the parents of 375 children aged from 9-12 ( middle school course 1 and 2 ) from the polluted zone and 523 children of the same age in a neighboring zone which was not polluted have filled in standardised questionnaires ( respiratory symptoms , previous infections and allergies , frequency of infection in infancy ; tobacco habits , professional and educational attainments of the parents , domestic environment ) .
C0020517
allergies
C0040329
tobacco