What Do We Really Know?

Plastic is a diverse material. Heather Leslie, PhD, senior researcher in Vrije Universiteit’s Department of Environment and Health, likens it to spaghetti with sauce. The noodles are the long polymer backbone that all plastic shares. The sauces are “the pigments, the antioxidants, the flame retardants, etc., that make it functional,” she says. 

What Makes Microplastics Dangerous?

There are more than 10,000 different chemicals, or “sauces,”  used to alter a plastic’s physical characteristics—making it softer, more rigid, or more flexible, says Hanna Dusza, PhD, of the Institute for Risk Assessment Sciences at Utrecht University.

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As plastics degrade and become microplastics, these chemicals likely remain. Recent research has shown that microplastics leach these chemicals locally in human tissues, or other areas of accumulation, says Dusza. Some 2,400 of the 10,000 chemical additives were classified as substances of potential concern, meeting the European Union’s criteria for persistence, bioaccumulation, or toxicity.

Many of these chemicals also act as endocrine-disrupting compounds, or toxicants that imitate hormones when they enter the body. Hormones are active at very low concentrations in your bloodstream, explains Leslie. To your body, some chemical additives in plastic resemble hormones, so the body responds. 

“Sometimes even a low dose of some of these additives can cause unwanted effects,” says Leslie.

Bisphenol A (BPA), for example, is one of the more infamous endocrine disruptors. It is used as an additive to make plastics more rigid and can be found in any number of plastic products, though areas of concern have been plastic water bottles, baby bottles, and the protective coatings in canned foods. 

BPA may mimic estrogen, the female sex hormone essential for reproduction, neurodevelopment, and bone density. In men, estrogen regulates sperm count, sex drive, and erectile function. BPA exposure has been linked with – but not proven to cause – multiple cancer types, ADHD, obesity, and low sperm count. Most everyone has some amount of BPA circulating within their blood, but microplastics may retain BPA as they degrade, potentially increasing our exposure, leading to its unwanted consequences, says Dusza. 

And BPA is just one of those 2,400 substances of “potential concern.”