Plastic fish: assessing the scale, chemical properties and biological effects of petrochemical plastics and bioplastics on aquaculture fish

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Disposable plastics are an everyday part of our lives but we do not fully understand their impacts on animal welfare. Biobased plastics, termed bioplastics, are marketed as a more envrionmentally friendly alternative to traditional petrochemical plastics. We need to be sure, however, that these bioplastics and their breakdown products are safe when consumed. This interdisciplinary project between three university departments (Cardiff University, Schools of Biosciences, Chemistry and Engineering), driven by industry-led questions, will assess the chemical properties and biological impacts of petrochemical and bioplastics on farmed fish.The combined mass of environmental plastic exceeds the mass of all fish on the planet. This is concerning on multiple levels; fish comprise the most abundant vertebrate species, they are a major source of protein for humans and aquaculture is the fastest growing food sector globally. If practiced sustainably, fish culturing can provide the lowest carbon source of animal protein for human populations. A key factor that threatens the welfare of managed fish stocks and their future sustainability is pollution. The scale of plastic pollution within managed fish stocks is largely unknown and this must be addressed now. Plastic particles have been detected in fish and human tissues demonstrating that plastics are part of the human food chain, so we must assess how this pervasive pollutant is impacting fish welfare. Our pilot data has shown that plastics without chemical additives impact fish welfare by reducing disease resistance and prolonging infections. However, this may just be 'the tip of the iceberg', as most plastics also have chemical additives, such as plasticisers and thermal stabilisers, and plastics can act as sponges for environmental toxins potentially causing more damage when consumed. An emerging strategy in addressing plastic pollution is the development of bioplastics. While bioplastics currently only constitute 1% share of annual plastic production, they are widely marketed as an alternative to petrochemical plastics. Bioplastics are openly advertised as eco-friendly and biodegradable, yet research on their environmental suitability is extremely limited and previous degradation studies (conducted under unrealistic scenarios) show minimal degradation. But even if bioplastics do degrade faster than petrochemical plastics, they might paradoxically generate higher rates of persistent micro and nanoplastics. Furthermore, bioplastics contain the same chemical additives as petrochemical plastics, so we must assess how efficient they are at releasing these chemicals and adsorbing other chemical pollutants within aquatic environments. Likewise, we must understand the functional impacts of bioplastics, and the associated additives, when they are consumed by animals. This project has three key objectives, which directly align with BBSRC strategic priorities on animal health, specifically welfare of managed animals, data driven biology and research that can inform public policy. Firstly, we will assess the scale of plastic pollution within aquaculture fish stocks across the UK. Secondly, in association with prevalent additives and environmental toxins that petrochemical plastics contain, we will assess the chemical properties of these plastics as well as their biological impacts on farmed fish with an emphasis on growth, metabolism, and disease resistance. Then, recognising the urgency to assess alternative plastic solutions, we will test the chemical properties and biological effects of bioplastics, when exposure and consumption occurs. In delivering this project, we will directly inform government agencies and aquaculture about the scale and associated effects of plastic pollution in fish stocks to support policies on plastic use and waste mitigation. By assessing the environmental suitability of bioplastics, future public outreach programmes can help prevent potential greenwashing.