Bits of plastic too small to see are in the air we breathe. They are in the water we drink and the food we eat. How many of them do we consume? And how does they affect our health? A team of researchers has now calculated an answer to the first question. Answering the second, they say, will require more study.
The team estimated that the average American consumes more than 70,000 particles of microplastics per year. People who drink only bottled water could consume even more. They could be drinking in an additional 90,000 microplastic particles per year. That’s probably from microplastics leaching into the water from the plastic bottles. Sticking to tap water adds only 4,000 particles annually.
The findings were published June 18 in Environmental Science & Technology.
Scientists have found microplastics all over the world — even in mosquitoes’ bellies. These tiny bits of plastic come from many sources. Some are created after plastic waste in landfills and oceans breaks down. In water, plastic breaks down when it’s exposed to light and wave action. Clothes made of nylon and other types of plastic also shed bits of lint as they are washed. When wash water goes down the drain, it can carry that lint into rivers and the ocean. There, fish and other aquatic creatures will eat it.
The scientists behind the new study hope that by estimating how much plastic people eat, drink and breathe, other researchers can figure out the health effects.
That’s because we need to know how much plastic is in our bodies before we can talk about its effect, explains Kieran Cox. Cox is a marine biologist who led the study. He’s a graduate student in Canada at the University of Victoria. That’s in British Columbia.
“We know how much plastic we’re putting into the environment,” says Cox. “We wanted to know how much plastic the environment is putting into us.”
To answer that question, Cox and his team looked at previous research that had analyzed the amount of microplastic particles in different items that people consume. The team checked fish, shellfish, sugars, salts, alcohol, tap and bottled water, and air. (There wasn’t enough information on other foods to include them in this study.) This represents about 15 percent of what people typically consume.
The researchers then estimated how much of these items — and any microplastic particles in them — that men, women and children eat. They used the U.S. government’s 2015-2020 Dietary Guidelines for Americans to make their estimates.
Depending on a person’s age and sex, Americans consume from 74,000 to 121,000 particles per year, they calculated. Boys consumed just over 81,000 particles per year. Girls consumed a little less — a bit more than 74,000. This was probably because girls typically eat less than boys. These calculations assume that boys and girls drink a mix of bottled and tap water.
Because the researchers considered only 15 percent of Americans’ caloric intake, these could be "drastic underestimates,” says Cox.
Cox was especially surprised to learn there are lot of microplastic particles in the air. Until, that is, he thought about how much plastic we are surrounded by every day. As that plastic breaks down, it can get into the air we breathe.
“You are probably sitting around two dozen plastic items right now,” he says. “I can count 50 in my office. And plastic can settle out of the air onto food sources.”
Scientists don’t yet know if or how microplastics could be harmful. But they have reason to worry. Plastics are made from many different chemicals. Researchers don’t know how many of these ingredients might affect human health. However, they do know that some ingredients can cause cancer. Polyvinyl chloride is one of those. Phthalates (THAAL-ayts) are also dangerous. These chemicals, used to soften some plastics or as solvents, are endocrine disruptors. Such chemicals mimic hormones found in the body. Hormones trigger natural changes in cells’ growth and development. But these chemicals can fake out the body’s normal signals and lead to disease.
Plastic alsocan act like a sponge, soaking up pollution. The pesticide DDT is one type of pollution that’s been found in plastics floating in the ocean. Polychlorinated biphenyls, or PCBs, are a second type.
We don't yet know enough to determine the risk of consuming microplastics, says Sam Athey. She studies sources of microplastics. She’s a graduate student in Canada at the University of Toronto in Ontario. “There are no guidelines or published studies on 'safe' limits of microplastics,” she notes.
Some researchers have shown that humans pee out microplastics, she says. But what’s not clear is how long microplastics take to move through the body after they’ve been consumed. If they stay in the body for just a short time, the risk of negative health effects might be lessened.
Some research suggests that breathing in microfibers (plastic and natural materials) might inflame the lungs, Athey says. This might increase the risk of lung cancer.
Erik Zettler agrees there isn’t enough research yet to responsibly estimate health risks. He’s a scientist who studies plastic marine debris. Zettler works at NIOZ Royal Netherlands Institute for Sea Research in Den Berg.
But like Cox, Zettler sees this study as a first step in figuring out the risks. For now, he says, it’s a good idea to “minimize exposure where we can.” His advice: “Drink tap water, not bottled water, which is better for you and the planet.”
Cox says doing the study made him change some of his behaviors. When it was time to replace his toothbrush, for example, he bought one made of bamboo, not plastic.
“If you have the freedom to chose, make these small choices,” he says. “They add up.”
aquatic An adjective that refers to water.
average (in science) A term for the arithmetic mean, which is the sum of a group of numbers that is then divided by the size of the group.
behavior The way something, often a person or other organism, acts towards others, or conducts itself.
biologist A scientist involved in the study of living things.
caloric An adjective that means having to do with calories. One calorie is the amount of energy needed to raise the temperature of 1 gram of water by 1 degree Celsius. It is typically used as a measurement of the energy contained in some defined amount of food.
cancer Any of more than 100 different diseases, each characterized by the rapid, uncontrolled growth of abnormal cells. The development and growth of cancers, also known as malignancies, can lead to tumors, pain and death.
cell The smallest structural and functional unit of an organism. Typically too small to see with the unaided eye, it consists of a watery fluid surrounded by a membrane or wall. Depending on their size, animals are made of anywhere from thousands to trillions of cells.
chemical A substance formed from two or more atoms that unite (bond) in a fixed proportion and structure. For example, water is a chemical made when two hydrogen atoms bond to one oxygen atom. Its chemical formula is H2O. Chemical also can be an adjective to describe properties of materials that are the result of various reactions between different compounds.
