Poor air quality inside classrooms could play a role in the development of asthma and allergies in children, the results of a French study show.
Researchers found that pupils exposed to high levels of fine particles with aerodynamic diameter of 2.5 µm or less (PM2.5), nitrogen dioxide (NO2), and acrolein were more likely to have had asthma in the previous year than those exposed to low levels. Furthermore, high classroom levels of formaldehyde were associated with an increased probability for rhinoconjunctivitis.
"The alarming consequence of poor air quality in classrooms was a deterioration of respiratory health," say Isabella Annesi-Maesano (Université Pierre et Marie Curie, Paris, France) and colleagues.
The study included 6590 children aged 9‑10 years enrolled at 108 schools across six French cities. The researchers assessed the children using a questionnaire that their parents completed, a skin prick test for 10 common allergens, and a run test for exercise-induced asthma. Concentrations of air pollutants were taken from their classrooms, in most cases during the same week.
The authors, reporting in Thorax, found that nearly a third of schoolchildren were exposed to levels of PM2.5 and NO2 at concentrations greater than the upper thresholds proposed by the World Health Organization.
Overall, 6.9% of pupils had had asthma in the previous year, and 11.8% had had rhinoconjunctivitis.
Pupils exposed to high levels of PM2.5 had a 21% increase in the odds for having asthma in the past year. Similarly, the probability increased by 22% amongst those exposed to high levels of acrolein, compared with low exposures. When just allergic asthma was considered, high NO2 exposure also significantly increased the probability, by 40% compared with low exposure to NO2.
High formaldehyde exposure was also associated with an increased probability of rhinoconjunctivitis, where the odds for the allergy were 19% greater than with low levels of exposure.
The authors say that their study helps to fill a gap in data about the effects of indoor air pollution on respiratory health, particularly in children.
"This lack of data is in spite of the fact that there is growing concern about the school environment, where children spend up to eight hours a day," they say.
They also recommend further research in younger children to elucidate the role of indoor air pollutants in the development of asthma and allergies.
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