The study that called the black plastic utensils had a major math error

The editors of the environmental chemistry journal Chemosphere have published a compelling correction to a study that reported toxic Flame retardants from electronics leach into some household products made of black plasticincluding kitchen utensils. The study raised a flurry of media reports a few weeks ago that urgently begged people drop his kitchen spatulas and spoons. Wirecutter also offered a buying guide for what will replace them.

The correctionpublished on Sunday, will probably take some heat from the besieged tools. The authors made a math error that put the estimated risk from kitchen utensils by an order of magnitude.

Specifically, the authors estimated that if a cookware contained average levels of a key toxic flame retardant (BDE-209), the cookware would transfer 34,700 nanograms of the pollutant per day based on regular use. while cooking and serving hot food. The authors compared this estimate to a reference level of BDE-209 considered safe by the Environmental Protection Agency. The EPA’s safe level is 7,000 ng—per kilogram of body weight—per day, and the authors used 60 kg as the adult weight (about 132 pounds) for their estimate. Therefore, the EPA safe limit would be 7,000 multiplied by 60, yielding 420,000 ng per day. That is 12 times more than the estimated exposure of 34,700 ng per day.

However, the authors missed a zero and reported the EPA’s safe limit as 42,000 ng per day for a 60 kg adult. The error made it appear that the estimated exposure was almost at the safe limit, even though it was actually less than one-tenth of the limit.

“(W)e miscalculated the reference dose for a 60 kg adult, initially estimated at 42,000 ng/day instead of the correct value of 420,000 ng/day,” the correction reads. “As a result, we revised our statement from ‘the calculated daily intake approached the US BDE-209 reference dose’ to ‘the US BDE-209 reference dose’ remains an order of magnitude lower than the reference dose of BDE-209.” We regret this error and have updated it in our manuscript.”

Conclusion without changes

While being off by an order of magnitude seems like a significant error, the authors don’t seem to think it changes anything. “This calculation error does not affect the overall conclusion of the paper,” the correction reads. The correct study still ends by saying that flame retardants “significantly contaminate” plastic products, which have “high exposure potential”.

Ars reached out to the lead author, Megan Liu, but did not receive a response. Liu works for the environmental health advocacy group Toxic-Free Future, which led the study.

The study highlighted that flame retardants used in plastic electronics can, in some cases, be recycled into household items.