Environment and Breast Cancer: Science Review

Evidence From Humans
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Environmental exposure and breast cancer among young women in Rio de Janeiro, Brazil
Ortega Jacome, G. P., Koifman, R. J., Rego Monteiro, G. T., Koifman, S. J Toxicol Environ Health A. 2010. 73:13-14, 858-65.
Topic area
Environmental pollutant - Household Pesticides Electromagnetic fields Ionizi
Study design
Hospital based case-control
Funding agency
Brazilian National Research Council (CNPq) State o
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: 101
Participant selection: Inclusion and exclusion criteria
Criteria used to select participants in the study.
Cases were women aged 23-35 diagnosed with breast cancer at Rio de Janeiro oncology center between 1999 to 2002. Hospital controls aged 26-49 and without cancer were recruited for a separate study of brain cancer and the environment from public hospitals in Rio de Janeiro.
Comment about participation selection
The lower participation rate for cases is not entirely attributable to patient refusal. The authors report that 41.6% of the eligible cases were not able to participate because of death, changes in contact information, or were in ongoing treatment. However, the low case participation rate suggests that those participating may not be representative of breast cancer cases in the region. The hospital-based controls may have similar or different risk factor profiles compared to the cases. It is possible that the controls were at the hospital for reasons that could be related to those risk factors. The controls were neither case matched nor frequency matched, and an age boundary that did not correspond with the case population was used (case population: 23-35 years old vs. control population: 26 to 49 years old). 71% of cases had no family history of breast, ovarian or prostate cancer. Authors note that high occurrence of sporadic cancers is unexpected in this age group, where family history is a main risk factor.
Exposure Investigated
Exposures investigated
Selected environmental exposures of interest included diet intake, hair dyes or hair straightening products, pesticide use at home (during adulthood), ionizing radiation (dental x-rays), and non-ionizing radiation (living near a power transformer).
How exposure was measured
Questionnaire, in person
Exposure assessment comment
Self-reported exposures ascertained via in-person questionnaire after diagnosis are subject to recall bias. The binary exposure categories may be less vulnerable to recall bias, but they result in imprecise classification of exposures.
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.
Mutual adjustment for the other environmental exposures assessed.
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
Ever use of home insecticides (adulthood) vs. never use: aOR 4.87 (95% CI 1.84-12.92)
Ever use of hair dyes or straightening cosmetics vs. never use: aOR 0.32 (95% CI 0.13-0.81)
Ever use of dental diagnostic x-rays vs. never use: aOR 1.41 (95% CI 0.64-3.14)
Live <20 meters from power transformer vs. not near power transformer: aOR: 1.90 (95% CI 0.87-4.12)
Results Comments
Each estimate was adjusted for the remaining exposures. The incomparable age ranges for cases and controls induces a negative association between age and breast cancer in this study population. If age is also associated with one or more of the environmental exposures, then observed relationships may be significantly confounded.
Author address
National School of Public Health, Oswaldo Cruz Foundation, Rio de Janeiro, Brazil. guipatortega@hotmail.com
Reviewers Comments
Women in the study were predominantly non-white. Methodological issues (e.g. different age range for cases and controls) prevent meaningful interpretation.