The World Health Organization is calling for further research to obtain a more accurate assessment of exposure to microplastics and their potential impact on human health.

This follows the release of an analysis of current research related to microplastics in drinking water, indicating that microplastics larger than 150 micrometers are not likely to be absorbed in the human body and uptake of smaller particles is expected to be limited.

"Absorption and distribution of very small microplastic particles including in the nanosized range may, however, be higher, although the data is extremely limited," a statement released by the UN agency on Thursday stated.

To obtain a more accurate assessment, the WHO expressed a need to develop standard methods for measuring microplastic particles in the water, more studies on the sources and occurrence of microplastics in freshwater, and the efficacy of different treatment processes.

The WHO research -- titled Microplastics in Freshwater and Drinking Water: Critical Review and Assessment of Data Quality -- stated that standardized methods will allow reproducibility and comparability of results and will lead to the quality of data needed to conduct risk assessments.

WHO recommends that drinking water suppliers and regulators prioritize removing microbial pathogens and chemicals that are known risks to human health, such as those causing diarrhea.

"This has a double advantage: Wastewater and drinking water treatment systems that treat fecal content and chemicals are also effective in removing microplastics," the WHO said.

According to the organization, wastewater treatment can remove more than 90 percent of microplastics from wastewater, with the highest removal coming from tertiary treatment such as filtration.

Additionally, conventional drinking water treatment can remove particles smaller than a micrometer.

By addressing the problem of human exposure to fecally contaminated water, the WHO said communities can simultaneously address concerns related to microplastics. This is against the backdrop that a significant proportion of the global population is currently suffering from inadequate water and sewage treatment.

Fragments, fibers, film, foam and pellets were the most frequently found microplastic shapes in surface water samples.

"More studies are needed to better understand occurrence, shape, polymer types and particle sizes, particularly for small plastic particles," the research concluded.