Is There an Association between Environmental Tobacco Smoke Exposure and the Risk of Wheezing among Rural and Urban Preschool Children in Mpumalanga Province, South Africa?

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Is There an Association between Environmental Tobacco Smoke Exposure and the Risk of Wheezing among Rural and Urban Preschool Children in Mpumalanga Province, South Africa?

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28 February 2024

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06 March 2024

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Abstract

Background: The study aimed to investigate the association between environmental tobacco smoke exposure and the risk of wheezing among rural and urban preschool children in Mpumalanga province, South Africa, an area associated with poor air quality. Methods: In this study, parents/caregivers of preschool children (n=3145) completed a modified International Study of Asthma and Allergies in Childhood (ISAAC) questionnaire. Data were analysed using multiple logistic regression models. Results: The overall prevalence of Wheeze ever was 15.14%, with a higher prevalence in urban pre-schoolers than rural pre-schoolers (20.71% vs 13.30 %, P<0.000). Moreover, the total prevalence of asthma ever was 2.34%. The prevalence was greater in urban pre-schoolers than in rural pre-schoolers (3.92% vs 1.81%, P<0.001). In the final adjusted model, both urban and rural area children who lived with one or more people who smoked in the same household (WE: OR 1.44, 95% CI 1.11-1.86) (CW: OR 2.09, 95% CI 1.38-3.16) and (AE: OR 2.49, 95% CI 1.12-5.54) were found to have an increased likelihood of having Wheeze Ever, Current Wheeze and Asthma Ever as compared to those who lived with non-smokers. Conclusions: The implementation of smoking limits and prohibition is crucial in areas that are frequented or utilized by children. Hence, it is imperative for healthcare providers to actively champion the rights of those who do not smoke within the society, while also endorsing legislative measures aimed at curtailing the extent of tobacco smoke exposure.

Keywords:

Subject: Public Health and Healthcare - Public Health and Health Services

1. Introduction

Wheeze can be described as a persistent high-pitched sound characterized by a melodic tone that originates from the chest during the act of exhaling [1]. Wheezing throughout early childhood is a prevalent yet intricate symptom characterized by multiple aetiologies and potential consequences. [2,3] It is common for children who exhibit wheezing symptoms before the age of three and persist with wheezing until the age of six to possess atopic tendencies and subsequently develop asthma over the period of eleven to thirteen years [4,5,6]. Moreover, it has been observed that the respiratory capacity of children experiencing wheezing tends to enhance as they grow older; however, their respiratory capacity never reaches the level observed in children who have never experienced wheezing [4].

The association between wheezing and asthma remains uncertain during the early stages of life. Asthma is a persistent inflammatory ailment affecting respiratory passages, exhibiting fluctuating symptoms such as wheezing, dyspnoea, thoracic constriction, and coughing [7]. Asthma has emerged as a significant public health concern on a global scale, with a particular impact on the paediatric population [8,9,10,11,12,13]. Despite the potential for asthma to manifest clinically at a later stage, [14] investigating asthma in young children holds the potential to mitigate and pre-empt the development of established asthma symptoms [14]. Asthma is considered an incurable condition, and recent research has revealed that recurrent asthma attacks can lead to irreversible lung damage. Asthma management can be effectively achieved by the implementation of proper healthcare interventions. Due to the diverse nature of asthma in the paediatric population, several scholars propose that the term "asthma" should not be employed to characterize episodes of wheezing in preschool-aged children. ¹

Children's asthma has been linked to frequent indoor exposure to environmental tobacco smoke (ETS) [15,16]. ETS possess comparable toxic components to those found in conventional tobacco smoke, consequently resulting in similar detrimental consequences akin to those observed in individuals who engage in active smoking [17]. The symptoms of asthma may exhibit temporary remission following therapy interventions and/or avoidance of triggers associated with the condition. Hence, it is advisable to enact legislation aimed at the elimination and regulation of children's exposure to ETS.

According to the Tobacco Products Control Act of 1993 in South Africa, specifically Section 2(1)(a)(iii), it is prohibited for individuals to engage in smoking any tobacco product within a motor vehicle in the presence of a child under the age of 12 years. This provision has been subject to amendments. The act of smoking is now prohibited within buildings designated for commercial childcare services. Sweets and toys resembling cigarettes are likewise prohibited. The implementation of new tobacco regulations was officially announced in September 2022 through the publication of Government Gazette Staats koerant, Regulation Gazette No. 11494, Vol. 68729, September No. 469942022. Regulation number R. 2560.

The following are highlights that will be considered in risk for childhood exposure to ETS:

In the event that a residence is utilized for educational purposes, tutoring services, or commercial childcare, the act of smoking would likewise be prohibited.
The implementation of a prohibition on smoking within motor vehicles in the presence of a minor under the age of 18, provided that there is more than one individual occupying said vehicle.
The proposed legislative expansion involves not only traditional cigarettes, but also embraces any devices used in connection with tobacco-related goods and electronic delivery systems, such as pipes, water pipes, and electronic devices.

There is a tendency for asthma prevalence to be lower in rural areas, with some evidence suggesting the presence of an urban-rural gradient. The rural-urban gradient of wheeze in preschool children is examined to determine whether this indicator differs along an urban-rural gradient. A study was undertaken by Lawson et al. to examine the relationship between asthma and its indicators throughout the rural-urban gradient. The findings revealed that the prevalence of children with smoking parents was lower in the large urban center [18].

The current tobacco control laws are introduced in a baseline and impact of the regulations will be seen in later years. This study presents the baseline of prevalence of wheeze and asthma in Mpumalanga where children are exposed to polluted air including ETS. The aim is to evaluate the association between exposure to environmental tobacco smoke and the occurrence of wheezing, a symptom commonly associated with asthma, among preschool children residing in rural and urban areas of Mpumalanga Province, South Africa.

2. Methods

2.1. Study Design and Settings

An analytical cross-sectional survey was conducted between November 2020 and April 2021. The objective of our study was to assess the association between environmental tobacco smoke exposure and the occurrence of wheezing, a common symptom of asthma, among preschool children residing in rural and urban areas. The research was carried out within the Mpumalanga province, specifically in the Gert Sibande district municipality, which is situated within the Highveld Priority Area. In accordance with the National Environmental Management: Air Quality Act, 2004 (Act No. 39 of 2004), the Minister of Environmental Affairs named this region as a priority area for air pollution in 2007.

The Gert Sibande district municipality was purposively selected because it is in the Highveld priority area. The Highveld Priority Area has substandard air quality and heightened levels of pollutants originating from both industrial and non-industrial origins. The district encompasses a diverse range of sectors, such as power generating, petrochemical, primary metallurgy, and open cast mining. The district municipality comprises seven local municipalities, specifically Dipaleseng, Govan Mbeki, Lekwa, Msukukaligwa, DR Pixley ka Seme, all of which are situated within the Highveld priority area. The Chief Albert Luthuli and Mkhondo municipalities are not encompassed under the Highveld priority area. Figure 1 illustrates the geographical distribution of seven local district municipalities, with Gert Sibande being visually distinguished by the use of a light-yellow highlighting.

2.2. Study Population, Sample Size Estimation and Sampling Procedure

The participants in this study consisted of preschool-aged children, ranging from one to eight years old, who resided in and attended preschools located in either rural or urban areas within the Mpumalanga province, specifically in the Gert Sibande district municipality. Based on the data from the 2019 Gert Sibande database, the number of children enrolled in preschool was recorded as 13,485 [19]. The overall sample size required for this study was determined to be 3,900, assuming a response rate of 70%. A study power of 80% was used for the investigation, with a significance level of 5%. The sample size was determined using the sample size calculator in Microsoft Excel.

