Thomas Ahern, Ph.D., M.P.H., Assistant Professor of Epidemiology (Photo: UVM Medical Photography)

Many modern consumer products include phthalates: food containers, construction materials, clothing, cosmetics, and medications. Phthalates are not chemically linked to other ingredients in these products, so they can easily leak out of them. As a result, people are exposed to them without realizing it. For example, skin absorbs the phthalates in makeup. Phthalates in plastic food containers can seep into leftovers.

Phthalates Exposure: What the Research Says

Our bodies turn phthalates into breakdown products called metabolites. They are flushed out in urine. A study by the U.S. National Health and Nutrition Examination Survey (NHANES) found that most U.S. adults had detectable phthalate metabolites in their urine. This tells us that low-level exposure from environmental sources is common in our population.

Another study by NHANES found that people who took medications with phthalates had much higher exposure than people not taking those medications. In some cases, phthalate metabolite levels were more than 50 times higher in medication users.

Are Phthalates Harmful to Human Health?

A big question is whether phthalates are harmful to our health. Studies show that they can mimic normal hormones in our bodies and disrupt the biological pathways they control. This raises concern that they might influence hormone-related health outcomes, including fertility, birth outcomes, and specific types of cancer.

There is concern that exposure raises breast cancer risk. Some metabolites behave like the hormone estrogen when applied to breast cancer cells in the laboratory. While there are a few studies in humans, evidence for the impact on breast cancer is conflicting. The National Academy of Medicine called for larger, more definitive studies in a 2012 report.

With support from Susan G. Komen for the Cure, my research group is evaluating whether use of phthalate-containing medications is associated with higher breast cancer risk. Our study includes more than 1 million women. Other researchers are using a similar approach to study the impact on fertility and birth outcomes. Together, the evidence from these studies will guide the medical and scientific communities in understanding the health impact of phthalate exposure.

How to Reduce Your Exposure to Phthalates

You can reduce phthalate exposure by checking product labels and avoiding goods that are manufactured with phthalates. For example, by storing leftover food in glass or phthalate-free plastic containers.

Some medications include phthalates for a very good reason. They give drug capsules traits that maximize effectiveness. Do not stop prescription medications due to concern about phthalate exposure until we know more. Some phthalate-containing drugs may be replaceable with phthalate-free alternatives. Your prescriber or pharmacist can determine if this is a good option for you.

Thomas Ahern, PhD, MPH, is an assistant professor in the Departments of Surgery and Biochemistry at the Larner College of Medicine at the University of Vermont.

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