Occupational Pesticide Use is Associated with Increased Risk of Lung Cancer

Written by Angeline A. De Leon, Staff Writer. Increased exposure to pesticide use is associated with an increased risk of lung cancer incidence among pesticide applicators in Iowa and North Carolina.

In both the U.S., as well as globally, the leading cause of cancer-related death is lung cancer ^1,2. Despite the fact that lung cancer incidence is lower in American farmers relative to the general population ³, there is evidence of increased lung cancer mortality among licensed pesticide applicators, ⁴ suggesting that lung cancer risk may be specifically associated with certain types of pesticides, but not others. Previous epidemiological studies have reported that, out of 50 pesticides examined, only seven types of pesticides (dicamba, metolachlor, pendimethalin, carbofuran, chlorpyrifos, diazinon, and dieldrin) showed positive associations with lung cancer incidence ⁵. Emerging evidence from pesticide-specific analyses indicate, for example, that lung cancer incidence among pesticide applicators is highest in those with greatest lifetime exposure to diazinon, but that any exposure to another pesticide, metolachlor, had no effect whatsoever ^6,7. As part of an effort to determine why occupational pesticide use is linked to lung cancer in some epidemiological studies, but not others, researchers involved in the Agricultural Health Study examined the relationship between lifetime use of various pesticides and incidence of lung cancer in a cohort of pesticide applicators.

In a prospective cohort study, a total of 57,310 restricted-use pesticide applicators residing in Iowa and North Carolina completed self-administered questionnaires evaluating the extent of their involvement in mixing or applying 50 specific pesticides (measuring lifetime exposure-days, exposure intensity, use of personal protective equipment, etc.). After a 10-year additional follow-up period, incident lung cancer cases were ascertained via linkage with state mortality files and the National Death Index.

A total of 654 lung cancer cases were documented. After adjusting for smoking, sex, and lifetime days of any pesticide use, analyses indicated that increased risk of lung cancer was associated with greater exposure (higher number of lifetime exposure days) to pendimethalin (Hazard Ratio = 1.50, 95% Confidence Interval: 0.98 to 2.31), dieldrin (HR = 1.93, 95% CI: 0.70 to 5.30), and chlorimuron ethyl (1.74, 95% CI: 1.02 to 2.96). HR’s for intensity-weighted lifetime days of pesticide use followed a similar trend for all three pesticides (pendimethalin = 1.47, 95% CI: 0.93 to 2.31; dieldrin = 2.06; 95% CI: 0.95 to 4.43; chlorimuron ethyl = 1.69, 95: 1.00 to 2.83). Parathion showed an exposure-response trend that was statistically significant for intensity-weighted lifetime days (p = 0.049), but only borderline for lifetime days (p = 0.073). None of the other pesticides examined in the study showed an association with lung cancer incidence.

Study findings provide additional evidence linking lung cancer risk to occupational pesticide exposure, specifically in relation to pendimethalin, dieldrin, parathion, and chlorimuron ethyl. Pesticide-specific analyses contribute to better discrimination of the genotoxic effects of different classes and/or mixtures of pesticides, however, further studies are needed to determine the impact of occupational pesticide exposure on clinical risk of other cancers and diseases.

Source: Bonner MR, Freeman LEB, Hoppin JA, et al. Occupational exposure to pesticides and incidence of lung cancer in the agricultural health study. Environ Health Perspect. 2017; 125(4): 544-551. DOI: 10.1289/EHP456.

EHP is an open access, free publication of the U.S. Federal Government, and its content lies in the public domain.

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Posted August 2, 2018.

Angeline A. De Leon, MA, graduated from the University of Illinois at Urbana-Champaign in 2010, completing a bachelor’s degree in psychology, with a concentration in neuroscience. She received her master’s degree from The Ohio State University in 2013, where she studied clinical neuroscience within an integrative health program. Her specialized area of research involves the complementary use of neuroimaging and neuropsychology-based methodologies to examine how lifestyle factors, such as physical activity and meditation, can influence brain plasticity and enhance overall connectivity.

References:

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