In other words, heating plastic essentially makes it softer and more porous. If you’ve ever microwaved marinara sauce in a plastic bowl, you’ve seen the sunset red, impossible-to-remove stain it leaves behind. “Passages in the plastic can open up, so the sauce gets inside,” says James Rogers, PhD the director of food safety research and testing at Consumer Reports. The opposite exchange happens too: “If something goes in, something can also come out,” he says.
Are those chemicals and microplastics unsafe?
Just about all Americans have measurable amounts of phthalates and BPA in their bodies. Mammalian animal studies strongly suggest that, once inside, these chemicals act like sneaky gatecrashers at a masquerade ball. They’re not welcome at the party, but they’re also tough to parse from the legitimate guests.
That’s because bisphenols and phthalates are endocrine disruptors. They can mimic, block, or interfere with the body’s hormones—possibly increasing the risk of various conditions, including infertility, some cancers, metabolic diseases, neurological conditions, and immune system dysfunction. According to Laura N. Vandenberg, PhD, a professor of environmental health sciences at the University of Massachusetts Amherst, “That’s just the short list.”
Various human studies have also reinforced the animal ones. Exposure to high phthalate levels in the womb has been linked to asthma in childhood. For boys, that early contact could cause behavioral problems as well as potentially lower sperm counts later in life. Pregnant people might experience lower thyroid hormone levels and more preterm births.
There’s a lot more that we don’t know. At Duke University, Jason Somarelli, PhD, the director of research at the Duke Comparative Oncology Group, is studying the thousands of other additives in plastics. “We’ve found at least 100 known carcinogens in these other chemicals,” he says. “And then there’s well over 2,000 others where we just don’t have enough data to know.” What he can say with confidence: “There’s bad stuff in plastic.”
Beyond the chemicals being leached by plastics, the particles themselves—which have been discovered in human hearts, bloodstreams, lungs, placentas, semen, and breastmilk—pose a threat too. The body sees the physical particles as intruders, so naturally they seem to fight back. That can trigger an immune response: Because plastics can’t be degraded, white blood cells die in the battle, causing inflammation. Those particles can also “act as transport vehicles for other pollutants,” says Vandenberg, bringing potentially toxic substances into the body.
Hussain wanted to see for himself what microplastics and nanoplastics might do inside our bodies. His team bathed human embryonic kidney cells in high concentrations of plastics shed by the containers they were testing. Within 48 hours, 76% of embryonic kidney cells died—about three times more than the percentage of cells that spent the same amount of time in a more diluted (less plastic-y) solution. Hussain’s findings corroborate another study published last year, which determined that direct microplastic exposure can cause cell death, inflammation, and oxidative stress.
