Microplastics infiltrate the human food chain

December 27, 2019

 

The average American is believed to ingest hundreds of thousands of minuscule pieces of plastic every year, equivalent to about five grams of plastic each week through the food we eat and the air we breath. Starting with first-level algae and ending with humans at the top of the trophic pyramid, microplastics have undeniably infiltrated the food chain, from seafood to beer.

"Human reliance on plastic packaging and food processing methods for major food groups such as meats, fruits and veggies is a growing problem. Our research suggests microplastics will continue to be found in the majority – if not all – of items intended for human consumption," said Kieran Cox, an oceanographer with the University of Victoria in British Columbia who was lead author on a 2019 study looking into human consumption of microplastics. "We need to reassess our reliance on synthetic materials and alter how we manage them to change our relationship with plastics."

The study, "Human Consumption of Microplastics,” looked at the presence of microplastics in fish, shellfish, sugars, salt, honey, sugar, beer and bottled water, as well as air intake.

Microplastics refers to tiny pieces of plastic that range from a single nanometer to about five millimeters. Sources include primary microplastics that are manufactured as microbes, capsules, fibers and pellets used in cosmetics, personal care products, abrasives and textiles. Other sources of microplastics include larger pieces of plastic that break down into smaller pieces when exposed to sunlight and other elements. Secondary microplastics include fragments from plastic bottles, bags, synthetic clothing and other debris.

Researchers evaluated about 15 percent of American's caloric intake and estimated that annual microplastic consumption ranges from 29,000 to 52,000 particles, depending on age and sex. The estimates increased to 74,000 to 121,000 particles when inhalation was considered. Further, the researchers said individuals who meet their recommended water intake through bottled water alone could be ingesting an additional 90,000 microplastics annually, compared to 4,000 for those who drink only tap water.

"Given methodological and data limitations, these values are likely underestimates," the study noted.

Despite the findings, the effects of microplastics on human health is still largely unknown. Overall, the majority of research into microplastics has focused on where it is, where it's coming from and the potential effects it could have on aquatic ecosystems.

A simple Google image search for "The Great Pacific Garbage Patch" will produce images of an island of plastic trash the size of Texas floating between California and Hawaii. However, scientists with the National Oceanic and Atmospheric Administration (NOAA) – which, yes, focuses on more than weather forecasts – are quick to point out that much of the debris includes a conglomeration of smaller bits of plastic and microplastics suspended throughout the water column.

Closer to home, concentrations of microplastics in the Great Lakes are considered the highest on earth. On the local level, concentrations of microplastics in the Clinton, Huron and Rouge rivers are among the highest of all the Great Lakes tributaries tested.

"We had samples in the Great Lakes that rivaled the most contaminated places in the world's oceans," said chemist Sherri Mason, who currently serves as sustainability coordinator for Penn State Berhrend, and is a lead author of studies into microplastics in the Great Lakes. "The point I try to drive home is that what we hear about in the oceans – and we hear about them more than freshwater – all the stuff you are hearing, it's happening much more localized. It's happening in our rivers and lakes. It's happening in the water you depend on to drink. It's happening in the water used to grow your food. It's happening."

Mason began studying microplastics by chance in 2011. The Texas native had already lived along the shores of Lake Erie for a decade, but admittedly hadn't been out on the lake much. But in 2011 she and a group of students boarded the replica sailing brig, Niagara, and started sampling the water for plastics as a teaching exercise. Expecting to find plastic bags, straws and bottles floating throughout the lake, Mason instead found countless pieces of tiny microplastics. As her work expanded, the findings were astonishing.

The study, which was completed in 2012, found microplastics gathered from surface waters of the Great Lakes had a median concentration of 5,350 particles per square kilometer, and a maximum concentration of 466,000 particles per square kilometer – levels as high or higher than in ocean gyres.

Looking at the areas of the Great Lakes, which hold 20 percent of the world's surface freshwater, the largest, Lake Superior, flows into Lake Huron, which geologically forms a single lake with Lake Michigan and is separated by the lower peninsula. Considered the most pristine of the Great Lakes, researchers estimate about 30,000 microplastic particles per square kilometer in Lake Superior; 17,000 particles per square kilometer throughout Lake Michigan; and 3,000 particles per square kilometer in Lake Huron.