A probability sample design was employed in order to achieve equitable representation of all preschool children throughout seven local municipalities. Preschools were identified in the northern, southern, eastern, and western regions of each of the seven municipalities within the Gert Sibande district (Figure 1). A representative sample of preschools was chosen from each of the four areas within each municipality. Preschool children were selected in a random manner from a class roster obtained from each designated preschool. Selected pre-schoolers were then given participant information leaflets inviting their parents to be part of the study. Parents, who consented to let their children participate, were then given a questionnaire to complete and return to the preschool. All necessary COVID-19 protocols were implemented.

2.3. Study Tools

Data was collected using the adapted International Study of Asthma and Allergies in Childhood (ISAAC) questionnaire. ⁹ The questionnaire was divided into two sections: namely demographic data and health outcomes. The questionnaire was in English, which is the common language in a region with multiple local languages. In order to evaluate the data collection procedure and the quality of the survey questions in light of COVID-19 limitations, a pre-test of the instrument was conducted with environmental health practitioners. These professionals were chosen owing to their regular interaction with parents and carers, which provides them with insights into the educational background of these individuals.

2.4. Health Outcomes of the Study

The following central questions on asthma symptoms were used in order to evaluate health outcomes: (1) Has your child ever experienced chest wheezing or whistling in the past? (Wheeze Ever) (2) Has he or she had chest wheezing or whistling in the previous 12 months? (Current Wheeze) (3) How many wheezing episodes did your child have in the last 12 months? (4) How frequently, on average, during the previous 12 months was your child's sleep interrupted by wheezing? (5) Has your child's wheezing ever been sufficiently severe to prevent them from speaking more than a few phrases at any time between breathing in the last 12 months? (6) Did the child ever suffer from asthma? (Asthma Ever) (7) Did a physician or nurse diagnose the asthma? (8) Has your child's chest ever made a wheezy noise while playing or right after? (9) Besides from a cough brought on by a cold or chest illness, has your child experienced a cough that is dry at night in the last 12 months?

The classification of Current Severe Wheeze was determined if parents provided affirmative responses to every one of the subsequent questions: 1) If children have severe wheezing, with a frequency of 4-12 bouts or over 12 episodes throughout the preceding 12-month period. 2) If the children experience disrupted sleep as a result of wheezing at least once a week or more. 3) In the event that children experienced a wheezing episode within the last 12 months, resulting in a restriction of their ability to speak to just a few phrases at a time due to intermittent breaths. 4) If the children have experienced wheezing symptoms during or following physical activity throughout the preceding 12-month period.

2.5. Environmental Tobacco Smoke Exposure

Parents and caregivers were requested to provide responses pertaining to risk factors associated with wheezing, a symptom commonly observed in individuals with asthma. The questions encompassed the following: Does the male parent engage in smoking behaviour? (yes/no), Is the female parent engaged in the act of smoking? (yes/no).

The present study examines the extent of children's exposure to smoking inside their household during the past 30 days, categorized into several frequency levels: never, 1-6 days, 7-10 days, 16-20 days, and more than 20 days. The present study examines the prevalence of children's exposure to smoking inside the school environment over a period of 30 days.

The duration of the observed time intervals ranges from never through 1-6 days, 7-10 days, 16-20 days, and more than 20 days. The present study examines the extent to which children have been exposed to smoking in cars or other modes of transportation within the preceding 30 days. The duration of the event might vary, ranging from less than a week to over three weeks. The present study examines the frequency of children being subjected to smoking within the past 30 days in a restaurant setting. Parents/caregivers were asked to indicate the number of days in which children were exposed to smoking, with response options ranging from never to more than 20 days. In addition, what is the number of individuals residing in the household of your child that engages in smoking?

2.6. Confounders

Parents and caregivers were asked to answer a series of questions about the following topics: Gender of the child (male/female), Location of the child (rural/urban), and How long has the child lived in the area? (6 to 12 months/1 to 2 years/3 years or longer), Was the child born in the area? (Hospital/Clinic/Home/does not apply), What kind of residence does the child live in? (Brick/Mud/Corrugated Iron/Mixture/Other), In the last 12 months, the child used analgesics/antibiotics (Never/At least once a year/At least once per month. What type of fuel is utilized for cooking and heating (electricity/gas/paraffin/coal/wood/other)? How does the child get to and from school? (walks/taxi/bus/motor vehicle/combination/other). How frequently do trucks, buses, and taxis pass through your neighbourhood? (Never/rarely/frequently throughout the day/almost the entire day. Other questions focused on pet ownership, education for parents/caregivers, Job occupation of parents/caregivers and family health history.

2.7. Data Processing and Analysis

The data were captured using EpiData version 3.1[20] for the purpose of ensuring quality and subsequently analysed using STATA 17. Descriptive statistics were computed, utilizing means and standard deviations for continuous data, and frequencies expressed as percentages for categorical data. Observations that were labelled as "not recorded" were designated as missing. Consequently, there were variations in the sample sizes utilized to address each respective question.

In this study, we assessed the association between demographic factors, including gender, age, location, and family history, with four outcome variables: Wheeze Ever, Current Wheeze, Current Severe Wheeze and Asthma Ever. Statistical comparisons were conducted using the chi-square test for independent samples. The researchers employed multiple logistic regression to account for any confounding variables, assessing the strength of the relationship using the odds ratio (OR) and 95% confidence intervals (CI). For outcomes with two categories, binary multiple logistic regression was utilized.

3. Results

Description of Study Participants

We identified 3900 pre-schoolers and invited their parents using participant information leaflets to be part of the study. Three thousand one-hundred and forty-five parents permitted their children and consented to participate, which was a participation rate of 80.6%. The pre-schoolers were, on average, 4.05 (SD=1.22) years old. Most pre-schoolers were within the age range of 3 to 5 years, which fell within the 50th percentile. There were 1 605 (51%) boys and 1 540 (48.9%) girls. Most pre-schoolers (75%) resided in rural areas, while 774 (25%) lived in urban areas. Moreover, a significant majority of pre-school-aged children (87%) were born in hospitals located in suburbs or township areas. Additionally, a substantial proportion of these children (80%) resided in these suburban or township regions for a duration of three years or more.

Table 1 provides a concise overview of the basic characteristics exhibited by children while Table 2 presents the environmental tobacco smoke exposure sources and health outcomes of the study participants. Study findings revealed that 23.56% of pre-school children had male parents who engaged in smoking, whereas just 3.10% of pre-school children had female parents who engaged in smoking. According to Table 2, a total of 28.86% of pre-schoolers resided in households where one or more individuals engaged in smoking activities within the same living space.

The study found that the overall prevalence of wheeze ever among the pre-schoolers was 15.14%, with a greater prevalence observed among urban pre-schoolers compared to their rural counterparts (20.7% vs 13.3%, p<0.001). Moreover, the total prevalence of asthma ever was 2.34% The prevalence was also greater in urban pre-schoolers compared to rural pre-schoolers (3.9% vs 1.8%, P<0.001). The prevalence of Current Wheeze was found to be higher than that of Current Severe Wheeze and Asthma ever, as indicated in Table 2.

The prevalence rates of Wheeze ever, Current wheeze, and Asthma ever among urban pre-schoolers residing in households with one or more individuals who engage in smoking were found to be 23.11%, 14.14%, and 5.97%, respectively. In comparison, their rural counterparts exhibited prevalence rates of 17.15%, 12.93%, and 2.32% for the same respiratory conditions.

Furthermore, urban pre-school children exposed to smoking at restaurants in the past 30 days had a 37.50% prevalence rate of Current wheeze, while their rural counterparts had a prevalence of 11.32% for the same exposure days. Contrary to the above, it was observed that rural pre-school children who had a female parent or caregiver who smoked exhibited a significantly higher prevalence of current wheeze, with a rate of 26.31%. The data presented in Table 3 illustrates the relevant information pertaining to the topic at hand.

