Nitrogen dioxide exposure assessment and cough among preschool children

The association between exposure to ambient air nitrogen dioxide and cough was evaluated in a panel study among 162 children aged 3-6 y. The weekly av erage nitrogen dioxide exposure was assessed with Palmes-tube measurements in three ways: (1) personally, (2) outside day-care centers, and (3) inside day-care centers. Ambient air nitrogen dioxide concentrations were obtaine d from the local network that monitored air quality. The parents recorded c ough episodes daily in a diary. The risk of cough increased significantly ( relative risk = 3.63; 95% confidence interval = 1.41, 9.30) in the highest personal nitrogen dioxide exposure category in winter, and a nonsignificant positive trend was noted for the other assessment groups. In spring, risk increased nonsignificantly in all exposure-assessment groups, except for th e fixed-site monitoring assessment. It is important that investigators sele ct an exposure-assessment method sufficiently accurate to reflect the effec tive pollutant dose in subjects.