The primary outfall for Lake Huron is Lake Erie, where researchers estimate about 46,000 particles per square kilometer. As Lake Erie pours into Lake Ontario to form the end of the lake system, researchers found the highest concentration estimates, with about 230,000 particles per square kilometer. All of the water then flows into the St. Lawrence Seaway and eventually into the North Atlantic.

The study found microplastic fragments formed through the degradation and breakdown of larger Styrofoam, bottles and other plastic items, made up an average of about 52 percent of all particles in each sample. Pellets from preproduction plastic items and beads from cleaners and other uses made up an average of 16 percent of particles – however, 97 percent of all pellets and beads were found in two samples. Microfibers from clothing and synthetic lines made up about two percent of the particles, on average.

"We started with the Great Lakes with the question, 'is it there?' because nobody was looking, oddly enough," Mason said. "So, then we looked at the rivers."

Working with the United States Geological Survey (USGS), researchers looked at microplastics in 29 Great Lakes tributaries in six states. Each tributary was sampled three or four times and plastic particles were sorted by size, counted and categorized as fibers/lines, pellets/beads/foams, films and fragments. Microplastics were found in all 107 samples, with a maximum concentration of 32.3 particles per cubic meter found in the Huron River, which flows from Springfield Township in northern Oakland County to Lake Erie.

The overall median concentration of particles for all the samples was found to be 1.9 particles per cubic meter. The highest median concentration of microplastics,  12.2 (21.5 maximum) particles per cubic meter, was found in the Clinton River, which flows mainly from Springfield Township to Lake St. Clair in Harrison Township. The Rouge River, which flows from Rochester Hills and goes through Birmingham, Bloomfield Township and Bloomfield Hills before reaching the Detroit River, had a median concentration of 10.2 particles per cubic meter (11.4 maximum) – the third highest of the tributaries sampled, behind the Ashtabula River, northeast of Cleveland.

"The Rouge River was the most urbanized river that we studied. All particle types were found, with fiber being the most common, which isn't uncommon," Mason said. "We were looking across different urbanizations, from rural areas to more urbanized, and we looked at high flows and low flows.

"With all the different shapes of particles, you can go from rural to urban, and low to high flow and see an increase with all of those, except fibers. When you have more people, you have more particles, so it's pretty logical. When you have rain and a lot of runoff, you see higher counts of fragments that are running off the roads. With fibers, they are always the same. They are omnipresent. It doesn't matter if you're looking in rural or urban tributaries."

Overall, fibers were the most commonly detected particle type found in tributaries, making up about 71 percent of all particles found in total samples. Microfibers often come from synthetic clothing. Mason said those findings are a sharp contrast to the percentage of fibers found in most Great Lakes samples.

"In tributaries, the turbulence keeps the fibers afloat. In the absence of that, they are sinking, so they are found in the sediment in the Great Lakes," she said. "With regard to fibers, they are readily transported around the globe in air. They are everywhere. They are in soil and water. They are in your beer. They are the most common type of microplastic."

Researchers found the Rouge River had an average concentration of about 6.5 fiber particles per cubic meter; the Clinton River had about five per cubic meter; and the Huron River had about three per cubic meter.

In terms of fragments, researchers found the Rouge had an average of two particles per cubic meter; the Clinton River had six particles per cubic meter; and the Huron River had about five particles per cubic meter.

Foams and film microplastics had lower concentrations in metro Detroit-area rivers, with Rouge River samples averaging about .25 film particles and 1.5 foam particles per cubic meter; The Clinton River had an average of one film and one foam particle per cubic meter; and the Huron River had an average of about .7 film particles and .3 foam particles per cubic foot. Pellet and bead particles per cubic meter in each of the three rivers were on average less than .25 particles.

Microbeads are the tiny plastic beads that had been used in some toothpastes, facial scrubs, toilet cleaners and other products that work as scrubbers or exfoliators. However, the beads don't dissolve and aren't easily removed from wastewater, as most treatment systems aren't designed to catch the tiny particles. Concern about the damage to aquatic ecosystems and humans from microbeads lead to a nationwide ban in 2015 on the use of them.

