The Case of the Black Plastic SpatulaThe Case of the Black Plastic Spatula

We’ve all seen the headlines telling us to ditch our black plastic spatulas immediately: They could kill you, they screamed. The panic stemmed largely from a study published in the journal Chemosphere in October, which stated that the spatulas and other black plastic items could shed flame retardants. Researchers found the chemicals in 17 of the more than 200 household products they tested, reported the New York Times on Dec. 10. “Some products were found to contain . . .  a flame retardant linked to cancer that the Environmental Protection Agency banned in 2021 based on studies that had shown it was dangerous for human health,” wrote the Times. There was just one problem with that paper in the peer-reviewed journal: The researchers got the math wrong.

Flame retardants may leach from black plastics

The study conducted by advocacy group Toxic-Free Future found signs of a flame retardant in black plastic and raised the possibility of it getting into your food if you use something like a black plastic spatula, reported NPR, among countless other media outlets. “The study miscalculated when it found the flame retardant was close to a hazardous level for adults. The chemicals were actually found at less than one-tenth that level, so the risk to people would seem to be far lower than previously suggested,” said NPR.

A missing zero

Specifically, the study estimated that “using contaminated kitchenware could cause a median intake of 34,700 nanograms per day of decabromodiphenyl ether, known as BDE-209. That is far more than the bodily intake previously estimated from other modes, such as ingesting dust,” reported Canada’s National Post. The paper correctly gives the reference dose — the amount of toxin generally considered safe — for BDE-209 as 7,000 nanograms per kilogram of body weight per day, but calculates this into a limit for a 60-kilogram adult of 42,000 nanograms per day, National Post went on to say. “So, as the paper claims, the estimated actual exposure from kitchen utensils of 34,700 nanograms per day is more than 80 per cent of the EPA limit of 42,000.”

“That sounds bad. But 60 times 7,000 is not 42,000. It is 420,000. The estimated exposure is not even a tenth of the reference dose. That does not sound as bad,” writes the National Post.

The lead author of the paper and a manager at Toxic-Free Future, Megan Liu has acknowledged the error, calling it a typo. “However, it is important to note that this does not impact our results,” Liu told 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.”

Pop quiz: Multiply 60 times 7,000

Maybe, or maybe not. That’s quite a mathematical error, especially when you consider that the paper was peer reviewed. I’m no math whiz — not by a long shot — but I’ve been an editor for most of my adult life and one of the first things I learned when starting my career was to double-check all numbers. That top 10 list? Count the bulleted items and make sure they equal 10. That may seem elementary — but you would be surprised how often proofreaders catch such simple errors — and it’s leagues removed from the complexity of calculating nanograms per kilogram of body weight. But is it that different from verifying the product of 60 times 7,000? I mean, you have a calculator, right? Hint: There’s one on your smartphone.