In a recent study published in Frontiers in Cancer Control and Society, researchers comprehensively evaluated the impact of pesticide use on cancer development in the United States (US).

Background

Pesticides are necessary for animal and plant control but can adversely impact agricultural and domestic life. Studies link pesticide exposure to various health problems, including neurological diseases, an elevated risk of cancer, and impaired immunological function. Pesticides such as glyphosate, malathion, parathion, tetrachlorvinphos, and diazinon are carcinogenic, particularly in animal models.

The Agricultural Health Study (AHS), which included 89,000 farmers, showed associations between pesticides and prostate, lung, pancreatic, colon, multiple myeloma, and leukemia. Thus, it warrants a thorough evaluation of cancer risk from a population health standpoint in the US.

About the study

In the present population-level study, researchers determined pesticide use-related cancer risk.

The researchers linked datasets based on county-level Federal Information Processing Standard (FIPS) codes. They used an eight-class latent-class analysis (LCA) to determine pesticide usage patterns, modeled against research factors such as county-level smoking rates, agricultural land use, and socioeconomic vulnerability. They translated individual pesticide consumption statistics into national-scale quartiles.

The researchers evaluated the impact of pesticide usage on the incidence of colon, bladder, lung, and pancreatic cancers, leukemia, and non-Hodgkin lymphoma. They received agricultural pesticide usage statistics and harvested acres from the US Geological Survey (USGS) and stratified them by chemical, state, and county FIPS codes, year, and kilogram amount.

The researchers obtained cancer incidences by county among every 100,000 individuals from the Centers for Disease Control and Prevention (CDC) State Cancer Profiles and National Institutes of Health (NIH) databases from 2015 to 2019. They used the Social Vulnerability Index (SVI) to compare sociodemographic disparities across counties. They assessed agricultural land usage using the US Department of Agriculture (USDA) data and the total population using the US Census Bureau’s American Community Survey (ACS) 2019 data.

The researchers used generalized linear models to assess the effect of agricultural usage patterns on cancer risk. They acquired county usage estimates by modeling investigations that produced high- and low-bound estimates; the low-bound estimate was the most conservative. They evaluated model performance using metrics such as log-likelihood, Bayesian and Akaike’s information criteria, the modified Bayesian criterion, and the consistent Akaike’s criterion. They also computed the number of new cancer cases caused by changes in pesticide usage each year.

Results

The study included data from 3,143 US counties and 69 agricultural chemicals. The researchers noted positive associations between pesticide use and increased rates of non-Hodgkin’s lymphoma, leukemia, colon, bladder, pancreatic, and lung cancer. The findings indicated that pesticide usage poses a cancer risk equivalent to tobacco smoking.

The study finds that particular pesticides, such as atrazine, Boscalid, dimethomorph, Dicamba, Dimethenamid, Dinotefuran, Glyphosate, Imazethapyr, and metolachlor, are primary contributors in areas with a high incidence of all malignancies and colon cancers. Dimethomorph is present in places with high risks of non-Hodgkin lymphoma and leukemia, as well as low-risk areas for lung cancer.

Dimethenamid is present in low-risk bladder cancers but only in conjunction with dimethenamid-P in high-risk pancreatic cancers. Dinotefuran is particularly effective in areas with high rates of leukemia, non-Hodgkin lymphoma, and colon cancer.

Bladder cancer, leukemia, and non-Hodgkin’s lymphoma were associated with sociodemographic vulnerability. Land use was relevant to all malignancies and lung cancers. There was no association between the overall population and any kind of cancer. The pattern-pattern-specific calculations revealed that no one pattern consistently has the highest or lowest increased cancer risk.

Pesticide use primarily affected the Midwest, with the Great Plains used as a reference for cancers due to their lowest increased risk. The annual increase in cancer cases between the reference and highest-added-risk locations is 154,541, with a median rate of 449 cases among every 100,000 individuals for all cancers.

Pesticides significantly increased non-Hodgkin’s lymphoma cases by 154% compared to smoking, while all malignancies, bladder cancers, and leukemia showed modest elevations of 19%, 19%, and 21%, respectively. Smoking significantly elevates cancer incidence, with pancreatic cancer accounting for 3.40% more cases than before, followed by cancers of the colon at 73% and of the lung at 325%.

Implications

The study found that agricultural pesticide use has a similar cancer risk to tobacco smoking for a variety of malignancies, particularly in places with high agricultural output. The findings underscore the importance of comprehensive assessments of pesticide hazards, considering sociodemographic factors, and prioritizing public health activities.

Certain pesticide combinations may have a more robust link with cancer incidence rates, emphasizing the need for human health services to exercise caution in preserving public safety. Authorities must evaluate property values based on proximity to pesticide usage, and public awareness of increased pesticide levels or dangerous pesticides should rise.