Nearly two decades ago, scientists showed that exposing pregnant rats to phthalates disrupts testosterone in their male offspring, leaving them with a suite of genital deformities and semen problems, dubbed “phthalate syndrome.”

“The whole process of making eggs and sperm is completely controlled by hormones,” said Patricia Hunt, Ph.D., a reproductive biologist at Washington State University. “In experiments, we can screw things up really, really badly with toxic exposures in developing males and females and permanently change an animal’s reproduction.”

Studies of phthalates’ effects on women have found problems. A 2018 study, for example, found an association between phthalate exposure and poor egg and embryo quality in women undergoing fertility treatments. But generally, the field of women’s health research is underfunded, Dr. Woodruff said.

Early clues to phthalates’ reproductive risks to women surfaced in 1975, when researchers found that Russian factory workers who were exposed to high phthalate levels on the job had fewer pregnancies and more miscarriages than unexposed women. In a study nearly two decades later, scientists found that phthalate exposures in rats targeted the ovaries, the primary regulator of reproduction and fertility in women.

Couples, like the Boyles, don’t usually read studies about rat infertility before trying to start a family. And Boyle wasn’t thinking about hormone-disrupting chemicals during her 20s, when she worked at radio stations in Seattle or when she landed a job as co-host for a TV morning show at the age of 31. It wasn’t until she went through several rounds of in vitro fertilization transfers that she started wondering if environmental chemicals, like those in the foundation and eye makeup she wore on camera, could affect fertility.

Boyle’s fertility doctor at Pacific NW Fertility clinic, Lora Shahine, M.D., had always told her patients to focus on exercising and eating well to boost fertility. She started advising them to reduce their exposures to phthalates and other hormone-disrupting chemicals after she read about “overwhelming evidence” linking them to gynecological and pregnancy problems when researching the 2015 book she co-wrote, “Planting the Seeds of Pregnancy.”