It is very common to hear that eating too much salmon is bad for health. This is not a lie, but the problem is not the fish itself, but the mercury that it accumulates during its life and is passed on to humans.
“We live today with the release of a large number of chemical substances into the environment. There is a need to develop research on the adverse toxic effects of these substances and what processes they could cause in organisms”, explains Sheila Cardoso, doctor at the USP Institute of Biosciences and researcher at the USP Oceanographic Institute. She adds that around 60 million chemical substances are released every year and knowledge of the consequences of contact with them is only around 50%.
Different terms, different meanings
The accumulation of a chemical substance in the body can have different nomenclatures, depending on the scenario in which it occurs. Biomagnification, probably the best-known term, corresponds to the chain summation, that is, at more than one trophic level — different stages of the food chain: “Biomagnification, basically, is the increase in the concentration of a chemical compound, of a substance chemicals along the food chain. So, it occurs at more than one trophic level, at least at two levels. There is a tendency for there to be a higher concentration the higher the level: the predators will present a higher concentration of the chemical substance in relation to the lower trophic levels”, says the researcher. The big question of biomagnification is, many times, the organism’s difficulty in “detoxifying” itself of the accumulated compound,
When the substance accumulates in only one level, the process is called bioaccumulation. It is important to emphasize that not every compound is able to biomagnify. Bioconcentration is the term used when the body has a higher concentration of the substance in its interior when compared to the environment where it is found.
Sheila summarizes: “It is necessary to differentiate these three terms: biomagnification occurs along the food chain; bioaccumulation is when the organism accumulates the substance, but it occurs only at a trophic level and bioconcentration is when the organism has a higher concentration of the substance in relation to the environment”.
Examples
Mercury is able to biomagnify even humans due to methylation. This process, carried out mainly by bacteria, when in the aquatic environment, makes this element capable of being accumulated through the ingestion of fish. “When we are talking about mercury, it is being biomagnified in the trophic chain. Human beings consume fish, so they tend to be the top animal in the chain, the most affected in terms of biomagnification. For this, the compound needs to have some specific characteristics such as being liposoluble, that is, able to enter cells. Mercury needs to be in the methylated form, that is, there must be environmental conditions for a chemical transformation and for it to be biomagnified”, explains the specialist.
He is just one of the examples. Another is DDT or Dichloro-Diphenyl-Trichloroethane, one of the best-known low-cost insecticides. It was banned in Brazil in 1998 and, in 2009, Law No. 11,936 was passed, prohibiting the manufacture, importation, maintenance in stock, commercialization and use of the compound in Brazilian soil. Widely used also in the control of malaria, DDT may be related to the death of several workers of the defunct National Health Foundation in the North Region.
Even microplastics are part of the biomagnification process, as Sheila puts it: “Microplastics and bisphenol A , common in some types of plastic, include a relatively recent branch of research. They biomagnify and, as an adverse toxic effect on human populations, can cause changes in the endocrine system, what we call an ‘endocrine disruptor’”.
Some drugs and perfluorinated compounds (PFCs) can build up in chains. The latter correspond to chemical products widely used in waterproofing pans and packaging. “The perfluorinated compounds are being studied more recently and they are present in Teflon pans, for example, in packaging coatings for fatty foods, including microwave popcorn. Some tissues may also have these compounds”, exemplifies the researcher.
Is there a benefit?
After so many examples and stating that, in most cases, biomagnification is not a good thing, is there any benefit? “They are not beneficial. What can happen is, for example, a substance that is being bioaccumulated, biomagnified in the presence of a second substance, having its adverse toxic effect restricted. So, she will not have a curse or it will be reduced.”
For Sheila, directly, there is no specific point to be placed as beneficial, but there are some situations in which biomagnification, but especially bioaccumulation, helps to neutralize the harmful effects of the accumulation of the chemical substance. “There is a specific situation when we talk about bioconcentration. In the bioaccumulation of metals in aquatic macrophytes, what happens? An aquatic crust tends to have high concentrations of metals, so these plants can be used to remove this contaminant from the environment, they would have this function of water treatment. This would be a beneficial function”, explains the specialist.