Higher usage of personal care products among pregnant or nursing women leads to higher levels of toxic PFAS “forever chemicals” in their blood and breast milk, new research shows, presenting a serious health threat to developing children.

The new study helps connect the dots among previous papers that have found concerning levels of PFAS in personal care products, umbilical cord blood, breast milk and shown health risks for developing children.

The analysis of data from 2,000 women is the largest to compare personal care product usage with PFAS levels, and the findings are “alarming” said Amber Hall, a Brown University researcher and study co-author.

“It’s not only getting in blood and breast milk, but it’s getting in there at high enough levels that we’re able to connect it with greater frequency of use,” Hall said.

PFAS are a class of about 15,000 compounds typically used to make products that resist water, stains and heat. They are called “forever chemicals” because they do not naturally break down and accumulate, and are linked to cancer, kidney disease, liver problems, immune disorders, birth defects and other serious health problems.

The chemicals are widely used across the economy, and have been added to personal care products from dental floss to cosmetics, often to help spread active ingredients, or aid the skin in absorbing them. They also leach into the products from packaging or other points in the supply chain.

The authors found those with the highest blood or milk levels were linked to nail care products, fragrances, makeup, hair dyes and hair sprays.

Women who wore makeup daily in the first and third trimesters had 14% and 17% higher plasma and breast milk PFAS concentrations, respectively.

Women who dyed their hair at least twice during pregnancy showed levels of PFOS, one of the most common and dangerous PFAS compounds, that were 36% higher than those who did not.

Meanwhile, women who used nail products after giving birth were found to have PFOS levels about 27% higher.

Previous research found PFAS in each of 30,000 umbilical cord blood samples taken across a five-year period in locations around the globe. Breast milk in 50 US samples were found to contain alarming levels of the chemicals.

Exposure is especially dangerous for developing children because they are more vulnerable and it can trigger lifelong health problems. Among other issues related to pregnancy and development, PFAS are linked to decreased birth weight, preterm birth, shorter lactation periods, a reduction in milk’s nutritional value, neuro-developmental disorders and diminished vaccine response in children.

Women can take some steps to protect themselves, like reducing non-essential personal care products while pregnant or nursing. They can also find products free from toxic chemicals, though it is difficult to identify PFAS on product labels, and sometimes their inclusion is not disclosed.

Some states have begun to ban or limit the use of PFAS in personal care products as an active ingredient. That may pressure companies to remove PFAS from their products across the nation so they do not have to produce different formulas for different states.

• The headline of this article was amended on 24 November 2024. An earlier version included reference to dental floss; while this is a product that may contain PFAS, as the article itself said, it was not among those covered in the study.