Environment and Breast Cancer: Science Review

Evidence From Humans
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Breast cancer risk associated with residential proximity to industrial plants in Canada
Pan, S. Y., Morrison, H., Gibbons, L., Zhou, J., Wen, S. W., DesMeules, M., Mao, Y. J Occup Environ Med. 2011. 53:5, 522-9.
Topic area
Environmental pollutant - Temporal and geographic trends Air pollution
Study design
Population based case-control
Funding agency
Not reported
Study Participants
Menopausal Status
The menopausal status of women included in this study is listed here.
Stratified analysis based on menopausal status
Number of Controls
Controls: 2,467
Participant selection: Inclusion and exclusion criteria
Criteria used to select participants in the study.
The National Enhanced Cancer Surveillance System (NECSS) collected individual information for a large population based sample of 21,020 cases with one of 19 types of pathologically confirmed incident cancer identified by provincial cancer registries, and 5,039 controls aged 26 to 79 years. Frequency matching to the overall case group was used to select controls with 5 year age-groups and sex distribution within reach province. The sampling strategy for control selection varied by province and included identification through public health insurance plans, property assessment database, and random digit dialing. Data were collected between 1994 and 1997 in collaboration with the Public Health Agency of Canada and 8 of the 10 Canadian provincial cancer registries. Questionnaires were sent out to 3,013 female breast cancer cases and 3,847 potential controls. Cases and controls who had incomplete postal code information were excluded.
Exposure Investigated
Exposures investigated
Geocoded residential postal code, from residential history from 1960 to 5 years before enrollment, used to determine residential proximity and duration of proximity to 10 types of industry in the NECSS Environmental Quality Database (EQDB). Types of indus
How exposure was measured
GIS/Geographic location
Exposure assessment comment
The Environmental Quality Database (EQDB) is a retrospective inventory of industries from 1960 to 1990 across Canada. The latency of cancer was addressed by considering the residential distance to industries for cases and controls from 1960 to 5 years before the completion of the questionnaire. This assessment accounts for participants moving addresses during the study period. Authors state that iron and steel production is a source of large-scale PAH, heavy metal, chlorophenol, and creosote discharges into air, water, and soil. Thermal power plant fuel use includes coal, diesel, fuel oil, natural gas, nuclear, spent pulping refuse, and waste heat, and can release carcinogenic metals, radioactive elements, and PAHs. Pulp mill air emissions include chemicals classified by IARC as human carcinogens. Petroleum refineries release many carcinogenic chemicals, including 1,3 butadiene, benzene, toluene.
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, educational level, family income, alcohol consumption, smoking, BMI, total calorie intake, recreational physical activity, menopausal status, age at menarche, number of births, province of residence, and employment in the industry under consideration
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
Compared to women living >3.2 km from a plant, overall breast cancer:

Ever lived 0.8-3.2 km from paper mills: aOR 1.06 (95% CI 0.88-1.27)
Ever lived <0.8 km from paper mills: aOR 0.85 (95% CI 0.60-1.19)

Ever lived 0.8-3.2 km from petroleum refineries: aOR 1.31 (95% CI 1.07-1.60)
Ever lived <0.8 km from petroleum refineries: aOR 1.25 (95% CI 0.75-2.06)

Ever lived 0.8-3.2 km from pulp mills: aOR 1.12 (95% CI 1.02-1.36)
Ever lived <0.8 km from pulp mills: aOR 1.32 (95% CI 0.93-1.85)

Ever lived 0.8-3.2 km from steel mills: aOR 1.18 (95% CI 1.02-1.37)
Ever lived <0.8 km from steel mills: aOR 0.85 (95% CI 0.60-1.20)
Lived ≤ 3.2 km from steel mills for 1-9 years: aOR 1.25 (95% CI 1.04-1.49)

Ever lived 0.8-3.2 km from thermal power plants: aOR 1.15 (95% CI 0.99-1.33)
Ever lived <0.8 km from thermal power plants: aOR 1.56 (95% CI 1.16-2.10)
Lived ≤ 3.2 km from thermal power plants for ≥ 10 years: aOR 2.18 (95% CI 1.21-3.94)

Ever lived 0.8-3.2 km from any plant: aOR 1.14 (1.00-1.29)
Ever lived <0.8 km from any plant: aOR 1.17 (0.97-1.41)
Results Comments
Although no dose-response relationship with length of residency was observed, increased risk among premenopausal women with longer length of residence was observed for some industries. Among premenopausal women, ORs were significantly elevated for living within <0.8km of thermal power plants for ≥10 years and non-significantly for living within <0.8km of steel mills for ≥10 years. No clear trends in duration or distance were observed for paper mills, petroleum refineries, pulp mills, steel mills either within 3.2km or 0.8km. ORs for living near thermal power plants did increase with shorter distance and longer duration.
Author address
Centre for Chronic Disease Prevention and Control, Public Health Agency of Canada, Ottawa, Ontario, Canada. sai.yi.pan@phac-aspc.gc.ca
Reviewers Comments
Other factors that may affect exposures were not evaluated, such as residential indoor air quality, prevailing winds, topography, or production level of the plant.