Solvent Exposure Before First Pregnancy Increases Breast Cancer Risk

When breast cancer is known to run in families, there are precautions that can be taken to minimize individual risk of getting it. The findings of a recent study from the National Institute of Environmental Health Sciences (NIEHS) indicate the kind of job a girl has during her teen and young adult years can make a difference. Young women who have jobs that involve exposure to organic solvents, chemicals that dissolve other substances, before their first full-term pregnancy are at increased risk of developing hormone receptor-positive breast cancer if it runs in the family.

Cleaning productsDr. Christine C. Ekenga, a postdoctoral fellow in the NIEHS epidemiology department, led the study of breast cancer and on-the-job (OTJ) exposure to solvents. The NIEHS is a branch of the National Institutes of Health.

According to Ekenga, “The time between puberty and before first birth is an important period of development when the breast may be more vulnerable to chemical exposures.” Her study “identified several occupations where solvent exposure was associated with an elevated risk for breast cancer.”

Ekenga and her research team turned to the Sister Study, an NIEHS study led by Dale P. Sandler. The Sister Study focused on 50,884 women who had a sister diagnosed with breast cancer. The 50,884 women in the study did not have breast cancer when they enrolled in the study between 2003 and 2009.

Each study participant completed a questionnaire each year describing occupational history and other risk factors linked to breast cancer. Solvent exposure in the workplace was measured as:

  • Duration of OTJ exposure to organic solvents
  • Weekly frequency of solvent exposure
  • Age when the woman first started working with solvents

By the end of the study, 47,661 women were still enrolled. Of them:

  • 1,798 were diagnosed with breast cancer during the study years
  • 1,255 were diagnosed with invasive cancer (spreading to tissue outside the original tumor site)
  • 77% were diagnosed with hormone receptor-positive cancers

The research team found the critical exposure period was from puberty until first full-term birth. Women exposed to solvents after having a first baby did not experience the same elevated risk of breast cancer as their counterparts exposed before first childbirth.

The occupations where young women got the highest levels of solvent exposure were:

  • Clinical laboratory technicians
  • Maids
  • Housekeepers
  • Production workers in factories

Women in these occupations before having their first child were approximately 40% more likely to develop hormone receptor-positive breast cancer than women in other occupations with the same inherited risk of breast cancer.


Source: Ekenga, Christine C, et al. “Breast Cancer Risk after Occupational Solvent Exposure: the Influence of Timing and Setting.” Cancer Research. American Association for Cancer Research. Jun 1, 2014. Web. Jun 15, 2014.