Assessment questions plastics' non-hazardous ranking
A study has questioned plastic's non-hazardous ranking, as an estimated 150 million tonnes "disappears" from the global waste stream each year.
Researchers outlined measures that can be used to shed light on the wider environmental impact of waste plastic.
An estimated 150 millions of tonnes of plastic "disappears" from the global waste stream each year, much of it is believed to end up in the environment.
The findings appear in the Proceedings of the Royal Society B.
"The issue with plastic waste in the environment is that plastic has a non-hazardous ranking," explained co-author Mark Browne, from the University of California, Santa Barbara.
"It has the same ranking - at the moment - as food scraps or grass clippings. This is in contrast to electrical goods, which have a hard ranking attached to them.
He added: "As you don't really have a structure to deal with the plastics we use in packaging or products, they find their way into the environment."
Quoting the estimated 150 million tonnes of "lost" plastic, Dr Browne - a member of the research team at the National Center for Ecological Analysis and Synthesis (NCEAS) - said the unaccounted plastic was a concern.
"We cannot account for it in the waste stream," he told BBC News.
"There is a real issue there, both in terms of the quantity and in terms of impacts.
Previous work by researchers at the NCEAS had shown that microscopic pieces of plastic (known as microplastic) were ingested by organisms, having a detrimental impact on their health.
Dr Browne observed: "We know a lot about the sub-lethal impact of bits of plastic but what about the ecological impacts?
"Are there impacts on populations or assemblages? Is this having an impact on ecosystems themselves?"
Dr Browne and his team set about reviewing existing literature to build up an understanding about what was known about plastic waste's large-scale impacts.
"We looked at combining all of the studies to try and find out what the evidence base was.
"What we found was that these types of plastics (from microscopic flecks to plastic nets stretching for hundreds of metres) could cause a whole range of impacts."
However, the team identified that most studies were isolated and did not provide a comprehensive overview needed by policymakers.
Dr Browne suggested that it was necessary to "plug the gap" between the materials' non-hazardous ranking and the scientific evidence that challenged that ranking.
In their paper, the team wrote: "Studies are required at multiple levels of biological organisation (from molecular and cellular levels through to populations and assemblages) that consider what is causing observed patterns of change to populations or assemblages at contaminated sites."
Dealing with the problem
It was important for policymakers and producers to fill the void in current measures to deal with waste that could harm the wider environment, they added.
"Through this, we shift the focus from traditional endpoints to developing mechanistic understanding of effects of debris at lower biological scales (where most is known) to lesser known and more worrisome ecological and policy-relevant effects."
Dr Browne added: "There has to be a concerted effort to either do the necessary research to find out how large those problems could be."
"If there is research available then it is used in the decision-making process and polices are adapted to take in the types of hazards."
He explained that there were already examples of where the release of plastic products were tightly regulated.
"It is quite interesting that within the medical field… a plastic product, such as an artificial joint, cannot go on the market until it has been adequately tested to determine how safe it is.
"But when it comes to products used in the environment, or could make their way into the environment, we do not see that sort of testing happening."
Dr Browne acknowledged that plastic products were omnipresent in modern society but he called on policymakers and manufacturers to move to an approach that "used science to make the decisions for us".
He added that there were other materials that had long been recognised as pollutants or hazardous, yet systems had been developed to control or manage the risks to the environment.
"The ones they treat most seriously are the ones that can cause impacts on a whole range of assemblages and populations, and there are a whole series of tools available.
"Yet - at the moment - before plastic products are going on the market, these tools are not being used."