Case Study: Water Quality and Microplastics

In this case study we will explore microplastics as an emerging concern to water quality, particularly due to the presence of endocrine disrupting chemicals. This issue was recently reviewed by Gallo et al. (2018) and will form the basis of this case study.

What are Microplastics?

Plastic marine litter is a mixture of polymers and chemicals in the marine environment. Items are very diverse, ranging from fishing gear, bottles, bags, straws, food packaging and cosmetic microbeads. This plastic has become a global problem as a result of the vast quantity of discarded plastic waste that is accumulating in our marine environments and its durability which allows it to persist once it enters. Over time this plastic breaks up and pieces of a diameter less than 5mm are known as microplastics. This small size is particularly concerning as it allows these plastics to be taken up by the marine biota and enter the food chain.

Microplastics as endocrine disrupters

The potential consequences of plastics and microplastics are well documented, from their physical obstruction in the marine environment (e.g. entangling species) to ingestion and physiological effects. An increasing concern surrounding microplastics are the complex mixtures of chemical contaminants which exist in plastic, especially those containing known or suspected endocrine disrupting chemicals as additives or contaminants. These chemical contaminants may leach into the marine environment as the plastic weathers and/or be release from the plastics when they reach the guts of marine species.

Chemicals with endocrine disrupting properties are a major concern as they can mimic, compete or disrupt the synthesis of endogenous hormones and thus interfere with any system in the body controlled by hormone (endocrine) systems. Experimental research has documented short and long term consequences in marine species including impaired reproduction, low birth rates, cancerous tumours and other developmental disorders.

Potential impacts of microplastics on food security and public health

The presence of microplastics in the marine environment has had negative impacts to the growth, development, reproduction, survival and mortality of different marine species. These microplastics are typically ingested by filter feeders, such as mussels, and are magnified through the food chain to top predators such as swordfish. The consequences on growth and development can potentially affect marine diversity and the productivity of our seas. This is particularly concerning due to the global challenges which already exist in feeding the growing population by 2050.

In terms of human health, there is no conclusive scientific studies to date which correlate the direct consumption of shellfish or fish contaminated with microplastics containing endocrine disrupting chemicals and the consequent endocrine disruption effects on human health. However, existing evidence on the uptake of microplastics by humans from other sources show diverse effects varying from DNA damage to lesions in organs.

Preventative Measures

There is a need to carry out focused scientific research to fill knowledge gaps about the impacts of plastic litter in the marine environment, the food chain and human health. However, based on the existing evidence and reasonable concerns around the extent of plastic pollution in our water ways, preventative measures to prevent and reduce the leaking of plastics into the marine environment is crucial.

There are a number of actions already in place, such as the ban on free single use plastic bags; recycling systems; penalties for littering; innovative materials for food packaging; and the UK wide ban on the manufacture of cosmetics and care products containing tiny pieces of plastic known as “microbeads”. However more needs to be done if we are to reduce the extent of pollution in our water from plastic.

The European Food Safety Authority (EFSA) Panel for Contaminants in the Food Chain has published a statement on the presence of microplastics in food, with a particular focus on seafood. You can find this report in the downloads section below.

Other Examples of Endocrine Disrupting Chemicals in Water

If you would like to explore water contamination further a recent article by Farinetti et al (2018) outlines the impact of of Tributylin (TBT), an anti-fouling agent that acts as an endocrine disruptor compound (EDC) using an adult mice model. TBT can bioaccumulate through the food chain and it may lead to chronic exposure to the consumer. The effect is sex specific. This study is an example of how academia can provide important studies to assess the long term effect of water pollutants. If you would like to read more about Tributylin, the link to the paper is included in the “See Also” section below.

Left image: Man lifting fish from net. Right image: A sample of microplastics in a test tube

What we would like you to do

Please conduct your own ‘internet scavenger hunt’ to get an idea of the concerns and issues around plastic in our marine environment. Please consider the following questions throughout your hunt and add your thoughts on two of the questions to the discussion area to finish.

• Were you aware of the emerging concerns around plastic in our marine environment? If so where did you hear this from?

• Do you think the concerns around plastic in the marine environment are justified?

• Can more be done to reduce plastics in our waterways and protect our marine environment? Name one thing you can do to help decrease microplastics spilling into our waters?

• Do you think marine plastics are a public health risk?

• Are you surprised by the complexity of the effects of these pollutants?

For more information additional reading materials are provided in the ‘See Also’ section below.