Silent Scourge: Microplastics in Water, Food, and Air

COVID-19 has had devastating consequences to the global economy and human health. Beyond causing a serious respiratory illness, the SARS-CoV-2 virus has brought a new and largely overlooked public health threat: more potentially harmful microplastics in the environment, this time from discarded personal protective equipment (PPE). PPE used to fight COVID-19 becomes plastic waste after its use, adding to the immense worldwide problem of plastic pollution, according to a 2020 World Wide Fund for Nature (WWF) Italy study. Plastic “invades our streets, our sidewalks and our parks,” states the report. Researchers at Italy's Polytechnic of Turin estimated that in phase two of the country's COVID-19 reopening (in which activities are gradually restarted), 1 billion masks and half a billion disposable gloves each month would be needed. “These are very high quantities that require those who use them to assume responsibility for their disposal,” according to WWF Italy documents. “Each of us must make an effort to ensure that we proceed with the least possible impact on nature.” If even only 1% of the masks were discarded incorrectly, that would result in 10 million masks per month dispersed in various ecosystems. With the weight of each mask about 4 grams, more than 40,000 kilograms of plastic would soon accumulate. “Just as citizens have acted responsibly in containing the virus by staying at home, now they must prove equally responsible for the management of individual protection devices,” says WWF Italy president Donatella Bianchi. “Once these devices become waste, they have a devastating effect on our natural environments.” PPE is just one of the sources of plastic now ubiquitous in the environment around the globe. Eventually, plastic products break down into microplastics; they then contaminate air, water, and soil. Researchers are intensifying efforts to understand the human health costs of microplastics. In January 2020, the US National Academies of Science, Engineering, and Medicine in Washington, DC, hosted one of the first workshops on the environmental health effects of microplastics. Since then, the COVID-19 epidemic has made the problem even worse. In the Mediterranean alone, 570,000 tons of plastic end up in the sea every year. It is the equivalent of 33,800 plastic bottles thrown into the water every minute, according to Bianchi. That is pre-COVID-19. Now, she says, “we ask that institutions prepare appropriate collectors for masks and gloves and install them near ports and in parks, around villas and at supermarkets. It would be an advantage for the environment—and for our health.” OceansAsia, a marine conservation organization headquartered in Discovery Bay, Hong Kong, maintains a remote, boat-access-only test beach on the Soko Islands south of Lantau, Hong Kong. Twice each month, OceansAsia researchers visit the beach to carry out microplastics surveys. “Because the area is so distant, all the plastic there has its origins in the sea,” says Teale Phelps Bondaroff, OceansAsia's director of research. “In late February, about 6 weeks after wearing masks became a widespread practice in Hong Kong, much to our surprise, we started noticing a massive influx of surgical masks.” Since then, he says, OceansAsia scientists have continued to find surgical masks “in considerable numbers at beaches around Hong Kong.” Gary Stokes, OceansAsia's director of operations, investigated another beach on 25 April—and came across dozens of masks in less than 5 minutes. Stokes returned to the beach in early June and again found handfuls of masks. “The masks break down into smaller and smaller pieces of microplastic,” Phelps Bondaroff says. Researchers often discover the source of the plastic by identifying certain characteristics, for example, a wrapper from a local restaurant or a pill bottle with the name of the prescribing doctor. “While that's not possible for face masks,” says Phelps Bondaroff, “we can look at similar items on the sand, along with the location of the beach and its tidal patterns, to help trace the masks’ origins.” The scientists think surgical masks retrieved from Soko Islands beaches likely came from Hong Kong or the nearby Pearl River system. “When you suddenly have a population of 7 million people wearing one to two masks each day, the amount of plastic discarded is going to be substantial,” says Stokes. That is bad news indeed. Researchers recently discovered that microscopic bits of plastic in the ocean are carried aloft in sea spray, where they can be ferried far and wide. More than 136,000 tons of microplastics are blowing ashore on the sea breeze every year, scientists at the United Kingdom's University of Strathclyde reported in a June 2020 paper in PLOS ONE. In medical masks, it is a case of circular microplastics; to protect human health, we have ultimately endangered human health. Microplastics pose a potential health problem on their own, but treating human diseases is adding to the problem. What constitutes microplastics is well defined. Plastic pieces less than 5 millimeters in size are microplastics, according to the National Institutes of Health. Microplastics form when