Methylmercury in the Gulf of Trieste (Northern Adriatic Sea): From Microbial Sources to Seafood Consumers

Tršćanski je zaljev (sjeverni Jadran) jedno od živom najonečišćenijih područja u Sredozemlju, a i u svijetu, zbog nekadašnje rudarske aktivnosti u Idriji (zapadna Slovenija). Veza je između mikrobnog nastanka metilirane žive i njezine bioakumulacije i biomagnifikacije u hranidbenim lancima voda zaljeva još slabo poznata, iako ključna za razumijevanje poveznica između izvora i organizama na višem stupnju hranidbenog lanca, npr. riba, koje su vektori prijenosa onečišćenja na ljude i druge organizme. Ovaj pregledni članak obuhvaća mikrobno biogeokemijsko kruženje žive u zaljevu, prijenos i bioakumulaciju metilirane žive u pelagičkim i bentičkim hranidbenim lancima, te izloženost ljudskog organizma živi nakon konzumacije ribe i školjaka. Svi su ti podaci važni zbog velikog gospodarskog značaja Tršćanskog zaljeva.The Gulf of Trieste (northern Adriatic Sea) is one of the most mercury-polluted areas in the Mediterranean and in the world due to the past mining activity in the Idrija region (western Slovenia). The link between microbial production of toxic methylmercury (MeHg), and its bioaccumulation and biomagnification in marine food webs of the gulf is at present rather poorly characterized but is critical to understanding the links between sources and higher trophic levels, such as fish, that are ultimately vectors of human and wildlife exposure. This overview explores three major topics: (i) the microbial biogeochemical cycling of Hg in the area, (ii) the trophic transfer and bioaccumulation of MeHg in pelagic and benthic marine food webs, and (iii) human exposure to Hg through marine fish and shellfish consumption. These are important goals since the Gulf of Trieste is an area of great economical importance

Human urinary arsenic species, associated exposure determinants and potential health risks assessed in the HBM4EU Aligned Studies

The European Joint Programme HBM4EU coordinated and advanced human biomonitoring (HBM) in Europe in order to provide science-based evidence for chemical policy development and improve chemical management. Arsenic (As) was selected as a priority substance under the HBM4EU initiative for which open, policy relevant questions like the status of exposure had to be answered. Internal exposure to inorganic arsenic (iAs), measured as Toxic Relevant Arsenic (TRA) (the sum of As(III), As(V), MMA, DMA) in urine samples of teenagers differed among the sampling sites (BEA (Spain) > Riksmaten adolescents (Sweden), ESTEBAN (France) > FLEHS IV (Belgium), SLO CRP (Slovenia)) with geometric means between 3.84 and 8.47 μg/L. The ratio TRA to TRA + arsenobetaine or the ratio TRA to total arsenic varied between 0.22 and 0.49. Main exposure determinants for TRA were the consumption of rice and seafood. When all studies were combined, Pearson correlation analysis showed significant associations between all considered As species. Higher concentrations of DMA, quantitatively a major constituent of TRA, were found with increasing arsenobetaine concentrations, a marker for organic As intake, e.g. through seafood, indicating that other sources of DMA than metabolism of inorganic As exist, e.g. direct intake of DMA or via the intake of arsenosugars or -lipids. Given the lower toxicity of DMA(V) versus iAs, estimating the amount of DMA not originating from iAs, or normalizing TRA for arsenobetaine intake could be useful for estimating iAs exposure and risk. Comparing urinary TRA concentrations with formerly derived biomonitoring equivalent (BE) for non-carcinogenic effects (6.4 μg/L) clearly shows that all 95th percentile exposure values in the different studies exceeded this BE. This together with the fact that cancer risk may not be excluded even at lower iAs levels, suggests a possible health concern for the general population of Europe.HBM4EU is co-financed under Horizon 2020 (grant agreement No 733032). The authors thank all investigators of the contributing studies for their participation and contribution to the joint HBM4EU survey and the national programme owners for their financial support. Also thanks to the participating teenagers and their families, the field workers that collected the samples. The FLEHS IV study was conducted within the framework of the Flemish Center of Expertise on Environment and Health (FLEHS 2016–2020) and funded by the Flemish Government, Department of Environment & Spatial Development. We thank the teenagers and their families that participated in the study, the field workers from the Pro vincial Institute of Hygiene and VITO for the sample and data collection. All collaborators of the scientific teams of the Flemish Center of Expertise on Environment and Health (https://www.milieu-en-gezondheid.be/en/about-the-center-0) and Karen Van Campenhout and Caroline Teughels from the Flemish Department of Environment & Spatial Development for their valuable input in the field work committee. The funding of the German Ministry for the Environment, Nature Conservation, Nuclear Safety and Consumer Protection is gratefully acknowledged. BEA study was co-funded by the Spanish Ministry of Agriculture, Fisheries and Food and the Insituto de Salud Carlos III (SEG 1321/15). In Slovenia the work was cofounded by the Slovenian Research Funding Agency – ARRS through a research programme P-0143. ESTEBAN was Funded by Sant´e Publique France and the French ministries of Health and the Environment. The study of RIKSMATEN was conducted and mainly financed by the Swedish Food Agency. Financial support was provided from the Swedish Civil Contingencies Agency and from the Swedish Environmental Pro tection Agency (SEPA).S

