Environment and Breast Cancer: Science Review

Evidence From Humans
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Cancer incidence and mortality in Swedish sterilant workers exposed to ethylene oxide: updated cohort study findings 1972-2006
Mikoczy, Z., Tinnerberg, H., Bjork, J., Albin, M. Int J Environ Res Public Health. 2011. 8:6, 2009-19.
Topic area
Environmental pollutant - Ethylene oxide
Study design
Retrospective cohort
Funding agency
Metalund Project
Study Participants
Menopausal Status
The menopausal status of women included in this study is listed here.
No analysis based on menopausal status
Number in Cohort
Cohort: 1,309 women
Cohort participation rate
Not applicable. This study was records-based.
Participant selection: Inclusion and exclusion criteria
Criteria used to select participants in the study.
The Swedish Sterilant Workers Cohort comprises workers employed for at least 1 year prior to 1986 at two medical equipment plants that used ethylene oxide (EtO) as a sterilant. EtO was used as a sterilant at plant A from 1970 to 1994, and in plant B from 1964 to 2002. Follow up of vital status in the cohort was determined in 2006.
Exposure Investigated
Exposures investigated
A detailed exposure assessment including 2 plant specific job exposure matrices was performed for exposures up to 1986. Work histories up to time that EtO use ceased, 1994 for plant A, and 2002 for plant B, were provided by the companies. Yearly hygienic
How exposure was measured
Job history at plant Other: Job exposure matrix
Exposure assessment comment
The cohort as a whole had low cumulative exposure to EtO, as compared to some recently studied cohorts.
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, calendar period
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
Breast cancer incidence within the cohort compared to Scania county population:
1972-2006: SIR 0.81 (95% CI 0.58-1.09)
1972-2006, accounting for ≥15 years induction latency period: SIR 0.86 (95% CI 0.59-1.20)

Within-cohort comparison (Ref = 0-0.13 ppm-years exposure):
0.14-0.21 ppm-years: aIRR 2.76 (95% CI 1.20-6.33)
≥0.22 ppm-years: aIRR 3.55 (95% CI 1.58-7.93)
Author address
Division of Occupational and Environmental Medicine, Department of Laboratory Medicine, Lund University, and Occupational and Environmental Medicine, Skane University Hospital, SE-221 85 Lund, Sweden. zoli.mikoczy@med.lu.se
Reviewers Comments
The average age of cohort members with estimated cumulative EtO exposure was 55.9, which is still relatively young for breast cancer diagnosis. A healthy worker effect was identified by significantly decreased overall mortality and mortality from cardiovascular diseases. Comparisons within the plant may thus be the more appropriate measures. Shift work occurred at both plants, although this variable, along with other breast cancer risk factors, was not ascertained.