Residential proximity to agricultural pesticide use and incidence of breast cancer in the California Teachers Study cohort.
Level 3 - non-randomized controlled study
Prospective cohort study
PubMed 15325881 · doi:10.1016/j.envres.2004.03.001
What was done
The authors evaluated the relationship between residential proximity to agricultural pesticide applications and invasive breast cancer risk within the California Teachers Study cohort. Among 114,835 participants followed from 1995, 1,552 incident cases of invasive breast cancer were identified between 1996 and 1999. California Pesticide Use Reporting data and Geographic Information System (GIS) mapping were used to estimate pesticide applications within a 0.5-mile radius of each participant's residence. Pesticides were categorized by carcinogenic potential, mammary toxicity, and endocrine-disrupting properties. Cox proportional hazards models were adjusted for age, race, and socioeconomic status, with additional stratification by menopausal status and family history.
What was found
No association was observed between proximity to recent agricultural pesticide use and breast cancer incidence. Adjusted hazard ratios (HR) comparing the highest to lowest exposure categories were: - Probable or likely carcinogens: HR 1.07 (95% CI: 0.86–1.32) - Possible or suggestive carcinogens: HR 1.06 (95% CI: 0.87–1.29) - Mammary carcinogens: HR 1.15 (95% CI: 0.90–1.48) - Endocrine disruptors: HR 1.03 (95% CI: 0.86–1.25) Individual pesticide agents and other groupings also showed hazard ratios not differing from unity, with no dose-response trends. Stratification by menopausal status or family history did not substantially change results.
Why it matters
This study provides large-scale prospective data indicating that living near recent agricultural pesticide applications does not meaningfully increase short-term invasive breast cancer risk in adult women.
Limits
Exposure was estimated using a 0.5-mile geographic buffer around residential addresses rather than direct biomonitoring or indoor sampling, leading to possible exposure misclassification. The follow-up duration (1996–1999) was short, limiting the ability to capture long cancer latency windows or lifetime/early-life exposures. The cohort comprises female school employees, potentially limiting generalizability.
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.