Maternal APOE ε2 as a possible risk factor for elevated prenatal Pb levels

Lead (Pb) is a global contaminant associated with multiple adverse health effects. Humans are especially vulnerable during critical developmental stages. During pregnancy, exposure to Pb can occur through diet and release from maternal bones. Apolipoprotein E gene (APOE) variants (ɛ2, ɛ3, ɛ4 alleles) may influence sex steroid hormones, bone metabolism, and Pb kinetics. We examined the interplay among maternal APOE (mAPOE) genotypes, fetal sex, parity, and Pb in maternal and cord blood (mB-Pb, CB-Pb) using linear regression models. Our study involved 817 pregnant women and 772 newborns with measured adequate levels of zinc and selenium. We compared carriers of the ε2 and ε4 alleles to those with the ε3/ε3 genotype. The geometric means (range) of mB-Pb and CB-Pb were 11.1 (3.58–87.6) and 9.31 (1.82–47.0) ng/g, respectively. In cases with female fetuses, the maternal mAPOE ε2 allele was associated with higher, while the mAPOE ε4 allele was associated with lower mB-Pb and CB-Pb levels. Nulliparity increased the strength of the observed associations. These findings highlight the significance of mAPOE genetics, fetal sex, and parity in prenatal Pb kinetics. Notably, the maternal ε2 allele may increase the risk of Pb exposure

METHYLATION AND DEMETHYLATION ACTIVITY IN THE MERCURY CYCLING IN COASTAL WATERS (GULF OF TRIESTE, NORTHERN ADRIATIC)

The Gulf of Trieste and adjacent Grado and Marano Lagoon (northern Adriatic Sea) are considered as an important \u201cnatural bioreactor\u201d that can increase sedimentary methylmercury (MeHg) production by mobilizing the extensive mercury (Hg) pool as a result of historical (500 years) Hg mining and smelting activities in Idrija (NW Slovenia), the world\u2019s second largest Hg mine. Even though the mine was definitely closed in 1995 the So\u10da/Isonzo River system still delivers about 1.5 t of Hg to the gulf annually and the MeHg is elevated in this marine environment. Research conducted by late M.E. Hines showed that Hg is readily methylated and demethylated in marine, lagoonary and freshwater sediments but the relative activities varied greatly with locality. Methylation activity increased from freshwater to the marine sites, conversely the highest demethylation was found in estuarine and lagoon sites. The methylation/demethylation ratios were consequently low in coastal sites but increased ib the gulf. Subsequent investigations in the southern, less contaminated (\u201cpristine\u201d) sediments of the gulf revealed that MeHg is also continuously produced especially in autumn in parallel with higher bottom water temperature and lower oxygen content. Sulphate reduction was found to control both processes. Hg methylation in sediments of coastal lagoon was controlled by rapid demethylation and the Hg bioavailability was affected by Hg adsorption and precipitation, In offshore marine sites, the sulphide produced by sulphate reduction lowers Hg methylation. Methylation of dissolved Hg, nearly 100% colloidally bonded, in the seawater column of the gulf was not detected (showing a pronounced Hg reduction potential) suggesting that sediments are the principal methylation site and the source of MeHg to the water column. It is likely that demethylation and reduction prevent the excessive accumulation of MeHg in the food webs of the Gulf of Trieste

Arsenic in sediments, soil and plants in a remediated area of the Iron Quadrangle, Brazil, and its accumulation and biotransformation in Eleocharis geniculata

Since arsenic (As) exposure is largely due to geochemical contamination, this study focused on the remediated area of Santana do Morro, a district of Santa Bárbara, Minas Gerais, Brazil, which was previously contaminated with As due to gold mining. Total As concentrations in sediment, soil and plants were determined, next to As species, anionic arsenic compounds As(III), As(V), monomethylarsonic acid (MMA) and dimethylarsinic acid (DMA), in plants samples. Total As concentrations in soil and sediments were slightly elevated (16-18 µg g-1) and most of the plants contained low levels of As (< 1 µg g-1). The exception was a native plant Eleocharis geniculata (L.) which contained elevated levels of As (4 µg g-1). The exposure of this plant to As under controlled conditions (hydroponics) indicated its possible tolerance to elevated As levels and suggesting its potential use in phytomonitoring of As-contaminated sites. This plant is able to metabolize arsenate to arsenite and contained MMA and DMA, both in its natural habitat and under controlled conditions

