Comparability of data obtained from farmers and surrogate respondents on use of agricultural pesticides.

Information from surrogates is increasingly being used in case-control studies to evaluate cancer risks from pesticides; however, little is known about the quality of this type of information. To address this concern, the authors compared interview data collected in 1987 from 95 male Iowa farmers and their wives or other surrogates on the use of specific agricultural pesticides. Agreement between direct and surrogate interviews was excellent (83-100%) for responses to dichotomous (yes/no) questions regarding past agricultural use of specific pesticides. Although there were more discrepancies for detailed questions (e.g., the number of days per year on which each pesticide was handled), responses from spouses appear to be adequate for epidemiologic studies of pesticides and cancer.