Environment and Breast Cancer: Science Review

Evidence From Humans
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Cancer incidence in a population accidentally exposed to 2,3,7,8-tetrachlorodibenzo-para-dioxin
Bertazzi, A., Pesatori, A. C., Consonni, D., Tironi, A., Landi, M. T., Zocchetti, C. Epidemiology. 1993. 4:5, 398-406.
Topic area
Environmental pollutant - Dioxin (TCDD)
Funding agency
Other: Government of the Region of Lombardy, Itali
Study Participants
Cohort participation rate
Evidence of successful tracing and case ascertainm
Participant selection: Inclusion and exclusion criteria
Criteria used to select participants in the study.
Residents ages 20-74 years living in three zones of contamination and a surrounding uncontaminated area in 1977 - 1986 (i.e., during or after the accidental release of TCDD).
Comment about participation selection
Fewer than 1% emigration from the Lombardy region of follow-up.
Exposure Investigated
Exposures investigated
TCDD from 1976 accident near Seveso, Italy. Exposure zones defined by level of TCDD contamination of soil.
How exposure was measured
GIS/geographic location
Exposure assessment comment
All exposure is attributed to the initial zone of residence, so migration is not taken into account. Indoor/outdoor time not accounted for. The validity of the zones as representing a gradient of exposure has been questioned.
Statistical Analysis
Breast cancer outcome investigated
Primary breast cancer from 1977-1986 ascertained from hospital records
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.
Not controlled
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
Poisson regression
Strength of associations reported
Deficit in breast cancer for women older than 45 years: relative risk = 0.7 (95% CI 0.3-1.5). Relative risk near one for women under 45.
Deficit in breast cancer in the most exposed zone: relative risk = 0.5 (0.1-3.3) based on one case.
Results Comments
Very small numbers of cases, limited follow-up time.
Author address
Institute of Occupational Health, School of Medicine, University of Milan, Italy.