Here are some of the places we've found microplastics (small pieces of plastic less than 5 mm/0.2 in) so far: rivers, glaciers, snow, the sea breeze, Mount Everest, human blood, human lungs. We're consuming about a credit card's worth of microplastics every week, and we're not really sure how they affect the human body. But (you may ask nervously), couldn't they just be... harmless? Well, the odds are unlikely.
We've only just started learning about microplastics a few years ago, and the only reason we don't know how bad they are for us is that researchers haven't had the time to carry out enough studies to analyze that in detail. Now, one such study is out, and it's exactly what you'd expect it to be: concerning.
Viruses and plastic
Researchers at the University of Stirling, in Scotland, experimented with tiny pieces of plastic and viruses. They wanted to see whether microplastics help viruses survive longer -- lo and behold, they did.
Microplastics in water become quickly colonized by microbial biofilm. Like bacteria, viruses can also sometimes form biofilms, which are communities of pathogens that are more resilient and more infectious than 'free' viral particles.
However, not all viruses seem to benefit from the presence of microplastics.
In the new study, researchers tested two types of viruses: enveloped viruses (such as the flu virus) and enteric viruses (such as the rotavirus and the norovirus). The envelope viruses were quickly destroyed, whereas enteric viruses were able to bind to the microplastic and form a biofilm that enabled them to survive for longer.
The researchers only ran their experiment for three days, which they concede is a significant limitation; we don't yet know exactly how much plastics help viruses, and more research is required to assess the impact on different types of viruses. This makes the study more of a proof of concept for future research, but even so, the fact that some plastics enabled the viruses to create resilient biofilms suggests that microplastics could be a hazard for human (and animal) infection.
"The recovery of infectious viruses from colonized microplastic pellets highlights the potential public health risk of surface waters becoming contaminated with microplastics, and subsequent human exposure to microplastics in the environment," the study authors note.
Every year, the world produces an ungodly amount of plastic, and the figure keeps growing. In 1990, the world produced about 100 million tons of plastic. In 2010, the figure increased to about 270. Now, it's at around 370 -- again, we're talking about millions of metric tons. Most of this plastic isn't recycled at all. Over half of this plastic is discarded, either in landfills, or in the world's waters.
In the water, it breaks down into smaller and smaller pieces: microplastics. Even if a wastewater treatment process does all it can to clean the sewage waste, current practices don't eliminate the microplastic. So many microplastics flow through rivers and reach the oceans.
As a result, humans are exposed to microplastics every day. We ingest microplastics, we breathe them in, and they even enter our bloodstream.
We don't really know what kind of health risk these microplastics carry, but increasingly, these small particles are starting to spell trouble. After all, it doesn't take many viral particles to get you sick.
"The presence and survival of human viruses associated with biofilm colonizing the surface of microplastics could play an important role in virus transfer. Although virus stability in the plastisphere is influenced by different environmental factors and viral structural characteristics, the recovery of both virus models used in this study emphasizes the potential for plastic pollution to act as a novel pathway for viral dissemination and persistence in the environment."
No doubt, future research will look at this problem in more detail.
The study "Binding, recovery, and infectiousness of enveloped and non-enveloped viruses associated with plastic pollution in surface water" was published in Environmental Pollution.