The global health agency said there doesn’t exist enough research and reliable data to conclude that the situation is alarming
The World Health Organization (WHO) on August 22, 2019 said microplastics were present in drinking water, but the levels were not alarming. The UN health agency, however, said there was lack of “enough research” and “reliable and conclusive data” on the subject.
The WHO released its first-ever report on presence of microplastics in drinking water on August 22, 2019. “This WHO assessment reassures the consumers of drinking water that risk of microplastics (in it) is low,” said Bruce Gordon, coordinator, Water, Sanitation and Hygiene programme, WHO.
There exist significant gaps in existing research studies on presence of microplastics in drinking water, said WHO officials.
For example, there is no consensus on the exact definition of microplastics. “A widely used definition describes microplastics as plastic particles smaller than 5 mm in length. However, this is a rather arbitrary definition and is of limited value in the context of drinking water. Some groups define a lower bound at about 1 μm (micrometre),” read the WHO report.
While the WHO assessment done by summarising existing researches does not categorically rule out the impact on health caused by microplastics in drinking water, the risk presented by these studies on the issue is overstated, said Gordon and Jennifer De France, technical officer with the same programme.
“I personally feel that a lot of inaccurate information has been put out,” said Gordon.
Microplastics can easily lodge themselves in the human body, but this doesn’t necessarily translate into a health risk, according to the WHO. “It is possible for some smaller plastic particles to be able to pass through the gut wall and translocate to tissues remote from the mucosa, but this may not necessarily translate to a health risk,” read the report.
“Humans have always ingested particles and have ingested plastic particles for decades with no related indication of adverse health effects,” it added.
Findings of existing studies
The WHO analysed 10 studies to come to this conclusion. The research on this subject started only in 2018, said the global health agency.
One of these 10 studies — conducted by researchers from State University of New York — checked the presence of microplastics in 11 global brands of bottled water purchased in 19 locations in nine countries — China, USA, Brazil, India, Indonesia, Mexico Lebanon, Thailand and Kenya.
“Of the 259 total bottles processed, 93 per cent showed some sign of microplastic contamination. After accounting for possible background (lab) contamination, an average of 10.4 microplastic particles, more than 100 μm in size per litre of bottled water processed, were found,” read the study.
It had also found that the contamination ranged from 0-10,000 microplastic particles per litre of water. After this study’s release, the WHO initiated its comprehensive review.
Another study the WHO analysed found microplastics in all the water samples the researchers had collected. According to this study, conducted by researchers from Czech Republic, the average abundance ranged from 1473- 3605 microplastic particles per litre in raw water and 338- 628 in treated water depending on the water treatment plant.
“This study is one of the very few that determines microplastics down to the size of 1 μm, while microplastics smaller than 10 μm were plentiful in both raw and treated water samples accounting for up to 95 per cent,” read the study.
Still, there is not enough comparability in the existing studies, said France while highlighting three important gaps in them.
“First, we need to know the exact magnitude of occurrence of microplastics in drinking water,” she said. While most of the studies say there are 0-1000 particles in a litre, some even say the number goes up to 10,000. “You can't asses risk based on that. Any number of particles (microplastics) a scientist would get in per litre drinking water would depend on the size of filter used by him/her,” said Gordon.
The smaller the size, the better the chances of particles not being absorbed, and so it is too early to suggest any conclusive number, said WHO officials. Also, the existing studies, don't mention the source of entry of these contaminants (if they are coming from the source of the water or water supply chain), they added.
When asked if bottled water had more microplastics than tap water, the WHO officials said, “There is no clear knowledge. However, since water bottles are made from polymers of PET and PP which themselves contain microplastics, there are chances that bottled water would have more.”
“So, if one has access to clean tap water, the physicians should suggest the person to avoid consuming bottled water,” they added.
About additives or chemicals getting attached to the microplastics that contaminate the water, the WHO report says they are of “low concern to human health”. “The maximum exposure these chemicals cause is much lower in level than what could have become a concern for us,” said WHO officials.
Another contaminant analysed was biolfilms — the bacteria that grows on different surfaces and can cause toxicity. “Colonisation of microplasics (to form biofilms) would be very small compared to what normal bacteria would do to form biofilms in case of other surfaces,” said the officials.
The WHO also cleared that since most water treatment systems installed for clearing drinking water impurities are capable of treating microplastics, no special resources were needed for these small particles.
“Conventional drinking water treatment (coagulation, sedimentation and filtration) is designed to remove particulates and is therefore expected to effectively remove microplastics. Wastewater treatment can typically remove more than 90 per cent of microplastic particles,” read the report.
The WHO also called for much more robust and better controlled studies to understand the impact of microplastics on human health. “The WHO, as a scientific organisation, has already decided to undertake an independent review of impact of microplastics in all forms of environment — food, air, and water. So, we hope to have better knowledge about their role in drinking water as well,” said Gordon.
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