Plastic levels are tricky to measure. To get the full picture, researchers used several different methods to measure MNPs in 91 brain samples collected from people who died as far back as 1997. The measurements all pointed to substantial increases over the years. From 2016 to 2024, the median concentration of MNPs increased by about 50 percent, from 3,345 micrograms per gram to 4,917 micrograms per gram.

“The levels of plastic being detected in the brain are almost unbelievable,” says study coauthor Andrew West, a neuroscientist at Duke University. “In fact, I didn’t believe it until I saw all the data” from multiple tests with different samples.