A study has just been published in the international scientific journal Science of the Total Environment, which involved measuring mercury levels in the hair of fisherman and people working in the fishing industry in the Marano and Grado lagoon, one of the largest in Europe. 

The study was conducted by Luca Cegolon (UCO of Hygiene and Preventive Medicine of UniTS) in collaboration with Giuseppe Mastrangelo (University of Padua), the MercuRILab research group of the University of Trieste (directed by Stefano Covelli) and UniTS’s Occupational Medicine Department (directed by Francesca Larese Filon). 

The Marano and Grado lagoon was identified as a Site of National Interest (SNI) due to contamination from centuries-old mercury ore (cinnabar) from the Soča/Isonzo river draining into the Idria mining district in Slovenia (the second largest natural deposit in the world after Almaden in Spain). Inorganic forms of mercury were also present in the contamination, and came from uncontrolled industrial discharge. 

In the eastern sector of the lagoon, at the mouth of the Isonzo river, previous studies detected mercury concentrations of up to 11 mg/kg in sediments, gradually decreasing to 5 mg/kg in the central area and 0.7 mg/kg in the western sector. 

While the contamination of the eastern sector of the Lagoon was mainly attributable to mercury of mineral origin (cinnabar or mercury sulphide) from the Isonzo river, the mercury detected near the mouth of the Aussa-Corno river had an inorganic component, of industrial origin. 

The investigation by the University of Trieste, carried out in early 2024 in Marano Lagunare, compared the concentration of mercury in the hair of 73 fishermen (32 from the open sea, 30 from the lagoon and 11 mixed) and 83 local residents working in the fishing industry, with 93 residents from the Belluno area (mainly farmers). The survey focused on this group of people as they inevitably have greater access and availability to fish consumption than the general population. Residents from a mountainous area were chosen as the comparison category for the opposite reason. 

The average level of mercury detected in fishermen (2.56 mg/kg) and workers of the industry (2.31 mg/kg) was significantly higher than that of farmers in the Dolomites (0.58 mg/kg) and increased with the consumption of local fish, particularly fresh fish. An increase was also detected in categories such as fishermen, fish sellers or restaurateurs.

Although these values are slightly above the limit (2 mg/kg) recommended by the World Health Organisation, these concentrations are still well below 11.5 mg/kg, the limit below which no adverse effects on human health have been observed to date. The current situation, therefore, can be considered balanced, and does not contraindicate the consumption of fish from the lagoon. This is also true since fish carries selenium, a chemical element which offsets the effects of mercury. However, it is recommended that pregnant women and growing children limit their consumption of fresh fish to no more than one meal per week.