Residential proximity to agricultural pesticide use and incidence of breast cancer in the California Teachers Study cohort

Robert B. Gunier,William E. Wright,Ronald K. Ross,Andrew Hertz,Peggy Reynolds,Susan E. Hurley,Leslie Bernstein,Pamela L. Horn-Ross,Argyrios Ziogas,Hoda Anton-Culver,Dennis Deapen,Dee West,Sauda Yerabati,Debbie E. Goldberg,Richard Pinder,David Peel

doi:10.1016/j.envres.2004.03.001

Abstract

We examined the association between residential proximity to agricultural pesticide use and breast cancer incidence among members of the California Teachers Study cohort, a large study of professional school employees with extensive information on breast cancer risk factors, followed for cancer incidence since 1995. We identified 1552 invasive breast cancer cases, diagnosed between 1996 and 1999, among 114,835 cohort members. We used California Pesticide Use Reporting data to select pesticides for analysis based on use volume, carcinogenic potential, and exposure potential; a Geographic Information System was used to estimate pesticide applications within a half-mile radius of subjects’ residences. We applied Cox proportional hazard models to estimate hazard rate ratios (HR) for selected pesticides, adjusting for age, race, and socioeconomic status. We saw no association between residential proximity to recent agricultural pesticide use and invasive breast cancer incidence. HR estimates for the highest compared to the lowest exposure categories for groups of agents were as follows: probable or likely carcinogens (1.07, 95% confidence interval (CI): 0.86–1.32), possible or suggestive carcinogens (1.06, 95% CI: 0.87–1.29), mammary carcinogens (1.15, 95% CI: 0.90–1.48), and endocrine disruptors (1.03, 95% CI: 0.86–1.25). HR estimates for other groups and individual pesticides did not differ from unity, nor was there a trend for any groupings of or individual pesticides examined. Stratifying by menopausal status or family history of breast cancer did not substantially affect our results. Our analyses suggest that breast cancer incidence is not elevated in areas of recent, high agricultural pesticide use in California.

Highlights

Breast cancer is the most common form of cancer among adult women in the United States (US) (Kosary et al, 1997; Ries et al, 1998) and known risk factors are thought to explain only about half of the cases occurring nationwide (Madigan et al, 1995)
We designed our study to look at the relationship between residential proximity to agricultural pesticide use, as reported in the Pesticide Use Reporting (PUR), and breast cancer incidence within a large, well-defined cohort of women residing throughout California
All California public school employees must pay into and receive retirement benefits through State Teachers Retirement System (STRS) and membership is in effect as long as retirement contributions remain on deposit with the program

Summary

Introduction

Breast cancer is the most common form of cancer among adult women in the United States (US) (Kosary et al, 1997; Ries et al, 1998) and known risk factors are thought to explain only about half of the cases occurring nationwide (Madigan et al, 1995). Considerable research has focused on the potential relationship between breast cancer and body burden levels of organochlorine pesticides (Aronson et al, 2000; Bagga et al, 2000; Dello Iacovo et al, 1999; Dewailly et al, 1994; Dorgan et al, 1999; Guttes et al, 1998; Helzlsouer et al, 1999; Hoyer et al, 2000; Hunter et al, 1997; Liljegren et al, 1998; Mendonca et al, 1999; Millikan et al, 2000; Moysich et al, 1998; Mussalo-Rauhamaa et al, 1990; Olaya-Contreras et al, 1998; Romieu et al, 2000; Schecter et al, 1997; Stellman et al, 2000; Unger et al, 1984; van’t Veer et al, 1997; Wolff et al, 1993, 2000; Zheng et al, 1999a-c) Results from these studies have been conflicting and methodologic differences in study design and measurement issues have hampered resolution of their differing results (Adami et al, 1995; Azevedo e Silva Mendonca, 1998; Gammon et al, 1998; Longnecker et al, 2000; Santodonato, 1997; Wassermann et al, 1976). We designed our study to look at the relationship between residential proximity to agricultural pesticide use, as reported in the PUR, and breast cancer incidence within a large, well-defined cohort of women residing throughout California

Study population

Follow-up and cancer incidence data

Geocoding

Pesticide data

Census data

Data analysis

Results

Discussion