Dozens of hair extensions—including artificial and natural braids—may contain synthetic chemicals that are a health and environmental hazard, a new study shows. At least 12 of the 169 chemicals detected in the new analysis have been associated with cancer, birth defects and reproductive issues and are included in California’s Proposition 65 hazardous chemicals list.
The study, published today in Environment & Health, tested 43 hair extensions, including those made with synthetic hair, as well as untreated “raw” human hair and other biobased hair, such as those made from banana-based fibers. All but two of the products contained a hazardous chemical, and nearly 10 percent of them had organotin compounds—synthetic chemicals linked to endocrine-disrupting effects. Some had concentrations above the European Union limits. More research is needed, however, for government agencies to determine whether the chemical levels found in these products requires greater regulation, the study authors say.
“The hazardous chemicals we identified each carry their own risks,” says Elissia T. Franklin, lead author of the new paper and a research scientist at the nonprofit research organization Silent Spring Institute. “Our findings showed that these products can expose [people] to multiple chemicals over time, and through repeated use, these combined exposures add up.”
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More than 70 percent of Black women in the U.S. use hair extensions at least once per year, including in hairstyles such as braiding—a staple of many Black cultures that’s been shaped by the slave trade, colonialism and Western beauty standards. Chemical relaxers—another product commonly used to style Black hair—that permanently straighten curly or kinky hair have previously been linked to higher risk of uterine cancer.
“On one hand, I’m excited to get the work out and share this new knowledge with the world,” Franklin says. “On the other hand, I’m learning this new information leans towards the idea that my community is deeply polluted with harmful chemicals, even down to practices that are so embedded in the culture, like getting braids.”
Using a chemical library, Franklin’s team winnowed more than 900 chemical signatures picked up from the hair extensions down to dozens of potentially harmful compounds. In samples of synthetic hair, they found levels of chlorine as high as 277,000 micrograms per gram. The Centers of Disease Control and Prevention reports that exposure to chlorine, a flame retardant, at 60 micrograms per gram for 60 minutes or more through inhalation can lead to lung irritation and impaired function. The researchers also flagged some samples with small traces of fluorine, a chemical that can lead to lower birth rates in high doses, as well as organohalogens and nitroaromatics—both known to have carcinogenic effects.
The study didn’t determine whether any particular amount of chemical exposure from the hair extensions was above legal standards or would necessarily cause health issues in people, however. This limitation makes it difficult to create safety guidance, Franklin says. But the work aligns with a growing trend: A 2022 study found traces of potentially harmful heavy metals in synthetic hair, and a 2025 analysis in Consumer Reports found that hair extensions used when braiding contained volatile organic chemicals—which can irritate the eyes, nose and throat as well as cause potential long-term kidney and liver damage.
In the new study, the “detection of more different classes of potentially harmful chemical contaminants is evidence that these products contain more chemical types than our findings” showed, says James Rogers, director of product and food safety research and testing at Consumer Reports, who led the 2025 analysis. He was not involved in the new paper.
Biobased hair products, such as those made from silk or banana-based fibers, are generally better options than other extensions. But the study found that some biobased extensions labeled as nontoxic contained unclassified complex chemicals. Although those chemicals might not be dangerous, Franklin advises caution: “Biobased doesn’t automatically mean safer.”
Editor’s Note (2/11/25): The image in this article was changed after posting. The caption of the original image mistakenly labeled natural hair as hair extensions.