The Microbead-Free Waters Act of 2015 was passed in December of that year, and amended the federal Food, Drug and Cosmetic Act by prohibiting the manufacture, packaging and distribution of rinse-off cosmetics containing plastic microbeads. The law applies to non-prescription items, like over-the-counter drugs, as well as cosmetic products, including toothpaste and facial scrubs.

The federal Food and Drug Administration (FDA) said the law specifically addresses concerns that microbeads may not be filtered and end up in lakes and oceans where they are mistaken for food by small fish and other wildlife. The law doesn't address consumer safety, with the FDA stating "we do not have evidence suggesting that plastic microbeads, used in cosmetics, pose a human health concern."

Under the law, manufacturers had until July 1, 2017, to stop the manufacture of products covered under the law, and until July 1, 2018, to stop the introduction of these products into interstate commerce. Rinse-off cosmetics that are also non-prescription drugs had until July 1, 2018, to stop manufacture and July 1, 2019, to stop their delivery.

Scientists studying the presence of microplastics in the digestive tracts of fish pulled from three Great Lakes tributaries found plastics in about 85 percent of all species tested. However, Tim Hollein, an assistant professor of biology at Loyola University who worked on the study, said the ban on microbeads could be having an impact.

"There might be a change or decrease in microbeads," he said. "The latest data looking at the transport of microplastics, in terms of where they are going and where they settle out, two of those studies were downstream of a wastewater treatment plant, and they observed microbeads at those and not the others. That suggests they are still coming out, so they are still around, but not in high abundance. They make up about 10 percent or less at those sites, and we don't see them at other locations that aren't near wastewater treatment plants.

"We did the same analysis in 2013, and found more microbeads – about 20 or 25 percent. I can't say for sure that there's a decrease, but data over time suggests that may be indicative of a pattern."

As with most plastics, the breakdown of microbeads in the environment is done slowly. The beads, which typically float, rather than sink, are decomposed by microbes and exposure to sunlight or ultraviolet light. Hollein said that as most microplastics break down, they tend to get sticky and group together, reducing the distance they spread. However, the process tends to take years.

While the study of microplastics in aquatic species and ecosystems is relatively new, Hollein said one of the studies he's worked on used data from Chicago's Field Museum of Natural History to help create a historic timeline and try to determine when microplastics first started to appear in the digestive tracts of fish.

"It's pretty much in line at what we expected. There were none found in fish before the last mid-century, and then they increased in the 1950s and 1960s," he said. "By shape, we found mostly fibers and some fragments. A lot of fibers from different materials. There were some synthetic polymers, like polyester, acrylic and others that were a mixture of cotton and spandex. That matches what our textiles are made of.

"Overall, there was a conglomerate of material types. There were also some semi-synthetics, like rayon, which is made of cellulose but are heavily processed and have dyes and wax additives and treatments, like flame retardants. Product availability changes over time. We expected to see a greater variety over time, and we did see that."

The first manmade plastic was introduced at the 1862 London International Exhibit and marketed as an alternative to ivory and horn, according to the Plastics Industry Association. The creator, Alexander Parkes, was trying to develop a synthetic substitute for shellac for waterproofing. The material was later developed into Parkesine, commonly known as celluloid. The first wholly synthetic plastic was created in 1907, under the name Bakelite. However, it wasn't until the 1930s and World War II that many modern plastics were created and began being popularly utilized, such as polyethylene, polystyrene and nylon.

By the 1950s, polyester and high-density polyethylene (HDPE) were created, and disposable plastics began coming on the market. For instance, HDPE, which is used for milk jugs, fueled the hula-hoop craze of the 1950s.

Today, plastics have led to innovations that have helped to improve the quality of life for countless people, offering access to items that previously didn't exist or were out of the economic range for the average consumer. At the same time, plastics have fueled a disposable society based on planned obsolescence and single-use products that some people claim, such as social critic Vance Packard, has led to "the systematic attempt of business to make us wasteful, debt-ridden, permanently discontented individuals," and degraded the environmental, financial and spiritual character of American society.

