Awareness of third-hand smoke: A cross-sectional study among medical students at Qassim University

ABSTRACT

Introduction:

Third-hand smoke refers to pollutants that linger on surfaces and in the environment well after smoking has stopped. These substances can be inhaled, ingested, or absorbed through the skin. These persistent toxins, which settle on walls, furniture, and clothing, are linked to serious health issues such as asthma, reproductive system disorders, postpartum depression, and sleep disturbances in children.

Methods:

The study employed a cross-sectional research design to assess the perceptions of Qassim University medical students regarding third-hand smoke. The study included 377 participants, with data collected through an electronic, self-administered Beliefs About Third-Hand Smoke (BATHS) questionnaire. The data analysis was conducted using SPSS Version 27.

Results:

The results show that majority of respondents believe that lingering air can harm the health of infants and children (78.6%). Almost two-thirds (74.6%) also believe that these particles are absorbed into furniture and walls, while a majority (62%) think that the particles can persist in a room for several weeks. Females demonstrated slightly higher median overall belief scores (33) compared with males (32), with a P value of 0.09. Smokers had a lower median persistent belief score (13) compared with nonsmokers (15); this difference was statistically significant with a P value of 0.041, suggesting that smokers may be less convinced about the persistence of smoke particles.

Conclusion:

The study found strong awareness among medical students about the persistence and health risks of third-hand smoke. The majority of the students understood that standard ventilation cannot fully eliminate smoke particles, which can linger on surfaces and pose health risks. However, smokers were less concerned about this persistence, and perceptions varied by gender. The findings suggest a need for targeted educational programs to improve understanding of third-hand smoke among both medical students and the general population.

Introduction

Third-hand smoke (THS) refers to the residual contaminants and by-products from tobacco smoke that persist on indoor surfaces and in dust even after smoking has ended. These contaminants can accumulate on walls, furniture, floors, and clothing, persisting for months even after smoking stops.[1,2] Unlike second-hand smoke, which includes smoke exhaled by a smoker or emitted from the burning end of a tobacco product, THS consists of substances that adhere to surfaces and can be re-emitted into the air, leading to prolonged exposure.[2]

THS comprises various compounds, including volatile, semivolatile, and nonvolatile substances such as furans and nitriles.[3] These components can react with atmospheric agents, forming additional pollutants that may be more harmful than the original smoke. Exposure to THS can occur through inhalation, ingestion, or skin contact with contaminated surfaces, resulting in potential health risks.[4]

Tobacco use is widely acknowledged as a significant health hazard, linked to various negative health outcomes such as cardiovascular and respiratory conditions, as well as more than 20 different types of cancer.[5] Globally, the smoking rate stands at approximately 22.3%,[6] with medical students reporting a smoking prevalence of 18.10% and second-hand smoke exposure at 47.30%.[7] According to the World Health Organization (WHO), tobacco use leads to more than 8 million deaths annually, with approximately 1.3 million of these deaths attributed to exposure to second-hand and third-hand smoke.[8]

While the harmful effects of second-hand smoke (SHS) are well-documented and widely acknowledged, awareness of THS remains insufficient. THS has been found to be less concentrated than SHS but causes prolonged exposure, making it a significant concern despite the growing body of evidence highlighting its dangers.[4]

Exposure to THS has been linked to various health issues, including asthma,[9] reproductive system disorders,[10] platelet aggregation in offspring,[11] postpartum depression, and poor sleep in children.[12,13] Furthermore, evidence indicates that THS and its components, such as tobacco-specific nitrosamines (TSNAs), can induce significant cellular and tissue damage at environmentally relevant concentrations.[14,15] Research has shown increased DNA fragmentation in human cells exposed to THS,[15] and studies in A/J mice have demonstrated a heightened risk of lung adenocarcinoma associated with THS exposure.[14]

Recent research reveals the complexity of THS exposure. Sleiman et al.[16] highlighted that THS pollutants undergo chemical transformations in indoor environments, creating secondary pollutants such as tobacco-specific nitrosamines (TSNAs) and polycyclic aromatic hydrocarbons (PAHs). Similarly, Matt et al.[17] demonstrate the extensive persistence of nicotine and other THS residues in household environments, even after smoking cessation. Recent studies have revealed that awareness of THS among health professionals is notably low, with only 35% having heard of THS and 69% believing it lacks sufficient attention.[18] Similarly, a study in Spain found that only 27% of parents were aware of THS, although 86% acknowledged its potential harm to children.[19] Despite the potential for THS to persist in indoor environments for extended periods, even with ventilation,[2] there are no specific management protocols for THS. However, measures such as enforcing strict home smoking bans and regular cleaning of household surfaces can help reduce exposure.[20]

