Respiratory and asthma symptoms in the past 12 months among primary school children in the highly polluted area were reported at around 1 in 4. Running nose without cold was reported in the highest numbers, and shortness of breath was reported in the lowest numbers. Tenant status, living near garment and clothing shops, and living in the presence of cigarette smoke and incense smoke were indicated to be risk factors for respiratory and asthma symptoms among the primary school children in this study.
Our study evaluated the association between residential environment and respiratory symptoms in an urban area of Bangkok, where the concentration of air pollution was the highest. We found that around 11% of the children in our study had wheezing symptoms. This percentage was less than in Liu et al. (2014), which was 21.7% among children in urban Shanghai. Mathew et al. (2015) found rank between 12.7–17.7% among Delhi children. In addition, we found that dry cough at night (32.5%) and phlegm (43.3%), which was similar to Mathew et al. (2015) at 26.9% and 29.0%, respectively.
Most of the children in this study lived in flats, apartments, and condominiums (62.9%). The average length of residence was more than 30 years, which was consistent with our observation that most of the buildings in the study area were old, and there was a high density of both buildings and people. Nearly 30.0% of the children were living in single-family dwellings (16.6%) and townhouses (12.9%). They were also living in the same environment, which caused respiratory effects. They lived near a garment/clothing factory (24.3%), garage/car care facility (9.7%), furniture shop (5.9%), fresh market or restaurant (cooking smoke) (2.4%). Our study found that living near a garment/clothing factory increased the likelihood of having the symptom of shortness of breath in the children. Brender, Maantay, and Chakraborty (2011) showed that the effects of residential proximity to a source of air pollution were associated with asthma among children. However, residential proximity to environmental hazards serves as a crude proxy for exposure. It does not accurately represent the individual exposure to ambient conditions or the effects on the body or organs. The residential exposure to site contaminants also varies according to the climatic and topographic characteristics of the geographic area. Our findings showed that most of the participants were tenants (77.1%) rather than owners of their residences (22.9%), which was also positively associated with wheezing or whistling in the chest. A possible reason for this result could be that owners take better care of their houses compared with tenants. Moreover, house ownership may be related to better health outcomes because it could indicate higher income, wealth, better housing infrastructure, and healthier neighborhood conditions.
Children’s exposure to the poor quality of indoor air has been the most important concern (World Health Organization, 2015, 2017a). Our study found that children living in areas of cigarette and incense smoke were significantly associated with the symptoms of dry cough at night and shortness of breath, which was consistent with many previous studies. Salo et al. (2004) found the strongest associations (OR > 1, 95% CI) between smoking (cigarette smoke) at home and respiratory symptoms (i.e., cough and phlegm without colds among children). In addition, Chen et al. (2011) and Pirastu et al. (2009) found similar results, which showed that children exposed to tobacco smoke since infancy had an increased prevalence of current wheeze and asthma. More than 7,000 chemicals have been found in tobacco and cigarette smoke, which are chemically active and trigger profound and potentially fatal changes in the body (State of Victoria, 2018). The effects of these dangerous chemicals in cigarette smoke, such as tar, carbon monoxide, hydrogen cyanide, oxidizing chemicals, metals, and radioactive compounds, on human health are well known. They are ingested in the body by inhaling. Moreover, this study found that smoking by family members was a possible risk factor (AOR > 1) for the symptoms of dry cough at night, phlegm, and running nose without cold.
Incense smoke is usually found in the houses of Buddhist families who burn incense while they pray to Buddha. Although incense sticks are made from natural materials such as bamboo and wood, some chemical materials are added as oxidizers and binders. When an incense stick is burned, it becomes smoke and ash, which contain many particles and gas products, such as carbon monoxide (CO), carbon dioxide (CO2), nitrogen dioxide (NO2), and sulfur dioxide (SO2), as well as many organic compounds, such as benzene, toluene, xylenes, aldehydes, and polycyclic aromatic hydrocarbons (PAH), which can affect the human respiratory system (Torben Eggert & Ole Christian Hansen, 2004; Wang, Lee, Ho, & Kang, 2004). Wang et al. (2011) found an association between the frequency of burning incense at home and the increased risk of current asthma and wheezing during exercise, especially in genetically susceptible children.