Composition of Colloidal Organic Matter in Phytoplankton Exudates

The colloidal organic matter (COM) was isolated from the exudates of three cultured phytoplonkters, namely the chlophyte nanoflagellate Tetraselmis sp., the diatom Chaetoceros socialis and the dinoflagellate Prorocentrum minimum, from the Gulf of Trieste (northern Adriatic Sea). The isolation of COM was performed by ultrafiltration with molecular weight cut-off membranes of 5 kDa and final desalinisation by dialysis. The composition of the COM was characterised using C elemental analysis and 1H NMR spectroscopy and compared with COM isolated from a marine sample from the same area (Gulf of Trieste). By using 1H NMR spectroscopy, it was possible to semi-quantitatively determine the concentrations of the main biochemical constituents present in the COM samples. The results showed that the phytoplankton COM was predominantly composed of polysaccharides, with minor contributions from proteins and especially lipids. Therefore, the phytoplankton COM mainly contributes to the marine COM pool in the polysaccharide fraction and less in the protein and lipid fractions

Selenium and Mercury Interactions in Apex Predators from the Gulf of Trieste (Northern Adriatic Sea)

Since the environmental levels of selenium (Se) can moderate the bioaccumulation and toxicity of mercury (Hg) in marine organisms, their interactions were studied in seawater, sediments, plankton and the benthic (Bull ray Pteromylaeus bovinus, Eagle ray Myliobatis aquila) and the pelagic (Pelagic stingray Dasyiatis violacea) rays, as apex predators in the Gulf of Trieste (Northern Adriatic Sea). Male and female rays showed no difference in the Se contents in muscle tissue. Pelagic species contained higher Se levels in muscle but slightly lower levels in the livers of both genders. The Hg/Se ratios in seawater dissolved and colloidal fractions, plankton and sediment were &lt;0.5, while those in particulate matter were &lt;1.3. In benthic ray species, a parallel increase in Se and Hg in muscle was observed, so that an increased in Hg (MeHg) bioaccumulation results in Se coaccumulation. The Hg/Se ratios (molar) in muscle and liver of pelagic and benthic rays were &lt;1.4 and &lt;0.7, respectively. The low levels of Hg in muscle and liver in all the ray species corresponded to low Hg/Se ratios and increases in muscle and liver to 1 at 7 µg/g, dry weight (dw) and 5 µg/g dw, respectively, i.e., about 1.6 µg/g wet weight (ww)

Cd, Cu, Zn, Se, and metallothioneins in two amphibians, Necturus maculosus (Amphibia, Caudata) and Bufo bufo (Amphibia, Anura)

The accumulation of cadmium, its affinity for metallothioneins (MTs), and its relation to copper, zinc, and selenium were investigated in the experimental mudpuppy Necturus maculosus and the common toad Bufo bufo captured in nature. Specimens of N. maculosus were exposed to waterborne Cd (85 Žg/L) for up to 40days. Exposure resulted in tissue-dependent accumulation of Cd in the order kidney, gills > intestine, liver, brain > pancreas, skin, spleen, and gonads. During the 40-day exposure, concentrations increased close to 1 Žg/g in kidneys and gills (0.64- 0.95 and 0.52-0.76n04), whereas the levels stayed below 0.5 in liver (0.14-0.29n04) and other organs. Cd exposure was accompanied by an increase of Zn and Cu in kidneys and Zn in skin, while a decrease of Cu was observed in muscles and skin. Cytosol metallothioneins (MTs) were detected as Cu,Zn-thioneins in liver and Zn,Cu-thioneins in gills and kidney, with the presence of Se in all cases. After exposure, Cd binding to MTs was clearly observed in cytosol of gills as Zn,Cu,Cd-thionein and in pellet extract of kidneys as Zn,Cu,Cd-thioneins. The results indicate low Cd storage in liver with almost undetectable Cd in liver MT fractions. In field trapped Bufo bufo (spring and autumn animals), Cd levels were followed in fourorgans and found to be in the order kidney > liver (0.56-5.0 Žg/g >0.03-0.72 Žg/gn011, spring and autumn animals), with no detectable Cd in muscle and skin. At the tissue level, high positive correlations between Cd, Cu, and Se were found in liver (all r>0.80Ž00.05, n05), and between Cd and Se in kidney (r00.76n05) of autumn animals, possibly connected with the storage of excess elements in biologically inert forms. In the liver of springanimals, having higher tissue level of Cd than autumn ones, part of the Cd was identified as Cu,Zn,Cd-thioneins with traces of Se. As both species arespecial in having liver Cu levels higher than Zn, the observed highly preferential Cd load in kidney seems reasonable. The relatively low Cd found in liver can be attributed to its excretion through bile and its inability to displace Cu from MTs. The associations of selenium observed with Cd and/or Cu (on the tissue and cell level) point to selenium involvement in the detoxification of excessive cadmium and copper through immobilization