The prevalence of wheeze ever in both rural and urban areas combined exhibited a greater incidence among boys (16.73%) compared to girls (13.49%). The data presented in Table 4 and Table 6 indicate that there is a larger prevalence of current severe wheeze among boys (1.75%) compared to girls (0.78%) in both rural and urban areas.

Table 3 shows the multiple logistic regression analysis of risk factors for Wheeze ever, Current Wheeze, Current Severe Wheeze and Asthma ever for rural and urban areas, with their respective odds ratios. Both urban and rural area children who lived with one or more people who smoked in the same house (WE: OR 1.44, 95% CI 1.11-1.86) (CW: OR 2.09, 95% CI 1.38-3.16) and (AE: OR 2.49, 95% CI 1.12-5.54) were found to have an increased likelihood for having Wheeze ever, Current Wheeze and Asthma ever as compared to those who lived with non-smokers. Moreover, those children exposed to smoking at the restaurant for one or more days in the past 30 days (CW: OR 2.27, 95% CI 1.17-4.38) were more likely to present with current wheeze as compared to those who lived with non-smokers.

In the context of combined rural and urban areas, Wheeze Ever and Current Wheeze shared similar ETS risk factors. The occurrence of symptoms was shown to be significantly higher in cases when a female parent or caregiver engaged in smoking behaviour. The crude odds ratios (OR) for Wheeze Ever and Current Wheeze were 3.11 (95% CI 2.00-4.83), and 3.12 (95% CI 1.90-5.12), respectively. In addition, there was a notable relationship between the number of smoking individuals residing in the same household as pre-schoolers and the likelihood of developing Wheeze ever, Current Wheeze, and Current Severe Wheeze. The adjusted odds ratios for these associations were 1.37 (1.08-1.74), 2.09 (1.38-3.16), and 2.46 (1.25-4.85), respectively, as indicated in Table 4, Table 5, and Table 6.

Some of the confounders that showed significant associations with Wheeze Ever in both rural and urban areas were children pre-schoolers using analgesic/antibiotics in the past 12 months at least once a year (adjusted OR 2.29, 95% CI 1.41-3.71) and pre-schoolers using a motorcar as their mode of transportation to school (adjusted OR 1.74, 95% CI 1.27-2.38) (refer to Table 4). The male gender was shown to be associated with a higher probability of experiencing both Wheeze ever (OR 1.35, 95% CI 1.08-1.70) and Current Severe Wheeze (OR 2.30, 95% CI 1.09-4.84) according to the data presented in Table 4 and Table 6. Having a female parent or caregiver who worked in the government sector was shown to be associated with an elevated probability of experiencing Current Wheeze, as indicated by an odds ratio of 1.64 (95% CI 1.06-2.54), as presented in Table 5. The presence of a dog in the household during a period of 12 months has been found to be associated with an increased probability of experiencing both Current Wheeze (OR 1.79, 95% CI 1.28-2.51) according to the crude odds ratios reported in Table 5.

4. Discussion

This study aimed to assess the association between environmental tobacco smoke exposure and the occurrence of wheeze, a common symptom of asthma, among pre-school children residing in rural and urban areas of Mpumalanga province, South Africa. The reported prevalence of wheeze in Mpumalanga is similar to that observed in previous research. Based on the findings of the ISAAC Phase Three study, it was determined that the worldwide prevalence of current wheeze among school-aged children was 11.5%. This prevalence showed significant regional variation, varying from 6.8% in the Indian subcontinent to 21% in Oceania [21]. Furthermore, the prevalence of current wheeze (10%) and lifetime asthma (3.4%) in Africa exhibited a comparable pattern to the outcomes observed in our study [21]. Additionally, the findings of Wichmann et al. [22] who conducted a study on the potential risk factors for asthma symptoms in school-aged children from Polokwane Limpopo province in South Africa, using the ISAAC questionnaire, support our study results. The prevalence of wheeze (11.2%) and severe wheeze (5.7%) observed in their study aligns with the findings of our study.

The potential influence of various factors on the prevalence of asthma symptoms within a given region can be attributed to several key variables, including the age range of children considered in the study, the prevailing climate conditions, the specific timing of the study, the size of the sampled population, the design of the study itself, and the presence or absence of certain risk factors. Research studies that specifically examine children within similar age groups, as well as children residing in a particular place for a duration beyond six months, have found comparable rates of asthma symptom prevalence. Based on the aforementioned findings, it is evident that the management of asthma symptoms poses a persistent problem. Consequently, it may be necessary to formulate and execute strategies aimed at mitigating these symptoms within this specific demographic promptly.

This study found that there was a higher prevalence of wheeze ever and asthma ever among pre-schoolers living in urban areas compared to those residing in rural areas. Consistent with the results of our study, Chakravarthy et al, [23] Wehrmeister et al, [24] Feng et al, [25] and Kutzora et al [26] conducted research in India, Brazil, China, and Germany respectively, which also indicated a greater prevalence of asthma symptoms among children residing in urban regions compared to those dwelling in rural areas. The present study found that children residing in the Mpumalanga Highveld region were predominantly impacted by wheeze ever, a common symptom of asthma, as well as a history of asthma ever, particularly if they attended an urban pre-school. The results of our study align with the majority of existing literature, which consistently demonstrates that residing in rural areas or on farms, being exposed to livestock, and the hygiene hypothesis confers protective advantages against the development of asthma symptoms in childhood, compared to children residing in urban areas [26,27,28,29,30]. Additionally, our research findings provide support for the notion that children residing in urban areas are more prone to increased exposure and heightened sensitivity to several risk factors associated with asthma symptoms [29,31].

The study outcome indicated above may have been influenced by specific environmental factors. The regions of Mpumalanga Highveld exhibit a notable deterioration in air quality, with heightened levels of pollutants stemming from both industrial and non-industrial origins. The district encompasses a variety of sectors, namely power generating, petrochemical, primary metallurgy, and open-cast mining. Urban environments possess a multitude of modifiable exposures that can impact the prevalence and morbidity of asthma symptoms. In the aggregate of both rural and urban areas, boys had a greater propensity for experiencing wheeze ever at any point and current severe wheeze in comparison to their girls' counterparts.

This observation aligns with previous research indicating that boys consistently have a higher incidence of wheezing and/or asthma symptoms relative to girls [32,33,34].

Risk factors and confounders associated with wheeze, a symptom commonly observed in individuals with asthma, were identified in our study. The risk factors with the highest potential for modification encompassed a female parent who engages in smoking, a male parent who engages in smoking, the number of individuals residing in the same household as a child who engages in smoking, exposure to smoking within the home (within the previous 30 days), exposure to smoking within a motor vehicle or transportation (within the previous 30 days), exposure to smoking within a restaurant (within the previous 30 days), the mode of transportation utilized to commute to school, and ownership of a pet.

This study found that pre-schoolers were more likely to experience wheeze ever and current wheeze in their lives, if they had a female parent or caregiver who smoked and also those who lived in the same household with one or more people who smoked. Those who were exposed to smoking in cars and restaurants in the past 30 days were more likely to present with current wheeze. The results of our study are consistent with existing literature, which indicates that children are primarily exposed to environmental tobacco smoke (ETS) through smoking by adults in environments where children reside and engage in recreational activities. This exposure significantly increases their susceptibility to developing asthma and respiratory symptoms [17,30,35,36].

