They pollute the air we breathe, the tea we suck, the water we drink, and the food we eat. They are spread over the deepest sea trenches and the highest mountains. They are in our own fish, insects, whales, corals and poo. They even appear in human placentas.
There are microplastics everywhere. But we still don’t know what, if anything, they are doing to us.
As a result of this remarkable collection of plastic grains in every environment on Earth, as well as signs from animal toxicology studies, ecotoxicologists are calling for an urgent study of the impact of microplastics on human health. This is in response to calls from the World Health Organization (WHO) back in 2019.
Speaking on the WHO report, Auckland University chemist Duncan McGillivray explained that there is no need to panic about the effects of microplastic, “but we should not rest any longer – there are too many unknowns about how microplastics affect health. “
Now, in their Look article for the magazine Science, Dick Vethaak from Vrije Universiteit Amsterdam and Juliette Legler from Utrecht University in the Netherlands warn that the scale of microplastic contamination, injection and inhalation of these particles could be another human health emergency.
They described the extent to which we do not yet know about the contribution of these microscopic synthetic materials to our psychology.
While it does not appear to be immediately toxic (we and everything living around us have been exposed to microplastics for years now), the potential harm from small effects is only gradual, long-term exposures, or increasing concentrations remain unknowingly difficult.
While larger microplastics appear to be eliminated in our bodies in the same way as food waste (we excrete them), it is the smallest material that has the greater potential for toxicity, the researchers explain.
“Studies using smaller particles are more likely to detect effects,” University of Toronto ecologists Kennedy Bucci and Chelsea Rochman wrote for The Conversation about their 2020 review of microplastics.
“This may be because it is easier to eat small products with small organisms, or because they can move across the cell membrane and cause harmful effects such as inflammation.”
Part of the problem is that we do not yet have the technology to separate, sample and detect smaller microparticles (less than 10 micrometres in size) and nanoparticles (less than one micrometer in size), Vethaak and Legler explain . So we still don’t understand our full exposure levels of these synthetic materials.
“The effects of dose-dependent microplastics in humans are not yet known,” the researchers wrote.
However “studies with human cells in culture, and in rodents and aquatic species show the movement of microplastics <10 µm from the cavity of the cleft to the lymph and circulatory systems, causing systemic exposure and accumulation in cigarettes. including the liver, kidneys and brain. "
It’s not just their size that is a problem when it comes to getting answers. Vethaak and Legler warn that the few studies appear to have published an inaccurate print, as they introduced testing of new microplastics in laboratory settings.
A recent study concluded that there is a risk that microplastics may shrink and behave differently within our bodies compared to external environments. The researchers cited studies that described how macrophages (our waste disposal cells) were more susceptible to environmental contamination, than pristine plastic microparticles.
But studies like this on human and rodent cell cultures have revealed some toxicity – including inflammation, cell damage, immune reactions, neurological and metabolic effects – at very high exposures. Workers of the plastics and clothing industry who have been exposed to large amounts of plastic dust have also been suffering from similar conditions, including swelling and allergies.
But we cannot deny the unprecedented effects of other chemicals on these grains: Microplastics are capable of smuggling other hazards to their travel. These could include bacteria with resistance to antibiotics, viruses, and other toxic molecules. They can also inhibit our own midges.
Other chemicals associated with toxic plastics, such as fire retardants and phthalates, have been found in animal products, but we are not sure what their effect is either.
In addition, different types of plastics can have a profound effect on us. In their 2019 review, Bucci and colleagues found two types of plastics exerting the same opposite effects in different studies. Exposure to polystyrene caused crucibles to produce more offspring, but polyethylene there were fewer descendants.
This is a mock-up of factors and interactions that need a lot more attention. At the same time, everyone – from businesses and governments to consumers – can help focus on how we can reduce the flood of our microplastics into the environment. The fashion industry is one of the largest producers of these microparticles, with the manufacture of synthetic clothing.
“Multidisciplinary research efforts, involving scientists from the environmental and medical sectors as well as polymer scientists, are needed to address this potential health risk,” he said. -the close of Vethaak and Legler.
You can read their full view piece in Science.