Microplastics are a growing global concern. Scientists agree that tiny particles from degraded plastic waste are ubiquitous, or completely widespread, across the planet and pose risks to the environment and human health.
Yet while oceans are often the focal point of this issue, microplastics are also highly prevalent in freshwater environments like Lake Erie. Much is unknown about how microplastics — and even smaller plastic particles called nanoplastics — interact with drinking water treatment in the region. Such information is needed to assess whether the particles present a potential public health risk.
Imagery of microplastics produced using a scanning electron microscope. Researchers worked to measure the size, shape, and number of plastic particles.
Now, new research funded by Ohio Sea Grant is helping scientists and decision-makers better understand this issue. Led by Dr. John Lenhart of The Ohio State University’s College of Engineering alongside Ph.D. student Megan Jamison, the project is evaluating microplastics in water treatment plants along the shore of Lake Erie and analyzing how effective treatment processes are at removing the plastic particles.
“We’re conducting this research because of increasing evidence demonstrating the presence of microplastics in the environment and the food and drink people consume,” Lenhart said. “The overarching goal is to develop guidance for water treatment plants to effectively remove microplastics, particularly for plants in Ohio that use Lake Erie as their raw water.”
The continued growth of plastic production drives the prevalence of microplastics around the world and in Ohio. Globally, the industry produces 400 million metric tons of plastic waste each year, and that number that is forecasted to reach 1,100 million by 2050. Meanwhile, more than 22 million pounds of plastic debris enters the Great Lakes each year.
“The overarching goal is to develop guidance for water treatment plants to effectively remove microplastics, particularly for plants in Ohio that use Lake Erie as their raw water.”
Dr. John Lenhart
When that plastic waste is discarded in the environment, it breaks down into smaller and smaller particles called microplastics. Particles that are less than 5 millimeters in length are defined as microplastics, and ones that are less than a micron — one millionth of a meter — in length are considered nanoplastics.
“We’re particularly interested in trying to evaluate the presence of the really smaller sized microplastics that are hundreds of nanometers in size.” Lenhart said. “Those are the ones that researchers believe have the greatest potential to have adverse health effects because of their mobility within the body. They can penetrate cell membranes and the blood brain barrier.”
The health effects of exposure to microplastics are still not well understood by scientists, yet research has shown that people are constantly ingesting the plastic particles. Researchers also know that very small plastics can move throughout the body and enter different organs, possibly leading to various health problems.
“For humans, drinking water is a concern because some of the smaller microplastics are making it through drinking water treatment and people are ingesting them,” Jamison said. “They’re ingesting them at unknown rates with unknown effects.”
Megan Jamison, Ph. D. student at The Ohio State University, collects water from a drinking water treatment plant on Lake Erie in order to measure the presence of microplastics.
To help ensure that drinking water treatments plants in Ohio are prepared to address these concerns, researchers aimed to study how well conventional treatment methods can remove microplastics and nanoplastics. Jamison first collected samples of both raw and treated water from four water treatment plants along Lake Erie. Notably, each plant uses different chemicals and processes to remove contaminants.
“Recently, we started collecting samples in between the treatment steps to try and figure out when microplastic removal is occurring and whether differences in the overall treatment plant configurations are influencing the different removal rates,” Jamison said.
After collecting samples, Jamison would bring them back to the lab to filter out any organic matter, such as algae and diatoms, and separate out the microplastics. Then, she used different techniques to produce useful microscopic imagery of the particles. A scanning electron microscope helped Jamison understand the size, shape, and number of particles, and she used optical photothermal infrared (IR) technology to identify different types of smaller plastic particles.
“Optical photothermal IR is a fairly new technique in terms of its development and has not been applied a great deal to these sorts of systems,” Lenhart said. “Other techniques that are applied, their spatial resolutions are such that you can’t really get below five or 10 microns. With the technique that Megan’s using, she can get down to half a micron.”
With this imagery, researchers are able to quantify the number of plastic particles and the overall mass of particles per liter of water. Together, both pieces of information provide important context about how prevalent microplastics are, Jamison said.
Jamison processes microplastic samples in the lab. It took the team about a year to develop their own methods to isolate small-sized microplastics and nanoplastics.
While results are preliminary and analysis is still ongoing, the team has found clear evidence of microplastic removal during treatment, and overall removal varied from 46% to 87%. Notably, about two thirds of the total microplastics from raw and treated samples were nanoplastics smaller than one micron.
“We’re seeing a much higher concentration of plastics in terms of particle count because we’re seeing a lot of those nanoplastics that have been unreported in other studies,” Jamison said.
So far, the results suggest that there was not a significant difference in removal of nanoplastics compared to overall microplastics, though the team is still processing data, Lenhart said. As analysis continues, researchers also hope to explore possible variations in how different treatment steps affected microplastic removal.
Lenhart said he expects the final results will provide public health officials in Ohio with new information about microplastics.
“It’s a pretty novel set of data,” he said. “Then, the next step will be to make a determination as to whether the potential exposure to these masses and particle concentrations is something that needs to be looked at from a public health perspective.”
“I also hope that this information will kind of spark more public awareness about microplastics and maybe dissuade some use of single-use plastics as people start to realize that the plastic habits we have are influencing every aspect of our lives,” Jamison said.
Looking ahead, Lenhart’s team hopes to explore related research topics, such as the propensity for microplastics to carry other contaminants and the presence of microplastics in food and human tissues.
For more information about this research, contact Dr. Lenhart at lenhart.49@osu.edu or watch his Freshwater Science webinar.
Ohio Sea Grant is supported by The Ohio State University College of Food, Agricultural, and Environmental Sciences (CFAES) School of Environment and Natural Resources, Ohio State University Extension, and NOAA Sea Grant, a network of 34 Sea Grant programs nation-wide dedicated to the protection and sustainable use of marine and Great Lakes resources. Stone Laboratory is Ohio State’s island campus on Lake Erie and is the research, education, and outreach facility of Ohio Sea Grant and part of CFAES School of Environment and Natural Resources.