Bioconcentration protection and testing

The environment and the organisms living in it are continuously exposed to a wide range of chemicals. From chlorine-based solutions that remove bacteria from water to pesticides that treat and protect crops. However, through bioconcentration and the theory of biomagnification, some of these chemicals can become dangerous to our world.

Here, Dr Rachael Benstead, senior aquatic ecotoxicologist at translational science and research organisation, Fera Science Ltd, looks at bioconcentration and biomagnification and what is being done to protect our planet.

With every chemical product that is used to treat or protect our environment, it is important to understand the true effect of its impact on the ecosystem and living beings. As established with Dichlorodiphenyltrichloroethane (DDT), a crystalline chemical compound used as an insecticide in the 1940’s, not knowing the effect can lead to detrimental results.

Developed as the first of the modern synthetic insecticides in the aftermath of World War II, DDT was used as a pesticide for insect control. Initially used by the military to control malaria, typhus, body lice and bubonic plague, the chemical compound was later used by farmers on food crops and in buildings for pest control purposes.

However, in 1972 the United States Environmental Protection Agency issued an order for the removal of DDT from use, based on its harmful environmental effects to wildlife as well as potential human health risks. The reason for these adverse consequences and threats is primarily due to bioconcentration and biomagnification.

Bioconcentration is the process of accumulation of chemicals that are dissolved in water and absorbed through the gills and body surface of fish and aquatic organisms. Bioconcentration is expressed in terms of the bioconcentration factor (BCF), which is the ratio of the concentration of the chemical in an organism to its concentration in the ambient environment.

The theory of biomagnification is the process of bioconcentration as it moves up the food chain. Adriaens, Gruden and McCormick in Treatise on Geochemistry (2007) describe biomagnification as “the accumulation of a chemical by an organism from water and food exposure that results in a concentration that is greater than would have resulted from water exposure only and thus greater than expected from equilibrium.”

Biomagnification is quantified through the biomagnification factor (BMF), which indicates the concentration in an organism and the total concentration in the organism’s diet.

A well-recognised example of bioconcentration and biomagnification is the mercury levels in fish, which can result in the element entering the food chain and affecting humans.

Mercury is a naturally occurring element in our environment, however, human activities produce approximately 75 per cent of the mercury released into the atmosphere each year (Dickson, 2009). Once in the atmosphere, the mercury settles into rivers, lakes and oceans where some microorganisms and abiotic reactions convert it to methylmercury.

The methylmercury then builds up in predatory fish like swordfish, tuna and mackerel through the process of biomagnification, as when the fish consume their food, they absorb any contaminants contained within that food source, including methylmercury.

The theory of biomagnification then extends through the food chain as other predators eat the fish and thus absorb the contaminants and methylmercury. Over time, humans who consume food sources contaminated with methylmercury will acquire levels greater than in either its habitat or its food. As a result, top predators acquire greater body burdens of mercury than the fish they consume (Government of Canada, 2013).

Being aware of the potential impact of chemical and treatment solutions on the environment is vital for the ongoing protection and sustainability of our food chain and planet as a whole.

To protect the aquatic environment, it is important that testing assesses each of the trophic levels (primary producers, primary consumers and secondary consumers). Fera Science Ltd provides aquatic testing of new chemicals and treatment solutions that have the potential to bioconcentrate in aquatic life.

A series of Organisation of Economic Co-operation and Development (OECD) tests are performed at Fera facilities, including OECD 305, which specifically looks at bioconcentration rates in fish.

Under current legislation, testing is only conducted on vertebrate species, However, should regulations change, looking at the risk of bioconcentration and biomagnification in invertebrates could be conducted at the ground-breaking E-Flows mesocosm site at Fera Science. The E-Flows mesocosm project, developed, designed, managed and operated by Fera Science Ltd in partnership with the Centre for Crop Health and Protection (CHAP), supported by Innovate UK, will provide scientific research opportunities across a wide range of industries.

Chemicals and compounds are constantly being developed in the agrichemical and crop protection sector yet assessing their potential bioconcentration impact is just as important as testing their effectiveness for its original purpose. Keeping our planet, environment and organisms safe should be the ultimate goal.