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School of Zebrafish

Summer Studentships 2022 Craig McHardy

Researcher: Craig McHardy

Location: University of Plymouth


2022 Summer Studentship winner Craig McHardy, studying at the University of Plymouth, received £2,820 for his project developing a model to help replace the use of live fish in tests to help protect the environment from the build up of hazardous chemicals.

The problem

Live fish are currently required in chemical safety assessment tests (OECD Test Guideline No. 305) to assess the bioaccumulation of substances, including chemicals. Bioaccumulation is where substances are retained within the tissue of organisms and as they accumulate this can negatively affect the health of the animals. This can also present a food chain risk affecting the health of animals that eat them, including humans. This bioaccumulation test is mandatory for every new chemical registered for industrial use where produced in sufficient quantities, including consumer goods. The individual test lasts four weeks and requires the use of 150 fish per test.

The project

Craig’s interest in ecotoxicology led him to undertake a dissertation project to develop a chemico digestibility assay – an in vitro analysis method to determine the presence or amount of a substance released from food, in this case using chemicals, by recreating the conditions of the fish stomach or intestine. This assay aims to replace the need for studies using live fish in chemical safety assessment tests.

Craig used the in chemico digestibility assay to assess the bioaccumulation potential of engineered nanomaterials that can be released from foods, in other words how ‘bioaccessible’ these materials are in the gut. If a chemical is not absorbed easily by the gut of a fish, then it cannot cause bioaccumulation, thus removing the need for further bioaccumulation tests. This project aims to provide data to show the potential of this assay to identify chemicals which have low bioaccessibility and do not require further testing on live animals.

The potential

Produced by modern technology, nanomaterials contain tiny particles (between 1 and 100 millionths of a millimeter) which behave very differently to larger particles, particularly due to their potential to cross membranes, such as those found around cells. Engineered nanomaterials are used in medicines, cleaning products, sunscreens, paints and pollution control devices. In the EU alone, there were over 136 registrations of new engineered nanomaterials this year. An in vitro test, which could identify materials that do not pose a bioaccumulation risk prior to conducting OECD Test No. 305, could potentially prevent the unnecessary use of thousands of live fish in tests each year.

“The lack of precursor tests for in vivo bioaccumulation testing in fish mean many animals could be used unnecessarily. Our hope is this work can act as a screening tool to demonstrate the most hazardous nanomaterials that require in vivo testing.”

Craig McHardy

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