Table 3.

Summaries of studies on cyanobacteria aerosols and health (n = 8).

Author	Location	Exposure assessment method	Population and study period	Measured outcome	Findings summary
Stewart 2006a	Southern Queensland and the Myall Lakes area of New South Wales, Australia; Northeast and central Florida, USA	Water samples for phytoplankton and cyanotoxin analysis were collected by a modified grab sample method. Faecal coliforms were also sampled. Total phytoplankton analyses, cell identification and enumeration, and analyses for various cyanotoxins were conducted. Cyanobacterial cell surface area was used as the main exposure variable of interest.	1331 study participants (n = 216 in Florida) comprised of adults and children engaging in recreational activities in enclosed waters (e.g., not marine waters) with cyanobacteria.	Reported symptoms were categorized as ear, eye, gastrointestinal, respiratory (difficulty breathing; dry cough; productive cough; runny nose; unusual sneezing; sore throat; wheezy breathing), cutaneous, fever, and the combined “any symptom” (any of the above). Symptoms were rated none, mild, and moderate/severe.	Respiratory symptoms were 2.1 (95% CI: 1.1–4.0) times more likely to be reported by subjects in the high-exposure group than the low-exposure group. Any symptoms were 1.7 (95%CI: 1.0–2.8) times more likely to be reported by subjects in the high-exposure group than the low-exposure group. Most reported respiratory symptoms were in the ‘mild’ category.
Backer 2008	Unspecified lakes, USA	Air and water samples were taken and cell densities and microcystin concentrations were measured. Microcystin concentration levels in blood samples were also measured via ELISA.	97 participants recruited from a lake with an ongoing Microcystis aeruginosa bloom, and another 7 from a nearby bloom-free lake for 3 days in August of 2006. Demographic information and symptoms were measured.	Respiratory (sore throat; congestion; cough; throat irritation; eye irritation; other), dermatologic (itchy skin, red skin, hives, skin irritation, rash, other); other (earache, agitation, headache, abdominal pain, diarrhoea) symptoms 7 days before study, before study activities, after study activities, and 7–10 days after study activities were recorded.	Low levels of microcystin were detected in both water and aerosol samples. No significant differences appeared in the symptom frequency between the exposed and control groups 1 week before, immediately before/after recreational activities, and after the study period. Results are somewhat suggestive that symptoms may occur a few days after initial exposure to microcystin aerosols.
Backer 2010	Two lakes in Siskiyou County, California, USA	Air and water samples were taken and cell densities and microcystin concentrations were measured	August 2007	Respiratory (sore throat; congestion; cough; throat irritation; eye irritation; other), dermatologic (itchy skin, red skin, hives, skin irritation, rash, other); other (earache, agitation, headache, abdominal pain, diarrhea) symptoms 7 days before study, before study activities, after study activities, and 7–10 days after study activities	No significant changes in symptoms were observed after exposure.
Hilborn 2014	US States participating in the CDC surveillance system (Florida, Iowa, Maryland, Massachusetts, New York, Oregon, South Carolina, Virginia, Washington, and Wisconsin).	Human health data and water sampling results voluntarily reported to CDC's Waterborne Disease and Outbreak Surveillance System (WBDOSS) via the National Outbreak Reporting System (NORS) and the Harmful Algal Bloom-Related Illness Surveillance System (HABISS) for 2009–2010.	During 2009–2010 in the United States, 11 outbreaks (3 in NY; 6 in OH; 2 in WA) associated with recreational activities at freshwater lakes that affected at least 61 persons. 8 outbreak investigations included the evaluation of cyanotoxins, with 4 evaluating multiple cyanotoxins; 3 identified cyanobacteria, while 2 identified potentially toxic cyanobacteria without quantification.	Gastrointestinal, general, dermatologic, eye/ear, neurologic, respiratory symptoms	Out of 58 persons with available data, seven (12%) visited an emergency department and 34 (59%) visited a health-care provider. 66% of persons were aged ≤19 years, suggesting that children might be at higher risk for HAB-related health effects.
