Millions of workers in occupational settings are exposed to organic solvents that are widely used in products such as, adhesives, glues, degreasing/cleaning agents, and in the production of dyes, plastics, and textiles. Several solvents have been recognized as human carcinogens; however, there is limited data on solvent exposure and the risk of breast cancer.
In this new study Dr. Christine C. Ekenga, MPH, PhD, postdoctoral fellow in the epidemiology branch of the National Institute of Environmental Health Sciences at the National Institutes of Health and lead researcher along with colleagues examined the relationship between occupational exposure to organic solvents and breast cancer among women enrolled in the Sister Study, a prospective cohort study of 50,884 initially breast cancer-free sisters of women who had been diagnosed with breast cancer, aged 35-74 with a family history of breast cancer
This study covered participants who were enrolled between 2003 and 2009. This analysis includes 47,763 women who reported working outside the home. Participants answered questionnaires about use of solvents on each job held for 12 months or longer, weekly frequency of exposure and age at first job involving organic solvents. Participants were followed-up on a yearly basis for health updates.
The results showed overall, there was no increased risk of breast cancer associated with lifetime use or duration of exposure to solvents.
Among the study participants 1,798 were diagnosed with breast cancer during follow-up, of whom 1,255 had invasive cancer. Of the invasive tumors, 77 percent were hormone-receptor positive.
The researchers adjusted for confounders including race/ethnicity, parity, exposure to tobacco smoke, and working night shifts.
Even though there was no increased risk for invasive breast cancer from lifetime exposure to solvents, the researchers did find that exposure to solvents prior to first full-term birth to be a critical period for breast cancer risk.
The results indicated that there was some increased risk for solvent-exposed women in production, service and healthcare occupations. A non-significant elevated risk was observed for women who worked as maids and housekeeping cleaners, and those who had factory-related occupations.
In their conclusion the researchers write “These findings suggest that occupational exposure to organic solvents prior to first birth, a critical period of breast tissue differentiation, may result in increased vulnerability for breast cancer.” “Future studies on solvent-related breast cancer risk should focus on exposure time window and types of organic solvents used across different occupational settings.”
Dr. Ekenga commented in a press release “We identified several occupations where solvent exposure was associated with an elevated risk for breast cancer.” “These include clinical laboratory technicians, maids and house cleaners, and production [factory] workers. All women should be familiar with the chemicals and hazards that are present in their workplace, and use personal protective equipment and minimize exposures when appropriate.”
Women who worked with organic solvents prior to giving birth to their first child had a 40% increased risk for developing hormone receptor-positive, invasive breast cancer, and all women who worked in clinical laboratories had a twofold increased risk for this type of breast cancer.
Dr. Ekenga commented “Our study is an important first step toward understanding how the timing of chemical exposures may impact breast cancer risk.” “We hope that our findings will generate additional interest in the possible role of solvents and other chemicals in the etiology of breast cancer.”