well written, the authors make it very clear that this is a pilot study, and thus findings and conclusions are naturally limited and cautious. However, the novelty and relevance of the research question(s) for international readers really needs to be addressed because at the moment it is not clear what the novelty of this work is, other than it is conducted in Canada. I provide more specific recommendations below.

1. I recommend a slight change to the title, as the work is better described as a prospective cohort pilot study.

2. The abstract should mention what kinds of illnesses were considered (gastrointestinal, respiratory, skin, ear and eye). The aims of the study should also be stated.

3. The methods section should include a description of sample size calculation/desired sample size and what this was based on. More information is needed about recruitment, for example, at what time of day were people recruited?

4. It is unclear how participant contact with algae was determined - I assume this was contact with seaweed at the beach, but algae could also refer to previous contact with harmful algal blooms, thus clarification is needed here.

5. How was ‘any sand contact’ defined? I’m not familiar with the study location, but at most beaches, people in contact with the water also have contact with sand as they walk across the beach to access the water. There could be misclassification here in terms of bathers reporting not having contact with sand, when they in fact did.

6. Table 6 needs reformatting as I couldn’t not see all the data. Figure 1 is not a histogram, it’s a bar chart.

7. I recommend a restructure of the discussion, which should start by repeating study objectives and main findings (in accordance with STROBE reporting). The detailed discussion of the merits of monetary incentives is not sufficiently interesting to start a discussion section, and this could be edited down to briefly state that studies with incentives for each participant report lower attrition rates, especially among under-represented groups (e.g. systematic reviews and meta-analyses by Jia et al 2021; Abdelazeem et al. 2022)

8. The discussion does not offer any explanation of the observation that incidence of some illnesses was slightly higher in the unexposed group compared to the exposed group (see water users and respiratory illness/skin infection, as well as eye infection in people not exposed to water and sand). Insufficient sample size, potentially misclassification bias or some unmeasured confounder/risk factor.

9. Antimicrobial resistant bacteria and fungi are mentioned in relation to sand quality and risks to health, but not the health threat the presence of these in water pose to bathers. There are several papers that could be usefully cited to evidence the reasons these microorganisms are concerning for recreational exposures.

10. The grammar is excellent. As PLOS ONE doesn't edit, I noted a few minor grammatical errors on the following lines:

- 29 - conducted a pilot of a prospective cohort study

- 124 - use a colon after the word 'beachgoers'

- 148 - remove the word 'to'

-Table 1 - acronyms should be included in the legend (applicable to other tables)

-line 263 - 'and there' should be 'and they'

Reviewer #2: Title: Recreational water exposures and illness outcomes at a freshwater beach in Toronto, Canada: a prospective pilot cohort study

Manuscript Number: PONE-D-22-34376

I appreciate the authors for their outstanding team work on such an interesting topic. Their work is novel. I have some suggestion for the authors as mentioned below.

Title: authors would entitle as “Incidence of recreational water activities and illness outcomes at a freshwater beach in Toronto, Canada: a prospective pilot cohort study”

Abstract: The authors would not describe the sentence “Water contact activities were lowest in June (39.1%), increasing in prevalence in July (57.4%) and August (70.8%).” in the abstract section because these findings were not part of their main study objectives. The abstract should include only pertinent findings.

Introduction:

Authors would detail the recreational water activities. What are those activities; how many types; and what are the commonest?

Line- 58: better to say “illnesses”

Authors confined the evidence searches only to Canada and U.S. What is the magnitude and impact of the phenomenon in the other continents?

“The study objectives were to determine characteristics of beachgoers, common water and sand exposures, the incidence of RWI, and the feasibility and recommendations for a larger, national cohort study” It is not clear why the authors included “…recommendations for a larger, national cohort study” to their objective. Recommendation must follow existing result.

Methods and materials

How did the authors identified base line health status was identified? How did authors ruled out previous exposure to bacterial or viral agents? Did authors use a lab-based investigation or used only participants’ verbal report?

What if the participant exposed to viral or bacterial sources (other than RW activities) amid the follow-up period? How did you controlled?

Is your tool validated?

Line-181: “low prevalence”. Is it incidence or prevalence in the eye of cohort study?

In the data analysis section, authors conducted cross-tabulations to compare water and sand exposures by age group, gender identity, highest education level in the household, and ethno-racial identity. However, they didn’t mention any statistical methods, such as chi-square tests or t-est to show differences in each category they used to compare.

Results:

Significant number of participants’ age of was below 16; however, authors mentioned as “To be eligible for participation, at least one household member aged 16 years or older needed to be present to conduct the survey in English” Can you explain this issue, please?

Discussion:

Authors reported that “parents and caregivers were often reluctant to take time to participate and complete surveys on the beach given their childcare duties, contributing to the responses of ‘not wanting to be bothered’ and ‘not having time” but they didn’t mentioned the average time each interview took.

Authors would limit their discussion to their research objectives. Most of the discussion, particularly the first and the second paragraphs, are not based on the objectives.

**********

6. PLOS authors have the option to publish the peer review history of their article (what does this mean?). If published, this will include your full peer review and any attached files.

If you choose “no”, your identity will remain anonymous but your review may still be made public.

Do you want your identity to be public for this peer review? For information about this choice, including consent withdrawal, please see our Privacy Policy.

