New ventilation systems at select schools in Sweden - Effects on asthma and exposure

The air-exchange rate is often low in schools. The authors studied the poss ible impact of improving school ventilation on health and exposure of pupil s. Questionnaire data on allergies, asthma, and asthmatic symptoms were obt ained in 1993 and 1995 for 1,476 primary- and secondary-school pupils in 39 randomly selected schools. Various exposure factors were measured in 1993 and 1995 in approximately 100 classrooms. In 12% of the classrooms, new ven tilation systems were installed between 1993 and 1995; the subsequent air-e xchange rate increased and the relative humidity and concentration of sever al airborne pollutants were reduced compared with classrooms in nonimproved buildings. The reporting of at least one asthmatic symptom and the reporti ng of more asthmatic symptoms in 1995 than in 1993 were less common among t he 143 pupils who attended schools with new ventilation systems.