Agricultural Pesticides and Lymphoproliferative Childhood Cancer in California

Objectives: This study evaluated whether the rates of lymphoproliferative malignancies among children are elevated in areas of intensive agricultural pesticide use in the state of California in the United States.

Methods: The study included all newly diagnosed, statewide cases of childhood lymphoma and acute lymphoblastic leukemia in 1988-1994 among children aged <15 years. Of the 2642 cases (over 6.6 million children in California and 46 million child-years of observation) during this period, 2570 (97.3%) could be successfully geocoded for the analyses. An a priori classification of the >850 chemical agents reported in use during the study was developed by assigning the agents to eight chemical groupings of interest and identifying seven individual high-use agents with high potential toxicity. Rate ratios for neighborhood (block group) levels of pesticide use were estimated with a Poisson regression and adjustment for age, race and ethnicity, and gender.

Results: The rates of childhood lymphoma and leukemia were not generally higher in high pesticide-use areas. Those of Hodgkin's disease, although based on small numbers (N=258), were slightly elevated in the areas with the highest use of several pesticide groupings.

Conclusions: The generally null results in this study systematically examining the risk relationships for residential proximity to agricultural pesticide use stand in contrast to existing epidemiologic literature suggesting elevated childhood cancer risks from reported household pesticide use. These differences may be due to different chemical agents or to differences in indoor versus outdoor exposure potential or both. Future studies should use refined methods that better characterize the exposure potential for children to these agents.