The impending risk of microplastic
Microplastic may have been an uninvited guest to your Thanksgiving Day feast. Or perhaps an unintentional ingredient in that healthy fruit plate you enjoyed. In fact, scientists have found Microplastic almost everywhere they’ve looked, from the bottom of the ocean to the top of mountains, in soil, drinking water, seafood, produce, and in our bodies.
Microplastic is a very large group of small to very small particles – less than 5 mm or one fifth of an inch in length. They can be intentionally made for some uses like sandblasting or the now-banned microbeads in cosmetic products. More commonly they are the result of larger plastic pieces breaking down in the environment after they’re discarded. When microplastics get very small, usually less than 0.1 mm, then they are termed nanoplastic.
We are in the relatively early days of scientific research into how this ubiquitous microplastic pollution may affect us and the environment, but the exponential growth of publishing on microplastic shows that scientists are worried about this risk. Nanoplastic, like other nanomaterials, may have different effects on organisms than larger microplastic.
Our thorough analysis of the literature tells us that scientists are deeply concerned about the extent to which microplastic contaminates our environment. Out of the almost 4500 articles we looked at, almost 35% examine how microplastic gets into the environment, how it is transported throughout, and how it accumulates in various ecosystems and organisms.
The news is not promising. Scientists have found that microplastic in the deep sea seems to concentrate in places that are hotspots for biodiversity. They are worried that organisms constantly exposed to microplastic may be detrimentally affected by them. What’s more, other scientific studies have shown that microplastic routinely takes up and disperses other environmental pollutants, like plasticizers, endocrine disrupters, pharmaceuticals, and heavy metals. That means that even if the microplastic by itself isn’t harmful to marine organisms, the other chemicals they’re exposed to via microplastic could be the source of harm.
Most microplastics don’t break down very easily either, so once an organism ingests microplastic it can be transmitted through the food web to higher trophic levels and even into the seafood we eat. Microplastic’s presence in food doesn’t end there, though. Studies conducted on produce obtained from markets in Italy found that fruits and vegetables – especially apples – have significant numbers of nanoplastic particles in them. This led to estimates of human ingestion of 46,000 to 1,4 million particles per day from apples alone.
With this ubiquitous exposure to microplastic resting on more and more evidence, scientists have predictably turned to try to answer the question of what it means for human health. To date, there have not been any studies conducted in humans that assess microplastic toxicity, either directly or indirectly. However, more than 650 studies have been published that investigate microplastic toxicity in animals, from the smallest zooplankton up to larger fish and mammals.
The results for microplastic so far are cause for concern, but not yet alarm. General Causation risk scores for six hypotheses of harm are approaching 0.5, the highest they can get without human evidence contributing to the literature base. We should expect scientists to continue to focus on the possible effects microplastic can have on human health, and epidemiology studies are likely to appear in the literature over the next several years.
What we do know is that microbes, animals, and plants exposed to microplastic are not faring very well. Lawsuits for water or environmental cleanup efforts may emerge to clean up the damage to the environment long before the science tells us whether microplastics harm us directly.
In the meantime, we offer this parting thought. A recent study just showed that we consume approximately a credit card amount of microplastic every one to two weeks. That may explain why your last meal may have tasted a little like Visa.