“I can’t think of many materials that are so present in our everyday existence,” says Ludmilla Aristilde.
The world is awash in plastics. Globally, we currently produce about 300 million additional tons of plastic waste per year—nearly equivalent to the weight of the entire human population. Most of that plastic—approximately 79 percent—ends up in landfills or the environment.
“We know that plastic pollution is everywhere, but we don’t have a good understanding of all the consequences,” says Aristilde, associate professor of civil and environmental engineering and (by courtesy) of chemical and biological engineering at Northwestern University. She has been studying what factors control the transport, persistence, and effects of organic contaminants in the environment for more than a decade. Her research interests include chemicals ranging from pharmaceuticals to herbicides and now, increasingly, plastic debris.
Because plastics were designed for uses that require resistance to degradation, most types of the material do not fully decompose in the environment. Instead, they simply become increasingly smaller over time as they are weathered in Earth’s ecosystems. These fine particles—known as microplastics and nanoplastics—accumulate up the food chain and have been found in everything from tap water to seafood. For the first time ever, researchers recently revealed that they had discovered microplastics in the human digestive tract.
While Aristilde is alarmed by the unknown effects of plastic consumption, she points to a less obvious concern whose impacts are quite well known:
“Plastics in the environment can be vectors for a lot of known contaminants that have proven health consequences. They can serve as vectors for known cancer-causing agents, contaminants that cause neurological damage, and others that are endocrine disruptors... Plastics change when they enter the environment. Reaction of plastics with sunlight causes photodegradation and subsequent other transformations. This all impacts how plastics act as contaminant vectors. This aspect of the role of plastics in the environment is an emerging research area in my group.”
There are documented reports showing plastics with high concentrations of polychlorinated biphenyls—a class of chemical linked to cancer, reduced fertility, birth defects, and neurological deficiencies. In fact, the National Institutes of Health states that microplastics can act as a host for a variety of known toxins—either through absorption or chemical makeup—including dioxin, persistent organic pollutants (POPs), polybrominated diphenyl ethers (PBDEs), and polycyclic aromatic hydrocarbons (PAHs).
Plastics in the environment can be vectors for a lot of known contaminants that have proven health consequences.”
Ludmilla Aristilde, Associate Professor at Northwestern University
Aristilde, a researcher within the Program on Plastics, Ecosystems and Public Health at the Institute for Sustainability and Energy at Northwestern (ISEN), has had an interest in plastic pollution for years with an eye on exploring biological solutions. In 2017, for example, she published an article reviewing how a common type of bacteria known as Pseudomonas could be used to break down plastics and their derivatives.
“Biological processes provide opportunities that allow you to tailor the metabolic pathways in bacteria to breakdown plastics and make certain chemical compounds that we want—materials that can be taken and used industrially not only to make new plastics but also to make things like pharmaceuticals,” she says. “I find biological solutions attractive because they do not usually require a purified plastic waste stream like many chemical processes do… That means biological solutions can be less energy intensive, and you don’t have to take extra steps like pre-sorting of different plastic types.”
Although Aristilde is concerned about the growing use and accumulation of plastics, she also recognizes that the material is quite valuable in many circumstances. Instead of aiming to stop the global use of plastics altogether, she is more concerned with getting smarter about when and how we use them.
“When people think of plastic use, we often think of things like water bottles. But it’s so much more than that,” she says. “Think about things like catheters and other medical devices—plastics can be very important for these types of materials... We need to think of more sustainable ways to make plastics and to deal with them after we use them.”
Academic institutions like Northwestern have an important role to play, Aristilde says, not only through research and educational training, but also through engagement with the general public.