Environment and Breast Cancer: Science Review

Evidence From Humans
Print this page
Self-reported chemicals exposure, beliefs about disease causation, and risk of breast cancer in the Cape Cod Breast Cancer and Environment Study: a case-control study
Zota, A. R., Aschengrau, A., Rudel, R. A., Brody, J. G. Environ Health. 2010. 9, 40.
Topic area
Environmental pollutant - Pesticides
Study design
Population based case-control
Funding agency
Massachusetts Department of Public Health Susan S.
Study Participants
Menopausal Status
The menopausal status of women included in this study is listed here.
No analyses by menopausal status
Number of Controls
Controls: 721
Participant selection: Inclusion and exclusion criteria
Criteria used to select participants in the study.
Study participants were of the Cape Cod Breast Cancer and Environment Study. All participants were permanent residents for at least six months on Cape Cod. Cases were women diagnosed with invasive breast cancer between 1988 and 1995, whose diagnosis was reported to the Massachusetts Cancer Registry. Frequency-matched controls (by date of birth and vital status) were chosen by random digit dialing (<65 years) or selected from CMS databases (>=65 years). Deceased controls were selected randomly from death certificates, frequency matched by age and year of death. Participants interviewed by proxy respondent were excluded from this study.
Comment about participation selection
Inclusion and exclusion criteria were designed to reduce the possibility of selection bias.
Exposure Investigated
Exposures investigated
At-home pesticide use patterns were obtained by questionnaire and categorized based on pest type, purpose of use, and a cumulative measure of combined pesticide exposure. Household cleaning product use was also ascertained (e.g. oven cleaner, surface clea
How exposure was measured
Questionnaire, by telephone
Exposure assessment comment
Self-report allows for aggregation of exposures over many years prior to diagnosis and across many types of products, including those with short half-lives, but does not assess exposures in possible critical periods of development.
Breast cancer outcome investigated
Primary incident breast cancer
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, birth decade, previous breast cancer diagnosis, family history, age at first birth, education.
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
Combined pesticide use:
Quartile 2 OR 1.0 (0.7-1.5)
Quartile 3 OR 1.1 (0.8-1.5)
Quartile 4 OR 1.1 (0.8-1.6)

Often/very often vs never insect repellent use OR 1.5 (1.0-2.3)

Lawn care:
Any use OR 1.1 (0.9-1.3)
Once/twice OR 1.2 (0.7-1.9)
3-20 times OR 1.2 (0.9-1.6)

Outdoor and indoor plant care:
Any use OR 1.0 (0.8-1.2)
Once/twice OR 1.1 (0.6-1.8)
3-20 times OR 1.0 (0.7-1.3)
>20 times OR 1.0 (0.7-1.3)

Combined cleaning product use, 4th quartile vs. 1st quartile: OR 2.1 (95% CI 1.4-3.3)
Combined air freshener use, 4th quartile vs. 1st quartile: OR 1.9 (95% CI 1.2-3.0)
Solid air freshener use, any use vs. never use: OR 1.7 (95% CI 1.2-2.3)
Mold/mildew control, any use vs. never use: OR 1.7 (95% CI 1.2-2.3)
Mold/mildew control with bleach, any use vs. never use: OR 1.5 (95% CI 1.0-2.1)
Results Comments
When analyses were stratified by beliefs about breast cancer etiology, the association between breast cancer risk and cleaning product use was elevated among those who believed that pollutants contribute "a lot" to breast cancer (aOR 3.2, 95% CI 1.8-5.9). However, a parallel analysis of family history and beliefs about breast cancer suggests the differences could be due to differences in access to information rather than biased self-report.
Author address
Silent Spring Institute, 29 Crafts Street, Newton, MA 02458, USA. brody@silentspring.org.
Reviewers Comments
While the study authors recognize the potential for recall bias, they advise against limiting the analysis to women who do not subscribe to the study hypothesis because the resulting subgroup may not be representative of the population of interest.