Microplastics in water are fragments of any type of plastic that have entered the aquatic environment.

A World Health Organization report released earlier this month estimated that human health risks from microplastics at worst-case exposure levels are low, but called for more research.

Here is an excerpt from the WHO news conference on Microplastics in drinking water:

Bruce Gordon, WHO's Coordinator of Water, Sanitation, Hygiene and Health said --

The headline message is to reassure drinking water consumers around the world that, based on this assessment, our assessment of the risk is that it is low. We've done this in three ways. The health concerns, the health threats essentially focus around three elements. One is the physical hazards potentially presented by the particles themselves so while plastic is inert and doesn't chemically react there have been questions raised about whether it disseminates in the body and organs and causes problems.

Plastic also has additives in it that are sometimes chemicals that are contaminants that have been well-characterised. We've looked at those and we've also looked at the issue of whether there are biofilms, whether bacteria colonise these microplastics and present health issues.

So very briefly we know that most particles, the vast majority or all particles above 150 micrometres in diameter are passing through the gut without being absorbed and the vast, vast majority of smaller ones are doing so as well.

As far as chemicals, having examined the occurrence data - that is the concentrations that were found in drinking water - and taking a worst-case scenario we've concluded that the maximum exposure that we would anticipate based on currently available data is much lower than the exposure level that we might be concerned at if there was to be an adverse effect.

Finally with respect to colonisation of microplastic particles we know that these particles are very, very small contributors to what normally bacteria would colonise in terms of biofilms and pipe distribution systems or other particles in the environment so we believe this is a negligible effect.

So again, the conclusions are there's a low health risk; we also looked at waste water treatment and drinking water treatment systems which, if operated efficiently, can reduce sufficiently the levels of microplastic. However there are a number of uncertainties and research gaps that Jennifer will talk about in just one moment.

Finally on the recommendations, we need to keep the focus on known risks. We know now from our WHO data and UNICEF data that two million people drink water currently that is faecally contaminated and that causes almost one million deaths per year. That has got to be the focus of regulators around the world and we don't recommend that regulators be monitoring for microplastics routinely. However we do recommend some investigative research.

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