Background: Household pesticide use has been associated with higher risk for several childhood malignancies, but few studies have evaluated risks associated with residential proximity to agricultural pesticide use. We conducted a population-based case-control study of early childhood cancer (age 0-4 years) among California children born between 1990 and 1997 and mother's residential proximity to agricultural applications of pesticides at the time of the child's birth.
Methods: Included in the study were 2189 case children and 4335 controls matched for birth date and sex. We estimated the in utero exposure potential from specific chemicals and chemical groups used in the 9 months before birth within a half mile of the maternal residence. We computed odds ratios (ORs) using conditional logistic regression.
Results: No striking patterns emerged. There were modestly elevated ORs for leukemias associated with probable and possible carcinogen use, and with nearby agricultural applications of organochlorines and organophosphates during pregnancy. Two commonly used pesticides were associated with higher leukemia risk when comparing the highest and lowest categories: metam sodium (OR=2.05; 95% confidence interval=1.01-4.17) and dicofol (1.83; 1.05-3.22).
Conclusions: The few elevated risk associations in this study are consistent with chance, given the large number of comparisons, but they may deserve more careful consideration. Future studies that integrate specific temporal and spatial exposure potential for targeted pesticides will be important in further evaluating risks associated with childhood cancer.