Researchers have identified 22 pesticides that are consistently linked to the incidence of prostate cancer in the United States, with four of the pesticides also linked to prostate cancer mortality. The results will be published in Cancer.

To assess the county-level associations of 295 pesticides with prostate cancer in various counties in the United States, researchers conducted an environmental-wide association study, using a lag time between exposure and prostate cancer incidence of 10–18 years to account for the slow-growing nature of the disease most prostate cancers. The years 1997–2001 were examined for pesticide use and 2011–2015 for prostate cancer outcomes. Similarly, the years 2002–2006 were analyzed for pesticide use and 2016–2020 for outcomes.

Among the 22 pesticides that showed a consistent direct association with prostate cancer incidence in both time-based analyses, there were three that have previously been linked to prostate cancer, including 2,4D, one of the most commonly used pesticides in the United States. The 19 possible pesticides not previously linked to prostate cancer included 10 herbicides, several fungicides and insecticides, and a soil fumigant.

Four pesticides that were associated with prostate cancer incidence were also associated with prostate cancer mortality: three herbicides (trifluralin, cloransulam-methyl, and diflufenzopyr) and one insecticide (thiamethoxam). Only trifluralin is classified by the Environmental Protection Agency as “possibly carcinogenic to humans,” while the other three are considered “probably not carcinogenic” or have been shown to be “not carcinogenic.”

“This research shows the importance of studying environmental exposures such as pesticide use to potentially explain some of the geographic differences we see in prostate cancer incidence and deaths across the United States,” said lead author Simon John Christoph Soerensen, MD, from Stanford University School of Medicine.

“By building on these findings, we can advance our efforts to identify risk factors for prostate cancer and work toward reducing the number of men affected by this disease.”