The results of our study found that vectors (i.e., cockroach and rat) in the house increased the odds of the symptoms of a dry cough at night (p < 0.05) and phlegm (p < 0.05) among the children who participated in the study. Home renovations and flowers with pollen were positively associated with respiratory symptoms, but statistical significance was not achieved. Our findings regarding vectors were inconsistent with the findings of Chen et al. (2011), which showed an association between children who were exposed to cockroaches since infancy and asthma (OR = 2.16; 95% CI, 1.15–4.07), which supported the findings of Kim Le et al. (2005). However, vectors have been recognized as risk factors for allergy symptoms and respiratory symptoms, including asthma, particularly the presence of cockroaches in indoor dirt and decay in the residence, which produce the key allergens in inner-city homes (Partners Asthma Center, 2010). Furthermore, some of the worst asthma cases were found to have exposure to high concentrations of cockroach allergens in the residence, as well as the tendency to allergic reactions to cockroach allergens, which increased the severity of asthma (Do, Zhao, & Gao, 2016). In addition, a review study by Do et al. (2016) showed a significant association with asthma induced by cockroach allergens.
Many substances are produced during home construction, such as chemicals in paint, dust in roofing materials, and cement. Such substances can cause allergic reactions and respiratory symptoms (Claire Gagné 2010). Dong et al. (2014) also showed that home renovations in the previous two years were significantly associated with respiratory symptoms and asthma among children and could increase the prevalence of those symptoms. Although our findings were inconsistent with Dong et al., we found that home renovation was a potential risk factor for almost all respiratory and asthma symptoms in this study.
Wall dampness in the residence, flowers with pollen, and charcoal smoke were found to be possible risk factors for the symptoms in our study. These findings were inconsistent with other studies that found associations. For example, Chen et al. (2011), Nguyen et al. (2010), and Wang et al. (2014) found that wall dampness was associated with asthma. Dampness is known as a cause of mold growth, which is an allergen (Centers for Disease Control and Prevention (CDC), 2017) that causes respiratory and asthma symptoms. Furthermore, Erbas et al. (2013) found that asthma in children could be increased by persistent exposure to pollen during infancy. In addition, Bautista et al. (2009) found an increasing trend toward the risk of respiratory infection in young children when they were exposed to charcoal smoke (Bautista, Correa, Baumgartner, Breysse, & Matanoski, 2009). Salo et al. (2004) found the strongest associations (OR > 1, 95% CI) between coal burned for cooking in the home and wheezing among children. Charcoal smoke was produced by the incomplete burning of carbon-containing materials, which formed a mixture of particles and chemicals. Exposure to the mixture of these particles in smoke, such as CO, CO2, and particulate matter (PM), is dangerous for humans (New York State Department of Health, 2016).
The present study has several limitations. First, a self-reported questionnaire was used as the measurement tool, which may have led to information bias. Moreover, parents who live in worse residential environments may be more likely to overreport respiratory symptoms (Visness et al., 2019). In a future study, hospital-based records of respiratory and asthma disease should be considered. Asthma status and symptoms should be validated by physician diagnosis, medications, or emergency department visits to minimize self-reporting biases. Second, only two primary schools in the Din Daneng district, which is controlled by the Bangkok Metropolitan Administration, were selected. Therefore, the findings of this study cannot be generalized to other primary school children in urban areas. However, to the best of our knowledge, this is the first study to investigate the relationship between home environments and respiratory symptoms among a large sample size of primary school children in a highly polluted area in Bangkok, Thailand. Third, the respiratory and asthma symptoms in this study were considered over a long term (12 months), which may have led to recall bias. Fourth, our study did not collect samples of indoor air quality to confirm an association between air quality and health outcomes. However, our study included all significant predictors in residential environments of respiratory health in children. Finally, our study did not consider the sizes or processes of businesses near the children’s residences, including furniture shops, garment/clothing factories, and garage/car care facilities. Differences in factory processes may lead to different emissions. A future study should investigate the emissions from each type of factory and business.
The findings of our study showed that residential environments, including tenant status, garment/clothing shops near residence, cigarette smoke, and incense smoke, were positively and significantly associated with respiratory and asthma symptoms. Further interventions to improve residential environments and control housing quality should be considered to reduce respiratory and asthma symptoms among children in urban areas.