A Plastic Waste Treaty while Scientists find microplastic in human lungs and blood
by Sheryll Mangahas and Adam Grossman
The recent international agreement to devise a treaty governing plastic waste from production through disposal may be the first step in limiting plastic pollution. Embedded in the agreement to devise this treaty was a provision that all the measures under consideration should be legally enforceable within each country that signs on. Assuming the US would properly ratify the treaty that could lead to significantly elevated litigation risk for businesses involved in the value chain for plastic. In the meantime, many commentators have already observed that this agreement could raise the risk of litigation.
Microplastic has been in the news a lot lately as scientists continue to discover the extent to which our world is contaminated with it. Microplastic has been found everywhere on Earth from the ocean floor to the highest peaks and from the north pole to the south. As with other environmental contaminants, the very properties that make plastic useful – durability – contribute significantly to its effects on the environment. Plastic’s durability means that instead of degrading into harmless chemical building blocks, plastic instead degrades into small pieces in the environment.
Unsurprisingly, the ubiquity of microplastic in the environment means that humans are exposed almost constantly. Scientists have shown that we take in microplastics from food, from drinks, and by inhaling these tiny particles both indoors and outside. The earliest study showing that humans are exposed to microplastic dates back to 1998, when Pauly et al. found that tissue samples from people’s lungs contained polyester fibers1. Ascertaining the extent of microplastic exposure in humans is a hot topic in the scientific literature but progress has been limited by the measurement technologies available to discern microplastic fibers, fragments, and films. Two recent studies have demonstrated new techniques to detect a variety of microplastic in human samples and have garnered headlines doing it.
The first paper was published online in early April and described using µFTIR spectroscopy to detect and analyze microplastic particles as small as 3 µm in human lung tissue2. The authors found 12 different types of plastic polymers across the 13 human lung samples they studied. The most abundant plastic polymers were polypropylene, polyester (specifically polyethylene terephthalate), and resin. These plastics come from a variety of products, ranging from food containers and fabrics to paints and coatings. The authors note the surprising fact that more microplastic was found in the lower parts of the lung than the upper part, contrary to the assumption that most microplastic particles would be too big to enter the lower recesses of the lung.
Although environmental exposure to microplastic is now well established, the simple fact of having microplastic particles in your lung or gut does not guarantee that it gets across those barriers and into the blood. The first study to develop methods to directly look for microplastic particles in human blood was published online in late March3. The authors looked for five different types of microplastic in blood: poly(methyl methacrylate), polypropylene, polystyrene, polyethylene, and polyethylene terephthalate. They found four of the five – all but polypropylene – in samples from 22 volunteers. The fact that microplastic was found in human blood is not a complete surprise given a prior study showing that babies’ meconium contained microplastic and the only way that could happen would be via maternal blood. The average concentration of microplastic in blood was small in this study, 1.6 µg per ml, but we know that microplastic in our bodies increases the likelihood that they could lead to deleterious health effects.
Now that microplastic has been definitively shown to be in human bodies it seems inevitable that scientists will use these techniques to study how microplastic exposure correlates with disease. Only time will tell what these studies will tell us, but the more quickly they confirm or refute hypotheses of human harm from microplastic exposure the sooner we will know the likelihood that this body of science will lead to litigation.