Comparison of assessment methods for pesticide exposure in a case-control interview study

In epidemiologic studies, much of the variation in disease risk estimates a ssociated with occupational pesticide exposure may be due to variation in e xposure classification. The authors compared five different methods of usin g interview information to assess occupational pesticide exposure in a US-C anada case-control study of neuroblastoma (1992-1994). For each method, exp osure assignment was compared with that of a reference method, and neurobla stoma effect estimates were calculated. Compared with the reference method, which included a complete review of occupation, industry, job tasks, and e xposure-specific activities, the use of occupation-industry groups alone or in combination with general job task information diluted the exposed group by including individuals who were unlikely to have been truly exposed. The effect estimates representing associations between each exposure method an d neuroblastoma were different enough to influence the study's conclusions, especially when the exposure was rare (for maternal occupational pesticide exposure, the odds ratio was 0.7 using the reference exposure assessment m ethod and 3.2 using the occupation-industry group exposure assessment metho d). Exposure-specific questions about work activities can help investigator s distinguish truly exposed individuals from those who report exposure but are unlikely to have been exposed above background levels and from those wh o have not been exposed but are misclassified as exposed because of their e mployment in an occupation-industry group determined a priori to be exposed .