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Humans have spread microplastics — tiny pieces of plastic that pollute the environment — everywhere. They’re in our drinking water, food, and air. But how many microplastics are in what we eat, drink, and breathe, and how harmful are they to human health?
Researchers evaluating the number of microplastics in commonly consumed foods, drinking water sources, and the air project that tens of thousands of microplastic particles are being consumed each year in the U.S. On average, American men, women, and children are consuming over 100 microplastics per day.
Although these are estimates, the researchers think that these values are likely underestimated and should not be taken lightly.
A plastic planet
Microplastics are widespread throughout ecosystems — both land and sea. We’ve spread them to the deepest rifts of the ocean and the most out-of-the-way places on earth.
Current projections imply that, if unchecked, there will be 12 billion metric tons of plastic waste by 2050. This is almost three times as much as the 4.9 billion metric tons found in 2015, which is 60% of all plastics produced ever.
What’s worse is that growing evidence suggests that microplastics are becoming part of widely consumed food items. This occurs mainly by animals eating or breathing these particles, as well as contamination during food production and plastic packaging.
Microplastic particles are usually tens of microns wide — a size that is virtually undetectable to the naked eye. In the ocean, the smallest microplastics reportedly detected are 1.6 micrometers. Tens to hundreds of microplastic particles could fit onto the period that ends this sentence.
Despite more and more evidence that microplastics taint a lot of food and beverages, and the possibility of harmful effects on human health, little is known about the exposure of microplastics to humans.
A compellingly compliant database
To address this, researchers created a microplastics database to estimate how many particles Americans were ingesting annually. The investigators did a thorough review of the literature and combined it with U.S. dietary data to make estimates of human exposure to microplastics.
To do so, they found the number of microplastics in commonly consumed items. They then combined this with the recommended or reported consumption amounts of these items for the American public. This was done according to information provided by several national and international organizations including the United States Department of Agriculture (USDA) and the World Health Organization (WHO).
Finally, the possible consumption of microplastics through breathing was surveyed using reported microplastic concentrations in the air and the U.S. Environmental Protection Agency’s (EPA) reported breathing rates.
And the most microplastic goes to…
The researchers found sources of microplastics in several commonly consumed items. This included seafood, from fish like tuna to bivalves (e.g., mussels and oysters), sugars, salts, honey, and beer, as well as tap and bottled water. Other food groups, such as meat (e.g., poultry and beef), dairy, grains, and vegetables, were not included due to a lack of data.
What they found was that Americans — adults and children — consuming the recommended or average amounts of the items that have been analyzed for are exposed to between 81,000 and 123,000 microplastics per year. That’s about the size of a softball’s worth of microplastics each year!
While water, air, and seafood were the three most sizable modes of microplastics consumption, microplastics breathing and drinking water was shown to pose the largest risk to adults and children, respectively. Regarding drinking water, the researchers clearly saw that bottled water contained vastly more microplastic than tap water.
What’s more, people who get their daily water through only bottled sources may be consuming additional tens of thousands of microplastics annually.
A plastic pill to swallow
The researchers note, worryingly, that these estimates of American consumption of microplastics are likely drastic underestimates overall. This is because their current information does not account for a person’s entire caloric intake but, instead, just a portion of it. So, if these findings are symbolic at all, the yearly microplastic consumption by an American could exceed several hundred thousand particles.
On top of this, the researchers did not consider to what extent food items sold in large amounts of plastic packaging are contaminated with microplastics. Given the insight gained from bottled versus tap water, it is possible that packaged foods contain many more microplastics than those estimated in the current survey.
It’s unclear whether or not inhaled microplastics are actually ingested. But, unless coughed or sneezed out of the mouth or nose, inhaled particles will either enter the gut or remain trapped in the lungs.
Microplastics can invade human tissues and trigger a localized immune response. However, the effects of consuming microplastics on human health are largely unknown.
One idea is that microplastics can carry harmful chemicals — such as fillers, pigments, plasticizers, stabilizers, and flame retardants, as well as medical additives — and absorbed toxins. These are then transported together into plants, animals, and people.
Once microplastics are consumed and travel to the gut, they can release these damaging passengers, including some that can cause cancer. What’s more, the microplastics can be taken up by cells in the gut and lungs from ingestion and inhalation, respectively.
How much microplastics are taken up by cells in the human body depends on different factors, such as their shape and size. For instance, particles on the scale of a few microns or less, of which there are many, may be directly taken up by gut or lung cells.
However, there is limited data on the sizes of microplastic particles that are present in consumed items. So, it is still unclear to what extent the estimates here of human microplastic consumption pose a risk to human health.
This survey suggests that using tap instead of bottled water might effectively reduce exposure to microplastics ingested by drinking. Still, this does not address the fact that the prevalence of plastic in marine environments is increasing. That would likely mean that microplastics will continually contaminate the majority of, if not all, items intended for human consumption.
Future research needs to be conducted to thoroughly investigate the contamination of other food groups. This is especially true of products that represent major sources of nutrition globally, like grains, vegetables, beef, and poultry.
In addition, the existing microplastics data for alcohol and added sugars is outdated and somewhat questionable. So, more studies using more recently developed methods should be carried out for these items.
New research with new data will yield updates to these estimates of human microplastic consumption. Importantly, this will allow scientists to eventually estimate the potential risk of microplastic ingestion to people.
There is only one real solution to reducing human consumption of microplastics — to reduce the production and use of plastics.