Environment and Breast Cancer: Science Review

Evidence From Humans
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Dioxin emissions from a municipal solid waste incinerator and risk of invasive breast cancer: a population-based case-control study with GIS-derived exposure
Viel, J. F., Clement, M. C., Hagi, M., Grandjean, S., Challier, B., Danzon, A. Int J Health Geogr. 2008. 7, 4.
Topic area
Environmental pollutant - PCDD Dioxin
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.
No analysis based on menopausal status
Number of Controls
Controls: 2,170
Participant selection: Inclusion and exclusion criteria
Criteria used to select participants in the study.
The study are consisted of 590 blocks northeast of the municipal solid waste incinerator in Besancon. Because the exposure assessment was unreliable for the 90 blocks southwest of the facility, this area was excluded from the analysis. Cases were women diagnosed with invasive breast cancer from 1996 to 2002, identified by the Doubs Cancer Registry, that lived within the study area. Age-matched controls were women randomly selected from the 1999 population census that lived within the study area.
Comment about participation selection
The use of limited census data -- sex, age categories and residence in a given census block -- to select controls meant that it was not possible to confirm that controls were actually free of breast cancer, resulting in likely outcome misclassification. Additionally, the use of census selected controls limited the ability to ascertain confounding covariates.
Exposure Investigated
Exposures investigated
Modeled ground-level air dioxin levels from the nearby municipal solid waste incinerator were used to determine categories of exposure (very low, low, intermediate, high) at the census block level. The model included dispersion and terrain information and
How exposure was measured
GIS/geographic location
Exposure assessment comment
Authors note that the waste incinerator was confirmed to be the main point source of dioxin in the area. However they do not discuss prevailing wind direction which may lend plausibility for the dispersion model (i.e. if the wind was predominantly in the NE direction). Because exposures are assigned to a geographical unit, as opposed to the individual, there is some concern about exposure misclassification. They also do not discuss the dioxin concentrations associated with the exposure categories (i.e. what concentration does the high category represent). Finally, duration of residence was not known, though authors note that the population > age 40 was relatively stable.
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 categories
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
Among women aged 20-59 years (ref = very low dioxin exposure):
Low exposure: OR 1.06 (95% CI 0.72-1.56)
Intermediate exposure: OR 1.25 (95% CI 0.82-1.89)
High exposure: OR 0.88 (95% CI 0.43-1.79)

Among women aged 60+ (ref = very low dioxin exposure):
Low exposure: OR 0.90 (95% CI 0.63-1.29)
Intermediate exposure: OR 0.96 (95% CI 0.66-1.41)
High exposure (4 cases): OR 0.31 (95% CI 0.08-0.89)
Results Comments
There are few participants who were in the high exposure category (15 cases total), while the majority of participants were estimated to have low dioxin exposure.
Author address
CNRS no 6249 Chrono-Environment, Faculty of Medicine, 2, place Saint Jacques, 25030 Besancon cedex, France. jean-francois.viel@univ-fcomte.fr
Controls participation rate
Not applicable. This study was records-based.
Reviewers Comments
The potential outcome misclassification, given limited information about controls, could have led to significant bias in these effect estimates. Though the authors demonstrate that several block-level socioeconomic characteristics related to education, employment, and home ownership did not appear to vary significantly by exposure category, the lack of control for any potential confounders other than age (which was only considered in categories) is also a concern.