Embarrassing Math Error ‘Scared the Pants Off People’ Over Toxic Black Kitchenware

Earlier this year, a study had people tossing their black spatulas and other black kitchenware in fear of toxic chemicals—but it turns out the alarming warning was based on a major math mistake.

In October, researchers from the environmental health advocacy group Toxic-Free Future and the Amsterdam Institute for Life and Environment published a study in the journal Chemosphere suggesting that black plastic kitchenware released worrying amounts of a toxic fire-resistant chemical. The warning took the internet by storm, convincing legions of people to toss their trusty black spatulas. Now, however, a chemist in Canada has spotted an arithmetic mistake in the fateful study that upends, or at least complicates, its results, as first reported by the National Post.

The Chemosphere study was based on the idea that some black electronic waste—containing the fire-resistant chemical Decabromodiphenyl ether, which is linked to serious health risks—is recycled into household products sold in the United States. As a consequence, the researchers sought to estimate how much of these chemicals are leaking out of black plastic kitchenware and contaminating people while cooking.

The team concluded that using this type of black kitchenware could result in people absorbing a median daily amount of 34,700 nanograms of Decabromodiphenyl ether, also known as BDE-209. This is significantly higher than previous models had estimated for human exposure through other means, and worryingly close to the U.S. Environmental Protection Agency’s (EPA) reference dose (recommended safety limit) of 42,000 nanograms per day for a 60-kilogram (132.3-pound) adult.

There’s only one problem—the EPA’s reference dose for BDE-209 is not 42,000 nanograms per day. The agency’s reference dose is 7,000 nanograms per kilogram (2.2 pounds) of body weight per day. When the researchers calculated this for a 60-kilogram (132.3-pound) individual, they multiplied 60 by 7,000 and got 42,000, but the correct result is 420,000.

The fundamental point of the study—that the recycling of some e-waste is putting a toxic chemical into kitchenware sold in the U.S.—remains true. However, the mistake significantly changes its implications, which had warned readers that their black kitchenware items were exposing them to over 80% of the EPA reference dose. In reality, it’s less than 10%.

“I think it does change the flavour of the whole thing somewhat when you’re off by a factor of ten in comparing something to the reference value,” Joe Schwarcz, director of McGill University’s Office for Science and Society and the plastics expert who caught the mistake while reading the study, told the National Post. “All of this merits attention,” he added. “But you have to do it properly, and you have to make sure your numbers are correct before you scare the pants off people.”

Megan Liu of Toxic-Free Future, who co-led the study, said that they’d submitted a correction for the “typo” but that the mistake “does not impact our results,” according to the National Post. “The levels of flame retardants that we found in black plastic household items are still of high concern, and our recommendations remain the same,” she added.

Tell that to all the people who threw out their favorite spatulas because of a warning that was off by a factor of 10.