According to studies conducted by Tsai et.al. [37] and Shahunja et al. [38] there exists a significant relationship between the prevalence of asthma symptoms in children and their exposure to household tobacco smoke. Moreover, Wang et al. [39] conducted a study that revealed a significant relationship between the presence of wheezing symptoms in children and their exposure to second-hand smoke. In addition, Tabuchi et al. [40] and Harju et al. [41] also reported that children who had two smoking parents were more likely to have asthma symptoms and had a greater chance of asthma attacks relative to children with non-smoking parents [42]. Tsai et al [43] provided additional support for the aforementioned results, since they demonstrated that the combined exposure to smoking from both fathers and mothers amplifies the impact of asthma symptoms. According to the findings of Jung et al. [44] there was a notable relationship between parental smoking and an increased incidence of respiratory complaints among children, as compared to those whose parents did not smoke.

Although the presence of second-hand smoke has been identified as a significant indicator of asthma symptoms, there remains a lack of consensus regarding the specific threshold at which exposure to smoking becomes detrimental. It is thus highly advisable to completely refrain from exposure to second-hand smoke and to ensure that household members who smoke confine their smoking activities to isolated areas that are inaccessible to these children [45]. Parents should additionally take into consideration the implementation of a prohibition on smoking within the confines of their residence or its immediate vicinity.

Additionally, our study revealed that preschool-aged children who have been subjected to ETS in cars or transport without a complete physical barrier within the last 30 days were shown to have a higher likelihood of experiencing current wheeze. In addition, our research revealed an association between the utilization of motor vehicles for transportation to school among preschool-aged children and an increased likelihood of experiencing wheeze ever.

The anticipated outcomes of this study are in line with expectations, as the act of parents or caregivers smoking in the car during the transportation of children to school has been found to elevate exposure to ETS and therefore raise the probability of experiencing symptoms associated with asthma. The existing body of literature on the exposure of children to ETS and its impact on the development of respiratory and asthma symptoms provides substantial data that aligns with the findings of the aforementioned study [15,16,17,35,46]. Additionally, the use of motor vehicles may contribute to an increased likelihood of experiencing symptoms associated with asthma. Gasana and colleagues [47] conducted a study that corroborated the aforementioned findings, as they concluded that children who are exposed to elevated amounts of air pollution from motor vehicles are more likely to exhibit symptoms of childhood wheezing. It is advisable to prioritize the avoidance of ETS exposure as a crucial factor in mitigating the onset and facilitating the control of asthma and related symptoms [48].

5. Strength and Limitation of the Study

Firstly, the ISAAC questionnaire is a valid tool for data collection for this investigated population group and has been utilized worldwide in studies investigating asthma symptoms. Secondly, this study had a great participation rate with over 3000 children, which is a requirement by ISAAC centres, thus increasing the study's statistical power. Final: The implementation of a standardized and validated tool facilitates the ability to compare study findings with those of other studies conducted at various levels, including local, regional, and international contexts.

The study outcomes may deviate slightly from the actual prevalence of investigated symptoms due to the presence of missing data. Future research endeavours should prioritize the meticulous completion of questionnaires, aiming to minimize the occurrence of missing data to a significant extent. The study gathered data from the past year by using a parental-completed questionnaire. It was anticipated that these parents, who primarily reside with the children, would be able to accurately recall the information requested. The one-year timeframe was considered sufficient for recollection, without posing significant obstacles.

6. Conclusions

The study found that in Mpumalanga, pre-schoolers living in urban areas had a higher prevalence of wheeze ever, current wheeze, current severe wheeze and asthma ever relative to rural pre-schoolers. The presence of ETS exposure among preschool-aged children in various settings, including their homes, restaurants, and during transportation, increased the probability of experiencing wheezing. The implementation of smoking limits and prohibition is crucial in areas that are frequented or utilized by children. Hence, it is imperative for healthcare providers to actively champion the rights of individuals who do not smoke within the society, while also endorsing legislative measures aimed at curtailing tobacco smoke exposure.

Author Contributions

RM: JS, and KV participated in the study's design, RM was involved in the data collection and statistical analysis, and RM, JS, and KV were involved in interpreting the results and drafting and critically revising the manuscript. The published version of the work has been reviewed and approved by all authors.

Funding

The study was financially supported by the South African Medical Research Council's Division of Research Capacity Development, specifically through the Bongani Mayosi National Health Scholars Programme. The funding for this program was obtained through the Public Health Enhancement Fund, which is administered by the South African National Department of Health. The authors bear sole responsibility for the content herein, and it should be noted that the opinions expressed do not necessarily reflect the official stance of the SAMRC.

Institutional Review Board Statement

The present study received approval from the University of Pretoria Research Ethics Committee (Ethics Number: 766/2019), as well as the Gert Sibande District Municipality - Environmental Health Department and school principals. Consent for participation in the study was obtained from all parents and caregivers of the children.

Informed Consent Statement

Prior to their participation in the study, parental or caregiver agreement was obtained for the children.

Data Availability Statement

We did not receive ethics approval to share raw field data publicly. The data belong to the University of Pretoria (UP). The raw data analysed in the current study are available from UP on reasonable request.

Acknowledgments

The authors would like to thank everybody who participated in the study, the South African Medical Research Council and the University of Pretoria.

Conflicts of Interest

The author(s) declare no potential conflicts of interest concerning this article's research, authorship, and/or publication.

Abbreviations

ETS- environmental tobacco smoke

OR- odds ratio

ISAAC- International study of asthma and allergies in childhood

SD- standard deviation

CI- confidence interval

χ²- chi square

P- P value

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Figure 1. Geographical distribution of preschools within the Gert Sibande District Municipality. a) Provides a visual representation of the global location of the preschools within the Gert Sibande municipality. b) Present the spatial distribution of the Gert Sibande municipality in the province of Mpumalanga within the broader context of the nine provinces of South Africa. c) An illustration depicting the inclusion of all seven local municipalities within the Gert Sibande district, wherein preschools were identified, highlighted in a light-yellow colour. Source: https://en.wikipedia.org/wiki/List_of_municipalities_in_Mpumalanga.

Table 1. The demographic characteristics of the participants in the study (n=3145).

Variables	N	Percentage (%)
1. Gender of the child Female Male	1540 1605	48.97 51.03
2. Age group of children < 3 years 3-5 years ≥ 5 years	414 1779 952	13.16 56.57 30.27
3. Child location Rural Urban	2372 773	75.42 24.58
4. Time lived in Suburb/township Less than 6 months 6 to 12 months 1 to 2 years 3 years or longer Missing	107 99 408 2450 81	3.40 (3.49) 3.14 (3.23) 12.9 (13.32) 77.90 (79.96) 2.57
5. Type of house the child lives in^a Brick Mud Corrugated iron Combination Other Missing	2547 116 255 93 81 53	80.98 (82.37) 3.68 (3.75) 8.10 (8.25) 2.95 (3.01) 2.57 (2.62) 1.68
6. Fuel used for cooking in the house^b Electricity Gas Paraffin Coal WoodOther Missing	2476 100 19 254 292 2 2	78.72 (78.78) 3.17 (3.18) 0.60 (0.60) 8.07 (8.08) 9.28 (9.29) 0.06 (0.06) 0.06
7. Fuel used for heating in the house^c Electricity Gas Paraffin Coal Wood Other Missing	2008 198 27 484 380 19 29	63.84 (64.44) 6.29 (6.35) 0.85 (0.87) 15.38 (15.53) 12.08 (12.20) 0.60 (0.61) 0.92
8. Child used Analgesic/antibiotic in the past 12 months Never At least once a year At least once per month Missing	445 921 1683 96	14.14 (14.59) 29.28 (30.21) 53.51 (55.20) 3.05
9. How does the child get to school^d Walk Taxi/bus Motor car Combination Other Missing	1666 848 525 57 23 26	52.97 (53.41) 26.96 (27.19) 16.69 (16.83) 1.81 (1.83) 0.73 (0.74) 0.82
10. How often has your child been absent from school (past 6 months) Never or occasionally Once or twice per week Three or more times a week Missing	1854 904 256 131	58.95 (61.51) 42.14 (29.99) 8.13 (8.49) 4.1
11. Child Ever Breastfed No Yes Missing	974 2125 46	30.96 (31.43) 67.46 (68.57) 1.46
12. Truck traffic pass through the street on weekend Never Seldom Frequent through the day Almost all day Missing	518 735 713 1083 96	16.47 (16.99) 23.37 (24.11) 22.67(23.38) 34.43 (35.52) 3.0
13. Female parent: Highest level of school completed Primary Secondary University Other Missing	246 1884 454 422 139	7.82 (8.18) 59.90 (62.67) 14.43 (15.10) 13.41 (14.04) 4.41
14. Female parent job industry Government sector Private sector Self-employed Not employed Missing	351 580 308 1745 161	11.16 (11.76) 18.44 (19.44) 9.79(10.32) 55.48 (58.48) 5.11
15. Female parent ever asthma No Yes Missing	2487 79 579	79.09 (96.92) 2.51 (3.08) 18.41
16.Cat inside the house No Yes Missing	2885 223 37	91.17 (92.82) 7.09 (7.18) 1.17
17.Dog inside the house No Yes Missing	2780 331 34	88.39 (89.36) 10.52 (10.64) 1.08

