Respiratory and asthma symptoms in the past 12months 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. Wall dampness, present of vectors, living near garment and clothing shops were indicated to be risk factors for respiratory and asthma symptoms among the primary school children in this study, while age and gender of children could modify the associations.
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. The prevalence of respiratory symptoms in our study was lower than a study of Liu et al.15 in urban Shanghai which was 21.7% and a study of Mathew et al.16 in Delhi which found rank between 12.717.7%. In addition, a majority of reported respiratory symptoms in our study was dry cough at night (32.5%) and phlegm (43.3%) which was accordance with a study of Mathew et al.16 in Delhi.
Home dampness-related exposure is a risk for childhood respiratory diseases17. In our study, present of wall dampness in the residence was associated with parent reported asthma and shortness of breath among their children. Our finding was consistent with several studies10,18. Dampness is known as a cause of mold growth which was a trigger allergen19. Sun et al.17 conducted a study between the dampness-exposure indices and childhood respiratory and allergic diseases and found that the dampness indices had exposureresponse relationships with childhood respiratory and allergic diseases. The possible mechanism is that microbes and mycotoxins produced irritative and volatile organic compounds which may induce IgE-mediated hypersensitivity of the respiratory tract11.
Residential proximity to a source of air pollution including garment and clothing factory was associated with shortness of breath among children in our finding. However, the proximity to source of pollution was a parent reported. Garment and clothing factory in the city can be a source of air pollutants including microplastics (MPs). The synthetic fabric from clothing is recognize as a source of MPs besided tire erosion (especially from automobiles and trucks), household objects, waste incineration, and building materials20. A garment may release approximately 1900 fibres per wash21. Beside, cutting and grinding processes for polymeric materials can contribute to the formation and release of these particles in the air22. Therefore, living near the garment factory in inner city may unintentionally expose to the MPs. The relationship between MPs exposure and respiratory effects is still unclear. The possible mechanism is that fibres can be deposited in terminal bronchioles, alveolar ducts, and alveoli which are contributed to chronic inflammation, granulomas or fibrosis23.
Exposure to vectors including 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. Vectors were recognized as risk factors for allergy symptoms and respiratory symptoms, including asthma in children. The presence of cockroaches in indoor dirt and decay in the residence was the key allergens in inner-city homes24. A possible mechanism could be cockroaches contain proteolytic digestive enzymes, which directly induce bronchial inflammation25 and associated with cockroach-specific IgE which is a critical factor in lowering pulmonary function26. The worst asthma cases were related to high concentrations of cockroach allergens in the residence, and the tendency to allergic reactions to cockroach allergens, which increased the severity of asthma27.
Type of residence and house owner status are the possible predictors of health status among children. Majority of children were living in flats, apartments, and condominiums with the length of residence was more than 30years. Most of parent also reported that their house was tenant. The results could suggested that being house 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.
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 symptoms28. 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 (12months), which may have led to recall bias. Fourth, our study did not collect samples of residential and school 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 childrens 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.