Many scientists have argued that microplastics pose a real, if often subtle, threat to human health. A study out this week may provide an important clue as to how this damage occurs.
Researchers from Columbia University and others have looked closely at how microplastics behave in water. They found that when plastic is broken into small fragments and surrounded by water, it can produce very reactive molecules. Although more study is still needed to understand the exact health effects of microplastics, the team’s work underscores the assumption that plastic is always chemically passive, the authors say.
“Our findings challenge the prevailing paradigm of plastic inertness [and] identify a possibly overlooked mechanism for the harmful effects of microplastics on health and the environment,” they wrote in their paper, published Wednesday in the journal Nature.
Not so inert
Microplastics are all pieces of plastic smaller than 5 millimeters. Over the years, scientists have raised more and more alarms about the possible dangers of microplastics to people and other animals.
We know that plastic commonly contains chemicals that can mimic and possibly disrupt the functioning of some natural hormones. There is also some research suggesting that microplastics can harm our bodies directly, but the data on these potential risks is more limited.
One reason why plastics are so widely used in society is that they are chemically inert under normal circumstances. However, the researchers’ experiments show that this assumption is not true when plastic is broken down into small pieces that enter our bodies. Specifically, they found that microplastics are able to spontaneously generate unstable molecules known as free radicals when in the presence of water.
“As plastic fragments into smaller and smaller particles, its surface area increases tremendously,” said senior study author Wei Min, a Columbia professor of chemical and biomedical engineering, in a Columbia statement. “Then the microplastic changes the water that surrounds it, generating high-energy, reactive radicals that very likely contribute to the biological damage we see in animals and potentially in humans as a result of microplastic exposure.”
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Of course, our body is filled with water, so it is certainly reasonable to think that microplastics can also create these radicals inside us. We may also be exposed to these molecules when we drink bottled water, the researchers speculate. Such radicals may then explain at least some of the harmful physical changes scientists have linked to microplastics, such as inflammation, immune dysfunction and altered metabolism.
At the same time, scientists are still trying to quantify the health risks of microplastics, which may be influenced by factors other than age. How much plastic exposure per day or year is needed to, for example, increase people’s chance of a certain health condition, and do these chances differ based on exactly where plastic ends up in the body? Important as these and other questions are, it is unlikely that microplastics are completely harmless to people (and there is strong evidence that they are particularly bad for the marine environment).
So this study should help scientists better understand the dangers of microplastics, and the researchers are hopeful that it will even lead to improved methods of plastic production that can generate the risk of free radicals.