Environmental Mercury Exposure in Residents and Occupational Groups of Coastal Areas of the Marano and Grado Lagoon (Northern Adriatic Sea, Italy)

Background: The Marano and Grado lagoon (Northern Adriatic Sea, Italy) has been affected by long-standing mercury (Hg) pollution due to inputs from the Isonzo River—mainly in the form of cinnabar (HgS)—and inorganic Hg conveyed into the lagoon by discharges from the chlor-alkali plant of Torviscosa. The present study compared different occupational sub-groups along the Marano and Grado lagoon against residents of the Dolomite Alps. Methods: Seventy-three local fishermen, 81 workers of the fish industry, and 76 local workers (52 employees of a large adhesive factory and 24 workers of an oil mill) of Porto Nogaro were recruited by convenience sampling. Hair mercury levels of the latter three groups were compared with those of 93 residents of the Dolomites Alps. Linear and logistic regression analyses were used to assess the association of hair mercury with various factors collected by a structured questionnaire. Results: Median hair Hg levels were significantly lower in Dolomites’ residents (0.58 mg/Kg) compared to Porto Nogaro workers (1.31 mg/Kg), workers of the fish industry (2.32 mg/Kg) or fishermen (2.56 mg/Kg), following an upward trend. After adjusting for a number of potential confounders, the concentration of hair Hg progressively increased with consumption of fish intake at linear and logistic regression analysis. Conclusions: Advising to limit the consumption of locally caught fish to no more than one meal per week should not be restricted to pregnant women and children, but should also be extended to adults, in order to avoid the potential long-term neurological effects of low-dose Hg exposure. It is crucial to remain vigilant and continue monitoring Hg environmental contamination in the lagoon across various environmental matrices, such as sediments, water, fish, shellfish and birds. Regardless of Hg levels measured in the workplace, occupational health protocols of steel plants along the coastal area of the Marano and Grado lagoon should include biological monitoring of Hg, to disentangle the effect of occupational exposure from non-occupational exposure to the metal.