Environment and Breast Cancer: Science Review

Evidence From Humans
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Breast cancer risk and historical exposure to pesticides from wide-area applications assessed with GIS
Brody, J. G., Aschengrau, A., McKelvey, W., Rudel, R. A., Swartz, C. H., Kennedy, T. Environ Health Perspect. 2004. 112:8, 889-97.
Topic area
Environmental pollutant - Pesticide
Study design
Population based case-control
Funding agency
Other: MA Department of Public Health
Study Participants
Menopausal Status
The menopausal status of women included in this study is listed here.
Pre menopausal
Post menopausal
Number of Controls
Controls: 1,006
Participant selection: Inclusion and exclusion criteria
Criteria used to select participants in the study.
Participants of the Cape Cod Breast Cancer and Environment Study. Cases were women with permanent residence on Cape Cod at the time of a breast cancer diagnosis in 1988-1995. Controls were chosen by random-digit-dialing and from Center for Medicare and Medicaid Services files
Exposure Investigated
Exposures investigated
Relative exposure scores were generated based on historical reconstruction of wide-area pesticide use dating back to 1948 in a geographic information system (GIS). The database included pesticides from wide-area application for tree pests, cranberry bogs
How exposure was measured
Questionnaire, by telephone GIS/geographic location Other: Environmental model
Exposure assessment comment
Exposures off Cape Cod were not assessed. Records of pesticide application are incomplete, resulting in understatement of exposure. The entire Cape was sprayed in some years, resulting in lack of variation in exposure within the study population. Time spent inside vs. outside is not taken into account. Few women were occupationally exposed.
Statistical Analysis
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.
Extensively taken into account
Genetic characterization included
If the study analyzed relationships between environmental factors and inherited genetic variations, this field will be marked “Yes.” “No”, if not.
Description of major analysis
Unconditional logistic regression, no and 5-year latency, 5-year promotion
Strength of associations reported
Selected results: Adjusted OR (95% CI) exposure group from low to high compared with not exposed

Persistent pesticides applied to cranberry bogs
group 1: 0.8 (0.4-1.6)
group 2: 1.2 (0.7 - 2.1)
group 3: 1.4 (0.7-2.5)
group 4: 1.8 (0.7-4.5)

Persistent pesticides for tree pests
group 1: 1.3 (0.8-2.0)
group 2: 1.2 (0.7-1.8)

Less persistent pesticides applied for tree pests
group 1: 1.7 (0.8-3.7)
group 2: 1.2 (0.6-4.0)

Less persistent pesticides applied for agriculture
group 1: 1.5 (1.1-1.9)
group 2: 1.8 (0.9 - 3.7)
group 3: 0.9 (0.3-3.0)
Results Comments
No overall pattern of association. Statistically unstable slightly elevated risk associated with use of persistent pesticides on cranberry bogs and for tree pests and for less persistent pesticides used for tree pests and agriculture other than cranberry cultivation.
Pesticides are of interest in etiologic studies of breast cancer because many mimic estrogen, a known breast cancer risk factor, or cause mammary tumors in animals, but most previous studies have been limited by using one-time tissue measurements of residues of only a few pesticides long banned in the United States. As an alternative method to assess historical exposures to banned and current-use pesticides, we used geographic information system (GIS) technology in a population-based case-control study of 1,165 women residing in Cape Cod, Massachusetts, who were diagnosed with breast cancer in 1988-1995 and 1,006 controls. We assessed exposures dating back to 1948 (when DDT was first used there) from pesticides applied for tree pests (e.g., gypsy moths), cranberry bogs, other agriculture, and mosquito control on wetlands. We found no overall pattern of association between pesticide use and breast cancer. We found modest increases in risk associated with aerial application of persistent pesticides on cranberry bogs and less persistent pesticides applied for tree pests or agriculture. Adjusted odds ratios for these exposures were 1.8 or lower, and, with a few exceptions, confidence intervals did not exclude the null. The study is limited by uncertainty about locations of home addresses (particularly before 1980) and unrecorded tree pest and mosquito control events as well as lack of information about exposures during years when women in the study lived off Cape Cod and about women with potentially important early life exposures on Cape Cod who were not included because they moved away.
Author address
Silent Spring Institute, 29 Crafts Street, Newton, MA 02458, USA. brody@silentspring.org
Reviewers Comments
GIS exposure assessment allows for historical exposure assessment, but many study participants were not residing on the Cape throughout the assessment period.