plastic breaks apart into tiny beads. As these wash down drains, they are not removed by wastewater treatment plants and, eventually, spread through the oceans. It does not take much to move microplastics from place to place. Just by opening a bottle or tearing a food wrapper, tiny pieces of plastic are sent flying, Zahra Sobhani of the University of Newcastle in Australia recently reported in Nature Scientific Reports. “We found that microplastics can be generated by simple tasks in our daily lives, such as scissoring, tearing, cutting, or twisting open plastic containers, bags, tapes, and caps,” Sobhani says. In spite of such far-reaching discoveries, scientists are still puzzling out the risks of microplastics to human health. The tiny plastics absorb and give off harmful pollutants, raising the specter of ill effects. Plastic's ingredients, and the toxic chemicals plastic absorbs, may build up over time and remain in the environment, eventually making their way into people. Persistent organic pollutants, polybrominated diphenyl ethers, polychlorinated biphenyls, and polycyclic aromatic hydrocarbons are all found in microplastics. Consumer products such as synthetic fabrics, toothpaste, and cosmetics are loaded with microplastics. Human health may be especially at risk in facilities that manufacture products made with plastics. Exposure to microplastics can also come from items made with plastic microbeads and from walking along shorelines and swimming in coastal or ocean waters. But the issue extends far beyond these products and locations. According to an editorial in The Lancet published in October 2017, an analysis of tap water found that 83% of the worldwide samples and 94% of those in the United States were contaminated with microscopic fragments of plastic. Other studies show that microplastics are not only in water; they are also in the air and in the soil. “The ubiquity of microplastic contamination can no longer be denied,” states The Lancet. “Microplastic contamination seems more widespread than we perhaps knew, and it is regularly being ingested by people worldwide. Most concerning is how little is known about the effects of microplastic consumption on human health.” Even with concerted global effort, microplastics in the environment will continue to increase. “What impact will this have on human health?” asks the editorial. “The answer is that no one knows.” What has been shown so far is that microplastics may lead to an array of health effects, including inflammation (linked to cancer, heart disease, and rheumatoid arthritis), genotoxicity (damage to the genetic information in a cell, causing mutations), and oxidative stress (leading to chronic diseases such as cancer, diabetes, stroke), according to the 2019 Center for International Environmental Law (CIEL) report Plastic and Health: The Hidden Costs of a Plastic Planet. Most plastic additives, the report states, “are not bound to their polymer matrix and easily leach out to the surrounding environment, including air, water, food, or body tissues. Plastic microparticles are increasingly being documented in the human bloodstream and human tissues.” Until more is known about the effects of microplastics on the human body, “the rising production and pervasive use of these persistent contaminants should be viewed as a significant health concern,” according to the CIEL document. Designing studies to look at the issue in depth is challenging, health researchers say. Observational, population-based studies are open to confounding, according to The Lancet, and experimental studies are ethically impractical. If effects exist, states the editorial, “people living in areas of high plastic contamination will develop greater disease burdens as levels continue to rise. Disease-reporting systems need to be linked to pollution databases to ensure that any effect is identified early, and action taken quickly.” Solving a problem of this magnitude will not be easy. As of 2015, 380 million metric tons of plastic waste were generated each year. Some 9% of that was ultimately recycled, 12% was incinerated, and 79% ended up in landfills or elsewhere in the environment. “Actions are urgently needed to reduce the use of microplastics and to understand the effects of these particles on both ecosystems and the human body,” The Lancet concludes. In August 2019, the World Health Organization (WHO) joined several institutions calling for more research into the health effects of microplastics. Following the release of a WHO analysis, Microplastics in Drinking-Water, the organization issued a statement that reducing plastic pollution would benefit the environment and reduce human exposure. “We urgently need to know more about the health impacts of microplastics because they are everywhere,” says Maria Neira, director of the WHO Department of Public Health, Environment, and Social Determinants of Health. “We also need to stop the rise in plastic pollution worldwide.” Potential health hazards from microplastics involve physical particles, chemicals, and microbial pathogens in biofilms. Particles likely cause impacts in the human body, depending on their size, surface area, and shape. Although plastic polymers may