A glass of drinking water riddled with tiny plastic particles could spread disease, and scientists want action.
A World Health Organisation (WHO) report released today warns microplastics in drinking water could carry bacteria – which in turn could help bacteria become resistant to antibiotics.
Water suppliers and regulators should be acting to stop it, but ultimately the best solution is to stop polluting the world with plastic, the report says.
Massey University environmental anthropologist Dr Trisia Farrelly says people should be "extremely worried" about microplastics.
"We now know that microplastics can move across the body and get in to your circulatory system, we know that they can travel to the organs and to your lymph system, and via the lymph system they can end up in the liver and the spleen," she said.
"There's clear potential for the risk to human health."
Worldwide, 81 per cent of drinking tap water tested from some metropolitan areas contained microplastics, she said.
A report from Royal Society Te Apārangi released last month found New Zealand's plastic waste causes microplastics to end up in our bottled and tap water, seafood, and table salt, and even our air, and the Auckland University has found seven common species of fish in NZ are consuming plastic.
Last year, research from Waste Management World found New Zealand produces 3.68kg of waste per capita per day – the worst in the developed world.
The WHO report says the attachment to microplastic could favour bacterial survival - including genes associated with antibiotic resistance.
However, more research was needed to better understand the capacity of microplastics to transport pathogenic bacteria.
ESR senior scientist Dr Olga Pantos said New Zealand does not have good information on microplastics in the environment, and how it gets there.
Due to the high mobility of microplastics in soil, they may end up in the water we drink, she said.
"We know from a recent New Zealand study that treated wastewater effluent also contains large amounts of microplastics, in line with international studies, which represents a direct source of microplastics to terrestrial, marine and freshwater environments."
Microplastics would continue to break down, creating nanoplastics, and the smaller they got, the greater the challenge, she said.
"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 the less there is to cause harm."
University of Auckland school of chemical sciences associate professor Duncan McGillivray said we were more exposed to microplastics than we thought.
"There are studies that have shown the presence of as much as 1000 particles per litre of bottled water."
There were too many unknowns about how plastic would affect human health, he said.
University of New South Wales civil and environmental engineering professor Stuart Khan said microplastic was "a sad indictment of our complete failure to manage pollution" caused by plastic materials.
"Microplastics are now being detected in drinking water, including both tap water and bottled water.
"As a global community, we must do better than this."
WHO department of public health director Dr Maria Neira said scientists needed to urgently know more about how microplastics would affect human health.
"We need to find out more. We also need to stop the rise in plastic pollution worldwide."
Based on limited information, microplastics in drinking water don't appear to pose a health risk at current levels, but Neira said that data was extremely limited.
WHO recommends drinking-water suppliers and regulators prioritise removing microbial pathogens and chemicals that are known risks to human health - wastewater treatment can remove more than 90 per cent of microplastics.
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