Globally, plastic production has increased to about 322 million tons in 2015, not including synthetic fibers, which accounted for an additional 61 million tons in 2015, according to the Food and Agriculture Organization of the United Nations. It's estimated that in 2010, between 4.8 million and 12.7 million tons of plastic waste entered the oceans. Microplastics contain a mixture of chemicals that are added during the manufacture process, which also absorb other chemicals and contaminants, which can bioaccumulate and attract even more toxic contaminants.

Back to the environment and ecosystems of the Great Lakes – the concern for microplastics isn't just among scientists or environmentalists. Dennis Eade, executive director of the Michigan Steelhead and Salmon Fisherman's Association (MSSFA), said microplastics fall under a larger concern of plastic litter in the Great Lakes.

"We have a lot of people in canoes and kayaks now, and they've come down the stream or river and stop to the side and have lunch. Instead of cleaning their litter, some just leave it on the riverbank," he said. “We had a clean-up event on the Manistee River, and we pulled more than 200 pounds of litter out. We had people coming from Indiana and all over to help.

"My top of mind is that we have to take a look and do some scientific analysis. If we are finding microplastic pollution, what are the principle sources of plastic pollution? Is it water bottles? Plastic bags? Is it other things? Then we put a hit list together on what we can do to replace that packaging,” Eade said. “That would be the way I would attack it."

Eade said the MSSFA worked in the past to try to implement a ban on microbeads in Michigan. However, he said the association began working with Michigan Congressman Fred Upton (R-Kalamazoo) on a national effort, resulting in a bipartisan effort that resulted in the ban. Among those Michigan congressional representatives who co-sponsored the bill were Republicans Upton, former Rep. Candice Miller (R-Harrison Township) and former Rep. Dave Trott (R-Birmingham), as well as Democrats Rep. Dan Kildee (D-Flint) and Brenda Lawrence (D-Southfield).

"The reason (microbeads) are so dangerous is that fish saw them as potential eggs or something edible, so they would consume them and not realize they were filling their stomachs without any nourishment, and possibly become contaminated with other chemicals," Eade said. "It was a dramatic problem, and one that I'm really pleased we were able to address."

Ingestion of microplastics isn't limited to microbeads. Rather fish, shellfish and other species are ingesting a variety of microplastics.

 A 2018 study by biologists at the University of Victoria in British Columbia found microplastics in juvenile Chinook salmon and in their nearshore environments on the east coast of Vancouver Island. In fact, the researchers said microplastics are becoming so globally ubiquitous in the marine environment that they are ingested by various fish species to the point that it may be a significant threat to marine ecosystems, with juvenile fish particularly at risk during a critical time in their lifecycle.

The study sampled 74 juvenile Chinook across four sites and found that 59 percent contained at least one plastic fiber. Still, the consequences of microplastic ingestion are still largely unknown.

Jamison Gove and Jonathan Whitney, oceanographers with NOAA's Ecosystems Division at the Pacific Islands Fisheries Science Center in Honolulu, Hawaii, are leading research into microplastics effects on larval fish nurseries in the Pacific. What they found is microplastics are in such abundance there that tiny larval fish are eating them, possibly slimming their chances of reaching maturity.

"We have limited understanding of where larval fish go: where they spend their time and who they spend their time with in the first 30 days of life. They just hatched and are trying to feed and grow until they go back to their natural habitat," Gove said. "Fish produce buoyant eggs, and they hatch and they swim until they grow. But there's limited understanding of where they are spending time and where their habitats are. We set out to understand this, which isn't historically known."

In starting their research, Gove and Whitney discovered currents pulling together small pools of organic particles on the surface that looked almost like oil slicks that were feeding grounds for larval fish. However, slicks, which contained tiny organic nutrients, were also pulling in large amounts of microplastics.

"We found they were surrounded by and ingesting small pieces of plastic," Gove said. "Most of the plastics look like fragments, and appeared to be weathered fragments. We did test polymers of quite a few, and most were polyethylene, which make up a lot of single-use bags and bottles, and polypropylene."

Gove said there are two main implications for the ingestion of plastics in larval fish.

"One, if ingesting plastic is a death sentence for a baby fish, that has real implications for adult fish populations. If every fish ends up dying, that has consequences," he said. "Secondly, larval fish are important prey for larger fish. That means there's opportunity for plastics to accumulate in the food web. We are looking at plastic at the base of the food web, and that can be consequential for the entire food web.