( ) Missing data was excluded from the data analysis. ^a Combination includes Brick & Corrugated iron: Other includes wood. ^b Other include generator. ^c Other include Solar energy/electricity. ^d Combination includes motorcar and Taxi/bus: Other includes animal cart.

Table 2. Environmental tobacco smoke exposure sources and health outcomes of the study participants (n=3145).

Variables	N	Percentages (%)
1. Female parent smokes Yes No Missing	94 2934 117	2.98 (3.10) 93.29 (96.90) 3.72
2. Male parent smokes Yes No Missing	451 1463 1231	14.34 (23.56) 46.51 (76.44) 39.14
3. How many people living in the same house as your child smoke? Zero One or more Missing	2051 832 262	65.21 (71.14) 26.45 (28.86) 8.33
4. Child exposure to smoking at home (past 30 days) Never One or more days* Missing	1947 396 802	61.90 (83.10) 12.59 (16.90) 25.50
5. Child exposure to smoking at school (past 30 days) Never One or more days* Missing	1444 40 1661	45.91 (97.30) 1.27 (2.70) 52.81
6. Child exposure to smoking in car/transport (past 30 days) Never One or more days* Missing	1390 70 1685	44.19 (95.21) 2.25 (4.79) 53.57
7. Child exposure to smoking at the restaurant (past 30 days) Never One or more days* Missing	1387 79 1678	44.10 (94.61) 2.51 (5.39) 53.35
8. Wheeze ever Yes No Missing	467 2617 61	14.8 (15.14) 83.2 (84.86) 1.9
9. Current wheeze Yes No Missing	292 2799 54	9.2 (9.45) 88.9 (90.55) 1.7
10. Current severe wheeze Yes No Missing	40 3076 29	1.27 (1.28) 97.8 (98.72) 0.92
11. Ever had asthma Yes No Missing	66 2810 269	2.09 (2.34) 89.34 (97.65) 8.55
12. Wheeze attack in the past 12 months Yes No Missing	274 2815 56	8.71(8.87) 89.50 (91.13) 1.78
13. Sleep disturbed due to wheeze in the past 12 months Yes No Missing	199 2888 58	6.32 (6.45) 91.82 (93.55) 1.82
14. Wheeze severe enough to limit speech in the past 12 months Yes No Missing	59 3016 75	1.87 (1.92) 95.89 (98.08) 2.38
15. Asthma diagnosed by a medical Doctor or Nurse Yes No Missing	54 2929 162	1.71 (1.81) 93.13 (98.19) 5.15
16. Chest ever sounded wheezy during/after playing Yes No Missing	232 2398 515	7.37 (8.82) 76.24 (91.18) 16.37
17. Dry cough at night apart from cough associated with cold or chest infection Yes No Missing	650 2229 266	20.66 (22.58) 70.87 (77.42) 8.45

( ) Missing data was excluded from the data analysis. * One or more days include the following days range:1-6 days;7-10 days;16-20 days; more than 20 days.

Table 3. Participants’ prevalence of wheeze ever, current wheeze, current severe wheeze and asthma ever for rural and urban areas with their respective odds ratios.

