(file image) Photo: 123rf
A miscalculation has been found in a study which went viral about the potential health risk posed by flame retardants in some items made from recycled black plastics.
US non-profit organisation Toxic-Free Future's peer-reviewed study, published in the Chemosphere journal, made news headlines around the world after it was published online in September.
The researchers found various amounts of flame retardant in about 85 percent of 203 black plastic products they tested, including spatulas, plastic takeout containers and children's jewellery.
While estimating how much one these toxins was getting out of the spatulas during cooking and into the human body, the researchers did not multiply correctly.
It resulted in a 10-fold overestimation of how close that potential exposure to a toxic chemical was to a dose that the United States Environmental Protection Agency would deem to be a health risk.
Canadian chemist Joe Schwarcz, director of McGill University's office for science and society, wrote about spotting the error in early December.
"The evaluation of risk often involves calculations that have to be done carefully. A small error can cause large worries."
A correction and apology was posted on the journal's website on 15 December, 2024.
Why do we have flame retardants in these items?
There are some challenges manufacturers face in sourcing black plastics from recyclables.
Black plastic items are often missed when they go through sorting facilities powered by machines using infrared light detectors, due to their colour, Schwarcz wrote. Another difficulty is that they are often a combination of polymer properties which require separation.
So instead of starting from scratch with raw materials and creating more plastic waste, some are resorting to using black plastic used in electronic devices, which contain flame retardants to help prevent them catching fire.
"Discarded electric and electronic equipment, ranging from cellphones and television sets to computers, ends up being dismantled for valuable metals, and the black plastic used in casings and circuit boards is sold to whoever may want to purchase it. That is usually companies in Asia that melt it down and convert it into consumer items," Schwarcz said.
It is hard for consumers to figure out which of these products could be contaminated with toxins, because they are unlikely to detail the components on the item.
Study co-author Megan Liu told the LA Times the study found higher levels of toxic flame retardants in polystyrene plastic, which is labelled with the number 6.
What's the verdict?
New Zealand Food Safety deputy director-general Vincent Arbuckle said the concerns raised by the Toxic-Free Future research were not supported by the evidence.
They had also contacted the Chemosphere journal about the error when they spotted it, he said.
Schwarcz said, based on the evidence, he didn't believe the risk was high enough to throw away his black plastic kitchenware, if he had any.
Furthermore, University of Birmingham researchers observed what it would take for the toxins to seep through; they found flame retardants were transferred to olive oil after bits of black plastic were immersed in it for 15 minutes at 160C.
"Hardly a mimic of using a spatula in a frying pan and, of course, when we fry not all the oil used ends up in our body," Schwarcz said.
On the other hand, the Toxic-Free Future researchers say the correction does not change their overall conclusion and what they sought in the hypothesis.
Schwarcz told the National Post he agreed with the hypothesis that recycled black plastic items containing flame retardants were re-entering the US supply chain.
"That being said, there should be no flame retardants in such items," he wrote in his post about spotting the error.
"Novel methods, including some based on artificial intelligence, are being developed to identify plastics on the recycling conveyor belt that will allow black plastics to be sorted and recycled, eliminating the need to resort to using plastics from electronic waste."
