Recycled black plastic can contain flame retardants, viral study found. That's still true — but their math was off

Editor's note: On Dec. 15, a correction was issued for the study described below. A mathematical error in the original manuscript that made the estimated daily exposure levels to a flame retardant — BDE-209 — seem much closer to the EPA's safe limit than they are. We've updated our story, which was first published on Oct. 17, 2024, to reflect this update.

Takeout sushi trays, spatulas and other household goods made with recycled black plastic can sometimes contain potentially toxic flame retardants, a new study suggests.

But don't rush to throw away your favorite black spatula — the jury is still out on whether these chemical remnants are cause for concern.

Since the 1970s, flame-retardant chemicals have been added to plastics used in electronic devices. Their purpose is to prevent electrical fires or slow their growth. But because many of these chemicals last longer than the devices they're used in, they may persist in plastics made from recycled electronics.

The exact amount of e-waste that ends up recycled into new products is contentious, but some estimates suggest about 4.2 million tons may be reused globally each year.

Related: What is brominated vegetable oil, and why did the FDA ban it in food?

"As a class, flame retardants are notorious for their persistence, tendency to bioaccumulate [build up in living tissues], and toxicity," said Megan Liu, science and policy manager at Toxic-Free Future, an advocacy group that aims to reduce toxic chemicals in products and the environment. Liu is first author of a study, published in the journal Chemosphere, that assessed levels of flame-retardant residues in household goods.

"We were concerned about human exposure to the flame retardants used in electronics," Liu told Live Science. "We suspected that flame retardants were contaminating household products through electronic waste recycling and creating unexpected exposures."

Flame retardants in household products

Liu and her colleagues chose 203 household products to test for flame-retardant contamination based on how often those items were made of black plastic — the most common color used in electronics — and whether previous studies of the items had found similar contamination.

All the products, which included cookware, food containers, toys and hair accessories, were screened for bromine, a component of so-called brominated flame retardants (BFRs). Products with high levels of bromine — over 50 parts per million (ppm) — were analyzed in more detail for BFRs and a second class of flame retardants called organophosphate flame retardants (OPFRs).

In studies in lab animals and population-level studies in humans, both classes of chemicals have been plausibly linked to health issues, including thyroid dysfunction, developmental disorders and bone weakness. But little is known about how much exposure would be needed for someone to experience these effects, or if the route of exposure makes a difference.

The researchers' initial screening found that only about 1 in 10 products contained high bromine levels. In those products, a more in-depth analysis found high levels of BFRs and OPFRs. About two-thirds of the items contained both types of flame retardants.

The worst offenders were beaded necklaces, including "party beads." One toy pirate medallion necklace that contained up to 22,800 ppm of flame retardants had the highest levels observed.

Related: Will we ever be able to stop using plastic?

The correction

However, notably, there was an error in the team's initial report, which was published online on Sept. 11. On Dec. 15, a correction was issued.

One flame retardant analyzed in the study was BDE-209, or decabromodiphenyl ether. The team estimated that, in a day, about 34,700 nanograms of the contaminant would be transferred to a person who used a contaminated utensil to cook and serve food.

Using a 132-pound (60 kilogram) adult as reference, the Environmental Protection Agency would define the safe daily limit of this chemical to be 420,000 ng per day. However, in their paper, the authors calculated the limit as 42,000 ng per day. So by their calculation, an average adult's exposure to BDE-209 was approaching that safe limit — when really, it would need to be more than 12 times higher to reach it.

"We regret this error and have updated it in our manuscript," the authors wrote in the correction. "This calculation error does not affect the overall conclusion of the paper."

What we know (and don't know)

Flame retardants can leach into food or be absorbed through the skin, according to the National Institute of Environmental Health Sciences. However, it's difficult to determine whether using these products would lead to health problems, said Michael Bockstaller, a professor of materials science and engineering at Carnegie Mellon University who was not involved in the new study.

"There is no general answer because the impact of these materials depends on the type of chemical, concentration, type of exposure and individual circumstance," Bockstaller told Live Science.

Not all flame-retardant chemicals are tied to health issues, and most of the goods analyzed did not contain flame retardants. However, the bromine-containing products Liu's team did identify included common items, such as slotted spoons, vegetable peelers and toy cars. Liu said she personally owned black-plastic kitchen utensils before conducting the study but replaced them with wood and stainless-steel versions.

"These are products that are often used on a daily basis, and with the findings of multiple flame retardants in each product, this creates concern about compounded effects," Liu said.

More research is needed to establish how much exposure comes from the day-to-day use of these products and whether it realistically presents a health risk. Liu said she hopes the growing body of research into these chemicals' longevity and potential health hazards leads to the development of safer plastics.

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