Reviewer #1: No

Reviewer #2: Yes: Wubishet Gezimu

**********

[NOTE: If reviewer comments were submitted as an attachment file, they will be attached to this email and accessible via the submission site. Please log into your account, locate the manuscript record, and check for the action link "View Attachments". If this link does not appear, there are no attachment files.]

While revising your submission, please upload your figure files to the Preflight Analysis and Conversion Engine (PACE) digital diagnostic tool, https://pacev2.apexcovantage.com/. PACE helps ensure that figures meet PLOS requirements. To use PACE, you must first register as a user. Registration is free. Then, login and navigate to the UPLOAD tab, where you will find detailed instructions on how to use the tool. If you encounter any issues or have any questions when using PACE, please email PLOS at figures@plos.org. Please note that Supporting Information files do not need this step.

Attachment

Submitted filename: Comments to authors.docx

Click here for additional data file.^{(14.1KB, docx)}

PLoS One. 2023 Jun 2;18(6):e0286584. doi: 10.1371/journal.pone.0286584.r002

Author response to Decision Letter 0

17 Feb 2023

Editor Comments:

Clarify the methodology part. Who was your study population? Source population? And what is your study unit? How did you select one (Woodbine beach) from the popular 11? (is popularity is a criteria? I did not think so). Please justify? What is the others beach?

We thank the editor for these comments. We have added and clarified these additional details as requested in the methods section (see revised study design and participant eligibility sections). The details on the other 10 beaches we believe are not relevant to this study, as we already pre-determined this beach as the ideal location for this study for the reasons specified in this methods section (i.e., large beachgoer population and most popular beach in the city ideal to assess recruitment feasibility).

While collecting data, what do think about more than 1 participants present in household?

We have explained in the participant eligibility and enrollment section of the methods how we completed separate surveys for each individual beachgoer, but surveyed households together for feasibility and logistical reasons. This is also the approach that has been used in prior, similar studies we cited.

Clearly describe the sample size calculation with rationale

Given that this was a pilot study aimed at determining feasibility of the methods for larger study, we did not have a specific sample size. Instead, we aimed to recruit as many beachgoers as possible each recruitment day to support power analysis calculations and planning for a larger study. This has been clarified in the participant eligibility and enrollment section of the methods.

Another of my concern is that about confidentiality (while emailing or calling the participants for the issue of get information)

As noted in the study design section of the methods, this study received research ethics board review and approval from Toronto Metropolitan University. This included comprehensive measures to ensure confidentiality of participants and their data. All participant identifying information was kept on secure servers, was available only to those in the research team, and was deleted after data collection was completed and the draw prizes administered.

Did you found a participant with illness? What did you do for them?

As noted in Table 7, we found that a small percentage of participants that completed the follow-up survey reported one or more acute illnesses. The purpose of this study was not to provide treatments or interventions for such individuals. However, we did include information about recreational water quality in the city and where to find more information for interested participants on the last page of the survey, providing a link to the local public health authority website on beach water quality.

Reviewer #1:

Thank you for inviting me to review this paper which describes a survey of water and sand exposures among visitors to one freshwater beach in Canada. It’s well written, the authors make it very clear that this is a pilot study, and thus findings and conclusions are naturally limited and cautious. However, the novelty and relevance of the research question(s) for international readers really needs to be addressed because at the moment it is not clear what the novelty of this work is, other than it is conducted in Canada. I provide more specific recommendations below.

We thank the reviewer for these comments and recommendations. We have provided more information on the potential global relevance of this study in the revised discussion.

1. I recommend a slight change to the title, as the work is better described as a prospective cohort pilot study.

We have adopted this suggestion.

2. The abstract should mention what kinds of illnesses were considered (gastrointestinal, respiratory, skin, ear and eye). The aims of the study should also be stated.

We have added these details as suggested.

Given that this was a pilot study aimed at determining feasibility of the methods for larger study, we did not have a specific sample size. Instead, we aimed to recruit as many beachgoers as possible each recruitment day to support power analysis calculations and planning for a larger study. We have added this information, along with more details on the recruitment, in the participant eligibility and enrollment section of the methods.

We have clarified that we meant contact with seaweed, not harmful algal blooms (which are not a concern at the beach examined in this study).

We have clarified how this is reported in the tables. We specifically defined “sand contact” in this study as either digging in the sand and/or burying oneself in the sand. This is how the question appeared in the survey and was aggregated for analysis and reporting purposes.

6. Table 6 needs reformatting as I couldn’t not see all the data. Figure 1 is not a histogram, it’s a bar chart.

We apologize for this, as it was our understanding that wide tables like this should be inserted as is into the manuscript file and it would display properly in the PDF form for reviewers. We have reformatted it to landscape to ensure it is visible. We appreciate that Fig 1 looks like a bar chart, but it is actually a histogram, as the beach water E. coli geometric mean was a numeric variable, with number of values equal to the number of recruitment days.

We appreciate these comments and have revised this part of the discussion accordingly. The discussion on incentives has been edited and reorganized to later in the discussion.

This a good point, and we have added a brief possible explanation for this finding as suggested in the discussion.

This is a good point, we have edited and revised this section to address both exposure pathways.

10. The grammar is excellent. As PLOS ONE doesn't edit, I noted a few minor grammatical errors on the following lines:

- 29 - conducted a pilot of a prospective cohort study

- 124 - use a colon after the word 'beachgoers'

- 148 - remove the word 'to'

-Table 1 - acronyms should be included in the legend (applicable to other tables)

-line 263 - 'and there' should be 'and they'

We have made these edits as suggested.

