A new study links pre-pregnancy exposure to phthalates to women's reproductive health. The study identifies how phthalates reduce chances of pregnancy, disrupt important reproductive hormones, and cause inflammation and oxidative stress, adding to growing evidence about the negative effects of these chemicals.

Phthalates are a group of man-made chemicals commonly used as solvents, plasticizers and stabilizers in personal care products such as soaps, body washes, perfumes, nail polishes, shampoos, hair gels and gels. They are also found in other products in the home, such as vinyl flooring, plastic packaging, garden hoses and toys.

According to the Centers for Disease Control and Prevention (CDC), people are exposed to phthalates by eating and drinking foods that have been exposed to phthalates, and some people are exposed by breathing particulates in the air. Research shows that exposure to certain types of phthalates can disrupt the endocrine system and increase inflammation and oxidative stress.

A new study by researchers at the University of Massachusetts Amherst (UMass Amherst) examines the relationship between preconception exposure to phthalates and a woman's chances of becoming pregnant and maintaining a pregnancy, as well as the effects of phthalates on inflammation and oxidative stress.

"Phthalates are ubiquitous endocrine disruptors and we are exposed to them every day," said Carrie Nobles, lead author of the study.

The researchers analyzed data obtained from the EAGeR (Aspirin Effects on Pregnancy and Reproduction) study, which followed 1,288 women for six menstrual cycles while they were trying to conceive, and followed women who became pregnant throughout their pregnancy. The average age of participants was 28 years old. Data were adjusted for age, body mass index, race/ethnicity, smoking and parity (i.e., the number of times a woman gave birth to a fetus at 24 weeks' gestation or older).

"We were able to study some environmental exposures, such as phthalates, and how that relates to the time it takes to get pregnant," Nobles said. "We have detailed data for each menstrual cycle, so we can get a good handle on the date of ovulation and the timing of pregnancy."

When the body breaks down phthalates, the metabolites are excreted in the urine. The researchers analyzed participants' urine samples for 20 phthalate metabolites and reproductive hormones, and measured serum levels of the inflammatory biomarker C-reactive protein (CRP).

Overall, preconception urinary concentrations of several phthalate metabolites were associated with reduced odds of pregnancy over a menstrual cycle (conception rate), including the metabolites of di(2-ethylhexyl) phthalate (DEHP), di-n-butyl phthalate (DBP), and benzylbutyl phthalate (BzBP). There was no clear association between phthalate metabolites and risk of pregnancy failure.

"We found that there were three parent compounds that appeared to be most strongly associated with prolonged pregnancy, although the overall trend we saw was that all of the phthalates we studied were associated with prolonged pregnancy. As exposure increased, we saw larger and larger effects," Nobles said.

DEHP is found in polyvinyl chloride (PVC) plastic products such as toys, vinyl upholstery, shower curtains, adhesives and some food packaging, as well as in pesticides and cosmetics. DBP is found in hairspray, nail polish and some perfumes, among other household products. BzBP is found in some handbags, belts and footwear, and to a lesser extent some personal care products.

Higher levels of certain phthalate metabolites are associated with lower estradiol levels throughout the menstrual cycle, and are consistently associated with higher levels of follicle-stimulating hormone (FSH) and luteinizing hormone (LH). Estradiol is a steroid hormone that regulates the menstrual cycle; FSH and LH work together to regulate ovulation. These hormones play an important role in early pregnancy.

"This situation—where estradiol remains at a low level and follicle-stimulating hormone remains at a high level—is actually what we see in women with ovarian insufficiency, which can occur with age and a number of other factors. Ovulation is no longer as smooth as it once was," Nobles said.

The researchers also found that women exposed to higher levels of phthalates also had higher levels of inflammation and oxidative stress, which can damage cells and DNA and lead to disease. They say the ubiquitous nature of phthalates makes it difficult for women to control their exposure, even though they take precautions such as checking consumer product labels and choosing phthalate-free products.

"Women may be exposed to the parent compounds of these metabolites (DEHP, DBP, and BzBP) through multiple routes, including dust from floors and other household items, absorption of personal care products (including nail polish and fragrance), dietary exposure through contamination of food packaging and food sources, and ingestion of contaminated drinking water," the researchers said.

The study was published in the journal Environmental Health Perspectives.

References:

https://ehp.niehs.nih.gov/doi/10.1289/EHP12287