Indoor air pollution and childhood asthma: variations between urban and rural areas.

UNLABELLED: Health effects of indoor pollution have been investigated overall in urban areas. To compare the potential effect of home air pollutants on asthma in urban and rural houses, two case-control populations, composed of children living in the city (32 asthmatics and 31 controls) and in the countryside (24 asthmatics and 27 controls) were included. During 1 week, nitrogen dioxide, fine particles, and volatile organic compounds (formaldehyde, acetaldehyde, benzene, toluene, ethylbenzene, and xylenes) were assessed at home. Urban dwellings were found to be more polluted than rural ones, with concentrations up to two times higher. In the whole population, exposure to acetaldehyde and toluene was significantly associated with a higher risk of asthma. In the urban population, the association with toluene was significant in children studied during winter, and with toluene, xylenes, and ethylbenzene when cases were restricted to current asthmatics. In rural settings, a relationship between asthma and formaldehyde exposure was observed (OR = 10.7; 95% CI 1.69-67.61). Our findings suggest that daily continuous exposures to pollutants may be implicated in asthma, even in the case of low exposure, as those found in rural areas. Our results could also indicate a specific effect of indoor pollution in the rural environment. PRACTICAL IMPLICATIONS: Everyday exposure to indoor pollution was associated with a higher risk of childhood asthma. These findings suggest that even at low concentrations, pollutants could be implicated in asthma and reinforce the importance of establishing guideline values to improve indoor air quality by limiting sources or by optimizing ventilation. Specific effects could occur in rural environments where pollution differs from urban area.