Plastics supercharge toxin absorption in plants and humans

Micro- and nanoscale plastic particles can greatly increase how much toxic chemicals enter plants and human cells, according to two studies led by Rutgers University. The findings deepen concerns about plastic pollution. 

The researchers discovered that these minute plastic particles, in combination with environmental pollutants, can intensify the uptake of poisons, heightening food safety risks.

One study, published in the journal NanoImpact, showed that lettuce plants exposed to both nanoparticles of plastic and common pollutants – such as arsenic – absorbed significantly more toxins than when exposed to the pollutants alone. 

A second study published in the journal Microplastics demonstrated a comparable effect in human intestinal tissue, signaling that these tiny plastics may be promoting more efficient transfer of both contaminants and plastics into our bodies.

Heightened levels of plastics and toxins

Together, these studies point to a potentially harmful cycle. As plastic degrades into micro- and nanoplastics, it pollutes soil and water, enabling plants to absorb more dangerous substances. 

Humans, consuming these plants, may then absorb heightened levels of toxins and plastic particles, posing elevated health risks.

Philip Demokritou is the director of the Nanoscience and Advanced Materials Center at the Environmental and Occupational Health Sciences Institute at Rutgers University and senior author on both papers. 

“We’ve already put about 7 billion metric tons of plastics into the environment that keep breaking apart,” said Demokritou. “They pollute everything around us – the water we drink, the food we eat, the air we breathe.”

Escalated toxin uptake in human cells

Using a simulated digestive system and lab-grown models of the human small intestine, the Rutgers researchers documented that nano-scale plastic particles increased the amount of arsenic absorbed by nearly sixfold compared to arsenic exposure alone. 

The same phenomenon was observed with the commonly used pesticide boscalid.

Even more concerning, in the presence of these chemicals, the cells also took in considerably more plastic. Plastic particle uptake roughly doubled when toxins were present.

“We know nanoscale materials can bypass biological barriers,” said Demokritou. “The smaller the particles, the more they can bypass biological barriers in our bodies that protect us.”

Plastics and toxin absorption in lettuce

In a separate study on lettuce, scientists exposed the plants to two sizes of polystyrene plastic particles – 20 nanometers and 1,000 nanometers – along with arsenic and boscalid. 

The researchers found that the smaller particles exerted the greatest influence, increasing arsenic levels in edible plant tissue nearly threefold compared to arsenic exposure alone.

These effects remained evident in both hydroponic systems and soil-based experiments. Using high-resolution imaging, the researchers verified that smaller plastic particles can travel from roots into the above-ground tissues of the plant, allowing them to accumulate in areas people typically eat.

Plastics keep breaking down

Micro- and nanoplastic pollution arises mainly from the progressive degradation of larger plastic debris. According to Demokritou, stopping new plastic production won’t erase what is already out in the environment.

“Even if we stop today producing plastics or using plastics, we have plenty of plastic waste unfortunately out there,” Demokritou said.

Because these smaller particles seem to raise absorption levels of both toxins and plastics, food contamination from plastic pollution could persist indefinitely, with potential impacts on overall public health.

Future directions and possible solutions

The team’s findings come from a broader USDA-funded project focused on ensuring food safety amid micro- and nanoplastic pollution.

The researchers argue for heightened efforts to minimize further plastic waste while also searching for long-term resolutions.

“We need to stick with the ‘three-R’ waste hierarchy – reduce the use of plastics, reuse, recycle,” Demokritou said. “For areas where you cannot apply these three Rs, like in agriculture where so much plastic is used for weed control and other things, use biodegradable plastics.”

Substitutes for conventional plastic

To address pollution, the scientists are developing new biodegradable materials as substitutes for conventional plastics. They are also refining techniques to detect and measure plastic contamination in food and water. 

Still, Demokritou stressed that fully mitigating plastic pollution will require grappling with social, economic, and technological obstacles.

“It’s not that technically we cannot address some of these issues. But it will definitely be a challenge to retain all the benefits from this very useful material while reducing the harms that it does. There are social and economic obstacles related to plastic production and use to overcome,” Demokritou concluded.

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