Environment and Breast Cancer: Science Review

Evidence From Humans
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Regression analysis of pesticide use and breast cancer incidence in California Latinas
Mills, P. K., Yang, R. J Environ Health. 2006. 68:6, 15-22; quiz 43-4.
Topic area
Environmental pollutant - Organochlorine pesticides
Study design
Funding agency
California Breast Cancer Research Program
Study Participants
Menopausal Status
The menopausal status of women included in this study is listed here.
No analysis based on menopausal status
Participant selection: Inclusion and exclusion criteria
Criteria used to select participants in the study.
Breast cancer cases were identified from the California Cancer Registry from 1988 to 1999. The analysis was restricted to Latinas diagnosed in California.
Comment about participation selection
This registry-based study lacks a comparison group of a population without breast cancer.
Exposure Investigated
Exposures investigated
Summation of county-level pesticide use information in pounds of active ingredients applied from 1970 to 1988. These were summed by pesticide for eight organochlorine pesticides (aldrin, chlordane, DDT, dieldrin, endosulfan, lindane, methoxychlor, & toxap
How exposure was measured
GIS/geographic location
Exposure assessment comment
The Pesticide Usage Database is a unique way to get at differences in exposure, but makes broad assumptions about exposures experienced by Latina women in each county regardless of occupational status. Further, while the study effectively applies an 18-year lag by using pesticide application data starting in 1970, and cancer cases from 1988-1999, the lack of residential history prior to diagnosis is problematic, especially in an area where many are seasonal/migrant workers. In combination with use of county level exposure data, this could result in substantial exposure misclassification. The exposure categories range from low, to medium, high, and highest chemical levels. It is not discussed how these categories are defined.
Breast cancer outcome investigated
Primary incident breast cancer
Ethnic groups with separate analysis
If this study provided a separate analysis by ethnic or racial group, the groups are listed here.
Confounders considered
Other breast cancer risk factors, such as family history, age at first birth, and hormone replacement therapy use, that were taken into account in the study.
Age at diagnosis, fertility (county-level, # births per 1,000 women 15-44 years of age), and SES (county-level, % of Latina population below the poverty level).
Genetic characterization included
If the study analyzed relationships between environmental factors and inherited genetic variations, this field will be marked “Yes.” “No”, if not.
Strength of associations reported
Diagnosis 1988-1993, high exposure vs. low exposure:
aldrin: aIRR 0.83 (95% CI 0.68-1.01)
chlordane: aIRR 1.08 (95% CI 0.59-1.94)
DDT: aIRR 0.94 (95% CI 0.85-1.03)
dieldrin: aIRR 0.78 (95% CI 0.54-1.14)
endosulfan: aIRR 1.12 (95% CI 0.95-1.32)
lindane: aIRR 0.88 (95% CI 0.67-1.16)
methoxychlor: aIRR 1.18 (95% CI 1.03-1.35)
toxaphene: aIRR 1.16 (95% CI 1.01-1.34)
atrazine: aIRR 0.86 (95% CI 0.70-1.05)
simazine: aIRR 1.05 (95% CI 0.93-1.19)

Diagnosis 1994-1999, high exposure vs. low exposure:
aldrin: aIRR 0.90 (95% CI 0.75-1.09)
chlordane: aIRR 0.83 (95% CI 0.54-1.29)
DDT: aIRR 1.02 (95% CI 0.94-1.11)
dieldrin: aIRR 1.05 (95% CI 0.76-1.42)
endosulfan: aIRR 1.02 (95% CI 0.88-1.19)
lindane: aIRR 0.82 (95% CI 0.63-1.07)
methoxychlor: aIRR 1.16 (95% CI 1.02-1.30)
toxaphene: aIRR 1.08 (95% CI 0.94-1.22)
atrazine: aIRR 0.87 (95% CI 0.73-1.04)
simazine: aIRR 1.07 (95% CI 0.95-1.20)
Author address
Cancer Registry of Central California, Fresno 93710, USA. paul.mills@fresno.ucsf.edu