Endocrine-disrupting pesticides and breast cancer incidence in the United States: an ecological analysis.
Level 4 - case-series / case-control
Ecological population-level observational study
PubMed 42223742 · doi:10.1007/s10552-026-02188-3
What was done
An ecological study evaluated data across 2,457 U.S. counties to determine whether county-level agricultural usage of 38 endocrine-disrupting pesticides (across eight chemical classes) between 2001 and 2015 was associated with age-adjusted breast cancer incidence rates from 2016 to 2020. Gamma regression models with a log-link function estimated rate ratios (RR) per interquartile range (IQR) increase in pesticide use, adjusting for county-level poverty, smoking, unemployment, education, health insurance status, and residential mobility, stratified by rural-urban continuum status.
What was found
Total median pesticide use was higher in rural counties than urban counties (17,523 kg vs. 14,743 kg; p < 0.05). In adjusted models, higher total pesticide use was associated with a small increase in breast cancer incidence in rural counties (RR = 1.02, 95% CI: 1.01 to 1.03), while no association was detected in urban counties (RR = 1.00, 95% CI: 1.00 to 1.00; p for interaction < 0.001). The abstract noted that associations varied by specific pesticide type, but numerical values for individual chemicals were not reported.
Why it matters
The study identifies a slight population-level signal linking agricultural endocrine-disrupting pesticide application to higher breast cancer rates in rural communities, suggesting potential environmental risk factors that warrant individual-level epidemiological evaluation.
Limits
The ecological design relies on county-wide aggregated estimates rather than individual pesticide exposures, creating vulnerability to ecological fallacy. The analysis could not adjust for individual-level reproductive risk factors, genetic susceptibility, or specific occupational handling. The observed effect size in rural areas was very modest (a 2% increase per IQR), and detailed risk estimates for specific chemical classes were omitted from the abstract.
Cited by
- context The highest rates of endocrine disruptors and pesticide exposures occur in rural crop-spraying areas, creating significant cancer and endocrine disruption risks.