Both primary care physicians and family physicians often serve as the first point of contact for patients and their families, making their understanding of THS particularly critical. Hence, they are well-positioned to identify vulnerable populations, such as children and pregnant women, who are disproportionately affected by THS exposure. Moreover, primary care physicians can advocate for preventative measures, such as promoting smoke-free environments, educating patients on the risks associated with THS, and implementing smoking cessation interventions. Enhanced awareness among healthcare providers could lead to better management of THS-related risks and improve overall community health outcomes. Given the crucial role of medical professionals in health education and policy, assessing their awareness of THS is essential. This study aims to evaluate the level of awareness regarding THS among medical students at Qassim University. The findings are expected to contribute to a deeper understanding of THS and inform strategies to enhance both public and professional awareness of this important health issue.

Methodology

Study design and population

The research used a cross-sectional design and targeted students at Qassim University. An online survey was distributed to all students in the medical faculty, and only the respondents were included in the analysis. This ensured that the target population was accurately represented.

Sampling and sample size

The study involved a total of 377 students. The initial sample size was calculated as 306 students based on a population size of 1,500, an expected frequency of 50%, and a margin of error of 5%. Epi Info software version 5.5.9 was used for the calculation, applying a 95% confidence interval, a P value of 0.05, and 80% power.

Data collection tools

The data collection was carried out using a prevalidated, self-administered questionnaire, which was adapted from the BATHS scale created by Haardörfer et al.[21] The BATHS-T scale included 9 items, divided into two categories: one assessed health impacts (items 1, 2, 3, 7, and 8) and the other evaluated the persistence of third-hand smoke in the environment (items 4, 5, 6, and 9). Responses were measured using a 5-point Likert scale, ranging from “strongly disagree” to “strongly agree”. In addition, the questionnaire collected sociodemographic data such as age, gender, academic year, smoking status, and information about whether the participant cohabitated with smokers.

Before the main study, a pilot study was carried out to assess the clarity, appropriateness, and practicality of the data collection tools. In addition, the pilot helped estimate the time required for participants to complete the questionnaire. Approximately 10–15% of the total sample (around 40 participants) were recruited for this pilot study. Those who participated in the pilot were excluded from the final analysis to avoid bias in the results.

Data analysis

Following data collection, the information was initially entered into an Excel spreadsheet for preliminary cleaning, which included removing duplicate entries, addressing outliers, and excluding incomplete responses. After data cleaning, it was coded and imported into SPSS version 27. Descriptive statistics, such as counts and frequencies, were employed to summarize the categorical variables, while the relationships between these variables were analyzed using the Chi-square test, with a P value of less than 0.05 considered statistically significant.

Ethical considerations

The study received ethical approval from the Qasim University Ethics Committee before data collection began. Written informed consent was obtained from all participants before participating in the study. Participation was completely voluntary, with no incentives provided. Strict confidentiality was maintained, and the data collected were solely used for research purposes.

Results

The study involved a total of 377 participants. Table 1 below reveals that the gender distribution involved 152 (40.3%) females and 225 (59.7%) males. Regarding academic year, the participants were distributed as follows: 23 (6.1%) in their first year, 54 (14.3%) in their second year, 113 (30%) in their third year, 88 (23.3%) in their fourth year, and 99 (26.3%) in their fifth year. In terms of smoking habits, only 19 (5%) participants reported being smokers, while an overwhelming majority, 358 (95%) were nonsmokers. In addition, 103 (27.3%) participants indicated that they live with a smoker, whereas 274 (72.7%) reported that they do not live with a smoker.

Table 1.

Social demographic variables of the respondents

Variable	Category	Count (%)
Gender	Female	152 (40.3%)
	Male	225 (59.7%)
Academic Year	First	23 (6.1%)
	Second	54 (14.3%)
	Third	113 (30.0%)
	Fourth	88 (23.3%)
	Five	99 (26.3%)
Smoker	Yes	19 (5.0%)
	No	358 (95.0%)
Do you live with a smoker	Yes	103 (27.3%)
	No	274 (76.7%)

Data have been presented as counts (n) and frequency (%)

Table 2 below illustrates that most respondents (78.6%) believe exposure to air in a room where smoking took place the day before can be harmful to infants and children, while a smaller percentage (59.1%) believe the same risk applies to adults. Concerns about cancer from smoke particles are less pronounced, with only 38.4% agreeing that these particles can cause cancer. While most agree that smoke particles can linger in a room for at least a day (65.8%), fewer believe they can linger for weeks (22.2%). The belief that smokes particles are absorbed by walls and furniture is more prevalent (74.6%), and there is moderate agreement that smoke particles on clothing, skin, and hair can be transferred to others (45.4%). However, there is less consensus on the idea that touching surfaces with settled smoke can introduce particles into the body through the skin (31.0%). Furthermore, most medical students (65.7%) think that simply opening windows or using air conditioners is not sufficient to fully remove smoke particles from the air.