	Rural						Urban
Variable	Total^a	Prevalence (%)	Crude OR^b		Adjusted OR^b		Total^a	Prevalence (%)	Crude OR^b		Adjusted OR^b
	Total^a	Prevalence (%)	(95% CI)	P	(95% CI)	P	Total^a	Prevalence (%)	(95% CI)	P	(95% CI)	P
Wheeze ever^c Child ever breastfed No Yes	736 1557	13.99 13.10	1 1.01 (0.82-1.26)	0.869	1 1.27 (0.96-1.67)	0.082	221 529	18.09 21.92	1 1.01 (0.82-1.26)	0.869	1 1.27 (0.96-1.67)	0.082
How often have you given your child medication (past 12 months)? Never At least once a year At least once per month	351 611 1300	4.55 12.43 16	1 2.78 (1.75-4.41) 3.98 (2.56-6.17)	0.000 0.000	1 2.24 (1.32-3.81) 2.83 (1.70-4.49)	0.003 0.000	84 298 350	8.33 18.45 36.18	1 2.78 (1.75-4.41) 3.98 (2.56-6.17)	0.000 0.000	1 2.24 (1.32-3.81) 2.83 (1.70-4.49)	0.0030.000
People living in the same house as your child smoke? Zero One or more	1500 618	11.4 17.15	1 1.46 (1.17-1.82)	0.001	1 1.44 (1.11-1.86)	0.006	511 199	20.15 23.11	1 1.46 (1.17-1.82)	0.001	1 1.44 (1.11-1.86)	0.006
Truck traffic where your child lives on weekdays Never Seldom Frequently Almost all day	389 492 517 854	13.11 12.19 14.89 12.99	1 1.05 (0.76-1.46) 1.32 (0.95-1.81) 1.07 (0.78-1.45)	0.76 0.08 0.65	1 1.10 (0.73-1.64) 1.40 (0.94-2.07) 1.10 (0.75-1.63)	0.636 0.092 0.601	120 237 187 199	15.83 21.09 25.13 19.59	1 1.05 (0.76-1.46)1.32 (0.95-1.81)1.07 (0.78-1.45)	0.76 0.08 0.65	1 1.10 (0.73-1.64) 1.40 (0.94-2.07) 1.10 (0.75-1.63)	0.6360.0920.601
Cat inside the house (past 12 months) No Yes	2143 156	13.06 16.02	1 1.54 (1.09-2.17)	0.012	1 1.39 (0.90-2.15)	0.136	687 64	19.65 34.37	1 1.54 (1.09-2.17)	0.012	1 1.39 (0.90-2.15)	0.136
Female parent level of school completion Primary Secondary University Other	222 1523 212 286	18.01 11.81 16.50 15.73	1 0.59 (0.41-0.84) 1.03 (0.68-1.55) 0.82 (0.54-1.24)	0.004 0.871 0.354	1 0.76 (0.46-1.25) 1.64 (0.97-2.80) 0.99 (0.59-1.73)	0.284 0.064 0.982	19 323 237 127	23.31 16.09 28.27 21.25	1 0.59 (0.41-0.84)1.03 (0.68-1.55)0.82 (0.54-1.24)	0.004 0.871 0.354	1 0.76 (0.46-1.25) 1.64 (0.97-2.80) 0.99 (0.59-1.73)	0.284 0.064 0.982
Female parent ever had Asthma No Yes	1852 43	12.41 25.58	1 3.65 (2.28-5.85)	0.000	1 3.25 (1.97-5.35)	0.000	599 36	18.19 55.55	1 3.65 (2.28-5.85)	0.000	1 3.25 (1.97-5.35)	0.000
Current wheeze^d Female parent ever had Asthma No Yes	1853 43	8.04 23.25	1 3.82 (2.26-6.45)	0.000	1 5.59 (2.77-11.26)	0.000	600 36	9.33 30.55	1 3.82 (2.26-6.45)	0.000	1 5.59 (2.77-11.26)	0.000
Child used Analgesic/antibiotic in the past 12 months Never At least once a year At least once per month	354 609 1307	1.97 7.38 11.40	1 3.85 (1.82-8.12) 7.94 (3.89-16.22)	0.000 0.000	1 3.41 (1.17-9.95) 4.74 (1.68-13.40)	0.024 0.003	86 297 349	1.16 6.06 18.33	1 3.85 (1.82-8.12) 7.94 (3.89-16.22	0.000 0.000	1 3.41 (1.17-9.95) 4.74 (1.68-13.40)	0.024 0.003
Truck traffic where your child lives on weekdays Never Seldom Frequently Almost all day	388 489 516 865	8.76 8.58 10.07 8.43	1 0.99 (0.66-1.48) 1.40 (0.95-2.06) 1.02 (0.70-1.48)	0.978 0.084 0.905	1 1.04 (0.55-1.94) 1.13 (0.60-2.11) 0.86 (0.45-1.64)	0.902 0.695 0.653	120 238 186 199	8.33 9.24 16.66 10.05	1 0.99 (0.66-1.48) 1.40 (0.95-2.06) 1.02 (0.70-1.48)	0.978 0.084 0.905	1 1.04 (0.55-1.94) 1.13 (0.60-2.11) 0.86 (0.45-1.64)	0.902 0.695 0.653
Female parent job industry Government sector Private sector Self-employed Not employed	183 371 199 1476	11.47 7.27 9.04 9.01	1 0.62 (0.40-0.96) 0.76 (0.46-1.25) 0.73 (0.50-1.06)	0.034 0.292 0.103	1 0.72 (0.38-1.36) 0.85 (0.42-1.71) 0.50 (0.28-0.87)	0.317 0.660 0.016	164 196 102 245	14.63 10.20 11.76 10.20	1 0.62 (0.40-0.96) 0.76 (0.46-1.25) 0.73 (0.50-1.06)	0.034 0.292 0.103	1 0.72 (0.38-1.36) 0.85 (0.42-1.71) 0.50 (0.28-0.87)	0.317 0.660 0.016
Dog inside the house (past 12 months) No Yes	2103 205	8.13 15.60	1 1.74 (1.24-2.44)	0.001	1 1.27 (0.70-2.32)	0.419	639 115	10.79 13.04	1 1.74 (1.24-2.44)	0.001	1 1.27 (0.70-2.32)	0.419
Female parent smoke No Yes	2186 76	8.26 26.31	1 3.19 (1.94-5.24)	0.000	1 0.65 (0.20-2.12)	0.488	698 17	11.31 11.76	1 3.19 (1.94-5.24)	0.000	1 0.65 (0.20-2.12)	0.488
People living in the same house as your child smoke? Zero One or more	1497 626	7.34 12.93	1 1.77 (1.36-2.30)	0.000	1 2.09 (1.38-3.16)	0.000	511 198	9.39 14.14	1 1.77 (1.36-2.30)	0.000	1 2.09 (1.38-3.16)	0.000
Child exposure to smoking at the restaurant (past 30 days) Never One or more days	984 53	8.23 11.32	1 2.35 (1.29-4.26)	0.005	1 2.27 (1.17-4.38)	0.014	381 24	11.81 37.5	1 2.35 (1.29-4.26)	0.005	1 2.27 (1.17-4.38)	0.014
Child ever breastfed No Yes	738 1561	8.40 9.22	1 1.14 (0.87-1.49)	0.312	1 1.40 (0.88-2.23)	0.154	221 529	9.50 11.72	1 1.14 (0.87-1.49)	0.312	1 1.40 (0.88-2.23)	0.154
Current severe wheeze^e Female parent ever had Asthma No Yes	1866 43	0.96 0.0	1 2.34 (0.53-10-19)	0.256	1 2.40 (0.19-29.90)	0.494	603 36	1.16 5.55	1 2.34 (0.53-10-19)	0.256	1 2.40 (0.19-29.90)	0.494
Child used Analgesic/antibiotic in the past 12 months Never At least once a year At least once per month	355 617 1315	0.28 1.45 1.36	1 4.8 (0.61-37.98) 6.95 (0.94-51.42)	0.134 0.057	1 1.43 (0.33-6.09) -	0.624	85 300 351	0.0 0.33 0.02	1 4.8 (0.61-37.98) 6.95 (0.94-51.42)	0.134 0.057	1 1.43 (0.33-6.09) -	0.624
Dry cough at night apart from cough associated with cold or chest infection No Yes	1664 492	0.30 4.06	1 16.75 (6.90-40.64)	0.000	1 53.19 (7.64-370.0)	0.000	564 156	0.17 5.12	1 16.75 (6.90-40.64)	0.000	1 53.19 (7.64-370.0)	0.000
Truck traffic where your child lives on weekdays Never Seldom Frequently Almost all day	392 493 522 869	1.53 1.01 0.57 1.72	1 0.59 (0.19-1.77) 0.82 (0.29-2.28) 1.24 (0.51-3.00)	0.348 0.707 0.626	1 0.04 (0.00-0.57) 1.19 (0.20-7.09) 0.32 (0.05-1.84)	0.018 0.847 0.204	121 238 187 201	0.82 0.42 2.67 1.49	1 0.59 (0.19-1.77) 0.82 (0.29-2.28) 1.24 (0.51-3.00)	0.348 0.707 0.626	1 0.04 (0.00-0.57) 1.19 (0.20-7.09) 0.32 (0.05-1.84)	0.018 0.847 0.204
Male parent job industry Government sector Private sector Self-employed Not employed	153 505 189 473	0.65 1.18 1.05 2.11	1 1.96 (0.43-8.95) 1.56 (0.25-9.51) 2.66 (0.56-12.64)	0.381 0.625 0.217	1 3.07 (0.40-23-15) 1.84 (0.17-19.07) 0.23 (0.14-4.01)	0.276 0.606 0.319	126 282 80 61	0.79 1.77 1.25 0.0	1 1.96 (0.43-8.95) 1.56 (0.25-9.51) 2.66 (0.56-12.64)	0.381 0.625 0.217	1 3.07 (0.40-23-15) 1.84 (0.17-19.07) 0.23 (0.14-4.01)	0.276 0.606 0.319
Dog inside the house (past 12 months) No Yes	2119 209	1.13 2.39	1 2.60 (1.21-5.55)	0.014	1 2.62 (0.38-18.03)	0.326	642 116	0.93 3.44	1 2.60 (1.21-5.55)	0.014	1 2.62 (0.38-18.03)	0.326
Male parent smoke NoYes	1017 321	0.98 2.49	1 2.57 (1.15-5.70)	0.020	1 1.52 (0.28-8.11)	0.624	431 128	0.92 2.34	1 2.57 (1.15-5.70)	0.020	1 1.52 (0.28-8.11)	0.624
People living in the same house as your child smoke? Zero One or more	1515 628	0.99 2.22	1 2.23 (1.17-4.24)	0.014	1 2.58 (0.55-11.95)	0.225	513 199	0.97 2.01	1 2.23 (1.17-4.24)	0.014	1 2.58 (0.55-11.95)	0.225
Child exposure to smoking at the restaurant (past 30 days) Never One or more days	994 54	1.20 3.70	1 2.67 (0.77-9.21)	0.119	1 1.54 (0.10-21.38)	0.748	383 24	2.08 4.16	1 2.67 (0.77-9.21)	0.119	1 1.54 (0.10-21.38)	0.748
Child exposure to smoking at the car (past 30 days) Never One or more days	990 47	1.11 6.38	1 3.03 (0.87-10.50)	0.079	1 9.44 (0.86-102.93)	0.065	390 22	2.30 0.00	1 3.03 (0.87-10.50)	0.079	1 9.44 (0.86-102.93)	0.065
Child exposure to smoking at the home (past 30 days) Never One or more days	1406 295	1.20 1.69	1 1.13 (0.46-2.77)	0.783	1 0.33 (0.04-2.65)	0.302	523 100	1.72 1.00	1 1.13 (0.46-2.77)	0.783	1 0.33 (0.04-2.65)	0.302
Child exposure to smoking at the school (past 30 days) Never One or more days	1045 30	1.24 3.333	1 1.82 (0.23-13.95)	0.562	1 0.13 (0.00-6.36)	0.311	389 10	1.79 0.00	1 1.82 (0.23-13.95)	0.562	1 0.13 (0.00-6.36)	0.311
Child ever breastfed No Yes	742 1575	1.21 1.33	1 1.20 (0.60-2.42)	0.596	1 2.11 (0.35-12.251)	0.408	221 533	0.90 1.50	1 1.20 (0.60-2.42)	0.596	1 2.11 (0.35-12.251)	0.408
How does the child get to school^g Walk Taxi/bus Motor car Combination Other	1527 554 201 39 14	1.50 0.72 1.49 0.00 0.00	1 0.62 (0.27-1.45) 0.84 (0.32-2.23) 1.16 (0.15-8.87) -	0.276 0.738 0.883	1 0.46 (0.08-2.50) 0.31(0.05-1.87) 27.48 (1.47-511.9)	0.375 0.203 0.026	126 283 320 18 9	0.79 1.41 1.25 5.55 0.00	1 0.62 (0.27-1.45) 0.84 (0.32-2.23) 1.16 (0.15-8.87) -	0.276 0.738 0.883	1 0.46 (0.08-2.50) 0.31(0.05-1.87) 27.48 (1.47-511.9)	0.375 0.203 0.026
Asthma ever^f People living in the same house as your child smoke? Zero One or more	1364 558	1.31 2.32	1 175 (1.03-2.98)	0.036	1 2.49 (1.12-5.54)	0.024	479 184	3.54 5.97	1 175 (1.03-2.98)	0.036	1 2.49 (1.12-5.54)	0.024
Child exposure to smoking at the car (past 30 days) Never One or more days	915 45	1.85 0.00	1 0.56 (0.07-4.21)	0.577	1 0.58 (0.07-4.53)	0.605	371 21	4.31 4.76	1 0.56 (0.07-4.21)	0.577	1 0.58 (0.07-4.53)	0.605
Child ever breastfed No Yes	683 1393	1.75 1.86	1 1.22 (0.70-2.12)	0.465	1 1.13 (0.48-2.68)	0.769	212 485	2.83 4.32	1 1.22 (0.70-2.12)	0.465	1 1.13 (0.48-2.68)	0.769
Child used Analgesic/antibiotic in the past 12 monthsNever At least once a year At least once per month	314 557 1176	0.31 1.97 0.22	1 3.14 (0.71-13.85) 6.14 (1.48-25.42)	0.130 0.012	1 1.35 (0.14-12.40) 4.03 (0.53-30.7)	0.788 0.178	76 277 328	1.31 1.44 6.40	1 3.14 (0.71-13.85) 6.14 (1.48-25.42)	0.130 0.012	1 1.35 (0.14-12.40) 4.03 (0.53-30.7)	0.788 0.178
Truck traffic where your child lives on weekdays Never Seldom Frequently Almost all day	351 452 480 755	2.56 1.32 2.29 1.58	1 0.49 (0.22-1.07) 0.86 (0.43-1.72) 0.63 (0.32-1.26)	0.075 0.680 0.201	1 0.63 (0.18-2.15) 1.05 (0.34-3.24) 0.55 (0.163-1.89)	0.464 0.921 0.350	110 222 175 184	5.45 2.70 4.57 3.80	1 0.49 (0.22-1.07) 0.86 (0.43-1.72) 0.63 (0.32-1.26)	0.075 0.680 0.201	1 0.63 (0.18-2.15) 1.05 (0.34-3.24) 0.55 (0.163-1.89)	0.464 0.921 0.350
Cat inside the house (past 12 months) No Yes	1937 145	1.70 3.44	1 2.7 (1.44-5.25)	0.002	1 1.44 (0.38-5.34)	0.584	636 62	3.30 11.29	1 2.7 (1.44-5.25)	0.002	1 1.44 (0.38-5.34)	0.584
Female parent level of school completion Primary Secondary University Other	171 338 178 1321	3.50 1.47 2.24 1.66	1 0.54 (0.24-1.23) 1.03 (0.45-2.36) 0.54 (0.27-1.09)	0.146 0.930 0.090	1 1.06 (0.22-5.04) 1.16 (0.21-6.47) 1.48 (0.27-7.96)	0.936 0.858 0.647	149 185 101 224	4.69 3.24 6.93 2.67	1 0.54 (0.24-1.23) 1.03 (0.45-2.36) 0.54 (0.27-1.09)	0.146 0.930 0.090	1 1.06 (0.22-5.04) 1.16 (0.21-6.47) 1.48 (0.27-7.96)	0.936 0.858 0.647
Female parent ever had Asthma No Yes	1730 39	1.56 15.3	1 7.63 (3.72-15.66)	0.000	1 4.05 (1.25-13.15)	0.020	560 35	3.21 14.28	1 7.63 (3.72-15.66)	0.000	1 4.05 (1.25-13.15)	0.020

