by Lisa Sheppard, Prairie Research Institute
Plastic products permeate our environment and over time they break down. The microscopic size of particles, how long they last, and what is associated with them raise health concerns.
Although the health effects are still largely uncertain, recent research at the Illinois Sustainability Technology Center (ISTC) has provided some insight into what happens to plastics once they’re used and thrown away.
Microplastics are everywhere: in what we eat, drink, and breathe, according to ISTC senior chemist John Scott. They’re found in surface water, sediments and soils, air and dust, wildlife, and everywhere else scientists look.
“Plastics don’t ever go away, they just break down to smaller and smaller sizes,” Scott said. “They’re always out there. If I analyze something that doesn’t have microplastics in it, I think there’s something wrong.”
Plastics have been mass-produced since the 1950s, with an estimated 8.3 billion metric tons produced globally. Nearly 80 percent of plastic waste ends up in landfills and in the environment. The COVID-19 pandemic has exacerbated the plastic waste problem with more shipping and packaging and the worldwide use of single-use products, such as gloves, gowns, and booties.
Since plastics have been engineered to last, the breakdown rates are incredibly long. Nylon fishing line lasts some 600 years, plastic bottles last 400 years, and plastic straws last 200 years.
“A child’s diaper can be around for 400 to 500 years—five to six times the child’s lifespan,” Scott said. “Even if we stopped producing plastics now, because of these legacy products, we would still have a plastic waste problem for many decades.”
What they absorb
Plastics act as sponges, absorbing all kinds of contaminants in the environment. In 2020, Scott and collaborators at the Annis Water Resources Institute submerged samples of different types of plastic for three months in Muskegon Lake in Michigan.
Findings showed that many pollutants such as polyaromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), and even pesticides concentrate on these materials at hundreds of times the background levels.
The group also found a group of chemicals, per- and polyfluoroalkyl substances (PFAS), can stick to microplastics submerged in lake water. PFASs are human-made chemicals used in products such as non-stick cookware, cleaning supplies, and food packaging. Their stability and water and oil resistance are useful for various products, but the PFASs don’t break down readily in the environment or in humans, causing potential adverse health effects.
Scott’s team also tested PFAS adsorption on plastic in the laboratory, without the presence of organic matter such as biofilms. In the laboratory, the amount of PFASs that was absorbed into the microplastics was small (about 25%), yet the lake-exposed samples showed 600 times more PFASs were attached to the microplastics compared with those in the laboratory tests.
“We found only small concentrations of PFASs, but what was interesting was the discovery that they don’t stick to the plastic,” Scott said. “We believe that they stick to a biofilm of organic material that develops over time on the plastic from the lake environment.”
The initial findings are published in the Journal of Great Lakes Research. A second paper reporting PFAS in currently in draft.
How to measure them
To understand microplastics and make accurate comparisons of plastic size and concentrations, researchers need to use a standardized method of detection limits. The National Oceanic and Atmospheric Administration (NOAA) developed a method in 2015, which was designed to measure large plastic debris in surface water and on beaches.
The smallest size detected through this process is 300 micrometers, which does not account for microplastics that are small enough to cross biological membranes.
“We needed to push the detection limits to measure smaller microplastics,” Scott said. “If we use the NOAA method, we’ll underestimate the amount of microplastics in a sample.
In 2020, Scott and Lee Green, ISTC chemist, developed a way to count microplastics down to the size of 20 micrometers, sizes that would have been missed by the NOAA standard.
Another challenge was to find a standardized way to report findings. Estimating the number of plastic particles per liter wasn’t accurate because the particles can further break down during the estimation process. Instead, Scott and his team applied a detailed analysis of particle dimensions to estimate its mass.
More study details are available at http://hdl.handle.net/2142/107799.
What happens to them from the landfill to the treatment plant
Microplastics might be everywhere, but the hotspots are landfills. Plastic breaks down in landfills and becomes more mobile. Leachate, or water and waste from the landfill, is piped to wastewater treatment plants (WWTP), which are not designed to handle microplastics.
The sludge produced by WWTPs is commonly used on crop fields since the biosolids are high in nutrients. Once applied, the sludge material—and microplastics—is taken up by plants and runs into surface water and groundwater.
Scott plans a pilot study to examine the feasibility of treating wastewater to remove microplastics that come into plants before sludge is pumped back out into the environment.
Ideally, though, keeping plastics out of the landfills by reducing the amount produced, using fewer single-use plastic products, and better plastic recycling would be the way to go, Scott said.
This story originally appeared on the Prairie Research Institute News Blog. View the original story.