Fishermen in Maceio, Brazil, found to 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 Maceio, 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 analysed showed an incidence of around 20% for hypertension and 10% for diabetes”, says Ana Catarina Rezende Leite, a professor at UFAL’s Institute of Chemistry and Biotechnology and one of the study’s coordinators. “However, the population that gets its food from the lagoon may be worse off because of the contamination”.

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 anaemia. 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 Maceio 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 litre in the first group, which is almost 2.5 times higher than the concentration in the control group (0.18 micrograms per litre).

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 litre compared to 0.93). The highest level of mercury found in the blood of lagoon fishermen’s families was 19 micrograms per litre.

Brazilian regulations set the maximum tolerable level at 20 micrograms of mercury per litre of blood. However, international agencies point to a margin of between five and ten for populations that consume fish, according to the International Program 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.

Team Maverick