^aThe Totals for each risk factor are different due to difference in missing values. ^bThe Values that are statistically significant for the crude OR and less than 0.05 for the adjusted OR are highlighted. ^c,The Model was adjusted for: people living in the same house as your child smoke, child ever breastfed, use of analgesic/antibiotics, Truck traffic during weekdays, cat in the house, female parent education & female parent ever had asthma. ^dThe Model was adjusted for: female parent ever had asthma, use of analgesic/antibiotics, Truck traffic during weekdays, female parent job, dog in the house, female parent smoke, Child exposure to smoking in the restaurant & child ever breastfed. ^eThe Model was adjusted for: female parent ever had asthma, use of analgesic/antibiotics, dry cough at night, Truck traffic during weekdays, male parent job, dog in the house, male parent smoke, people living in the same house as your child smoke, Child exposure to smoking in the restaurant, Child exposure to smoking in the car/transport, child ever breastfed, How the child get to school, Child exposure to smoking at home, Child exposure to smoking at school. ^f The Model was adjusted for: people living in the same house as your child smoke, Child exposure to smoking in the car/transport, child ever breastfed, use of analgesic/antibiotics, Truck traffic during weekdays, Cat in the house, female parent education, female parent ever had asthma. ^g Combination includes motorcar and Taxi/bus: Other includes animal cart. -: variable contains !=0, which predicts failure perfectly. Therefore, were omitted and observations not used.

Table 4. Participants (combined Rural and Urban areas) prevalence of wheeze ever with their respective odds ratios.