Reviewer #2:

I appreciate the authors for their outstanding team work on such an interesting topic. Their work is novel. I have some suggestion for the authors as mentioned below.

We thank the reviewer for their comments and suggestions.

Title: authors would entitle as “Incidence of recreational water activities and illness outcomes at a freshwater beach in Toronto, Canada: a prospective pilot cohort study”

We appreciate this suggestion but have decided to keep the original wording in the title as we feel it accurately describes the study and objectives.

We have revised this part of the abstract as suggested.

Introduction:

Authors would detail the recreational water activities. What are those activities; how many types; and what are the commonest?

We have added more information on different types of recreational water activities, including their popularity in Canada.

Line- 58: better to say “illnesses”

We have made this change.

Authors confined the evidence searches only to Canada and U.S. What is the magnitude and impact of the phenomenon in the other continents?

We have focused more on Canada and the U.S. given that this study was conducted in Canada and the U.S. is the most comparable and closest country to Canada, so data from the U.S. is most relevant to the Canadian context. However, we’ve also added some additional outbreak data from the Netherlands to provide another country for comparison.

We have edited this sentence to remove “recommendations” as suggested.

Methods and materials

We collected baseline health status and all other data via beachgoer self-reported surveys. Being a pilot study, the goal of this study was to assess common exposures and outcomes and to determine feasibility of recruitment methods, not to determine causal estimates of the exposure on the outcomes. Nevertheless, as noted in the data analysis section, we excluded those who reported an illness at baseline from the summary of RWI outcomes reported in Table 7 to exclude those who might have been exposed to microbial hazards from other sources prior to their beach visit.

What if the participant exposed to viral or bacterial sources (other than RW activities) amid the follow-up period? How did you controlled?

As noted above, this was a pilot study that did not aim to determine causal estimates of the exposure on the outcomes. It was primarily designed as a feasibility study and to assess and categorize common exposures and outcomes at the study site. Therefore, we did not conduct regression modelling to determine causal estimates, we only reported the raw incidence of each outcome for descriptive purposes. You are correct that there could be confounding factors associated with the exposure and outcome and that would need to be adjusted for in a model to determine the appropriate casual effect of the exposure, but that was beyond the scope of this pilot study. Nevertheless, we have added a brief explanation to the discussion section to indicate that confounding factors might explain any of the differences noted in Table 7.

Is your tool validated?

As noted in the “data collection surveys” part of the methods, our questionnaire was pre-tested with 10 individual beachgoers using a cognitive interviewing technique prior to use in the current study. Additionally, the tool was based on previous validated U.S. cohort studies. Given that this is a pilot study, its use in this study provides further validation for its adoption in a larger national study in Canada.

Line-181: “low prevalence”. Is it incidence or prevalence in the eye of cohort study?

Good point, we have revised to incidence.

We decided to focus on descriptive cross-tabulations instead of null-hypothesis significance testing, as we did not have any pre-specified hypotheses to test for statistical significance. Additionally, there is a propensity for such tests and P values to be misinterpreted (e.g., https://doi.org/10.1007/s10654-016-0149-3). Instead, differences can be noted by visually examining the contingency tables, and we have aimed to highlight and comment on the key findings in the results text.

Results:

This statement means that children and youth were only permitted to participate in the study if a parent or guardian aged 16 years or older in their household was also present to provide consent for them. This has been clarified in the study design section of the methods.

Discussion:

We have added details on the survey completion time to the results section as suggested.

Authors would limit their discussion to their research objectives. Most of the discussion, particularly the first and the second paragraphs, are not based on the objectives.

We appreciate these comments and have revised the discussion accordingly.

Attachment

Submitted filename: Response to reviewers.docx

Click here for additional data file.^{(23.1KB, docx)}

PLoS One. doi: 10.1371/journal.pone.0286584.r003

Decision Letter 1

Timothy J Wade

8 May 2023

PONE-D-22-34376R1Recreational water exposures and illness outcomes at a freshwater beach in Toronto, Canada: a prospective cohort pilot studyPLOS ONE

Dear Dr. Young,

Thank you for submitting your manuscript to PLOS ONE. After careful consideration, we feel that it has merit but does not fully meet PLOS ONE’s publication criteria as it currently stands. Therefore, we invite you to submit a revised version of the manuscript that addresses the points raised during the review process. Please submit your revised manuscript by Jun 22 2023 11:59PM. If you will need more time than this to complete your revisions, please reply to this message or contact the journal office at plosone@plos.org. When you're ready to submit your revision, log on to https://www.editorialmanager.com/pone/ and select the 'Submissions Needing Revision' folder to locate your manuscript file.

Please include the following items when submitting your revised manuscript:

A rebuttal letter that responds to each point raised by the academic editor and reviewer(s). You should upload this letter as a separate file labeled 'Response to Reviewers'.
A marked-up copy of your manuscript that highlights changes made to the original version. You should upload this as a separate file labeled 'Revised Manuscript with Track Changes'.
An unmarked version of your revised paper without tracked changes. You should upload this as a separate file labeled 'Manuscript'.

We look forward to receiving your revised manuscript.

Kind regards,

Timothy J Wade, Ph.D

Academic Editor

PLOS ONE

Journal Requirements:

Please review your reference list to ensure that it is complete and correct. If you have cited papers that have been retracted, please include the rationale for doing so in the manuscript text, or remove these references and replace them with relevant current references. Any changes to the reference list should be mentioned in the rebuttal letter that accompanies your revised manuscript. If you need to cite a retracted article, indicate the article’s retracted status in the References list and also include a citation and full reference for the retraction notice.