"There's no research on the impacts on larval fish. There is a little on adults, but we hypothesize that because they are more vulnerable and their digestion tract is small, we believe their impact is more severe. They are so underdeveloped and don't have any fat stores. It's possible if there is plastic in their stomachs, they may feel satiated and not look for food. And just one day without food is possibly a death sentence for these small fish."

Gove said the surface slicks where nutrients and microplastics pool are found in marine systems globally. In other words, they aren't isolated to the Pacific, but are believed to be happening everywhere, possibly impacting larval fish species throughout the world.

In early December, Honolulu passed a bill banning most single-use plastics, such as plastic utensils, food containers and straws on the island of Oahu. The ban is one of the strictest against single-use plastics in the country.

Gove said the ban is evidence of a groundswell of support to address plastic pollution, an issue that he hadn't considered as part of his work until he began finding microplastics in larval fish.

"When we first started this research, we weren't focused on plastics, but there were so many that we couldn't ignore it," he said. "I have no background in plastics, but this is like climate change now – it's just part of everyone's research in the world."

Back in Michigan, the presence of microplastica in local tributaries confirms they aren't just present in oceans and the Great Lakes, but suggests their presence exists even in the small lakes around Oakland County. While no lakes in the county have specifically been studied for microplastics, research on inland lakes in Minnesota have shown the presence of microplastics there.

Kathryn Schreiner, an environmental chemist with the Large Lakes Observatory and assistant professor at the University of Minnesota in Duluth, said the university has been working with the Minnesota Department of Natural Resources there to look at several inland lakes. While results of the study aren't yet complete, she said the work will focus on concentrations, types, morphology of the microplastics and different chemical types.

"We hope to have a good set of preliminary results in the spring and will present them in June," she said. "We did work on microplastics in Lake Superior, and we extended that into the inland lakes. We wanted more connection with smaller lakes that are used for recreation and fishing in Minnesota."

Ed Golder, spokesman for the Michigan Department of Natural Resources, said the department hasn't conducted any research into microplastics. Despite the department's lack of any research, the scientific community at some of the state's major schools are taking a lead on understanding microplastics.

Professor Donna Kashian with Wayne State University's Department of Biological Sciences is a visiting scientist at NOAA's Great Lakes Environmental Research Laboratory. She said a large grant from the Great Lakes Protection Fund is helping to make the Great Lakes "the epicenter" for microplastics research by pulling in resources around the region.

"One study that just wrapped up was a paper that took an in-depth look at quagga mussels, which a lot of people still call zebra mussels, but they aren't. They are filter feeders on the bottom of the sediment, and they have a lot of opportunity to take in microplastics," she said. "We brought them in the lab and targeted them with microplastics, and we looked at how they affected reproduction, oxygen consumption and other functions."

Kashian said researchers used imagining technology to track microplastics once they entered the mussel's system. What they found was that it was affecting both their ability to breathe and the filtration rate. The findings are particularly interesting, as Kashian said mussels are considered "selective" filter feeders, meaning they take all the contents of water they filter through their system, but do so by spitting out organic matter that may be harmful.

"Many of the microplastics don't pass through their system, they are staying in the organism. Even small amounts affect digestion, so they aren't able to eat normally. There was no effect in the gills, so there was no impact on oxygen consumption," she said. "In zebra mussels, for instance, when they are exposed to toxic algae, they filter feed everything in the water, but they spit out the microcystin. We watched, and we couldn't see them spitting out microplastics. It's different than a toxin, and the plastics may not have something that triggers them to spit it out.

"We can see it building up in their guts, and we expect that over time it will impact an organism's ability to get nutrition. That gives an indication that others in the environment could have these effects."

Kashian said research is also being done on how to reduce the flow of microplastics into waterways, as well as work to promote education and public outreach. For instance, one of the students in her lab is working on a project to help pull microplastics out of the environment by using green infrastructure, such as a number of bioswales throughout the city of Detroit.

The Graham Sustainability Institute at the University of Michigan in Ann Arbor has also pushed to increase research into microplastics.