Table 2.

Perceptions of third-hand smoke risks among the medical students

Statement	Strongly Disagree (%)	Disagree (%)	Not Sure (%)	Agree (%)	Strongly Agree (%)
Smoke particles are not entirely cleared from a room by simply opening windows or using an air conditioner.	10 (2.7%)	50 (13.3%)	69 (18.3%)	151 (40.0%)	97 (25.7%)
Particles from cigarette smoke can be absorbed into the body through the skin after coming into contact with surfaces where the smoke has settled.	30 (8.0)%	74 (19.6%)	155 (41.4%)	77 (20.4%)	40 (10.6%)
Smoke particles on clothing, hair, and skin can transfer to others through physical contact.	14 (3.7%)	51 (13.5%)	141 (37.4%)	116 (30.8%)	55 (14.6%)
Smoke particles can be absorbed by walls and furniture.	5 (1.3%)	17 (4.7%)	74 (19.6%)	127 (33.7%)	154 (40.9%)
Smoke particles can linger in a room for several weeks.	26 (6.9%)	72 (19.1%)	195 (51.7%)	39 (10.3%)	45 (11.9%)
Smoke particles can linger in a room for several days.	6 (1.6%)	20 (5.3%)	103 (27.3%)	149 (39.5%)	99 (26.3)%
Smoke particles lingering in rooms where people smoked the previous day can contribute to cancer risk.	16 (4.2%)	49 (13%)	167 (44.3%)	85 (22.5%)	60 (15.9%)
Inhaling air in a room today where people smoked the day before can negatively impact adult health.	8 (2.1%)	33 (8.8%)	113 (30%)	120 (31.8%)	103 (27.3%)
Inhaling air in a room today where smoking occurred yesterday can negatively affect the health of infants and children	4 (1.1%)	19 (5.0%)	58 (15.4%)	128 (34%)	168 (44.6%)

Data have been presented as counts (n) and frequency (%)

Table 3 below shows that only gender shows a significant association with smoking habits, as evidenced by a P value of 0.001. Specifically, 8.0% of males are smokers compared with only 0.7% of females. In contrast, no significant associations were found between smoking habits and academic year or living with a smoker, as shown by P values of 0.489 and 0.138, respectively.

Table 3.

Association between social demographic variables and smoking pattern

Variable	Category	Smoking Habit				P
		Smoker		Nonsmoker
		Count	Frequency	Count	Frequency
Gender	Female	1	0.7%	151	99.3%	0.001
	Male	18	8.0%	207	92.0%
Academic Year	First	0	0.0%	23	100.0%	0.489
	Second	1	1.9%	53	98.1%
	Third	8	7.1%	105	92.9%
	Fourth	5	5.7%	83	94.3%
	Five	5	5.1%	94	94.9%
Do you live with a smoker	Yes	8	7.8%	95	92.2%	0.138
	No	11	4.0%	263	96.0%

Data have been presented as counts (n) and frequency (%). Chi-square test used to determine statistical significance at P<0.05

The analysis of belief scores, as presented in Table 3, indicated that females had a slightly higher median overall belief score of 33 (IQR 8.0) compared with males, who had a median score of 32 (IQR 8.0); however, this difference did not reach statistical significance (P = 0.090). A similar pattern was seen in both health belief and persistence belief scores, where females had marginally higher scores. When comparing belief scores across academic years in Table 4, there were no significant variations in overall belief, health belief, or persistence belief scores (P = 0.239, P = 0.265, and P = 0.49, respectively). Smokers demonstrated a lower median persistence belief score of 13 (IQR 3.0) compared with nonsmokers, who had a median score of 15 (IQR 3.0), with this difference being statistically significant (P = 0.041). However, no significant differences were found between smokers and nonsmokers regarding their overall belief scores (P = 0.309) or health belief scores (P = 0.879). Furthermore, participants who lived with smokers had slightly lower median scores in all belief categories compared with those not living with smokers, but not significant (overall belief P = 0.173, health belief P = 0.381, persistence belief P = 0.180).

Table 4.

