Study: Phthalate exposure during early pregnancy can alter hormone levels in developing fetuses

Exposure during early pregnancy to some phthalates—man-made chemicals commonly found in household plastics, food and personal care products—can have adverse impacts on developing fetuses, according to a new study led by Dr. Sheela Sathyanarayana, a pediatric environmental health specialist at Seattle Children's Research Institute and associate professor at the University of Washington.

The study, published in The Journal of Clinical Endocrinology & Metabolism, found that increases in exposure to certain phthalates during the first trimester of pregnancy was associated with higher estrogen concentrations and lower testosterone concentrations in the fetus, thus increasing the chance of a genital abnormality in male babies at birth.

The study reinforces that some phthalates are endocrine disrupting chemicals (EDCs) and can alter concentrations of naturally-produced hormones, which help regulate and control different cells and organs in the body. Sathyanarayana's previous research has directly linked fetal exposure to diethylhexyl phthalate (DEHP) to the development of genital abnormalities and increased risk of future reproductive health issues in boys.

Sathyanarayana sat down with On the Pulse to discuss the key findings of the study:

Q: What are the new, significant findings from this study?

We found that increases in phthalate exposure in early pregnancy was associated with higher estrogen concentrations (MBzP, DEHP, MiBP) and lower testosterone (MCNP and DEHP) concentrations. In other words, the phthalates were associated with increases in female hormones and decreases in male hormones.  We also found that having higher testosterone in pregnancy was associated with a lower chance of having a male baby with a genital abnormality, which means that anything that reduces testosterone, like the hormone DEHP, will increase chances of having a male baby with a genital abnormality.

Q: How is that different from your most recent published study on phthalates?

The study I published previously showed the link between phthalates and male genital abnormalities in the male reproductive track. This study looks at one of the possible causes of the genital abnormalities—changes in hormone concentration. One of the biggest criticisms of epidemiology, which studies the causes and effects of health issues in a specific population, is that we identify associations but we don't really know how or why those associations occur.

Another big take-home point is that there is little evidence in humans that EDCs actually affect endocrine pathways. This is some of the strongest evidence showing that these chemicals actually do affect endocrine pathways.

Q: Why would it matter that someone's endocrine system is affected?

Our endocrine systems control all the hormones in our body. Hormones are essential for us to live. Estrogen is vital for female reproductive function, as well as mental and cardiovascular health, which is a point that people sometimes miss. Estrogen and testosterone are not only for reproductive development. If you don't have proper levels of estrogen or testosterone, your mood, your cardiovascular health will be affected. Our hormones keep us balanced every day.

Q: Are female babies as affected as male babies by phthalates?

We can't say that females aren't as affected because there just isn't as much data. .It's more challenging to study females because their reproductive organs are internal, so at birth, there are no markers to look at. With males, it's much easier to study the external factors.

Q: What is your advice for expecting mothers around how to avoid exposure to phthalates?

Phthalates are used to soften and increase the flexibility of plastic and vinyl products; including medical tubing, food storage containers, flooring, wallpaper, shampoo, lotion makeup and perfume. Food is the most likely source of exposure to the most harmful phthalates. To limit exposure, expecting moms should do the following:

Buy low-fat dairy products like skim milk and low fat cheeses instead of high-fat dairy products like cream and whole milk.

Buy fresh or frozen fruits whenever possible. Avoid canned and processed foods.

Look for items that are labeled phthalate or BPA-free.

Minimize personal care products, and focus on simple products with clear ingredients.

Use glass, stainless steel, ceramic or wood to hold and store foods instead of plastics, and do not microwave food in plastic.

Do not heat a baby's milk or food in plastics or put hot liquids in plastic products like sippy cups.

Check plastic symbols and avoid plastics known to contain phthalates including numbers 3 (PVC and vinyl), 6 (polystyrene foam) and 7 (other, can contain BPA).

Perform frequent handwashing.

Minimize handling of receipts.

Take shoes off at home to avoid tracking dust in that may contain phthalates.

Keep carpets and windowsills clean because these are areas that can often collect phthalates.