Duke researchers are aiming to make plastic use safer for humans, animals, and the environment. Plastics are made up of hydrocarbon polymers along with thousands of chemical compounds that alter their function, known as additives. If ingested, these chemicals could cause serious health issues including cancer. Jason Somarelli, PhD, assistant professor of medical oncology in the Duke Department of Medicine, is working with two teams to find out which mixtures of plastic additives are the most harmful instead of looking at the impact of the chemicals separately.
“The current understanding is that some of these additives are co-occurring, like they're all together in one product. Then we [researchers] deconstruct it, separate the additives, and test them individually. But that's not how they go into your body,” Somarelli said.
“It gets into your body as a mixture. It’s the plastic, plus the chemicals, plus environmental toxins, which is more like a chemical soup and that’s what we want to test. We want to discover which additive combinations have the most negative impacts on your health.”
Recent studies show that when plastic products begin to decay and weather, they release microplastics and nano-plastics that contain the additives that humans are routinely exposed to. They’ve been detected in soil, water, and air and can be absorbed through the skin and inhaled when breathing. As a result, these particles have been found in the lungs, colon, breast milk, and placenta, and many additives have been found in human blood.
“We’re consuming these plastic particles every day. You’re breathing them in when you’re in your office, when you’re walking down the street and tires are moving on the road. It even comes in through our food,” Somarelli said.
The Duke Plastics Pollution Working Group, housed in the Duke University Nicholas Institute for Energy, Environment and Sustainability, received a $600,000 grant from the UL Research Institutes to better understand how plastic additives in food packaging impact DNA.
Somarelli is a co-founder of the group, and they have already pinpointed 60 additives of concern found in plastics and people. Over a three-year period, they will test the compounds on their ability to induce DNA damage using animal cells and zebrafish. “DNA damage increases mutation rate, which can lead to cancer,” he said. Working group member Nishad Jayasundara, PhD, assistant professor in Duke’s Nicholas School of Environment, will lend his expertise in ecological toxicology and fish models of toxic exposures.
Plastic Pollution Working Group members, Mark Wiesner, PhD, James B. Duke Distinguished Professor of Civil and Environmental Engineering, and Nathan Bossa, PhD, research scientist in the Duke University Pratt School of Engineering, will specifically look at how these additives leach out of food packaging and find out which ones are more likely to enter food and water.
“We’re going to be analyzing anything with the word ‘food’ in it. That includes polypropylene food packaging, polystyrene food packaging, and water bottles. Then we’re going to compare the additives we find in those products with the chemicals that have already been found in our blood. Once we figure out where the chemical compounds are coming from, we’ll learn what they do and how they work together as a mixture.”
Once Somarelli and the team discover which additive combinations lead to worse health outcomes together, they want to share that information with manufacturers. “We hope this information can help manufacturers and regulatory agencies make policy decisions on which chemicals can be allowed or removed from food packaging plastics.”
Finding a Way Forward
Somarelli gained an interest in the environment while growing up in upstate New York. He was raised in a rural tri-state area valley that was surrounded by manufacturing plants, but markedly picturesque. “Some of my family members got cancer and this got me thinking about how negative impacts on the environment can lead to health issues. Then, I just wanted to do some good for that problem.”
He began exploring plastics and the connection to cancer while working with a long-time Duke Bass Connections group, which is comprised of people in multiple disciplines and education levels across Duke University. A student suggested they take a new approach to the topic, instead of looking at plastics as a product, look at the chemicals they’re made of. Building on this work, the working group received a National Science Foundation 5-year $2.3 million Growing Convergence Research grant to understand the impacts of plastic additives on organismal wellbeing.
“We’re not the only species ingesting this stuff and encountering this problem. It's important to understand as pollution increases, as the stress of climate change increases, as more plastic is in the environment, how will ecosystems be affected? What's going to happen to the ability of animals and other organisms to reproduce and function?”
Additives deregulate metabolism, disrupt proper development of reproductive cells, and alter reproductive hormone levels and function in multiple animal species.
Earlier this year Duke researchers, including Somarelli, compiled a list of more than 2,000 known plastic additives and then categorized them by how they impacted health. They discovered over 150 plastic additives contain carcinogens. The Bass Connections group plans to use that information to discover which mixtures increase DNA mutations and decrease cell death or immune function.
“Imagine an additive has made it into your body, and it’s increasing the mutation rate in your cells. Normally, the mutated cell would be killed at the benefit of the body. It won’t turn into cancer because that cell is now dead. But what if another additive comes along and shuts off that death pathway? Then you get a higher mutation rate, the mutated cells aren’t dying as they should, and it eventually leads to cancer.”
They’ll then develop a database for others in the scientific and medical communities to screen additive combinations. “Researchers will be able to pull all the additives that have to do with their discipline, find which products they’re in and see what they do in combination,” he said. Somarelli and the team are hoping to find as many concerning additive combinations as they can.
Tackling Policy and Education
The team is also working with Durham Public School students interested in STEM. Meagan Dunphy-Daly, PhD, assistant professor in Duke’s Nicholas School of Environment, is leading the team. They’ll be teaching students about their plastic use and compare students’ use of plastic products with information in the additive database.
On the policy front, John Virdin, PhD, assistant professor in Duke's Nicholas School, Michelle Nowlin, J.D., M.A., clinical professor in Duke University’s School of Law, and Nancy Lauer, PhD, lecturing fellow in Duke’s School of Law, are working with government agencies, including the North Carolina Department of Environmental Quality and the United Nations Environment Programme, to develop and test plans that may lower or mitigate the risk of exposure from these toxins in the community.