June 15, 2023 | University Partners

University of Hull leading the way in microplastics research

On World Environment Day, Jeanette Rotchell, Professor in Environmental Toxicology in the Faculty of Science and Engineering, looks at one of the many significant threats to our environment – microplastics. The University of Hull is one of the world-leaders in microplastics research – and will continue to drive advances in our understanding of the scale and impact of these contaminants on our health and in our surroundings.

Microplastics are usually defined as being 1 micron to 5 mm in size which is less than a diameter of a human hair, invisible to the naked eye and up to the size of a sesame seed.

We first started looking for microplastics in mussels. As filter feeders they are often used by scientists to provide a snapshot of the level of contaminants in the marine environment. Our goal was to find out whether the mussels were taking up microplastics from the seawater, where we know levels can be high, as well as via seafood to humans. We found microplastics in every single mussel we tested.

We also went to supermarkets, testing the mussels available to eat. It didn’t matter which supermarket, we found microplastics in all the mussels. This led us to examining various different types of fish and the story was the same – bottom dwellers or pelagic in the water above, it didn’t make a difference, we found microplastics in their gills and digestive systems.

Next we started analysing the air. We conducted a long study inside 20 household’s living rooms, collecting the settled dust and testing the air for microplastics presence once a month. The levels and types of microplastics differed across the households and the time of year, which raised interesting questions about what types of furnishings or cleaning habits resulted in the higher microplastic levels. Moving our sampling and analysis outdoors, our results detected in the Hull and East Riding area air chimed with other studies around the world finding microplastics in London, Shanghai, and Australia.

When sea life encountered microplastics in its environment, those microplastics found their way into their bodies. It was logical to ask the same question about ourselves. To do that, we began collaborating with biomedical scientists and surgeons. When these surgeons operated on lungs, they were able to provide small tissue samples for us to analyse. While conducting this work, we also set up blank samples which are used to detect and account for any background levels of microplastics that might be floating in the surrounding air and contaminate any samples we wanted to analyse. We found microplastics in all the human lung tissue samples, and in our next experiment, in a number of human vein samples. We’re in the process of testing blood and urine.

So what? We spend our lives breathing and eating dust and countless tiny particles which don’t seem to do us much harm. There are two answers to this question, both concerning in their own ways.

The first answer details the dangers that we do know, or at least suspect – specifically, inflammation and chemical leaching. Inflammation can be especially hazardous if it exacerbates existing conditions. Take chronic obstructive pulmonary disease (COPD) as an example. COPD is a condition that causes shortness of breath, frequent chest infections, and a persistent cough. It can be life limiting and cannot be cured or reversed. Inflammation makes this regression worse and, remember, we found microplastics in the air we breathe and each of the lung samples we analysed. Similarly in China, preliminary research has connected microplastic levels to inflammation and irritable bowel type conditions.

Chemical leaching happens when the added chemicals involved in plastic production migrate into the tissues around them. Our research found that the several of the microplastics detected contained chemical additives, some of them known to be toxic. In human lung samples, we found PTFE, better known as Teflon, which is one of the “forever chemicals” as it is extremely slow to break down. We have no information yet on the levels of these chemicals that are leaching, but, in nature, we’ve found that even very low levels of such chemicals cause hormonal changes in fish, causing conditions such as intersex where fish develop both eggs and sperm rather than one or the other.

All of this should be taken with a pinch of salt – this is preliminary research and there’s been no robust studies yet on the actual impact of microplastics in humans. Which brings us on to the second, more worrying, answer. We know far too little about the scale of this problem. As far as we know, microplastics are everywhere, but we don’t know how harmful they are to humans or the environment, which types may have the most significant impacts, and how to effectively mitigate those impacts.

We need to stop facing this microplastics dilemma blind and there are two steps we can take right now fix it.

The first is to improve the quality of our analysis, making it more robust, and moving towards standardised methods. Most current analyses don’t include a blank control – given what we know about the ubiquity of microplastics all around us, we can’t make reliable findings about microplastics without considering those already around us which are highly likely to contaminate any analysis. Blanks allow us to make allowances for this and have more confidence in the results when microplastics are then observed. The initial analyses of microplastic impact on humans also have a repeating flaw. When conducting experiments on microplastics in cells within tubes or petri dishes, many researchers have used a shape of microplastic that essentially looks like a tiny ball. The problem is that most microplastics we’ve found in humans and mussels are not perfect balls, they are more like shards, with irregular, worn shapes, which have a very different impact on cells. If you can’t visualise the difference, imagine swallowing a whole grape vs a piece of uncooked spaghetti.

The second step needs more than academics. We need policy makers, governments on board. We need to actively monitor and regulate the levels of microplastics in our air and water. This is already starting at other points around the globe. In California, the Water Board authorities that look after the water supply have started to use monitoring methods to look at the levels of microplastics in the water. The UK, by contrast, despite some recent, high profile, waterway contamination events, has made no such progress as yet.

Human microplastic contamination could be insignificant, it could be seriously impacting us, or it could be somewhere in-between. We just don’t know. And until we start seriously and robustly analysing the levels of microplastics in our environment and bodies, and how it impacts us, we will continue to be the subjects of an experiment over which we have little control.

World Environment Day is the United Nations day for encouraging worldwide awareness and action to protect our environment.