by Elizabeth Grossman

Nurses face many hazards on the job, and one that clearly demands more detailed analysis than it’s received to date is the effect of occupational chemical exposures on nurses’ reproductive health. A recent study by researchers at the National Institute of Occupational Safety and Health (NIOSH), Harvard School of Public Health, and Brigham and Women’s Hospital has found that female nurses exposed to sterilizing agents and chemotherapy drugs at work are at least twice as likely to have miscarriages than those who are not. The study, published in The American Journal of Obstetrics and Gynecology, surveyed more than 7,000 female nurses and found that their exposure to sterilizing agents was associated with a two-fold increase in the risk of miscarriage between the 12th and 20th weeks of pregnancy. Exposure to chemotherapy drugs was associated with a two-fold increase in risk of miscarriage before the 12th week of pregnancy, while for women pregnant for the first time, this exposure appears to increase miscarriage risk three-fold. The study also found that exposure to x-rays was associated with some increased risk of early pregnancy loss.

Similar effects have been reported before, but this is one of the largest studies ever to look at these exposures, explained Christina Lawson, a reproductive epidemiologist with NIOSH and study author. Because these results reflect adjustment for a number of variables — including age, hours worked, and shift-work — and because the study was designed to avoid overestimation, its findings may be conservative, said Lawson.

The chemicals involved in the nurses’ sterilizing agent exposures likely include ethylene oxide, formaldehyde, glutaraldehyde, hydrogen peroxide, orthopthalaldehyde, and peracetic acid, all powerful chemicals used to disinfect medical equipment and surgical instruments. Because the survey only asked nurses whether they were exposed, follow-up studies will be required to determine precisely which sterilizing agents nurses are being exposed to and exactly how they are affecting pregnant nurses, as well as what kind of protective and safe-handling measures nurses are using. But there is little, if any, uncertainty that these substances pose human health hazards. Here’s an overview of what researchers have found:

Formaldehyde
Formaldehyde is recognized as carcinogenic and mutagenic. The authors of the new NIOSH nurses study note that other studies of formaldehyde’s reproductive toxicity have been limited. However, a 2011 University of California Berkeley School of Public Health review of past studies found formaldehyde exposure to be associated with miscarriage, as well as other adverse reproductive and developmental health effects. A 1994 study of exposure to formaldehyde-based disinfectants and manicure products among women who worked in beauty salons in North Carolina also found these exposures associated with miscarriages.

Ethylene oxide
Like formaldehyde, ethylene oxide is a recognized carcinogen and mutagen. Although the authors of the new study caution that previous studies on ethylene oxide’s reproductive toxicity have had limited sample sizes, these effects have been documented in peer-reviewed studies, some dating back to the 1980s. Studies of nurses in South Africa, Finland and the US, and of dental assistants in California exposed to ethylene oxide have all found associations with miscarriage. A 1984 study estimated that 75,000 US healthcare workers were at that time exposed to ethylene oxide and pointed out that in animal studies this chemical has been shown to cause birth defects, fetal loss, and reduced fertility (both male and female). That study also reported a human epidemiological association with leukemia and referenced an additional study that suggested brief occupational exposure to ethylyne oxide (twice daily at concentrations of 20 parts per million or more) among pregnant women increased risk of miscarriage.

More recently, a 2007 survey of 1,500 nurses undertaken by Environmental Working Group, Healthcare Without Harm, American Nurses Associations, and University of Maryland School of Nursing found that nurses exposed to sterilizing agents had a 20% higher incidence of miscarriage than those who were not. This survey – which specifically examined exposure to ethylene oxide and glutaraldehyde – also found increased incidence of birth defects in these nurses’ children.

Orthopthalaldehyde
Orthopthalaldehyde (OPA), which was introduced as a less-toxic alternative to ethylene oxide and glutaraldehyde, is less extensively studied than the other commonly used medical sterilizing agents. However, a 2005 Canadian study of risks to healthcare workers from these exposures noted that OPA has similar structural and reactive properties to glutaraldehyde and acted similarly as a chemical sensitizer. Glutaraldehyde is also used as a hydrofracking fluid, and one such Material Safety Data Sheet (MSDS) warns that ingestion of “glutaraldehyde by pregnant women can cause reproductive toxicity to the fetus.” OPA does not currently have a recommended exposure limit. A 2010 Johnson & Johnson MSDS for an OPA product says reproductive effects are unknown.

Formaldehyde exposure in both nursing and beauty salons
Studying the reproductive health effects of chemical exposures is particularly important in professions dominated by women, as nursing is. Another such field is hair and nail salon work, where formaldehyde exposure is a concern since formaldehyde and compounds that release formaldehyde have long been used in numerous cosmetic products.

The well publicized recent discovery of formaldehyde released by the use of Brazilian Blowout hair treatment has drawn attention to this hazard, but formaldehyde and formaldehyde-releasing chemicals have been used in many other beauty salon products. Although this product had no formaldehyde warning labels and some of this brand’s products were labeled “formaldehyde-free,” it was found to release hazardous levels of formaldehyde gas. A California lawsuit and a class-action lawsuit against the company have just been settled. The settlement requires new labels on products and MSDSs, but it does not require formaldehyde to be removed from the product.

But Brazilian Blowout is far from the only hair, cosmetic or personal care product to expose users to formaldehyde. The Occupational Safety & Health Administration (OSHA) lists about a dozen such hair products known to contain formaldehyde and that can cause formaldehyde exposure during use, even though they do not name formaldehyde on their labels or material safety data sheets. OSHA also lists more than two dozen other chemical compounds that can release formaldehyde – and so have comparable health risks and are subject to OSHA’s formaldehyde rules – that are not called formaldehyde or methylene glycol (which is formaldehyde dissolved in water). Any such compound, because it is potentially carcinogenic requires a label if the product contains more than 0.1% of that substance. These two dozen formaldehyde-containing or releasing compounds have at least twice as many trade or other names, which may appear on ingredient labels or MSDSs. Some of these compound names are more than 26 letters long; some are simply initials. One of theses synonyms, Quaternium 15, turns up in 405 products listed on the Environmental Working Group’s “Skin Deep” database of cosmetic and personal care product ingredients. Another, listed as DMDM, I’ve just found listed in the Organix brand hair conditioner in my own bathroom.

More questions about occupational exposure to the sterilizing agents, chemotherapy drugs, and other chemicals will be asked as part of the next Nurses Health Study, one of the largest and longest-running investigations of factors that influence women’s health. The new NIOSH study on nurses’ chemical concludes that “the effect of commonly encountered occupational exposures on reproductive health remains unclear within this predominantly female occupation.” But the literature thus far appears to indicate that much more needs to be done to prevent these exposures.

Elizabeth Grossman is the author of Chasing Molecules: Poisonous Products, Human Health, and the Promise of Green Chemistry, High Tech Trash: Digital Devices, Hidden Toxics, and Human Health, and other books. Her work has appeared in a variety of publications including Scientific American, Salon, The Washington Post, The Nation, Mother Jones, Grist, and the Huffington Post. Chasing Molecules was chosen by Booklist as one of the Top 10 Science & Technology Books of 2009 and won a 2010 Gold Nautilus Award for investigative journalism.