King's College Scientists Warn of Potential Health Risks from Microplastics

Scientists from King's College London warn of the potential human health risks of microplastics from both dietary and inhalation exposure.

"Although microplastics are widely studied in the context of the marine environment where they are a prolific pollutant, we are only just recognising the potential human exposure pathways," say Stephanie Wright and Frank Kelly.

In a review article in Environmental Science and Technology, they pull together the sparse evidence for a possible inhalation exposure pathway. This includes from "atmospheric fallout", including rainfall. Car tyres are also a possible source of inhaled microplastics, they add.

Microplastics' biopersistence could lead to a "suite of biological responses", including inflammation and genotoxicity, they suggest.

Chemical toxicity could result from unbound chemicals and unreacted residual polymers leaching from the microplastics or from associated hydrophobic organic contaminants.

The researchers have compiled a long list of "key knowledge gaps", including:

> Are microplastics able to accumulate in the body? Do they become lodged or are they engulfed by cells?

> If taken up by cells, what is the cellular mechanism of uptake?

> Are accumulative effects the same as those observed in occupational exposures?

Finally, the researchers point to current technical limitations in sampling and identifying them. Current predicted exposure levels are likely to be an underestimate, they say.

"Once we have a better understanding of human exposure levels, and whether microplastics are uptaken/able to translocate, we can begin to unravel the potential toxicological mechanisms and hence therein possible health effects," they conclude.

The Kings College researchers are currently working on a way to detect airborne microplastics. If they find evidence of airborne particles, they intend to implement monitoring campaigns.

In 2016, Professor Kelly gave evidence on microplastics to the UK government's Environmental Audit Committee. "Up until very recently, we have just been worried about the ingestion through shellfish and other molluscs. If we can breathe them in, they could potentially deliver chemicals to the lower parts of our lungs, maybe even across into our circulation," he said.