Breast milk samples from moms in the Seattle area contained chemicals linked to health problems, new research has found.

The chemicals are often used in beverage can liners, receipt paper, and other products, and they’ve been linked to reproductive problems, cancer, and immune problems like asthma.

Ryan Babadi is the science director at the nonprofit Toxic Free Future, which co-authored the research. He said breast milk is still the best food for most babies.

“The problem is not breast milk,” he said. “The problem is that we have chemical policies that are allowing these contaminants to end up in women and breastmilk and result in exposure to infants during a very sensitive time period of development.”

Researchers collected breast milk from 50 women and tested it for various chemicals. They found that the majority of the samples contained BPA and the related chemical BPS, triclosan, and melamine. All three of these chemical groups are known as “endocrine disruptors” because they can mimic, block, or alter human hormones and thus affect a large number of systems. BPA, for example, has been linked to diabetes, the early onset of puberty, and a number of cancers. Triclosan interferes with thyroid function and could increase cancer risk. And melamine has been linked to kidney problems.

“This isn’t a problem that mothers or people in general can shop their way out of,” Babadi said. “We need government decision-makers and policymakers as well as the corporate environment to come up with policy solutions that protect us.”

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Breast milk for the study was collected in 2019. In the years since, Washington state has started regulating some of the chemicals the researchers found.

For example, as of last year, beverage cans in Washington aren’t allowed to contain BPA and related chemicals. And as of January, those chemicals aren’t allowed in receipt paper in the state.

That’s because, under a state law passed in 2019, the ecology department prioritizes harmful chemicals, identifies consumer products that contain those chemicals, and writes new regulations to ban or restrict them.

So far, the state has regulated not only BPA and related chemicals, but also phthalates in personal care products and vinyl flooring, triclosan in cosmetics, and PFAS chemicals in carpets, rugs, and furniture. Those last are known as “forever” chemicals because they do not degrade over time.

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The state is now looking at chemicals in cosmetics, jewelry, cookware, paint, and artificial turf, among other products, for possible future regulation.

The state has not looked at banning or restricting melamine, one of the chemicals the researchers found in breast milk.

Babadi said in an email that Washington’s law is the nation’s strongest for regulating toxic chemicals, but he said it needed to be improved “to be able to enact bans in urgent scenarios when, for example, we observe harmful chemicals in breast milk.” The process for restricting new chemicals currently takes at least five years.

Marissa Smith is a toxicologist and the former technical lead for the Safer Products for Washington program. She now works on chemical policies across the ecology department.

She said the state’s current process of chemical regulation helps build compliance by giving manufacturers and industries plenty of lead time and compliance assistance.

“We generally do see compliance with state laws,” she added. “Most manufacturers want to sell products that are compliant.”

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Smith emphasized that state-level chemical regulations like those in Washington and California can have an effect across the country, as manufacturers switch over to safer alternatives for their entire supply chain.

And Smith sees other reasons for hope.

“ Products are getting safer over time,” she said. “ There were some toxic flame retardants that were used in kids’ pajamas and other products, and we banned those, and we actually saw concentrations in our bodies and in our environment go down.”

For another example, Smith pointed to the dramatic decline in how much lead was in children’s blood after the U.S. banned leaded gasoline in 1996.

“ There’s just a lot of examples where we have actually regulated products and we’ve seen reductions in people’s exposure,” Smith said.