Additional Editor Comments:

The authors have adequately addressed all comments by the reviewers. I have a few additional comments that should be addressed in a revised version:

1) The authors conclude that a larger national cohort study is needed, but they do not address one finding of the pilot study- namely at the site they studied, the water was likely to be much too clean to see observable health relationships. Any larger study should encompass a wider range of water quality, including sites that do not have excellent water quality and sites that are impacted by sources of human sewage which are the riskiest for beachgoers. Also note that this study may be considerably expensive so the benefits should outweigh the costs

2) This study only considered limited measures of water quality, there are many advancement in water quality testing including human markers, rapid methods, and viral indicators. Any large national study should consider these as well

3) The conclusion that routine monitoring of sand quality should be considered based on this study seems premature- simply because more people are in contact with sand does not necessarily mean it should be monitored which could be considerably expensive, and may come at the trade off of other types of water quality testing. I do not know anywhere where sand is currently regularly monitored, although WHO provided a provisional value, this has not really been tested or validated broadly. Please reconsider this recommendation, at least until results of a larger study provide more conclusive evidence

[Note: HTML markup is below. Please do not edit.]

Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. If the authors have adequately addressed your comments raised in a previous round of review and you feel that this manuscript is now acceptable for publication, you may indicate that here to bypass the “Comments to the Author” section, enter your conflict of interest statement in the “Confidential to Editor” section, and submit your "Accept" recommendation.

Reviewer #2: All comments have been addressed

**********

2. Is the manuscript technically sound, and do the data support the conclusions?

Reviewer #2: Yes

**********

3. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #2: Yes

**********

4. Have the authors made all data underlying the findings in their manuscript fully available?

Reviewer #2: Yes

**********

5. Is the manuscript presented in an intelligible fashion and written in standard English?

Reviewer #2: Yes

**********

6. Review Comments to the Author

Reviewer #2: All comments were well addressed. Authors gave point-by-point responses to my comments and queries.

The manuscript is suitable for publication in the current status.

**********

7. PLOS authors have the option to publish the peer review history of their article (what does this mean?). If published, this will include your full peer review and any attached files.

If you choose “no”, your identity will remain anonymous but your review may still be made public.

Do you want your identity to be public for this peer review? For information about this choice, including consent withdrawal, please see our Privacy Policy.

Reviewer #2: Yes: Wubishet Gezimu

**********

PLoS One. 2023 Jun 2;18(6):e0286584. doi: 10.1371/journal.pone.0286584.r004

Author response to Decision Letter 1

10 May 2023

Editor Comments:

We agree with these points – we had a brief statement about this at the end of the limitations section, but have moved this earlier in the discussion where we discuss the water quality results, and have expanded on it accordingly.

This is also a good point and we have added this to our suggestions for follow-up research in the discussion.

We have revised this recommendation as suggested, to instead suggest that further research is needed on possible sand contamination and its role in causing RWI. See the modified paragraph in the discussion and revised statement in the conclusion.

Note that the reference list has been slightly altered to accommodate a few additional articles cited as part of this revised discussion, and to update bibliographic details of a couple of the other references.

Attachment

Submitted filename: Response to reviewers.docx

Click here for additional data file.^{(15.1KB, docx)}

PLoS One. doi: 10.1371/journal.pone.0286584.r005

Decision Letter 2

Timothy J Wade

19 May 2023

Recreational water exposures and illness outcomes at a freshwater beach in Toronto, Canada: a prospective cohort pilot study

PONE-D-22-34376R2

Dear Dr. Young,

We’re pleased to inform you that your manuscript has been judged scientifically suitable for publication and will be formally accepted for publication once it meets all outstanding technical requirements.

Within one week, you’ll receive an e-mail detailing the required amendments. When these have been addressed, you’ll receive a formal acceptance letter and your manuscript will be scheduled for publication.

An invoice for payment will follow shortly after the formal acceptance. To ensure an efficient process, please log into Editorial Manager at http://www.editorialmanager.com/pone/, click the 'Update My Information' link at the top of the page, and double check that your user information is up-to-date. If you have any billing related questions, please contact our Author Billing department directly at authorbilling@plos.org.

If your institution or institutions have a press office, please notify them about your upcoming paper to help maximize its impact. If they’ll be preparing press materials, please inform our press team as soon as possible -- no later than 48 hours after receiving the formal acceptance. Your manuscript will remain under strict press embargo until 2 pm Eastern Time on the date of publication. For more information, please contact onepress@plos.org.

Kind regards,

Timothy J Wade, Ph.D

Academic Editor

PLOS ONE

Additional Editor Comments (optional):

Reviewers' comments:

PLoS One. doi: 10.1371/journal.pone.0286584.r006

Acceptance letter

Timothy J Wade

23 May 2023

PONE-D-22-34376R2

Recreational water exposures and illness outcomes at a freshwater beach in Toronto, Canada: a prospective cohort pilot study

Dear Dr. Young:

I'm pleased to inform you that your manuscript has been deemed suitable for publication in PLOS ONE. Congratulations! Your manuscript is now with our production department.

