News that microplastics have been discovered in human blood samples confirms what many scientists had been predicting. While the health effects over the longer term are uncertain, the news raises concerns about the extent that plastic pollution extends. A Dutch study revealed that 17 out of 22 blood donor samples contained plastic particles.
Micro- and nano-plastics
Microplastics are formed by weathering and physicochemical or biological degradation processes from macroscopic plastic products, such as the tonnes of plastic waste in the oceans. The degradation processes go beyond the micrometer scale, leading to nanoplastics (<1 μm). As well as the general impact on ecosystems, plastic particles have been shown to enter the human food chain and humans also inhale considerable quantities of plastic particles due to atmospheric fallout.
Evidence in blood
Microplastics in the blood were first predicted in 1988 and detected in 2015. Where humans ingest microplastics through eating, research by Swiss Federal Laboratories for Materials Science and Technology (EMPA) finds although there is evidence concerning chemical and particle toxicity effects of plastic in the human body including in the blood (genotoxic and cytotoxic), there is evidence that the actual particles can enter the bloodstream or the brain (although they are mostly excreted again, as demonstrated in tests of human faecal material, creating a problem for wastewater systems). These findings are unsurprising given the detection levels in the blood of fish.
Types of plastics discovered in blood
The types of plastic nanoparticles that have been detected in blood are:
- Polyethylene terephthalate (PET) – the plastic used in making drink bottles, food packaging and fabrics.
- Polystyrene – the plastic used to make disposable bowls, plates and food containers.
- Polyethylene – found in paints and shopping bags.
- Polypropylene – used in making food containers.
Particles in the submicron range and, in particular, nanoplastics below 100 nm, have been shown to penetrate cell membranes and reach the blood stream, as reported in a rat model. The evidence for microplastic detection in blood is from tests on plasma proteins such as albumin and globulin, which interact with nano-sized plastic particles to form protein–plastic complexes. There is a risk that aggregated protein–plastic complexes could potentially lead to blockage of blood vessels. Other research suggests it remains to be determined whether plastic particles are present in human blood plasma long-term.
Particle levels of concern
The concerns with plastic particles and blood relate to size (with the risk increasing below 250 nm) and quantity. It would appear that a loading of red blood cells at a low 1:50 ratio does not affect the functions of red blood cells. However, a 10–50-fold higher loading damages red blood cells, causing mechanical, osmotic, and oxidative stresses. However, there are no reported causes of this large acute accumulation in the human circulation under natural conditions. Researchers also acknowledge this and state that it is currently too early to consistently assess the levels of microplastics in the blood or to evaluate the health effects on humans, although the risks are potentially serious.
A comprehensive human health risk assessment for plastic particle pollution is currently not possible – due to lack of data on both toxicological hazard and human exposure – is supported by other researchers.
Future research
It is expected to take several years to build datasets for human exposure to plastic particles based on mass concentrations and for appropriate methods to be designed.
