LAUSR

Background: There are few school environment studies from tropical countries. We studied associations between wheeze, current asthma and self-reported respiratory infections among students and formaldehyde, nitrogen dioxide (NO2) and volatile organic compounds (VOC) in schools in Malaysia. Methods: Totally 462 pupils from 8 randomly selected secondary schools in Johor Bahru, Malaysia, participated (96% participated). Formaldehyde, NO2 and VOC were measured by diffusion sampling during 1 week inside and outside the 32 classrooms. Carbon dioxide (CO2), an indicator of the ventilation in the classroom, was measured during class by a direct reading instrument. Multilevel logistic regression was applied. Results: Totally 10.3% had current wheeze, 9.3% current asthma (asthma medication or attacks of breathlessness), 18.8% respiratory infections in the past 3 months and 21.1% a history of pollen or furry pet allergy (atopy). Wheeze was associated with ethnicity (p=0.02; lower among Chinese), atopy (p=0.002) and current smoking (p=0.01) only. Current asthma was associated with ethnicity (p=0.001; lower among Indian) and the concentration of para-dichlorobenzene in classroom air (p=0.001). Current respiratory infections was associated with atopy (p=0.002) and the concentrations of ethylbenzene (p=0.03) and para-dichlorobenzene (p=0.01) in classroom air. There were no associations between CO2, NO2 or formaldehyde in classroom air and respiratory health. Conclusion: Para-dichlorobenzene in classroom air can be a risk factor for current asthma and respiratory infections among students in the tropical country Malaysia. Para-dichlorobenzene is commonly used indoors in Asia against insects. The aromatic compound ethylbenzene can be another risk factor for respiratory infections in the schools.