DDT (short for dichlorodiphenyltrichloroethane) This toxic chemical was for a time widely used as an insect-killing agent. It proved so effective that Swiss chemist Paul Müller received the 1948 Nobel Prize (for physiology or medicine) just eight years after establishing the chemical’s incredible effectiveness in killing bugs. But many developed countries, including the United States, eventually banned its use for its poisoning of non-targeted wildlife, such as birds.
debris Scattered fragments, typically of trash or of something that has been destroyed. Space debris, for instance, includes the wreckage of defunct satellites and spacecraft.
development (in biology) The growth of an organism from conception through adulthood, often undergoing changes in chemistry, size and sometimes even shape.
endocrine disruptor A substance that mimics the action (sometimes well, sometimes poorly) of one of the body’s natural hormones. By doing this, the fake hormone can inappropriately turn on, speed up or shut down important cellular processes.
environment The sum of all of the things that exist around some organism or the process and the condition those things create. Environment may refer to the weather and ecosystem in which some animal lives, or, perhaps, the temperature and humidity (or even the placement of things in the vicinity of an item of interest).
environmental science The study of ecosystems to help identify environmental problems and possible solutions. Environmental science can bring together many fields including physics, chemistry, biology and oceanography to understand how ecosystems function and how humans can coexist with them in harmony. People who work in this field are known as environmental scientists.
factor Something that plays a role in a particular condition or event; a contributor.
graduate student Someone working toward an advanced degree by taking classes and performing research. This work is done after the student has already graduated from college (usually with a four-year degree).
hormone (in zoology and medicine) A chemical produced in a gland and then carried in the bloodstream to another part of the body. Hormones control many important body activities, such as growth. Hormones act by triggering or regulating chemical reactions in the body. (in botany) A chemical that serves as a signaling compound that tells cells of a plant when and how to develop, or when to grow old and die.
landfill A site where trash is dumped and then covered with dirt to reduce smells. If they are not lined with impermeable materials, rains washing through these waste sites can leach out toxic materials and carry them downstream or into groundwater. Because trash in these facilities is covered by dirt, the wastes do not get ready access to sunlight and microbes to aid in their breakdown. As a result, even newspaper sent to a landfill may resist breakdown for many decades.
marine Having to do with the ocean world or environment.
marine biologist A scientist who studies creatures that live in ocean water, from bacteria and shellfish to kelp and whales.
microplastic A small piece of plastic, 5 millimeters (0.2 inch) or smaller in size. Microplastics may have been produced at that small size, or their size may be the result of the breakdown of water bottles, plastic bags or other things that started out larger.
nylon A silky material that is made from long, manufactured molecules called polymers. These are long chains of atoms linked together.
particle A minute amount of something.
PCBs Short for polychlorinated biphenyls. A family of 209 chlorine-based compounds with a similar chemical structure. They were used for many decades as a nonflammable fluid for insulating electrical transformers. Some companies also used them in making certain hydraulic fluids, lubricants and inks. Their production has been banned in North America and many countries throughout the world since around 1980.
pesticide A chemical or mix of compounds used to kill insects, rodents or other organisms harmful to cultivated plants, pets or livestock; or unwanted organisms that infest homes, offices, farm buildings and other protected structures.
phthalates A family of chemicals used as solvents and added to plastics to increase their flexibility.
plastic Any of a series of materials that are easily deformable; or synthetic materials that have been made from polymers (long strings of some building-block molecule) that tend to be lightweight, inexpensive and resistant to degradation.
polyvinyl chloride (or PVC) This is a plastic formed by using heat to turn a liquid resin into a solid. The plastic can be soft and flexible or rigid and hard. The raw ingredients consist primarily of chlorine and carbon.
risk The chance or mathematical likelihood that some bad thing might happen. For instance, exposure to radiation poses a risk of cancer. Or the hazard — or peril — itself. (For instance: Among cancer risks that the people faced were radiation and drinking water tainted with arsenic.)
salt A compound made by combining an acid with a base (in a reaction that also creates water). The ocean contains many different salts — collectively called “sea salt.” Common table salt is a made of sodium and chlorine.
sea An ocean (or region that is part of an ocean). Unlike lakes and streams, seawater — or ocean water — is salty.
sponge Something that sops up liquids or other materials and holds them until squeezed out or removed in some other way. (in biology) A primitive aquatic animal with a soft, porous body.
technology The application of scientific knowledge for practical purposes, especially in industry — or the devices, processes and systems that result from those efforts.
waste Any materials that are left over from biological or other systems that have no value, so they can be disposed of as trash or recycled for some new use.