This article appears as part of the Winds of Change newsletter.

This week, the world is coming together to thrash out an agreement on the UN Global Plastics Treaty. In a world where plastic production is exponential increasing, this is crucial. Plastics and particularly microplastics, into which these useful and adaptable materials break down, are of increasing concern, and contributing to a global plastic pollution crisis.

At the heart of the concern are microplastics, small pieces of plastic less than 5 mm in diameter. They vary widely in terms of the chemicals associated with them – making assessing their health impact and risk difficult. Increasingly they are everywhere from the placenta of unborn babies to the Arctic - and it's the plastic waste sources we don't talk about that most worry me.

But what is the problem with them? And what do we actually know about their impact on human and planetary health?

1. Research is starting to show microplastic impact on human health

It's still early days in research terms. Indeed the European Environment Agency says, “While much data is available on the presence of microplastics in the environment, knowledge on the health impacts of microplastics is currently lacking.”

But the evidence is gradually building. A recent US study, for instance, found both microplastics and nanoplastics in higher concentrations in placentas from premature births than in those births that went to full term.

Last week The Lancet launched an independent, indicator-based global monitoring system: titled the Lancet Countdown on health and plastics.

“Plastics,” the Lancet report said, “cause disease and death from infancy to old age and are responsible for health-related economic losses exceeding US$1·5 trillion [£1.1 trillion] annually. These impacts fall disproportionately upon low-income and at-risk populations.”

In a series of letters published last week, titled Act Boldly or Fail, scientists called for “legally binding targets to cap and reduce plastic production and the phase-out of toxic additives and chemicals in plastics”. They reminded negotiators that the costs of inaction are not abstract, but "can be counted in........

© Herald Scotland