Over the past few years, several studies have reported the presence of microplastics in treated tap and bottled water, raising questions and concerns about the impact that microplastics in drinking-water might have on human health. In its first report on the issue, the World Health Organisation (WHO) has found that the microplastics pass through the body without being absorbed.

According to the analysis, which summarises the latest knowledge on microplastics in drinking-water, microplastics larger than 150 micrometres are not likely to be absorbed in the human body, while the uptake of smaller particles is limited. Absorption and distribution of very small microplastic particles, including in the nano size range may, however, be higher, although the data is extremely limited.

However, the WHO says the evidence available so far on microplastics in water is limited. The UN body called for the need of more research to obtain a more accurate assessment of exposure to microplastics and their potential impacts on human health. These include developing standard methods for measuring microplastic particles in water; more studies on the sources and occurrence of microplastics in fresh water; and the efficacy of different treatment processes.

“The overall conclusion is that consumers shouldn’t be too worried,” said Bruce Gordon, one of the authors of the study, though he urged more extensive research. “With the data we have, we believe the risk is low, but can’t say conclusively that there won’t be a risk in the future. We aren’t alarmed by any means.”

Furthermore, WHO recommends drinking-water suppliers prioritise removing microbial pathogens and chemicals that are known risks to human health, such as those causing deadly diarrhoeal diseases. This has a double advantage: wastewater and drinking-water treatment systems that treat faecal content and chemicals are also effective in removing microplastics.

Proper waste water treatment, involving the removal of faecal content and chemicals, should, the WHO says, also remove more than 90% of microplastics. That is why the WHO’s recommendations in the wake of this report do not include routine checks for microplastics in water. Instead, the WHO wants drinking water suppliers and regulators to concentrate on “known risks”.

Nevertheless, the WHO views plastic pollution as an urgent problem and it advises reducing the use of plastics by phasing out single-use plastics and improving recycling programmes.

Further information on the report is available here: https://www.who.int/water_sanitation_health/publications/microplastics-in-drinking-water/en/