If your institution or institutions have a press office, please let them know about your upcoming paper now to help maximize its impact. If they'll be preparing press materials, please inform our press team within the next 48 hours. Your manuscript will remain under strict press embargo until 2 pm Eastern Time on the date of publication. For more information please contact onepress@plos.org.

If we can help with anything else, please email us at plosone@plos.org.

Thank you for submitting your work to PLOS ONE and supporting open access.

Kind regards,

PLOS ONE Editorial Office Staff

on behalf of

Dr. Timothy J Wade

Academic Editor

PLOS ONE

Associated Data

This section collects any data citations, data availability statements, or supplementary materials included in this article.

Supplementary Materials

S1 File. STROBE checklist for cohort studies.

(DOCX)

Click here for additional data file.^{(33KB, docx)}

S2 File. Beach cohort study questionnaires, Woodbine Beach, Toronto, 2022.

(DOCX)

Click here for additional data file.^{(34.9KB, docx)}

S1 Table. Comparison of participants who completed the follow-up survey vs. those who did not complete the follow-up survey, Woodbine Beach, Toronto, 2022.

(DOCX)

Click here for additional data file.^{(22.1KB, docx)}

Attachment

Submitted filename: Comments to authors.docx

Click here for additional data file.^{(14.1KB, docx)}

Attachment

Submitted filename: Response to reviewers.docx

Click here for additional data file.^{(23.1KB, docx)}

Attachment

Submitted filename: Response to reviewers.docx

Click here for additional data file.^{(15.1KB, docx)}

Data Availability Statement

The deidentified dataset and R script files for this study can be obtained at the following publicly available Github repository: https://github.com/iany33/beachcohortpilot2022.

[pone.0286584.ref001] 1.Janicki R, Thomas KM, Pintar K, Fleury M, Nesbitt A. Drinking and recreational water exposures among Canadians: Foodbook study 2014–2015. J Water Health. 2018;16: 197–211. doi: 10.2166/wh.2018.261 [DOI] [PubMed] [Google Scholar]

[pone.0286584.ref002] 2.Statistics Canada. Participation in outdoor activities in the past 12 months by age group, sex, current employment status, and perceived health, Canada, provinces and regions. 2020. https://www150.statcan.gc.ca/t1/tbl1/en/tv.action?pid=4510003001

[pone.0286584.ref003] 3.Graciaa DS, Cope JR, Roberts VA, Cikesh BL, Kahler AM, Vigar M, et al. Outbreaks associated with untreated recreational water—United States, 2000–2014. MMWR Morb Mortal Wkly Rep. 2018;67: 701–706. doi: 10.15585/mmwr.mm6725a1 [DOI] [PMC free article] [PubMed] [Google Scholar]

[pone.0286584.ref004] 4.Soller JA, Bartrand T, Ashbolt NJ, Ravenscroft J, Wade TJ. Estimating the primary etiologic agents in recreational freshwaters impacted by human sources of faecal contamination. Water Res. 2010;44: 4736–4747. doi: 10.1016/j.watres.2010.07.064 [DOI] [PubMed] [Google Scholar]

[pone.0286584.ref005] 5.Schoen ME, Ashbolt NJ. Assessing pathogen risk to swimmers at non-sewage impacted recreational beaches. Environ Sci Tech. 2010;44: 2286–2291. doi: 10.1021/es903523q [DOI] [PubMed] [Google Scholar]

[pone.0286584.ref006] 6.DeFlorio-Barker S, Wing C, Jones RM, Dorevitch S. Estimate of incidence and cost of recreational waterborne illness on United States surface waters. Environ Health. 2018;17: 3. doi: 10.1186/s12940-017-0347-9 [DOI] [PMC free article] [PubMed] [Google Scholar]

[pone.0286584.ref007] 7.Schets FM, Husman AMDR, Havelaar AH. Disease outbreaks associated with untreated recreational water use. Epidemiol Infect. 2011;139: 1114–1125. doi: 10.1017/S0950268810002347 [DOI] [PubMed] [Google Scholar]

[pone.0286584.ref008] 8.Leonard AF, Singer A, Ukoumunne OC, Gaze WH, Garside R, AFC L, et al. Is it safe to go back into the water? A systematic review and meta-analysis of the risk of acquiring infections from recreational exposure to seawater. Int J Epidemiol. 2018;47: 572–586. doi: 10.1093/ije/dyx281 [DOI] [PMC free article] [PubMed] [Google Scholar]

[pone.0286584.ref009] 9.Russo GS, Eftim SE, Goldstone AE, Dufour AP, Nappier SP, Wade TJ. Evaluating health risks associated with exposure to ambient surface waters during recreational activities: a systematic review and meta-analysis. Water Res. 2020;176: 115729. doi: 10.1016/j.watres.2020.115729 [DOI] [PMC free article] [PubMed] [Google Scholar]

[pone.0286584.ref010] 10.Arnold BF, Wade TJ, Benjamin-Chung J, Schiff KC, Griffith JF, Dufour AP, et al. Acute gastroenteritis and recreational water: highest burden among young US children. Am J Public Health. 2016;106: 1690–1697. doi: 10.2105/AJPH.2016.303279 [DOI] [PMC free article] [PubMed] [Google Scholar]

[pone.0286584.ref011] 11.Heaney CD, Sams E, Wing S, Marshall S, Brenner K, Dufour AP, et al. Contact with beach sand among beachgoers and risk of illness. Am J Epidemiol. 2009;170: 164–72. doi: 10.1093/aje/kwp152 [DOI] [PubMed] [Google Scholar]

