Concentration of mercury in human hair and its associated factors in residents of the Gulf of Trieste (North-Eastern Italy)

The Gulf of Trieste (Northern Adriatic Sea, Italy) is the coastal area of the Mediterranean Sea most highly contaminated by mercury (Hg) due to fluvial inputs from the Isonzo/Soča River system, draining over 500 years’ worth of cinnabar extraction activity from the Idrija mining district (Western Slovenia). The aim of this research is to investigate the concentration of Hg in hair samples taken from participants from the general population from the coast of the Friuli Venezia Giulia Region (FVG), as a marker of chronic exposure to Hg.Three hundred and one individuals - 119 males and 182 females - were recruited by convenience sampling in Trieste in September 2021. An amount of approximately 100 mg of hair was collected from the occipital scalp of each participant to measure the respective Hg concentrations (expressed as mg/kg). Moreover, participants completed a self-report questionnaire collecting extensive socio-demographic and life-style information. A multiple linear regression analysis was performed to investigate the relationships among Hg concentrations in hair and several factors potentially related to an increase in the Hg content of hair.A mean Hg concentration in hair of 1.63 mg/kg was found, slightly above the 1.0 mg/kg threshold recommended by the WHO, although still well below the no observed adverse effects level (NOAEL) of 10 mg/kg. Among respondents, 55.6% showed a Hg concentration in hair > 1 mg/kg, 22.9% > 2 mg/kg and 2 participants exhibited Hg levels >10 mg/kg. Factors associated with higher concentrations of Hg in hair were male sex, ingestion of > 4 servings of fish per month and preferred consumption of small/medium size fish or shell/crayfish/molluscs. Conversely, ingestion of frozen fish represents a protective factor.Though a risk alert for Hg exposure for coastal residents from FVG is deemed unnecessary at this time, it is recommended that pregnant women limit their ingestion of locally caught fish to < 4 servings/month.