Does working with pesticides increase your risk of cancer?

Multiple types of cancer have been linked to pesticide exposure in research. These are associations, not proven causal relationships, but the patterns are consistent enough to take seriously. The risks are strongest for people who are occupationally exposed: agricultural and industrial workers who spray without protection.

Bladder cancer shows the most concrete figure: people with high exposure had, on average, a 65% greater chance of developing bladder cancer than people with little or no exposure. For colon and rectal cancer the risk increases are lower, but still measurable: herbicides were associated with roughly 20 to 30% greater risk of colon cancer, and insecticides with 20 to 85% greater risk of rectal cancer, depending on how exposure was measured. Blood cancers such as leukemia and lymphoma, and cancers of the prostate, pancreas, and liver, are also linked to pesticides in the epidemiological literature.

For breast cancer in women, an elevated risk exists with direct, repeated exposure, such as spraying in the field or prolonged unprotected household use. Young women and women who entered puberty early appear to be more susceptible. One possible explanation is that some pesticides mimic the action of estrogen. In men, no link with breast cancer has been found.

A particularly vulnerable group is unborn children: mothers who are exposed during pregnancy, at home or at work, have a greater chance of having a child who later develops leukemia. The odds ratios across multiple meta-analyses range around 1.2 to 1.6, corresponding to 20 to 60% greater risk. For the insecticide permethrin specifically, results for most cancer types are not elevated in humans, although the studies on this are limited. For bile duct cancer, one study found no clear association, but that research was too limited to draw firm conclusions. Avoiding unprotected and prolonged contact with pesticides is sensible, especially during pregnancy.