Do pesticides cause childhood cancer?

Epidemiological studies have reported associations between childhood cancer and either parental or child exposure to pesticides. Reviews have been published in 1997 and 1998, where the evidence was found suggestive but not conclusive. An update of the current state of knowledge is warranted.

A literature search has been conducted to identify and evaluate new research results on this topic issued between 1998 and 2004.

Eighteen new studies have been identified for this review. Collectively, the studies suggest an increase in the risk of different cancer types associated with exposure to pesticides. However, the evidence is conflicting with regard to cancer types as well as to causative factors across studies. The major shortcomings concern exposure assessment, where, e.g., "farming" is treated equal to "exposure to pesticides," disregarding other possible exposures, e.g., to biological or infectious agents, and hitherto unidentified lifestyle factors. Also, many exposure questionnaires used in case-control studies are based on broad and sometimes implausible categories. In most studies exposures were categorized as "ever vs. never," with no regard for exposure intensity or duration.

The available literature does not allow firm conclusions with regard to pesticides and any type of childhood cancer. Investing in the acquisition and critical review of exposure information appears to be the crucial step for causal assessment in future research. However, focusing on the presence of pesticides, and not asking the question why they were used, might mask relevant associations to other causative agents.