Objective To explore associations between occupational exposure to four specific organic solvents, respectively, and female breast cancer, including subtypes.
Methods Using the Danish Cancer Registry, we identified 38 375 women under age 70 years with primary breast cancer. Five randomly selected breast-cancer-free controls per case matched on year of birth were retrieved from the Danish Civil Registration System . A nationwide pension fund was used to retrieve full employment history, and exposure to 1,1,1-trichloroethane, trichloroethylene (TCE), benzene and toluene was assessed using a job exposure matrix. ORs were estimated using conditional logistic regression with adjustment for reproductive factors and socioeconomic status.
Results Overall results indicated no noteworthy associations between the specific organic solvents and breast cancer before and after age 50 years, except for a small increased risk after age 50 in women exposed to TCE (OR=1.15, 95% CI: 0.97–1.36). After age 50 years, exposure to TCE was associated with a small increased risk in women with over 20 years of latency (OR=1.26, 95% CI: 1.02–1.56). Further, an increased risk of oestrogen receptor positive (ER+) tumours was also observed (OR=1.21, 95% CI: 1.01–1.47), and high cumulative exposure and longer latency also increased the risk of this subtype.
Conclusion This study provides limited evidence supporting the association between occupational exposure to each of the four organic solvents and breast cancer. The risk of ER+ breast tumours after age 50 years may be increased in women with TCE exposure, and this possible association therefore needs further attention in future studies.
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Contributors JEP contributed considerably to the conception of the study, executed the analyses, interpreted the results and wrote the manuscript. KS-L and MA contributed to the study design, interpreted the results and revised the manuscript critically. JH was a key contributor in the design process of the study and the analyses that were carried out and revised the manuscript critically. All authors have approved the final version to be published and are accountable for all aspects of the work.
Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.
Competing interests None declared.
Patient consent for publication Not required.
Provenance and peer review Not commissioned; externally peer reviewed.
Data availability statement No data are available. No reuse of data is permitted.
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