Tiny particles of plastic carrying ‘biofilms’ that could contain disease causing bacteria and which may already be entering our guts have contaminated drinking water supplies around the world, a landmark UN report has warned.
The World Health Organization (WHO) has compiled the most comprehensive review to date of the evidence of microplastics – tiny plastic particles measuring less than five millimetres (0.2 inches).
Microplastics have hit headlines over recent years, as they have been detected in marine water, wastewater, fresh water, food, air and drinking-water, both bottled and tap water.
Now, for the first time, WHO has examined the potential human health impacts of exposure to microplastics through drinking-water.
The study also outlines areas for future research that could shed light on the scale of the problem and what we can do about it.
That includes finding out where most microplastic pollution is, where it is coming from, how it may impact human health and what can be done to stop more of these particles from entering our drinking water.
Some of the key findings include the revelation that larger microplastic particles, bigger than 150 micrometres, are likely to be passed out of our bodies without harm.
Smaller particles could potentially be absorbed into our organs, however.
It also suggests microplastics have the potential to both carry disease-causing bacteria and help bacteria become resistant to antibiotics.
There has been very little research to date that has looked at the issue of microplastics in drinking water, the WHO report warns.
The information within it was collected through literature reviews on all scientific studies carried out on the occurrence of microplastics in the water cycle.
It also gathered evidence on the potential health impacts from microplastic exposure and the removal of microplastics during wastewater and drinking-water treatment.
Based on existing data, the risk to health posed by microplastics is judged to be low because particles larger than 150 micrometres are unlikely to be absorbed into the human body through the gut.
WHO experts examined and rated the quality and relevance of all of the studies they found during this process.
The report recommends that drinking-water suppliers and regulators prioritise removing disease-causing bacteria and harmful chemicals from the water supply, as that would also remove microplastics from drinking water.
It found existing treatments are very effective at removing them from drinking water.
Up to 90 per cent of microplastics can be removed via commonly-used water treatments to prevent faecal contamination, with filtration found to be the most effective method.
Scientists expect the uptake of smaller particles to be low, but said the data relating to the absorption and distribution of nano-sized particles of plastic is extremely limited.
Ultimately, the best solution is to stop polluting the world with plastics, the report says.
Dr Andrew Mayes, from the University of East Anglia’s School of Chemistry, developed a test that revealed microplastics in bottled water around the world.
The rapid screening method identifies microscopic plastic particles – as small as a few micrometres – in water and sediment samples.
The authors cite the problem of classifying microplastics as they come from a multitude of different materials and sizes. They can also be combined with numerous different chemicals – for example flame retardants – depending on their original purpose
The method ‘sees’ microplastic particles, by staining them using fluorescent Nile Red dye. The dye adsorbs onto plastic surfaces, making them fluorescent when irradiated with blue light. These fluorescent particles can then be visualised and counted.
This research led to the report, which also calls for a reduction in plastic pollution to benefit the environment and reduce human exposure.
Commenting on the report, Dr Mayes, said: ‘As might be expected from a WHO-commissioned report, this is a pretty comprehensive synthesis of all the currently-available scientific evidence.
‘The report is well balanced and seeks to assess the risks in an overall context relative to other likely risk factors. By drawing together all the available and often disparate evidence, the working group has added considerable value to the literature through thoughtful and detailed analysis.
‘The key finding, that microplastics in drinking water pose a low risk to human health, based on current available evidence, will no doubt come as a relief to worried members of the public.
‘Lack of rapid, cost effective and reliable methods for detecting and analyzing microplastics is a key bottleneck in much of the required research effort to understand the sources, distribution behaviour and fate of microplastics, both in environmental and medical contexts.
‘Hopefully, highlighting this issue in such a prominent way in the report will encourage the research community and funding agencies to address this gap in an urgent and concerted way.’
The report also urged for more research to increase the understanding of microplastics.
WHO scientists say the limitations of current data mean it is difficult to gauge the potential impact on human health if concentrations of microplastic in drinking water continue to rise.
The authors cite the problem of classifying microplastics as they come from a multitude of different materials and sizes.
They can also be combined with numerous different chemicals – for example flame retardants – depending on their original purpose.
Plastic fragments and fibres from synthetic fabrics were the most commonly found microplastics found in drinking water, the report found.
Dr Maria Neira, head of the department of public health, environment and social determinants at WHO, said: ‘We urgently need to know more about the health impact of microplastics because they are everywhere – including in our drinking-water.
‘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. We also need to stop the rise in plastic pollution worldwide.’