The Center for Environmental Health said it sent letters to eight clothing brands after it conducted tests on clothing for the chemical bisphenol.
The group said the products violate California’s Safe Drinking Water and Toxic Enforcement Act.
The Center for Environmental Health said it would give companies 60 days to respond to their letter before filing a complaint with the state.
According to the group, unsafe levels of chemical bisphenol, or BPA, were found in Athleta, PINK, Asics, The North Face, Brooks, All in Motion, Nike and FILA sports bras.
The group also said it discovered unsafe levels of BPA in activewear shirts made by The North Face, Brooks, Mizuno, Athleta, New Balance and Reebok.
The CEH said some of the clothes contained up to 22 times the safe limit of BPA.
“People are exposed to BPA through ingestion (e.g., from eating food or drinking water from containers that have leached BPA) or by absorption through skin,” said Kaya Allan Sugerman, illegal toxic threats program director at CEH. “Studies have shown that BPA can be absorbed through skin and end up in the bloodstream after handling receipt paper for seconds or a few minutes at a time. Sports bras and athletic shirts are worn for hours at a time, and you are meant to sweat in them, so it is concerning to be finding such high levels of BPA in our clothing.”
The Centers for Disease Control and Prevention said, "Human health effects from BPA at low environmental exposures are unknown. BPA has been shown to affect the reproductive systems of laboratory animals. More research is needed to understand the human health effects of exposure to BPA.”
In addition to clothing, BPA is commonly found on plastic food containers, aluminum cans and toys.