A Comparison of Belief Scores across social demographic variables

Variable	Category	Overall belief score		The Health Belief Score		Persistent Belief Score
		Median (IQR)	P	Median (IQR)	P	Median (IQR)	P
Gender	Female	33 (8.0)	0.090	18 (4.0)	0.142	15 (3.0)	0.090
	Male	32 (8.0)		17 (5.0)		14 (4.0)
Academic Year	First	30 (8.0)	0.239	16 (4.0)	0.265	14 (3.0)	0.490
	Second	32.5 (8.0)		17 (5.0)		15 (4.0)
	Third	32 (7.0)		18 (5.0)		14 (3.0)
	Fourth	32 (7.0)		18 (4.0)		15 (3.0)
	Five	32 (8.0)		17 (5.0)		14 (3.0)
Smoker	Yes	31 (10.0)	0.309	17 (6.0)	0.879	13 (3.0)	0.041
	No	32 (7.0)		18 (5.0)		15 (3.0)
Do you live with a smoker	Yes	31 (8.0)	0.173	17 (5.0)	0.381	14 (4.0)	0.180
	No	32 (7.0)		18 (4.0)		15 (3.0)

The Mann–Whitney U test and Kruskal–Wallis test were employed to compare differences between the groups

Discussion

Third-hand smoke (THS) unlike second-hand smoke, which is inhaled by those near a smoker, remains in the environment, exposing nonsmokers, particularly vulnerable populations like children, to harmful chemicals over extended periods.[2] Our study hence aimed to evaluate the perception of medical students toward thirdhand smoke. Most medical students demonstrated a good awareness of the lingering effects on human health. In addition, the study holds significant implications for primary care physicians and family physicians, as these professionals are often tasked with addressing smoking-related health issues in both clinical and community settings. Nearly two-thirds of the medical students (65.7%) agreed or strongly agreed that smoke particles are not entirely cleared from a room by simply opening windows or using an air conditioner. Almost three-quarters of the students (74.6%) also agree that third-hand smoke lingers in the air and smoke particles can get engrossed into walls and furniture. Our results align with a study by Çoşğun et al.,[22] which found that 80.2% of medical students recognized that ventilation or opening windows does not fully remove smoke particles from a room.

Smoke particles can persist in the environment for a long duration of time ranging from days to weeks thereby having a prolonged effect on the quality of air and health.[23] In this study, more than half (59.1%) express concerns about potential health risks to adults from exposure to smoke particles. Another 60.8% of the medical students believe these smoke particles have a carcinogenic potential. Our findings align with the growing body of evidence that links long-term exposure to smoke particles with an increased risk of developing cancers, particularly lung cancer. A study by Holme et al.[24] For instance, found an association between increased lung cancers and polycyclic aromatic hydrocarbons from smoking.

The medical students filled out the Beliefs About Third-Hand Smoke (BATHS) questionnaire and its analysis gave interesting findings. Some social demographic variables demonstrated statistical significance in aspects of health and persistent scores. Regarding gender, females reported slightly higher median overall belief scores (33) compared to males (32), with a P value of 0.09, suggesting a borderline significance in their overall belief about the health impacts and persistence of smoke particles. The health belief score and persistent belief score were also slightly higher in females than males, though these differences were not statistically significant (P values of 0.142 and 0.090, respectively). When examining differences across academic years, first-year students reported the lowest overall belief scores (median 30), with a gradual increase in scores among students in higher academic years, though the P value was not statistically significant. Some interesting results emerged when comparing smokers to nonsmokers; while smokers had a lower median persistent belief score (17) compared to nonsmokers (19), this difference was statistically significant with a P value of 0.041, suggesting that smokers may be less convinced about the persistence of smoke particles. A similar study conducted among medical students at Atatürk University Faculty found that gender and smoking patterns were associated with scale scores.[25] The differences could be attributed to disparities in sociocultural factors or educational exposure.

When evaluating the results, it is imperative to acknowledge some limitations. The study adopted a cross-sectional design which identifies associations between the variables studied but does not establish causal relationships. In addition, because the study relied on self-reported data collected through an online survey, the accuracy and reliability of the findings may be affected by recall bias and social desirability bias. Furthermore, since the study was conducted exclusively among participants from the Qassim region, the results may not be generalizable to other populations.

Conclusion

This study found that there was strong awareness among medical students at Qassim University regarding the persistent nature and health risks of third-hand smoke. Most students recognized that standard ventilation methods cannot fully eliminate smoke particles and acknowledged the potential for these particles to linger on surfaces, posing significant health risks. The data reveal a nuanced understanding of third-hand smoke’s impact, with notable differences in perceptions based on smoking status and gender. Smokers, in particular, showed less concern about the persistence of smoke particles. Tailored educational programs not only among the medical colleges but also among the general population would be imperative to enhance the understanding and awareness about third-hand smoke.

Conflicts of interest

There are no conflicts of interest.

Funding Statement

Nil.