The Impact of Pesticide Exposure on Breast Cancer Incidence: Evidence from Costa Rica, 1996-2000

Carolina Santamaria, University of Wisconsin at Madison

The low percentage of breast cancer (BC) cases related to reproductive history risk factors and to genetics suggests that the environment may play a role in BC etiology. Pesticide exposure has been hypothesized to have an important effect. This ecological study tests whether BC incidence in Costa Rica is related to pesticide exposure, after controlling for parity, socioeconomic status, age at first full-term pregnancy, and access to health care. Spatial analysis techniques were used to test for spatial autocorrelation and to rule out the heterogeneity of a possible relationship between BC and pesticides. Because of the time-lag between exposure and incidence, migration bias was also mitigated. Results suggest that there is a heterogeneous association between pesticides and BC, which is significant only in some rural agricultural areas of the country. Conclusions about causality can not be drawn from an ecologic approach, like the one taken in this study.