By Victoria Witke
Doctoral student Christina Petalas studies herring gulls to figure out how plastic pollutants are accumulating around the St. Lawrence River in Quebec.
In two studies published this year, Petalas and her colleagues at McGill University tested gull blood and egg and samples to see how exposed seabirds are to plastic additives called ultraviolet absorbents.
Ultraviolet absorbents are added to plastic to protect it from damage caused by radiation, which can lead to problems like packaging becoming weak or losing color.
Additives are essential – without them, packaging would deteriorate quickly, failing to keep food safe for human consumption, for example.
But when plastic enters the environment, contaminants can leach into the soil, water and air – and eventually to wildlife.
Every herring gull Petalas sampled was exposed to plastic additives.
“These contaminants are pervasive,” Petalas said. “It doesn’t matter where you’re going to go, you’re going to get exposed to them because they’re so widely used in different industries.”
Herring gulls are bioindicators – they’re good at reflecting what’s going on in the environment. Seabirds live for a long time, forage in many areas and are easy to take samples from, Petalas said.
Her studies appeared in the journal Environmental Pollution and the Journal of Hazardous Materials.
In the study using eggs, Petalas collected samples near Montreal and on islands as far as 800 kilometers away from the city.
Birds in all nine colonies in the study were contaminated – despite whether the gulls were feeding from the river, agricultural fields or landfills.
“We see plastic on all these islands, remote or not,” Petalas said. “These birds are regurgitating plastics, garbage and food waste, McDonald’s sausages, things like that. So it’s really everywhere.”
“That was the most shocking thing to me, how pervasive plastic pollution is and how much it’s affecting the lives of these species,” she said.
Eggs from bird colonies that were closer to Montreal and human activity had higher levels of exposure, but more research is needed to find the main contamination sources, according to the study.
A study from 2017 shows plastic additives were found in nearly all gull eggs sampled near lakes Superior, Huron, Ontario and Erie.
Not much is known about plastic additives as contaminants because they’re “relatively new and emerging,” Petalas said.
But people are being exposed.
“We’ve already found many of the plastic additives I study [in the environment],” Petalas said. “We find them in plants and in human tissues, even breast milk and urine. We know that they’re ubiquitously found in all wildlife and us.”
One way people are exposed to plastic additives is through food.
Farms use recycled wastewater to water crops, sewage sludge as fertilizer and plastic mulch to increase crop yields. Farmers put plastic film over rows of crops, Petalas said.
“Because these gulls were foraging so much in agricultural fields, we know these contaminants can leach into the plants,” Petalas said. “That’s a way they can be getting exposed to us.”
Because plastic additives are an emerging contaminant, little is known about their effects on human health.
Petalas said lab studies on rats and fish show the pollutants can be toxic and carcinogenic. Plastic contaminants accumulate in the body and could cause hormone disruptions.
Jason Somarelli is an assistant professor of medicine at Duke University. He’s also a member of the Duke Plastic Pollution Group, which studies the contaminant and was not involved in Petalas’s research.
Somarelli said there are “definitely associations between plastic ingestion and cancer” but that there’s not enough research yet to prove plastic explicitly causes cancer.
“Does that mean that the dose someone’s exposed to is going to cause cancer? That’s a question mark,” Somarelli said. “But are there carcinogenic chemicals in our plastic? There is no question that’s a yes.”
Some studies show a correlation between microplastics and additives potentially causing chronic inflammation.
Somarelli said while inflammation doesn’t create cancer cells, it provides an environment where cancer cells can thrive.
He said plastic pollution regulation should be managed as a chemical problem, not just a solid waste problem – solutions should go beyond what’s seen in a landfill.
“There’s enough cause for concern here to keep studying this,” Somarelli said. “I would strongly advocate until we know more, we limit as much of our plastic use as possible within reason.”
He said more research needs to be done to understand “what’s happening and to get this stuff out of our environment.”