Fishermen in Maceió, Brazil, have higher-than-average mercury levels

Researchers from the Federal University of Alagoas (UFAL) and the State University of Campinas (UNICAMP) in Brazil have found high levels of mercury in the blood and urine of people living on the shores of the Mundaú Lagoon in Maceió, the capital of the Brazilian state of Alagoas. These levels are higher than those found in other populations within the same municipality that have a similar socioeconomic level but live far from the lagoon.

The study, which was published in the Journal of Hazardous Materials, is the result of an agreement between FAPESP and the Alagoas State Research Foundation (FAPEAL).

“We observed systemic oxidative stress in the population exposed to mercury contamination, a phenomenon related to the onset and worsening of various diseases, including cardiometabolic diseases. Both populations analyzed showed an incidence of around 20% for hypertension and 10% for diabetes. However, the population that gets its food from the lagoon may be worse off because of the contamination,” says Ana Catarina Rezende Leite, a professor at UFAL’s Institute of Chemistry and Biotechnology and one of the study’s coordinators.

The researchers found changes in the quantity, size, volume, and function of red blood cells in the population exposed to mercury contamination, which can lead to anemia. Changes in other biomarkers also indicate damage to organs such as the liver and kidneys.

Mercury was found to increase triglyceride levels, which are a risk factor for cardiovascular disease. Additionally, creatinine and urea levels were high in the contaminated population, suggesting kidney dysfunction.

The Mundaú lagoon complex is connected to the sea and receives water from both the ocean and the mainland. It connects to secondary domestic and industrial effluent channels from Maceió and two other cities on its shores. These channels are the most likely sources of mercury and metal contamination.

Of the 125 people who had blood and urine samples taken, 60 were lagoon residents who consumed fish and shellfish (mainly sururu) from the site. The other 65 participants were from other parts of the city and had little to no contact with the contaminated site.

The concentration of mercury in the urine was 0.48 micrograms per liter in the first group, which is almost 2.5 times higher than the concentration in the control group (0.18 micrograms per liter).

The average mercury concentration in the blood of the group exposed to contamination was almost four times higher than that of the unexposed population (3.40 micrograms per liter compared to 0.93). The highest level of mercury found in the blood of lagoon fishermen’s families was 19 micrograms per liter.

Brazilian regulations set the maximum tolerable level at 20 micrograms of mercury per liter of blood. However, international agencies point to a margin of between five and ten for populations that consume fish, according to the International Programme on Chemical Safety (IPCS), and less than six for the U.S. Environmental Protection Agency (EPA).

“Our legislation is very permissive. We’d need to follow the populations for a few years to accurately assess the effects of mercury contamination, but our results already show significant changes in metabolism, with less oxygen reaching the cells, which affects their functioning,” says Josué Carinhanha Caldas Santos, a professor at UFAL who also coordinated the study.

Previous evidence

The results of the human analysis were consistent with those of a previous experimental study conducted by the same group. The study examined the impact of inorganic mercury contamination on mice with high cholesterol, exacerbating the condition as well as oxidative stress and atherosclerosis.

“In the animals, a dose considered low-to-moderate of the inorganic form of mercury [less toxic than the organic forms found in food, for example] was administered for just four weeks and caused significant damage to various tissues, including the brain. In addition, it markedly aggravated the lesions characteristic of atherosclerosis,” says Helena Coutinho Franco de Oliveira, a professor at UNICAMP’s Institute of Biology and coordinator of the project that supported the study.

Both papers were written by Maiara Queiroz and were part of her master’s degree. She was supervised by Leite at UFAL and co-supervised by Oliveira at UNICAMP.

Queiroz is currently doing her doctorate at the Institute of Chemistry of the University of São Paulo (IQ-USP) on a scholarship from FAPESP. 

Public policies

The researchers warn that the results provide strong evidence to support the implementation of environmental and health policies. Pollution in the lagoon must be stopped, or at the very least, mitigated. At the same time, the health of the affected populations must be monitored.

“This will enable us to better understand and perhaps reduce the impacts of contamination,” Santos from UFAL points out.

Further research will also monitor other metals that make up the lagoon’s contaminants and can potentiate the effects of mercury.

However, Bebedouro, one of the neighborhoods monitored by the researchers and one of the oldest in Maceió, can no longer be visited. It was evacuated in recent years due to the risk of collapse from underground rock salt mining activities.

The work was also supported by FAPESP through a project coordinated by Professor Aníbal Vercesi from the School of Medical Sciences at UNICAMP.

About São Paulo Research Foundation (FAPESP)
The São Paulo Research Foundation (FAPESP) is a public institution with the mission of supporting scientific research in all fields of knowledge by awarding scholarships, fellowships and grants to investigators linked with higher education and research institutions in the State of São Paulo, Brazil. FAPESP is aware that the very best research can only be done by working with the best researchers internationally. Therefore, it has established partnerships with funding agencies, higher education, private companies, and research organizations in other countries known for the quality of their research and has been encouraging scientists funded by its grants to further develop their international collaboration. You can learn more about FAPESP at www.fapesp.br/en and visit FAPESP news agency at www.agencia.fapesp.br/en to keep updated with the latest scientific breakthroughs FAPESP helps achieve through its many programs, awards and research centers. You may also subscribe to FAPESP news agency at http://agencia.fapesp.br/subscribe.
 

 

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