Assistant Professor Melissa Duhaime, who investigates ecology and biology at the institute, recently studied the transport of plastic pollution in the Great Lakes. She said the dominant microplastics found were small fragments of larger plastics.

"People think we solved the problem because we don't put plastic beads in products anymore, but a huge part of the problem is these secondary plastics, or what is breaking down from larger plastic," she said. "That was the first work that came out of the Graham study. The other big twist and what we continue to study, as we study the microbes that live on plastic, is how they differ from microbes in the water itself. That can inform us of other things, like if they are also agents of the environment or a health concern."

Duhaime said they have confirmed microbes living on plastics are "unquestionably different" than those living on land or water, thus providing a niche environment. The microbes, she said, can help to tell where the plastic particles come from.

"It's sort of a tracer of where it has been, and whether its from a wastewater treatment plant, from the coast, or from a boat," she said. "It has a different history and it will have picked up different microbes along the way."

Another project, she said, suggests that microplastics pick up higher amounts of pathogens, particularly those near urban and wastewater treatment sites. Still, she said, more research on micro-DNA is being done to learn more. Work is also being done to determine how fast plastics are breaking down.

"How fast does it break down? Will it float or sink? Those are things we don't know," she said. "Right now, there is a lot of missing plastic. Our estimate of how much is out there versus what we predict to be entering the system is off by magnitude. It's not all at the surface, so it could be distributed throughout the water column. There's evidence it migrates through the water column on a daily cycle, and that organisms that live on the plastic can control where it sits in the water column."

As research continues, there remains much concern about how to reduce the amount of waste entering the environment and our waterbodies.

"This should be a call to us as a society. We are flooded with plastic. We can't ship it off anymore because nobody is taking it," said Mason, with Penn State. "This should be a call to us that some of that plastic isn't very recyclable material, so we really have to reduce or not use it.

"Our top program at Penn State is plastic engineering technology, and I moved to Erie, Pennsylvania, here where a lot of plastics manufacturing happens. I didn't know when I moved here, but now I'm in on the conversations that I wasn't privy to with the people making bottles and laundry detergent – they come to me and say, 'Johnson & Johnson wants to change the packaging. What ideas do you have for us?' These corporations are feeling the push from consumer pressure."

Professor Ramani Narayan, with Michigan State University's School of Engineering and Materials Science, recently participated in a study looking at plastic debris in the oceans. He also works in the area of developing biodegradable plastics, which he said do break down faster than other traditional plastics. However, he warned that the substances are far from a silver bullet solution.

"The lesson from the paper is two-fold," he said. "One, which is always presented, is the fact that 8-14 million tons of plastic are leaking into the ocean, and if you don't do anything about it, it will continue to grow and not be manageable, and plastic debris will outnumber plankton, which is the lowest form of food on the food  chain, and which is very scary when you look at that."

"The second part that missed everybody is that there is a strategy to address the issue. It's pretty straight: if the mismanaged waste is generated, why not try to reduce it? If you reduce by 'x' percent, you'll make s big dent. So the solution that you have to have is intervention. You do that by managing the mismanaged waste."

Narayan said recycling in North America and Europe alone won't solve the problem. Rather, he said, all of the world's emerging economies must be included in the solution. Further, he said, addressing plastic food and paper appears to make up at least half of the source of plastic pollution. If those sources were made 100 percent biodegradable, it would reduce pollution in our waterways, as well as reduce CO2 and greenhouse gas emissions.

"Unfortunately, biodegradability is presented as a solution to this ocean plastics problem. These are claims made by companies that say their fishing net or other item is marine biodegradable. That's where I take strong exception," he said. "Biodegradability isn't a solution of plastic waste leakage. It's useful because it lasts less than polyethylene plastic, but it still lasts 10 or 25 years."

Narayan said claims of biodegradable plastics that are proven in a lab don't actually hold up to real world use, however.

"The tests are done at 23 to 30 degrees centigrade. That's about room temperature. But ocean temperatures are about four degrees centigrade," he said. "We know from simple chemical engineering, that for every 10 degree drop in temperature, the rate of something breaking down is reduced by half. By the time you get to four degrees – what are you talking about? This is going to last for a very long time."

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