[pone.0286584.ref012] 12.Heaney CD, Sams E, Dufour AP, Brenner KP, Haugland RA, Chern E, et al. Fecal indicators in sand, sand contact, and risk of enteric illness among beachgoers. Epidemiol. 2012;23: 95–106. doi: 10.1097/EDE.0b013e31823b504c [DOI] [PMC free article] [PubMed] [Google Scholar]

[pone.0286584.ref013] 13.Wade TJ, Calderon RL, Brenner KP, Sams E, Beach M, Haugland R, et al. High sensitivity of children to swimming-associated gastrointestinal illness: results using a rapid assay of recreational water quality. Epidemiol. 2008;19: 375–383. doi: 10.1097/EDE.0b013e318169cc87 [DOI] [PubMed] [Google Scholar]

[pone.0286584.ref014] 14.Deflorio-Barker S, Arnold BF, Sams EA, Dufour AP, Colford JM, Weisberg SB, et al. Child environmental exposures to water and sand at the beach: findings from studies of over 68,000 subjects at 12 beaches. J Expo Sci Environ Epidemiol. 2018;28: 93–100. doi: 10.1038/jes.2017.23 [DOI] [PMC free article] [PubMed] [Google Scholar]

[pone.0286584.ref015] 15.Dufour AP, Behymer TD, Cantú R, Magnuson M, Wymer LJ. Ingestion of swimming pool water by recreational swimmers. J Water Health. 2017;15: 429–437. doi: 10.2166/wh.2017.255 [DOI] [PubMed] [Google Scholar]

[pone.0286584.ref016] 16.Wade TJ, Calderon RL, Sams E, Beach M, Brenner KP, Williams AH, et al. Rapidly measured indicators of recreational water quality are predictive of swimming-associated gastrointestinal illness. Env Health Perspect. 2006;114: 24–28. doi: 10.1289/ehp.8273 [DOI] [PMC free article] [PubMed] [Google Scholar]

[pone.0286584.ref017] 17.Dorevitch S, Pratap P, Wroblewski M, Hryhorczuk DO, Li H, Liu LC, et al. Health risks of limited-contact water recreation. Env Health Perspect. 2012;120: 192–197. doi: 10.1289/ehp.1103934 [DOI] [PMC free article] [PubMed] [Google Scholar]

[pone.0286584.ref018] 18.Wade TJ, Sams EA, Haugland RA, Brenner KP, Li Q, Wymer L, et al. Report on 2009 national epidemiologic and environmental assessment of recreational water epidemiology studies. Washington, DC; 2010. https://www.epa.gov/sites/default/files/2019-03/documents/report-2009-national-epidemiologic-studies.pdf

[pone.0286584.ref019] 19.Seyfried PL, Tobin RS, Brown NE, Ness PF. A prospective study of swimming-related illness I. Swimming-associated health risk. Am J Public Health. 1985;75: 1068–1070. doi: 10.2105/AJPH.75.9.1068 [DOI] [PMC free article] [PubMed] [Google Scholar]

[pone.0286584.ref020] 20.Health Canada. Guidelines for Canadian recreational water quality: indicators of fecal contamination. 2021. https://www.canada.ca/en/health-canada/programs/consultation-guidelines-recreational-water-quality-fecal-contamination/document.html

[pone.0286584.ref021] 21.Ontario Ministry of Health and Long-Term Care. Operational approaches for recreational water guideline. 2018. https://www.health.gov.on.ca/en/pro/programs/publichealth/oph_standards/docs/protocols_guidelines/Operational_Approaches_to_Rec_Water_Guideline_2018_en.pdf

[pone.0286584.ref022] 22.Collier SA, Wade TJ, Sams EA, Hlavsa MC, Dufour AP, Beach MJ. Swimming in the USA: beachgoer characteristics and health outcomes at US marine and freshwater beaches. J Water Health. 2015;13: 531–543. doi: 10.2166/wh.2014.095 [DOI] [PMC free article] [PubMed] [Google Scholar]

[pone.0286584.ref023] 23.Nevers MB, Whitman RL. Efficacy of monitoring and empirical predictive modeling at improving public health protection at Chicago beaches. Water Res. 2011;45: 1659–1668. doi: 10.1016/j.watres.2010.12.010 [DOI] [PubMed] [Google Scholar]

[pone.0286584.ref024] 24.Francy DS, Stelzer EA, Duris JW, Brady AMG, Harrison JH, Johnson HE, et al. Predictive models for Escherichia coli concentrations at inland lake beaches and relationship of model variables to pathogen detection. Appl Environ Microbiol. 2013;79: 1676–88. doi: 10.1128/AEM.02995-12 [DOI] [PMC free article] [PubMed] [Google Scholar]

[pone.0286584.ref025] 25.von Elm E, Altman DG, Egger M, Pocock SJ, Gøtzsche PC, Vandenbroucke JP. The Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) statement: guidelines for reporting observational studies. J Clin Epidemiol. 2008;61: 344–349. doi: 10.1016/j.jclinepi.2007.11.008 [DOI] [PubMed] [Google Scholar]

[pone.0286584.ref026] 26.City of Toronto. About beach water quality. 2023. https://www.toronto.ca/community-people/health-wellness-care/health-inspections-monitoring/swimsafe/beach-water-quality/about-beach-water-quality/