Levesque 2014	Quebec province, Canada	Daily surface water samples and cyanobacterial cells were counted and identified. Dissolved microcystin was measured in filtered water samples.	267 families consisting of 466 subjects living near three lakes filled out questionnaires and journals of daily symptoms and contact (full or limited contact, location, and duration) with water	Eye, ear, respiratory, gastrointestinal, skin, muscle pain, headaches, mouth ulcers	Only gastrointestinal symptoms were significantly associated with recreational contact with lakes and higher cyanobacteria concentrations
Figgatt 2017	New York state, USA	New York State Department of Environmental Conservation (NYSDEC) evaluated bodies of water for HABs in response to reports of possible HABs from the public, staff, and lake associations. HABs were confirmed by laboratory tests. Public health workers received training and surveillance tools, which included outreach material to public to encourage reporting suspected exposures. When an HAB was identified, other surveillance activities were conducted, such as monitoring of hospital data; providing education material to healthcare providers and veterinarians; and coordination with poison control centres.	16 (out of 62) New York counties were selected for participation in the pilot surveillance system based on interest and likelihood of HABs. During June to September 2015, HAB-associated human and animal illnesses reported by local health departments (LHD) were collected.	Each HAB illness report was investigated using a questionnaire given by either the LHD or NYSDOH and assessed using the CDC case definitions. Case definitions take into consideration information such as environmental/visual evidence of an HAB; confirmation via toxin-detecting test strips or laboratory confirmation; and clinical evidence of HAB exposure.	In this pilot cyanobacteria HAB-associated illness surveillance system in 16 counties, 51 human and canine HAB-associated illnesses were reported, including 32 human and 3 canine cases that met the CDC case definition. The pilot surveillance during a 4-month period suggest that HAB-associated illnesses might be more common than previously reported. Commonly reported symptoms included: skin problems; respiratory; gastrointestinal; other symptoms (e.g., chills, muscle aches, watery eyes); fatigue/general weakness; and sore throat.
Wu 2021	Greater Boston area, Massachusetts, USA	Satellite-derived cyanobacteria cell concentrations were estimated in the source of drinking water for the Greater Boston area. 300-m resolution imageries from the MEdium Resolution Imaging Spectrometer (MERIS) were processed.	Patients who visited the emergency rooms of approximately 70 Massachusetts hospitals for gastrointestinal, respiratory, and dermal illnesses during 2008–2011.	Daily counts of hospital emergency room visit for gastrointestinal (ICD-9: 001–009.9, 558.9, 787.91, 787.01, and 787.03); respiratory (460, 461, 465.9, 493, 786.2, 786.05, and 786.07); and dermal illnesses (782.1, 136.9, 686.9, 692, and 691.8) from approximately 70 Massachusetts hospitals.	Time-series models adjusting for confounding effects (day of the week, ambient ozone concentration, average mean ambient temperature, school days, and holidays) showed that there were no significant associations between cyanobacteria concentrations and daily visits for gastrointestinal illness. There was a significant positive association between satellite-derived cyanobacteria abundance and visits for respiratory illnesses at the 2-day lag. Associations at all other lags were not significant. Visits for dermal illnesses were not significantly associated with the level of cyanobacteria concentrations.
Lee 2022	South Korea	Chlorophyll-a (chl-a) concentrations during HAB seasons in 2005–2017 obtained from 939 locations, from a Korean governmental agency conducting monitoring of cyanobacterial cell counts, geosmin, and chl-a concentrations during HAB seasons. Annual average chl-a concentrations, as a proxy for blooms, per location were used for analysis. A secondary pilot study was conducted to sample and confirm the presence of microcystins and BMAA in water and air samples downstream of a large river (Nakdong River).	Annual number of neurodegenerative diseases (NDs) between 2005 and 2017.	Three neurodegenerative disease outcomes including motor neuron disease (ICD-10 code G12.2), Alzheimer's disease (G30.0), and Parkinson's disease (G20).	The increase in the chl-a concentrations showed significantly positive correlations with the same-year annual incidence rate of motor neuron disease, Alzheimer's disease, and Parkinson's disease, separately. For Parkinson's disease, a positive correlation was found for the HAB measures with lags of 1, 2, and 3 years. For motor neuron disease and Alzheimer's disease, a positive correlation was found for the HAB measures for the previous year.