Microplastics come from many sources: synthetic clothing fibres, dust from tyres, road paints, and the breakdown of larger items. Orb Media's recent investigation has brought the issue of microplastics in the environment into sharp focus. The analysis of tap water samples from around the world found that a high proportion of drinking water is contaminated with microscopic fragments of plastic (83% of samples collected worldwide, but up to 94% in the USA). Microplastic contamination seems more widespread than we perhaps knew, and they are regularly being ingested by people worldwide. Most concerning is how little is known about the effects of microplastic consumption on human health.

It is no small problem. As of 2015, 6300 million tonnes of plastic waste have been generated, around 9% of which was recycled, 12% was incinerated, and 79% ended up in landfills or the environment. The issue of large plastic items polluting the world's oceans is well known, leading to policies that aim to limit the production and use of plastic bags and bottles, and increase recycling. However, a key problem with plastics is that they are essentially indestructible; rather than being biodegraded, they break down into smaller and smaller pieces, eventually becoming microscopic fragments. We should no longer just be concerned with large plastic items clogging up oceans and waterways, but also more attention needs to be paid to these tiny fragments and their effects on planetary health.

The tapwater study is not the first to indicate that microplastics are being consumed by humans. A 2014 study of German beer brands found that microplastics were present in all of the samples, and a Parisian study showed microplastics not just in water but also in the air. Microplastics are also routinely ingested by fish and shellfish. But the apparent widespread presence of microplastics in tapwater is particularly concerning because it points to substantial contamination of terrestrial and freshwater—as well as marine—ecosystems.

The ubiquity of microplastic contamination can no longer be denied. To mitigate this global problem, several actions need to be taken, and quickly. First, the amount of plastic being released into the environment must be drastically reduced. Some policies have already been formulated with this goal in mind, for example, many countries have made it illegal for retailers to give away plastic bags for free, and deposit schemes for plastic bottles are in place in parts of the USA and Europe. However, progress on this front has been slow and piecemeal.

To speed up progress on reducing plastic waste, manufacturers of plastic could be forced to take responsibility for the damage wrought on the environment; this is beginning to happen through extender producer responsibility (EPR) laws, which require plastic producers to fund and manage recycling and disposal of their products. EPR laws are already being used in the USA for electronic products such as phones, televisions and batteries that contain lead, mercury, and cadmium; many states now require manufacturers of these products to support their recycling and disposal at the end of the product's lifespan. Consumers should also be encouraged to change their behaviours to reduce the amount of plastic consumed.

Even with concerted global effort, the amount of microplastics in the environment will continue to grow, and the question remains—what impact will this have on human health? The concerning answer is that no-one knows. To date, there have been no studies of the effects of microplastic consumption by humans.

Designing robust studies to look at this issue will be difficult—observational, population-based studies will be open to confounding, while experimental studies will be impractical (ethically, if nothing else). The deleterious effect of current levels of microplastics might be small, by contrast with the known risks of industrial pollutants such as heavy metals or black carbon, so teasing out the effect at the population level will be hard, and will require a sophisticated surveillance system. If an effect exists, people living in areas of high plastic contamination will develop greater disease burdens as levels continue to rise. Disease-reporting systems need to be linked to pollution databases to ensure any effect is identified early, and action taken quickly.

Solving a problem of this magnitude will not be an easy task. Public education, product innovation, and industry leadership along with strong commitment from local, national and international governments, are urgently needed to reduce the use of microplastics and to understand the effects of these particles on both ecosystems and the human body.

Orb Media's investigation of microplastics in tapwater see Forsee https://orbmedia.org/stories/Invisibles_plastics For more on plastic waste see Sci Adv 2017; 3: e1700782. For the study of microplastics in beer see Food Addit Contam Part A 2014; 31: 1574–78. For more on microplastics and fish see Mar Pollut Bull 2013; 67: 94–99. For more on microplastics in shellfish see Environ Pollut 2014; 193: 65e70 global legislation around plastic bags see For more onsee http://www.bigfatbags.co.uk/bans-taxes-charges-plastic-bags extender producer responsibility laws see For more onsee http://www.urthpact.com/plastic-makers-facing-new-regulations-around-circular-economy

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