[pone.0286584.ref027] 27.Toronto and Region Conservation Authority. Ashbridges Bay landform project. 2021. https://trca.ca/conservation/green-infrastructure/ashbridges-bay-erosion-sediment-control-project/

[pone.0286584.ref028] 28.Swim Drink Fish. Woodbine beach. 2023. https://www.theswimguide.org/beach/83

[pone.0286584.ref029] 29.Sanchez J, Tustin J, Heasley C, Patel M, Kelly J, Habjan A, et al. Region-specific associations between environmental factors and Escherichia coli in freshwater beaches in Toronto and Niagara region, Canada. Int J Environ Res Public Health. 2021;18: 12841. doi: 10.3390/IJERPH182312841 [DOI] [PMC free article] [PubMed] [Google Scholar]

[pone.0286584.ref030] 30.Peterson CH, Peterson NA, Powell KG. Cognitive interviewing for item development: validity evidence based on content and response processes. Meas Eval Couns Dev. 2017;50: 217–223. doi: 10.1080/07481756.2017.1339564 [DOI] [Google Scholar]

[pone.0286584.ref031] 31.Lee RM, Lessler J, Lee RA, Rudolph KE, Reich NG, Perl TM, et al. Incubation periods of viral gastroenteritis: a systematic review. BMC Infect Dis. 2013;13: 1–11. doi: 10.1186/1471-2334-13-446 [DOI] [PMC free article] [PubMed] [Google Scholar]

[pone.0286584.ref032] 32.Chai SJ, Gu W, O’Connor KA, Richardson LC, Tauxe RV. Incubation periods of enteric illnesses in foodborne outbreaks, United States, 1998–2013. Epidemiol Infect. 2019;147: e285. doi: 10.1017/S0950268819001651 [DOI] [PMC free article] [PubMed] [Google Scholar]

[pone.0286584.ref033] 33.Wade TJ, Sams E, Brenner KP, Haugland R, Chern E, Beach M, et al. Rapidly measured indicators of recreational water quality and swimming-associated illness at marine beaches: a prospective cohort study. Environ Health. 2010;9: 66. doi: 10.1186/1476-069X-9-66 [DOI] [PMC free article] [PubMed] [Google Scholar]

[pone.0286584.ref034] 34.Colford JM, Wade TJ, Schiff KC, Wright CC, Griffith JF, Sandhu SK, et al. Water quality indicators and the risk of illness at beaches with nonpoint sources of fecal contamination. Epidemiol. 2007;18: 27–35. doi: 10.1097/01.ede.0000249425.32990.b9 [DOI] [PubMed] [Google Scholar]

[pone.0286584.ref035] 35.Public Health Ontario. Public health inspector’s guide to environmental microbiology laboratory testing. 2021. https://www.publichealthontario.ca/-/media/documents/lab/phi-guide.pdf?la=en

[pone.0286584.ref036] 36.R Core Team. R: a language and environment for statistical computing. Vienna, Austria: R Foundation for Statistical Computing; 2022.

[pone.0286584.ref037] 37.Posit Team. RStudio: integrated development for R. Boston, MA: Posit Software, PBC; 2023.

[pone.0286584.ref038] 38.Marion JW, Lee J, Lemeshow S, Buckley TJ. Association of gastrointestinal illness and recreational water exposure at an inland U.S. beach. Water Res. 2010;44: 4796–4804. doi: 10.1016/j.watres.2010.07.065 [DOI] [PubMed] [Google Scholar]

[pone.0286584.ref039] 39.Arnold BF, Schiff KC, Griffith JF, Gruber JS, Yau V, Wright CC, et al. Swimmer illness associated with marine water exposure and water quality indicators: impact of widely used assumptions. Epidemiol. 2013;24: 845–853. doi: 10.1097/01.ede.0000434431.06765.4a [DOI] [PubMed] [Google Scholar]

[pone.0286584.ref040] 40.Statistics Canada. Census profile. 2021 census of population. 2023. https://www12.statcan.gc.ca/census-recensement/2021/dp-pd/prof/index.cfm?Lang=E

[pone.0286584.ref041] 41.Health Canada. Guidelines for Canadian recreational water quality: understanding and managing risks in recreational waters. 2023. https://www.canada.ca/en/health-canada/services/publications/healthy-living/guidelines-understanding-managing-risks-recreational-waters.html

[pone.0286584.ref042] 42.World Health Organization. Guidelines on recreational water quality: volume 1 coastal and fresh waters. 2021. https://www.who.int/publications/i/item/9789240031302 [PubMed]

[pone.0286584.ref043] 43.Brandão J, Gangneux JP, Arikan-Akdagli S, Barac A, Bostanaru AC, Brito S, et al. Mycosands: Fungal diversity and abundance in beach sand and recreational waters—Relevance to human health. Sci Total Environ. 2021;781: 146598. doi: 10.1016/j.scitotenv.2021.146598 [DOI] [PubMed] [Google Scholar]

[pone.0286584.ref044] 44.Thapaliya D, Hellwig EJ, Kadariya J, Grenier D, Jefferson AJ, Dalman M, et al. Prevalence and characterization of Staphylococcus aureus and methicillin-resistant Staphylococcus aureus on public recreational beaches in northeast Ohio. Geohealth. 2017;1: 320–332. doi: 10.1002/2017GH000106 [DOI] [PMC free article] [PubMed] [Google Scholar]

