We're drinking microplastics, but no one knows if that's bad yet - WHO report

"Plastic is not supposed to be in the environment."

While that might seem obvious, scientists are concerned how little we know about the effects of microplastics on human health.

A new World Health Organization report, released on Thursday, says we need to figure out how bad the problem is, and fast.

"We urgently need to know more about the health impact of microplastics because they are everywhere -  including in our drinking- water," said Maria Neira, director of the WHO's Department of Public Health, Environment and Social Determinants of Health.

"Based on the limited information we have, microplastics in drinking water don't appear to pose a health risk at current levels. But we need to find out more."

Research last year found even bottled water, usually expected to be clean, often contains about double the amount of microplastics as tap water. One even had 10,000 pieces per litre.

That study, published by Washington DC-based data reporters Orb Media, prompted the WHO to look into the problem.

The WHO's analysis of the existing research suggests pieces larger than 150 micrometres across - about one seventh of a millimetre - are easily expelled by the body. But there is concern pieces smaller than that can end up in organs and the bloodstream, and for nano-sized small particles - one-thousandth of a micrometre - the science is even less clear.

"Despite the widespread occurrence of microplastic pollution, the WHO has determined that there is currently insufficient information from which to draw conclusions on the toxicity of these particles, and no reliable information to suggest it is a concern," said Professor Stuart Khan from the University of New South Wales' School of Civil and Environmental Engineering.

"The key message for water authorities is that concerns over microplastics in drinking-water should not divert resources or attention away from the things which do present real public health risks in drinking water. These are microorganisms such as viruses and bacteria, as well as some chemical contaminants such as lead."

Filtration systems are highly effective at getting rid of all but the smallest pieces of microplastics, said Institute of Environmental Science and Research senior scientist Olga Pantos.

"Although we do not know what the levels of microplastics are in New Zealand drinking water, based on international studies we may expect that the treatments used for the removal of microbiological contamination and turbidity of municipal supplies in New Zealand will be effective in also removing microplastics.

"There is still a lot of work to be done to develop robust testing methods for microplastic contamination.  We also know that microplastics continue to break down, creating nanoplastics and the smaller they get, the greater the challenge for isolating and identifying them accurately."

The WHO says about 90 percent of it can be removed via treatment, particularly filtration.

"Conventional drinking-water treatment can remove particles smaller than a micrometre... By addressing the problem of human exposure to faecally contaminated water, communities can simultaneously address the concern related to microplastics."

Prof Duncan McGillivray of the University of Auckland's School of Chemical Sciences said it wasn't time to panic - yet.

"Any potential health risk appears to be much less than other potential contaminants in drinking water such as bacteria and pollutant chemicals, and treatment systems that reduce those contaminants can do a good job of dealing with microplastics as well. 

"But we should not relax either - there are too many unknowns about how microplastics impact health, and the WHO report strongly encourages further research in the area."

The WHO says about 90 percent of microplastics can be removed via treatment, particularly filtration. Photo credit: Getty

He says nano particles can behave very differently to microplastics of larger sizes.

"However, at this scale we face technological challenges to even detect them, and they are small enough to be absorbed into the body and avoid some natural biological defence mechanisms. 

"It has already been established that nanoplastics can cause toxic effects to marine organisms, but little to nothing is known of their effects on human physiology, and this is lack of knowledge that should be rectified."

Dr Pantos perhaps summed it up best.

"One thing we do know is plastic is not supposed to be in the environment... We need to reduce the amount of plastics we use. The less that ends up in the environment, the less there is to deal with, and less there is to cause harm."

The WHO report notes however plastic production is actually on the rise, and is expected to double by 2025 and more than triple by 2050. The plastics industry also has some clear health benefits, including food storage and medical applications.