Here’s the Rub: Skin Care Products and Children’s Phthalate Exposures

Short abstract

Racial and ethnic differences in exposures to phthalates and their replacements through use of soaps, lotions, etc. appear to begin in childhood.

Skin care products have been identified as a key source of phthalate exposure in adults,¹ but less is known about children’s exposure.² What is known is that children are more vulnerable than adults to dermal exposures, partly because children have greater blood flow to the skin and a greater surface area-to-body mass ratio.³

A study recently published in Environmental Health Perspectives⁴ compared children’s use of skin care products (including those applied by a parent or caregiver) with the presence of phthalate and phthalate replacement metabolites in the children’s urine. Phthalate replacements are being used more widely, and there are few data about their human health risk, notes Michael S. Bloom, first author of the study and a professor of global and community health at George Mason University.

For the children in this study, patterns of exposure by race and ethnicity were comparable to patterns previously observed in adults, suggesting that exposure disparities may begin at an early age. Image: © iStock.com/LumiNola.

The researchers identified several associations that warrant further investigation, says senior author Kelly Hunt, a professor of epidemiology at the Medical University of South Carolina. “It is one of the first studies that’s been able to look at use of skin care products and levels of phthalates in children,” says Hunt.

Phthalates are synthetic chemical compounds used in a variety of consumer products, including pharmaceuticals,⁵ food packaging,⁶ and personal care products.⁷ Researchers using cell culture⁸ and animal models⁹ have shown that exposure to some phthalates can cause reproductive problems. In humans, observational studies have established associations between phthalate exposure and neurocognitive problems, reproductive problems, and metabolic disease.¹⁰ Children’s exposures have been associated with differences in body composition,¹¹ neurodevelopment,¹² and pulmonary and immune function.^13,14 Nevertheless, as recently as 2022, the US Food and Drug Administration stated that it “does not have evidence that phthalates as used in cosmetics [including skin care products] pose a safety risk.”¹⁵

The researchers looked at data for 630 children between 4 and 8 years old and their mothers who were enrolled in the Environmental Influences on Child Health Outcomes—Fetal Growth Study (https://echochildren.org/). Urine samples collected from the children were analyzed for the presence of 16 metabolites of phthalates and phthalate replacements.

At enrollment, caregivers completed an open-ended questionnaire about skin care products their child had used in the previous 24 hours, including soaps, lotions, shampoos, and cosmetics.

The survey data were sorted into exposure profiles, or trends in product use, using a machine learning tool called a self-organizing map. “We wanted to try an approach that could look at patterns of using all these personal care products and then classify people who use products differently,” Bloom explains. A self-organizing map explores how products and exposures might group together because participants may use multiple products at a time, notes Bhavna Shamasunder, an associate professor and chair of urban and environmental policy at Occidental College who was not involved in the study.

Researchers also looked for associations across race and sex assigned at birth. Approximately half of the children were male, and the children (or their parent/guardian) self-reported being either non-Hispanic Black (30%), non-Hispanic White (30%), Hispanic (26%), or Asian/Pacific Islander (13%).

Bloom, left, studies the intersection of environmental pollutants and human health, both in the United States and abroad. Hunt, right, focuses on diabetes and cardiovascular epidemiology, maternal and child health epidemiology, and genetic epidemiology. Images: George Mason University, left, and Kelly Hunt, right.

The researchers found notable associations between race, skin care product use, and metabolite concentrations. “The children who identified as non-Hispanic Black had higher concentrations of most of the phthalates,” says Bloom. This was true for metabolites of both low- and high-molecular-weight phthalates/replacements when viewed as groups (findings varied for individual chemicals). “And that’s unfortunately what we expected to see based on data^{16,17,18,19,20} from adults in the United States.” Although the findings may have been expected, Shamasunder says, “understanding that [these disparities] begin in childhood is an important addition to our knowledge.”

Higher urinary concentrations of low-molecular-weight phthalate metabolites were associated with use of lotions in non-Hispanic White children and use of hair oils in Hispanic and Asian/Pacific Islander children. Low-molecular-weight phthalates are added to personal care products as excipients, or carriers, says Bloom, whereas high-molecular-weight phthalates are used as plasticizers in packaging.

Some of the results pointed to the influence of other exposures, he explains. First, girls tended to use more skin care products than boys, but there was not a substantial difference in urinary metabolite concentrations across sex. Second, the urine of children who used phthalate-free skin care products still contained phthalate-associated metabolites—perhaps from packaging. Nearly three-fourths of the children in the study used at least one product labeled as phthalate-free.

Reliance on caregivers’ accounts of product use also limited the study, and products were not brought to the research team for chemical analysis, says Bloom. Moreover, notes Hunt, about a quarter of respondents completed the survey more than 24 hours after urine collection—longer than the half-lives in urine of many phthalate and phthalate replacements. Both factors could have influenced results.

“Children are a vulnerable population,” says Elissia Franklin, an analytical chemist and postdoctoral research associate at Silent Spring Institute who was not part of the study. “Knowing that certain products can affect their phthalate exposure is an important step toward a world where we don’t have to personally vet products before we bring them into our home, because they will be required to be safe.”

Biography

Lindsay Key is a science writer based in Virginia.