have low toxicity, states the WHO report, microplastics can contain unbound polymers with larger issues. Chemicals in the environment, including persistent organic pollutants, may also bind to plastic particles. Biofilms in drinking water are formed when microorganisms grow on water distribution systems and other surfaces like microplastics. “Most microorganisms in biofilms are non-pathogenic,” the report states. “However, biofilms can include pathogens such as Pseudomonas aeruginosa, Legionella spp., nontuberculosis Mycobacterium spp. and Naegleria fowleri.” The latter causes a brain infection called primary amebic meningoencephalitis, which is usually fatal. The WHO has now initiated a broader assessment of microplastics in the environment. A future report, the organization says, “will characterize the human health risks due to total microplastics exposure from the environment, including through food and air.” Microplastics research is still in its infancy, according to Kieran Cox, of the University of Victoria in British Columbia, who moved the field forward with a look at the American diet. Cox evaluated the number of microplastics particles in commonly consumed foods. From Americans’ caloric intake, Cox and colleagues estimate that annual microplastics consumption ranges from 39,000 to 52,000 particles per person. These estimates increase to 74,000 to 121,000 when what Americans breathe in is added. People who meet their recommended daily water intake only through plastic bottled sources may be ingesting an additional 90,000 microplastic pieces each year, compared with those who drink solely tap water, the biologists report in a 2019 paper in Environmental Science and Technology. “These estimates substantially increase values previously provided by researchers who focused on single types of food or beverages,” state Cox and his coauthors. “Drinking water, respiration, sugars, and seafood represent substantial vectors of microplastics consumption, with microplastics inhalation perhaps posing the largest risk to adults and drinking water the largest risk to children.” Whether inhaled microplastics count as being ingested has been a subject of debate. “Unless coughed or sneezed out,” according to Cox, “inhaled particles enter the digestive system or remain trapped in the lungs, suggesting that most inhaled particles will in fact be ingested.” Following Cox's work, researchers at King's College London carried out the first study of microplastics in the atmosphere above the city to determine exposure levels of people in the area. The results were published in December 2019, in Environment International. Stephanie Wright and colleagues found that microplastics are present in the air over London. The discovery indicates that urban areas are likely sources of microplastics to the wider environment, Wright says. Weather and meteorological patterns had little influence on the particles’ abundance, she found, although microplastics can travel as far as 95 kilometers on the wind. Microplastics were present in every sample above London and were higher there than in, for example, Dongguan, China; Paris, France; and Hamburg, Germany. Some 92% were fibrous microplastics that come from textiles, including clothing, upholstery, and carpets. Other sources included items such as disposable plastic bags and foam from polystyrene. Across all samples, 15 petrochemical-based polymers were identified. “We found some of the highest reported levels of microplastics in atmospheric dust, with local sources appearing influential,” says Wright. “Fibers were the most abundant, for the size range we looked at. How long they remain airborne is unknown, but the answer is key to understanding long-range transport. An important next step is to estimate human exposure risks to airborne microplastics.” Occupational studies show that workers exposed to high levels of plastic dust suffer chronic inflammation of their airways and, in the worst cases, interstitial lung disease and tissue scarring. Wright is now quantifying microplastics in size fractions capable of being deposited in human airways. Microplastic particles can be washed out of the air by precipitation, especially by snow, found scientists at the Alfred Wegener Institute in Germany. They reported their results in Science Advances in August 2019. The paper, “White and wonderful? Microplastics prevail in snow from the Alps to the Arctic,” compared snow samples from remote sites in the Swiss Alps to populated sites in Bavaria and Bremen, as well as from Svalbard in the Arctic. Snow forms around aerosol nuclei that often contain pollutants such as microplastics, the researchers report. Of the scientists’ numerous study sites, the highest concentrations of microplastics were in samples from a rural road in Bavaria: 154,000 particles per liter. These samples, says Melanie Bergmann, the paper's lead author, contained various types of rubber, such as that used in car tires. The findings are “relevant in the context of human and animal health,” state Bergmann and colleagues, “especially in terms of inhabited European sites, where residents may breathe in airborne microplastics. 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