Pesticide levels in blood associated with prostate cancer

Blood levels of three types of banned organochlorine pesticides are associated with prostate cancer in the general US population, researchers report in a recent study.

Researchers who analyzed data from a large, long-term national study found that levels of organochlorine pesticides in the blood are associated with a higher risk of prostate cancer. A link was not found for an increased risk of breast cancer.

The findings suggest that exposure to these chemicals represents a significant cancer health risk and that reducing exposures would be an important step in lowering that risk. Although the compounds are banned in some countries, they can persist in the environment, exposing people through food, air and water. In some countries, they are still heavily used to control mosquitoes.

Organochlorines – an example is DDT – are a class of compounds that were used as pesticides starting in the 1940s and were no longer on the market in the US by the 1990s. As a group, they resist breaking down, accumulate in the food chain and have known health effects. Some of them can mimic estrogen hormones, producing very mixed responses on reproduction, fertility, development and overall health.

The data for this study came from interviews conducted as part of the National Health and Nutrition Examination Survey (NHANES) study in 1999-2000, 2001-2002 and 2003-2004. Blood samples were collected from one-third of the original study participants for this investigation. The study sample included 4,237 people – 4,109 were free from cancer, 63 had breast cancer and 65 had prostate cancer. The statistical models used were adjusted for other factors that could influence the risk of prostate cancer.

The authors examined the association between levels of the pesticides in the blood and prostrate and breast cancer. They report an association between prostate cancer and serum levels of three specific pesticides: Beta-HCH, trans-nonachlor and dieldrin.

Prior epidemiology and occupational studies had mixed results: some found associations between exposure and the hormonally-related prostate and breast cancers while others did not. The results of the current study support those that did find an association. It adds stronger evidence of a link because of its large sample size, its four-year data gathering period and its representation of exposure levels in the general US population.