Environment and Breast Cancer: Science Review

Evidence From Humans
Print this page
Breast cancer risk, fungicide exposure and CYP1A1*2A gene-environment interactions in a province-wide case control study in Prince Edward Island, Canada
Ashley-Martin, J., VanLeeuwen, J., Cribb, A., Andreou, P., Guernsey, J. R. Int J Environ Res Public Health. 2012. 9:5, 1846-58.
Topic area
Environmental pollutant - Fungicides Genetic variability
Study design
Hospital based case-control
Funding agency
Canadian Institutes for Health Research Institute
Study Participants
Menopausal Status
The menopausal status of women included in this study is listed here.
No analysis based on menopausal status
Number of Controls
Controls: 621
Participant selection: Inclusion and exclusion criteria
Criteria used to select participants in the study.
Women with breast cancer were recruited from hospital oncology unit in Charlottetown, Prince Edward Island, Canada, between 1999-2002. Controls were recruited from the hospital's mammography screening program during the same time period and frequency matched to cases on 5 year age groups, menopausal status, and family history of breast cancer. They had no previous personal history of breast cancer or abnormal mammography and were full time residents of Prince Edward Island (PEI) at the time of screening.
Comment about participation selection
The authors state that Queen Elizabeth Hospital was the primary oncology clinic at the time of study, and all breast cancer diagnoses were recorded in the PEI cancer registry. They also state that about 2/3 of all women on the island undergo mammography screening at QEH. There may have been selection bias that excluded women who do not seek mammograms in the study population.
Exposure Investigated
Exposures investigated
Fungicide exposure levels were derived using 1991 Canadian Agricultural Census data, which provides information on the number of hectares in each census subdivision that were treated with fungicides. Participants provided their postal code, which was mapp
How exposure was measured
GIS/geographic location Biological
Exposure assessment comment
There are concerns about exposure misclassification for the reference group. Authors note that air quality studies on this small island indicate that all residents may be highly exposed. CYP1A1 allele variations have been shown to affect breast cancer risk in women with high exposures to PCBs and pesticides in other studies.
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, menopausal status, family history of breast cancer
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
Fungicide exposure:
Medium: OR 1.19 (95% CI 0.76-1.87)
High: OR 0.74 (95% CI 0.47-1.17)
Results Comments
No evidence for interaction between fungicide exposure and CYP1A1*2A polymorphisms, which may affect the metabolism of estrogenic and environmental chemicals. No association with fungicide use treated as a continuous or binary variable.
Author address
Department of Community Health & Epidemiology, Faculty of Medicine, Dalhousie University, 5790 University Ave., Halifax, NS B3H1V7, Canada. jillian.ashley-martin@dal.ca
Reviewers Comments
The effect of confounding from other agricultural applications in the same study areas may have an effect on the associations seen. Because CYP1A1 is induced by many environmental contaminants, which may become more toxic once metabolized, investigating CYP1A1 variants is relevant to examining exposure to potentially carcinogenic compounds, such as fungicides.