In an important new study, researchers identified 22 pesticides connected to an increased risk of prostate cancer in the United States, four of which were also associated with higher prostate cancer mortality rates. The American Cancer Society's peer-reviewed magazine CANCER published the study, which analysed county-level data from the United States to investigate the potential contribution of certain pesticide exposures to prostate cancer outcomes. This study examines the potential impact of environmental factors on prostate cancer, which is one of the most common tumours among men in the United States.

Researchers from Stanford University School of Medicine investigated the links between 295 pesticides and prostate cancer prevalence in areas across the United States. The researchers used an "environment-wide association study" approach to detect associations between pesticide use and cancer outcomes, with a 10- to 18-year lag period to account for prostate cancer's slow progression. We collected data over two time periods: pesticide use from 1997 to 2001 and the prostate cancer outcomes from 2011 to 2015, and pesticide use from 2002 to 2006 and cancer outcomes from 2016 to 2020.

"This research demonstrates the importance of studying environmental exposures, such as pesticide use, to potentially explain some of the geographic variations we observe in prostate cancer incidence and deaths across the United States," said lead author Dr Simon John Christoph Soerensen of Stanford University. "By building on these findings, we can advance our efforts to pinpoint risk factors for prostate cancer and work toward reducing the number of men affected by this disease."

2,4-D, a common herbicide in the United States, was one of the 22 chemicals with consistent ties to prostate cancer. The study also uncovered 19 pesticides, including 10 herbicides, several fungicides and insecticides, and a soil fumigant, which was not previously associated with prostate cancer, thereby shedding new light on potential carcinogens in agricultural and residential settings.

Research has linked four pesticides to prostate cancer incidence and mortality, a particularly concerning finding. These include three herbicides (trifluralin, cloransulam-methyl, and diflufenzopyr) and one insecticide (thiamethoxam). Notably, the Environmental Protection Agency (EPA) classifies trifluralin as a "possible human carcinogen," whereas the other three pesticides are deemed "not likely to be carcinogenic" or have data indicating "non-carcinogenicity."

The findings raise serious concerns about the potential health dangers linked with some of the country's most widely used pesticides, highlighting the need for additional research into environmental contributors to cancer risk. Prostate cancer disproportionately affects older men and has a slow growth rate, making it crucial to understand long-term environmental effects.

Researchers believe these data could inform future restrictions and preventative measures for communities with significant pesticide exposure, particularly in agricultural areas. With pesticide use so prevalent, the study highlights the potential need for re-evaluating EPA classifications and tightening safety measures for handling these chemicals.

The study emphasizes that understanding geographical variations in prostate cancer incidence and prognosis may open up new possibilities for preventative healthcare and public policy. While further research is needed to completely determine causal linkages, this study highlights the potential impact of environmental factors on cancer risk and the need to address such hazards to enhance public health outcomes in the United States.