Variable	Total^a	Prevalence (%)	Crude OR^b		Adjusted OR^b,c
			(95% CI)	P	(95% CI)	P
People living in the same house as your child smoke? Zero One or more	2011 817	13.60 18.60	1 1.44 (1.16-1.40)	0.001	1.37 (1.08-1.74)	0.009
Female parent smoke No Yes	2878 92	14.62 34.78	1 3.11 (2.00-4.83)	0.000	1 2.58 (1.57-4.23)	0.000
Sex of child Female Male	1512 1572	13.49 16.73	1 1.28 (1.05-1.57)	0.012	1 1.35 (1.08-1.70)	0.008
Child ever breastfed No Yes	957 2086	15.10 15.34	1 1.03 (0.83-1.27)	0.777	1 1.10 (0.86-1.40)	0.436
Child used Analgesic/antibiotic in the past 12 months Never At least once a year At least once per month	435 909 1650	5.28 14.41 18.24	1 3.01 (1.90-4.77)3.99 (2.57-6.19)	0.000 0.000	1 2.29 (1.41-3.71) 3.04 (1.92-4.81)	0.001 0.000
Truck traffic where your child lives on weekdays NeverSeldom Frequently Almost all day	509 729 704 1053	13.75 15.08 17.61 14.24	1 1.11 (0.80-1.54) 1.34 (0.97-1.84) 1.04 (0.76-1.41)	0.512 0.071 0.793	1 1.00 (0.69-1.45) 1.22 (0.85-1.75) 1.00 (0.71-1.42)	0.966 0.270 0.960
Cat in the house (past 12 months) No Yes	2830 220	17.18 21.36	1 1.58 (1.12-2.21)	0.008	1 1.83 (0.65-5.12)	0.246
Female parent level of school completion Secondary University Other Primary	1846 449 413 241	12.56 22.71 17.43 18.67	1 2.04 (1.57-2.65) 1.46 (1.10-1.96) 1.59 (1.12-2.27)	0.000 0.009 0.009	1.84 (1.36-2.49) 1.30 (0.94-1.80) 1.39 (0.90-2.16)	0.000 0.106 0.129
How does the child get to school^g Walk Taxi/bus Motor car Combination Other	1633 828 518 57 23	13.16 15.57 21.62 12.28 4.34	1 1.21 (0.96-1.54) 1.81 (1.41-2.34) 0.92 (0.41-2.06) 0.29 (0.04-2.23)	0.103 0.000 0.846 0.240	1 1.31 (1.00 -1.71) 1.74 (1.27-2.38) 1.07 (0.46-2.49) 0.32 (0.04-2.48)	0.048 0.000 0.863 0.279

^a The Totals for individual risk factors differ owing to the absence of values. ^b The statistically significant values for the crude OR and less than 0.05 for the adjusted OR are highlighted. ^c Model adjustments were made for all the variables in the table. 1: Unless declared in another manner, the referent category for individual risk factors is the lack of the risk factor.

Table 5. Participants (combined Rural and Urban areas) prevalence of current wheeze with their respective odds ratios.

Variables	Total^a	Prevalence (%)	Crude OR^b		Adjusted OR^b,c
			(95% CI)	P	(95% CI)	P
Female parent ever asthma No Yes	2453 79	8.35 26.58	1 3.97 (2.36-6.67)	0.000	1 5.59 (2.77-11.26)	0.000
Child used Analgesic/antibiotic in the past 12 months Never At least once a year At least once per month	440 906 1656	1.81 6.95 12.86	1 4.03 (1.91-8.49) 7.97 (3.90-16.27)	0.000 0.000	1 3.41 (1.17-9.95) 4.74 (1.68-13.40)	0.024 0.003
Truck traffic where your child lives on weekdays Never Seldom Frequently Almost all day	508 727 702 1064	8.66 8.80 11.82 8.74	1 1.01 (0.68-1.52) 1.41 (0.96-2.07) 1.01 (0.69-1.47)	0.931 0.078 0.958	1 1.04 (0.55-1.94) 1.13 (0.60-2.22) 0.86 (0.45-1.64)	0.902 0.695 0.653
Female parent job industry Private sector Government sector Self-employed Not employed	567 347 301 1721	8.28 12.96 9.96 9.18	1 1.64 (1.06-2.54) 1.22 (0.75-1.98) 1.11 (0.79-1.57)	0.024 0.409 0.519	1 1.38 (0.73-2.60) 1.18 (0.73-2.32) 0.69 (0.41-1.17)	0.317 0.629 0.177
Dog in the house (past 12 months) No Yes	2742 320	8.75 14.68	1 1.79 (1.28-2.51)	0.001	1 1.27 (0.70-2.32)	0.419
Female parent smoke No Yes	2884 93	9.01 23.65	1 3.12 (1.90-5.12)	0.000	1 0.65 (0.20-2.15)	0.488
People living in the same house as your child smoke? Zero One or more	2008 823	7.86 13.12	1 1.78 (1.36-2.29)	0.000	1 2.09 (1.38-3.16)	0.000
Child exposure to smoking at the car (past 30 days) Never One or more days	1368 69	9.50 11.59	1 2.37 (1.31-4.30)	0.004	1 2.27 (1.17-4.38)	0.014
Child ever breastfed No Yes	959 2090	8.65 8.65	1 1.15 (0.88-1.50)	0.293	1.40 (0.88-2.23)	0.154

Table 6. Participants (combined Rural and Urban areas) prevalence of current severe wheeze with their respective odds ratios.

Variable	Total^a	Prevalence (%)	Crude OR^b		Adjusted OR^b,c
			(95% CI)	P	(95% CI)	P
People living in the same house as your child smoke? Zero One or more	2028 827	0.98 2.17	1 2.23 (1.17-4.24)	0.014	1 2.46 (1.25-4.85)	0.009
Sex of child Female Male	1524 1592	0.78 1.75	1 2.25 (1.14-4.45)	0.019	1 2.30 (1.09-4.84)	0.027
Child plays with dogs/cats No Yes	2535 556	1.18 1.61	1 1.27 (0.64-2.91)	0.407	1 0.95 (0.41-2.22)	0.919
Child used Analgesic/antibiotic in the past 12 months Never At least once a year At least once per month	440 917 1666	0.22 1.09 1.56	1 4.84 (0.61-37.92) 6.95 (0.94-51-42)	0.133 0.057	1 4.34 (0.54-34.68) 6.14 (0.82-45-75)	0.166 0.077
Truck traffic where your child lives on weekdays Never Seldom Frequently Almost all day	513 731 709 1070	1.36 0.82 1.12 1.68	1 0.59 (0.19-1.79) 0.83 (0.29-2.28) 1.23 (0.51-2.98)	0.358 0.712 0.636	1 0.46 (0.14-1.48) 0.65 (0.23-1.85) 0.89 (0.35-2.23)	0.196 0.428 0.808
Child ever breastfed No Yes	964 2108	1.14 1.37	1 1.20 (0.60-2.42)	0.595	1 1.16 (0.55-2.45)	0.690
Female parent job industry Private sector Government sector Self-employed Not employed	571 349 303 1736	0.87 2.29 1.98 1.15	1 2.65 (0.86-8.18) 2.28 (0.69-7.55) 1.31 (0.49-3.53)	0.089 0.175 0.581	1 2.20 (0.68-7.08) 2.23 (0.66-7.47) 1.09 (0.39-3.00)	0.185 0.192 0.859

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Is There an Association between Environmental Tobacco Smoke Exposure and the Risk of Wheezing among Rural and Urban Preschool Children in Mpumalanga Province, South Africa?

Abstract

1. Introduction

2. Methods

2.1. Study Design and Settings

2.2. Study Population, Sample Size Estimation and Sampling Procedure

2.3. Study Tools

2.4. Health Outcomes of the Study

2.5. Environmental Tobacco Smoke Exposure

2.6. Confounders

2.7. Data Processing and Analysis

3. Results

Description of Study Participants

4. Discussion

5. Strength and Limitation of the Study

6. Conclusions

Author Contributions

Funding

Institutional Review Board Statement

Informed Consent Statement

Data Availability Statement

Acknowledgments

Conflicts of Interest

Abbreviations

References

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