[pone.0286584.ref045] 45.Fogarty LR, Haack SK, Johnson HE, Brennan AK, Isaacs NM, Spencer C. Staphylococcus aureus and methicillin-resistant S. aureus (MRSA) at ambient freshwater beaches. J Water Health. 2015;13: 680–692. doi: 10.2166/wh.2014.278 [DOI] [PubMed] [Google Scholar]

[pone.0286584.ref046] 46.Quilliam RS, Taylor J, Oliver DM. The disparity between regulatory measurements of E. coli in public bathing waters and the public expectation of bathing water quality. J Environ Manag. 2019;232: 868–874. doi: 10.1016/j.jenvman.2018.11.138 [DOI] [PubMed] [Google Scholar]

[pone.0286584.ref047] 47.Pratap PL, Redman S, Fagen MC, Dorevitch S. Improving water quality communications at beaches: input from stakeholders. J Water Health. 2013;11: 647–658. doi: 10.2166/wh.2013.077 [DOI] [PubMed] [Google Scholar]

[pone.0286584.ref048] 48.Wade TJ, Arnold BF, Schiff K, Colford JM, Weisberg SB, Griffith JF, et al. Health risks to children from exposure to fecally-contaminated recreational water. PLoS One. 2022;17: e0266749. doi: 10.1371/journal.pone.0266749 [DOI] [PMC free article] [PubMed] [Google Scholar]

[pone.0286584.ref049] 49.Shrestha A, Dorevitch S. Slow adoption of rapid testing: beach monitoring and notification using qPCR. J Microbiol Methods. 2020;174: 105947. doi: 10.1016/j.mimet.2020.105947 [DOI] [PubMed] [Google Scholar]

[pone.0286584.ref050] 50.Harwood VJ, Staley C, Badgley BD, Borges K, Korajkic A. Microbial source tracking markers for detection of fecal contamination in environmental waters: relationships between pathogens and human health outcomes. FEMS Microbiol Rev. 2014;38: 1–40. doi: 10.1111/1574-6976.12031 [DOI] [PubMed] [Google Scholar]

[pone.0286584.ref051] 51.Teague S, Youssef GJ, Macdonald JA, Sciberras E, Shatte A, Fuller-Tyszkiewicz M, et al. Retention strategies in longitudinal cohort studies: a systematic review and meta-analysis. BMC Med Res Methodol. 2018;18: 1–22. doi: 10.1186/S12874-018-0586-7 [DOI] [PMC free article] [PubMed] [Google Scholar]

[pone.0286584.ref052] 52.Abdelazeem B, Abbas KS, Amin MA, El-Shahat NA, Malik B, Kalantary A, et al. The effectiveness of incentives for research participation: a systematic review and meta-analysis of randomized controlled trials. PLoS One. 2022;17: e0267534. doi: 10.1371/journal.pone.0267534 [DOI] [PMC free article] [PubMed] [Google Scholar]

[pone.0286584.ref053] 53.Gillies K, Kearney A, Keenan C, Treweek S, Hudson J, Brueton V, et al. Strategies to improve retention in randomised trials. Cochrane Database Syst Rev. 2021. doi: 10.1002/14651858.MR000032.pub3 [DOI] [PMC free article] [PubMed] [Google Scholar]

PERMALINK

Recreational water exposures and illness outcomes at a freshwater beach in Toronto, Canada: A prospective cohort pilot study

Ian Young

J Johanna Sanchez

Binyam Negussie Desta

Cole Heasley

Jordan Tustin

Roles

Abstract

Background

Methods

Results

Conclusions

Background

Materials and methods

Study design and setting

Participation eligibility and enrollment

Data collection surveys

Exposures and outcomes of interest

Data analysis

Results

Participant characteristics

Table 1. Characteristics of 831 beachgoers surveyed at Woodbine Beach, Toronto, 2022, stratified by enrollment month.

Beach exposures

Table 2. Water and sand exposures reported among beachgoers, stratified by study enrollment month, at Woodbine Beach, Toronto, 2022.

Table 3. Water and sand exposures reported among beachgoers, stratified by age group, Woodbine Beach, Toronto, 2022.

Table 6. Water and sand exposures reported among beachgoers, stratified by ethno-racial identity, Woodbine Beach, Toronto, 2022.

Table 4. Water and sand exposures reported among beachgoers, stratified by gender identity, Woodbine Beach, Toronto, 2022.

Table 5. Water and sand exposures reported among beachgoers, stratified by highest education completed in the household, Woodbine Beach, Toronto, 2022.

Fig 1. Histogram of geometric mean E. coli level exposures (CFU / 100 mL) by participant, Woodbine Beach, Toronto, 2022.

Illness outcomes

Table 7. Incidence of RWI outcomes among beachgoers, stratified by water and sand contact status, at Woodbine Beach, Toronto, 2022a.

Discussion

Conclusion

Supporting information

Acknowledgments

Data Availability

Funding Statement

References

Decision Letter 0

Zakir Abdu

Roles

Author response to Decision Letter 0

Decision Letter 1

Timothy J Wade

Roles

Author response to Decision Letter 1

Decision Letter 2

Timothy J Wade

Roles

Acceptance letter

Timothy J Wade

Roles

Associated Data

Supplementary Materials

Data Availability Statement

ACTIONS

PERMALINK

RESOURCES

Similar articles

Cited by other articles

Links to NCBI Databases

Table 7. Incidence of RWI outcomes among beachgoers, stratified by water and sand contact status, at Woodbine Beach, Toronto, 2022^a.