Occupational exposure to organic solvents and risk of breast cancer: Results of the CECILE study, a population-based case-control study in France

Abstract

Introduction Breast cancer is the leading cause of cancer death in women worldwide. Its incidence is only partially explained by well-established risk factors related to hormones and reproduction. It has been suggested that exposure to organic solvents in the workplace may play a role in the etiology of breast cancer, but epidemiological studies on these occupational exposures in female breast cancer did not assess exposure to specific solvents and reported inconsistent results. Methods We examined the risk of breast cancer-related to lifetime exposure to organic solvents in a large population-based case-control study carried out in France between 2005 and 2008; 1230 women newly diagnosed for a breast cancer and 1315 population controls were included. A standardized questionnaire was administered during in-person interviews by trained interviewers to obtain information on socio-demographic characteristics, medical and family history, anthropometric measurements, reproductive history, tobacco and alcohol consumption, diet, and lifetime occupational history. All jobs held during occupational history were coded using the International Standard Classification of Occupations (ISCO 1968) and the Classification of Activities in the European Community (NACE 1991). Exposure to chlorinated (n = 4), petroleum (n = 5) and oxygenated (n = 5) solvents was assessed using a detailed job-exposure matrix (JEM) developed by the French National Agency for Public Health. Each job held was assigned indices of exposure probability, frequency and intensity. A Cumulative Exposure Score (CES) was calculated for each subject as the sum of the products of exposure probability, frequency and intensity, and duration for each job held over the entire occupational life. Odds ratio (ORs) and their 95% confidence intervals (95% CI) were estimated using unconditional logistic regression adjusting for potential confounders. Results The highest lifetime exposure prevalence was found for alcoholic solvents (41.8% of the cases and 41.4% of the controls); white spirit (8.3% of the cases and 10.2% of the controls); and trichloroethylene (10.7% of the cases and 11.8% of the controls). Compared to non-exposed subjects, women in the highest cumulative exposure quartile for alcoholic solvents had an OR of 1.17 (95% CI = 0.90–1.52). This OR increased to 1.61 (95% CI = 1.06–2.46) in premenopausal women. Exposure to ethylene glycol was also associated with an increased OR of 1.36 (95% CI = 0.93–1.97) in premenopausal women. No association was observed for other oxygenated solvents, petroleum solvents or chlorinated solvents. Conclusions These findings suggest a role of occupational exposure to oxygenated solvents, notably to alcohols, in the occurrence of breast cancer. Further studies conducted in cohorts of women with high prevalence of exposure to solvents are needed to confirm these results.