EXPERT REACTION: We're all drinking microplastics, and we don't know if they're making us sick

One thing we do know is plastic is not supposed to be in the environment. 

Whilst the focus of the impacts of microplastics has traditionally been focused on the impacts on the marine environment and human exposure through seafood, the WHO report and recent research here and overseas is starting to include fresh water, land and air.

In New Zealand, groundwater and surface water are our major sources of drinking water.  We do not have good information on the burden of microplastics in those environments, or how it is getting there.

Our MBIE funded project is the first comprehensive research investigating the impact of microplastics in New Zealand’s environment.

There is a small, but growing body of work worldwide looking at the fate of microplastics in the terrestrial environment. Due to the high mobility of microplastics in the soil, they may end up in groundwater and surface water, along with atmospheric microplastics.

As the WHO report points out, wastewater is another major source of microplastics in the environment.  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.

Although we do not know what the levels of microplastics are in New Zealand drinking water, based on international studies we may expect that the treatments used for the removal of microbiological contamination and turbidity of municipal supplies in New Zealand will be effective in also removing microplastics.

There is still a lot of work to be done to develop robust testing methods for microplastic contamination.  We also know that microplastics continue to break down, creating nanoplastics and the smaller they get, the greater the challenge for isolating and identifying them accurately.

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 less there is to cause harm.

Given the growing consciousness of the use of plastic, amount of plastic waste, and the microplastics formed from its breakdown, it is very timely for WHO to release a report on microplastics in drinking water. We are more exposed to microplastics than we think. There are studies that have shown the presence of as much as 1000 particles per litre of bottled water.

The main message from the report is not to panic about microplastics – any potential health risk appears to be much less than other potential contaminants in drinking water such as bacteria and pollutant chemicals, and treatment systems that reduce those contaminants can do a good job of dealing with microplastics as well. But we should not relax either - there are too many unknowns about how microplastics impact health, and the WHO report strongly encourages further research in the area. Even the definition of microplastics is not clearly agreed on, and the biological effect of a microplastic depends on complex combinations of factors including what it’s made of, how big it is, and whatever it may have picked up as a surface coating. And overall, we just need to reduce the amount of plastic waste we are creating.

The report also notes that even less understood are the smaller particles formed when microplastics break down – nanoplastics. When particles get to the nanometre size range (1 billionth of a meters), i.e., are nanoparticles, they can behave quite differently to bulk material – this can be very useful and is the basis of many important nanotechnologies. However, at this scale we face technological challenges to even detect them, and they are small enough to be absorbed into the body and avoid some natural biological defence mechanisms. It has already been established that nanoplastics can cause toxic effects to marine organisms, but little to nothing is known of their effects on human physiology, and this is lack of knowledge that should be rectified.

This report is a timely reminder of the global 'platastrophe'. The research shows us that plastic is all around us in all environmental media and indeed the WHO report adds to this consensus.

While it is encouraging to see the WHO take the lead on this issue and conduct this large scale review of microplastics in drinking water, the conclusions could be better refined. The report highlights a paucity of research and subsequent knowledge surrounding both the health impacts of microplastic ingestion and microplastics in drinking water, however errs on the side of microplastics in drinking water being of no health concern.

The conclusions reached by the WHO are often reminiscent of the 'no data, no problem' paradigm which could be used to misrepresent the impacts of microplastic pollution by some stakeholders.

To the credit of the WHO report, it does argue for improved research funding in the area of microplastic pollution to answer the unknowns presented by the review. This report once again demonstrates the need for a focus on environmental pollutant research broadly, and a commitment by countries such as Australia to be leaders in this field of expertise

This report ties together very nicely the key findings to date, and highlights the knowledge gaps relating to microplastics in water. Its findings mirror very closely those of the study undertaken by the University of Newcastle in collaboration with WWF [World Wide Fund for Nature], presented during the launch of the Plastic Diet in June 2019 (Senathirajah et al, 2019). The University of Newcastle study is the first global assessment of the dietary intake of microplastics.

The World Health Organisation has produced an important document, reviewing recent scientific reports relating to microplastics in drinking water. This report provides a very clear and valuable picture of the current state of the science on this topic. 

Microplastics can now be found throughout the environment, including in fresh water sources and marine waters. This is 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 and we must seek opportunities to reduce global pollution, including microplastics. 

Despite the widespread occurrence of microplastic pollution, the WHO has determined that there is currently insufficient information from which to draw conclusions on the toxicity of these particles, and no reliable information to suggest it is a concern. The key message for water authorities is that concerns over microplastics in drinking-water should not divert resources or attention away from the things which do present real public health risks in drinking water. These are microorganisms such as viruses and bacteria, as well as some chemical contaminants such as lead.

But the message for scientists is different. For scientists, the WHO is calling for well-designed studies to better understand the sources and occurrence of microplastics in fresh water and drinking-water, as well as the effectiveness of our water treatment processes to remove them from drinking water and wastewater. These are important challenges and some which Australian universities and researchers should play an important role.