Amazon: mercury in fish is higher than recommended – 05/30/2023 – Health

A technical note published this Tuesday (30) concluded that fish sold in six states in the Amazon region had a higher amount of mercury than recommended. The scenario causes problems for animals and also for humans: fish are contaminated in the waters, usually by the action of illegal mining, and, by consuming them, the population is also contaminated.

Mercury is used in gold mining. Without proper care, it is dumped in rivers and accumulates there. It is also in the aquatic environment that mercury can turn into methylmercury, a neurotoxic substance that passes between living beings in the food chain. That is, the substance accumulates as the animals feed on other already contaminated beings.

Therefore, methylmercury is of high risk, says Paulo Basta, researcher at Fiocruz and one of the authors of the technical note. “We consider it the most toxic form for humans.” For the purposes of the research, carried out by several organizations, such as ISA (Instituto Socioambiental), Fiocruz and Greenpeace, all mercury detections were considered methylmercury.

In total, 1,010 samples of carnivorous and non-carnivorous fish were analyzed in the laboratory. The animals came from 17 municipalities in six states that have territory in the Amazon rainforest: Acre, Amapá, Amazonas, Pará, Rondônia and Roraima.

Analyzes of all fish indicated that 21% of them contained more mercury than acceptable: the maximum recommended by Anvisa (National Health Surveillance Agency) is 0.5μg (micrograms) per gram.

“Our goal was to collect fish that are usually sold at free fairs, in municipal markets or directly from fishermen’s hands, in order to show society that the problem of mercury contamination is not restricted to indigenous peoples or other traditional peoples”, said Basta.

Some cities recorded a low percentage of fish with high concentrations, such as Maraã, in the Amazon, where only 2% of fish exceeded the indicated maximum.

Meanwhile, other municipalities had much higher rates: in Santo Isabel do Rio Negro and São Gabriel da Cachoeira, also in Amazonas, half of the animals had a dangerous amount of mercury.

Variation is also seen across states. Basta explains that this is due to factors associated with the very presence of mercury in rivers. For example, as the substance is released mainly by mining, places with higher rates of this activity may have a higher number of contaminated fish.

This is the case of Roraima. In the state, there is a good part of the Yanomami territory, which suffers from the presence of mining. When looking at the index of fish with a high concentration of mercury, the state has the highest value among all six analysed: 40% of the animals had a mark higher than what is indicated.

in humans

In addition to measuring the mercury present in the animals, another part of the study considered the ingestion of mercury in the human body when consuming the fish.

For this, one of the variables was the weight of the population, relying on information from 2008 from the POF (Family Budget Survey) of the IBGE. With this data, it was possible to have an average of the weight of four pre-defined groups: women of childbearing age, adult men, children aged 5 to 12 years and children aged between 2 and 4 years.

This is necessary because the average daily mercury intake needs to be divided by the person’s weight – in this case, the average weight of the group. So, if the daily value is up to 0.1μg of mercury per 1 kg, it is within the acceptable range for the US Environmental Protection Agency (US-EPA). Otherwise, the population is at risk.

The survey also estimated the amount of fish consumed and possibly mercury. First, a 2011 report was considered to estimate the amount of fish eaten by the population in urban environments in the Amazon – this number was around 100 g per day. As for mercury, the researchers considered the assumption that 80% of what is consumed from the substance is absorbed by the person.

So, crossing data on fish contamination by state with information on weight and daily consumption, it was possible to calculate whether or not intake exceeded the recommended value of up to 0.1 μg per 1 kg each day.

Children from 2 to 4 years old in Acre, for example, had the highest consumption rate of the substance: 3.15. That is, it is as if they were consuming 35 times the recommended maximum. The data is more critical because this group is one of the most at risk for the substance.

On the other hand, the smallest record was among adult men in Amapá. With a rate of 0.17, this group slightly surpassed that recommended by the US-EPA. “Even in regions where the contamination was not so great, depending on the amount of fish consumed, it may exceed the recommended maximum mercury level”, summarized Bata.

How to solve

For the researcher, solving the problem involves several areas of the government. One of them is the fight against mining, since it is the main cause of river contamination.

“Just as it is happening in the Yanomami indigenous land, which is having a federal government task force to remove the miners from there, this same process has to be extended to other areas of the Amazon that are conflagrated by the presence of illegal mining”, he says. .

In addition to this, other measures are monitoring contaminated areas to mitigate the impact, offering assistance to fishermen who may suffer financial difficulties for not selling more contaminated fish, and inspecting fish to stop the sale of contaminated fish.