[INFORMATIVE] Bioaccumulation

Bioaccumulation

Written by: Stefania Jaramillo

According to the Encyclopedia of Earth Science “bioaccumulation is the gradual accumulation of substances, such as pesticides, or other chemicals, in an organism” (Alexander, 1999, pg 44). This process occurs when an organism absorbs these substances more quickly than it can break them down or eliminate them, and it affects plants, animals and humans, which for us may result in several health issues.

These toxins, such as Mercury or DDT, which was one of the first insecticides, widely used in the 1940-70s, proved to be deadly to both the environment and human health. These are generally absorbed by organisms at the base of the food chain, such as plankton. Then, animals that are higher up in the food chain consume them, and the toxins still remain in their tissues, leading to bioaccumulation at each trophic level.

The most common example of this process is Mercury food poisoning resulting from eating contaminated tuna, although in the present the use of the element as an insecticide or in daily-use goods such as batteries, thermometers or even skin-lightening creams has been heavily regulated, even banned by some countries, Mercury is still being released, primarily by mining and burning coal. Although its levels in the atmosphere have drastically diminished since 1971, when people became aware of its effects on public health, its levels have remained stable in tuna. This is because there are old lurks of this element remaining in the sea, and some types of bacteria turn Mercury into Methylmercury, which is the most dangerous form this chemical can take, due to its easy absorption by aquatic organisms, as it tends to stick to fatty tissues.

This compound can enter a tuna’s body if it eats contaminated prey, such as small fish, which accumulate methylmercury in their tissues by consuming plankton that absorb the chemical from high exposition in their environment. Tuna are at top of the food chain and when they eat other contaminated smaller fish, the methylmercury is gradually absorbed into their own tissues.

(BBC, 2024)

When we eat fish containing methylmercury, it enters our bloodstream, which distributes it throughout the body to key areas such as the brain, liver and kidneys. This chemical is not easily excited, so it can persist in our bodies for months or if not years. When this compound exceeds a certain quantity, it can lead to significant health risks, especially to the nervous system, like tremors, cognitive deficits and memory losses, mainly in small children. Pregnant women who consume methylmercury can transfer it to their babies, leading to unrepairable neurological damage. Similarly, it can also affect other organs, like the kidneys or the heart. Bioaccumulation is particularly concerning because it doesn’t only affect a single organism or species, but it can impact the entire food chain in a process called biomagnification.

According to the Global Mercury Assessment in 2018, these are the operations responsible for the emission of Mercury in the atmosphere:

(Global Mercury Assessment, 2018)

The biggest source of Mercury is mining operations, mining alongside fossil fuel burning accounts for 56.5% of the amount of Mercury released to the atmosphere daily.

So what can be done to stop this from happening? First of all, not only do we need to reduce Mercury levels in the atmosphere and in the oceans, but also need to prevent the planet’s temperature from rising, as this will affect ecosystems and the species that inhibit them.To achieve this, we must support the transition to clean energies, so we are not so dependent on coal or other fossil fuels, whose extraction and burning can be detrimental to Earth. Additionally, There must be stricter policies or new international agreements regarding the use of harmful chemicals in daily-use products, ensuring these regulations are enforced globally, not just in a single country or group of nations. For example, in 2013, under the United Nations Environment Programme (UNEP), the Minamata Convention on Mercury took place in Japan to limit the use of Mercury in industries like mining and in products like fluorescent lamps, thermometers or cosmetics. It was signed by representatives from 149 nations, including United States, China, India, Brazil, Australia and the European Union (minamataconvention, 2017, para. 11).

Countries who have ratified the Minamata Convention
(mercuryconvention, 2022)

However, on a more personal level, we can also encourage sustainable farming practices by buying foods that use minimal pesticides or are organic, as well as using products that contain any harsh chemicals in them, (such as paint without lead), even if those substances are not banned where you live. It is important to recognize that the negative impacts humans have on the environment do not only affect ecosystems and the wildlife within them, but will also have severe consequences for our own species.


Sources:
Alexander, David E. “Bioaccumulation, Bioconcentration, Biomagnification.” SpringerLink, Springer Netherlands, 1 Jan. 1999, link.springer.com/referenceworkentry/10.1007/1-4020-4494-1_31.

“Bioaccumulation and Eutrophication - How Are Populations Affected by Conditions in an Ecosystem? - GCSE Biology (Single Science) Revision - OCR 21st Century - BBC Bitesize.” BBC News, BBC, 30 Mar. 2023, www.bbc.co.uk/bitesize/guides/zxgn97h/revision/5.

“Homepage: Minamata Convention on Mercury.” Homepage | Minamata Convention on Mercury, minamataconvention.org/en.

McGrath, Matt. “Mercury Mystery: Poisonous Element Persists in Tuna.” BBC News, BBC, 21 Feb. 2024, www.bbc.com/news/science-environment-68339664.

“Party Profiles.” Party Profiles | Minamata Convention on Mercury, minamataconvention.org/en/parties/overview.Wu, Yuan-Seng, et al. “The Toxicity of Mercury and Its Chemical Compounds: Molecular Mechanisms and Environmental and Human Health Implications: A Comprehensive Review.” ACS Omega, U.S. National Library of Medicine, 22 Jan. 2024, www.ncbi.nlm.nih.gov/pmc/articles/PMC10851382/.