Asthma symptoms and respiratory infections in Malaysian students-associations with ethnicity and chemical exposure at home and school

Little is known on respiratory effects of indoor chemicals in the tropics. We investigated associations between asthma and respiratory infections in Malaysian students and chemical exposure at home and at school. Moreover, we investigated differences in home environment between the three main ethnic groups in Malaysia (Malay, Chinese, Indian). Totally, 462 students from 8 junior high schools in Johor Bahru participated (96% participation rate). The students answered a questionnaire on health and home environment. Climate, carbon dioxide (CO2), volatile organic compounds (VOC), formaldehyde and nitrogen dioxide (NO2) were measured inside and outside the schools. Multilevel logistic regression was applied to study associations between exposure and health. Totally 4.8% were smokers, 10.3% had wheeze, 9.3% current asthma, and had 18.8% any respiratory infection in the past 3 months. Malay students had more dampness or mould (p < 0.001), more environmental tobacco smoke (ETS) (p < 0.001) and more cats (p < 0.001) at home as compared to Chinese or Indian students. Wheeze was associated with ethnicity (p = 0.02; lower in Indian), atopy (p = 0.002), current smoking (p = 0.02) and recent indoor painting at home (p = 0.03). Current asthma was associated with ethnicity (p = 0.001; lower in Chinese) and para-dichlorobenzene in classroom air (p = 0.008). Respiratory infections were related to atopy (p = 0.002), ethylbenzene (p = 0.02) and para-dichlorobenzene (p = 0.01) in classroom air. Para-dichlorobenzene is used in Asia against insects. In conclusion, chemical emissions from recent indoor painting at home can increase the risk of wheeze. In schools, para-dichlorobenzene can increase the risk of current asthma and respiratory infections while ethylbenzene can increase the risk of respiratory infections.