EcoLog,  2/7/2020


Science assessment report on plastics calls for more science

by Mark Sabourin

There is no avoiding plastics pollution — at least not yet — according to the federal government’s new “Draft Science Assessment of Plastic Pollution”. Canadians released 29,000 tonnes of it into the environment in 2016, and because plastics degrade very slowly, the cumulative impact of those releases will continue to grow. The effects are widespread but still not clearly understood. However, it appears that at least one of the alternatives, bioplastics, may not be much better.

The science assessment is an important piece of a much larger puzzle: the federal plan to ban harmful single-use plastics as part of the “Strategy on Zero Plastic Waste”, an initiative of the Canadian Council of Ministers of the Environment. The science assessment — a thorough review of current knowledge about the impact of plastic waste — will help distinguish “harmful” single-use plastics from all the rest.

Some effects are obvious or relatively easy to detect, such as entanglements and the presence of plastics in the gastrointestinal tracts of marine animals and seabirds. But the effect of plastics on humans needs more research. Though single-use plastics make up the bulk of plastic waste in Canada’s freshwater, sampling methods are not standardized, particularly with respect to microplastics. Claims have also been made about plastics’ ability to absorb harmful chemicals and transfer them to the food chain when they are ingested by animals. But current science says that while that may be possible, its impact on humans is likely low.

As to biodegradable plastics, the science assessment finds that they do not necessarily degrade any faster than petroleum-based plastics. Biodegradable plastics need sunlight, heat or oxygen to degrade, and all are in short supply in landfills or at lake bottoms. They may be beneficial as a source of demand for biomass, but a full life-cycle analysis would be needed to make that case.

Right now, the precautionary principle probably serves as the soundest argument for keeping plastics out of the environment. Additional research should be focussed on the following five areas:

The “Draft Science Assessment of Plastic Pollution” is open for comment until April 1, 2020. Comment to eccc.substances.eccc@canada.ca.

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