Bioaccumulation and public health implications of trace metals in edible tissues of the crustaceans Scylla serrata and Penaeus monodon from the Tanzanian coast.

The coastal population in East Africa is growing rapidly but sewage treatment and recycling facilities in major cities and towns are poorly developed. Since estuarine mangroves are the main hotspots for pollutants, there is a potential for contaminants to accumulate in edible fauna and threaten public health. This study analysed trace metals in muscle tissues of the giant mud crabs (Scylla serrata) and the giant tiger prawns (Penaeus monodon) from the Tanzanian coast, in order to determine the extent of bioaccumulation and public health risks. A total of 180 samples of muscle tissues of S. serrata and 80 of P. monodon were collected from nine sites along the coast. Both species showed high levels of trace metals in the wet season and significant bioaccumulation of As, Cu and Zn. Due to their burrowing and feeding habits, mud crabs were more contaminated compared to tiger prawns sampled from the same sites. Apart from that, the measured levels of Cd, Cr and Pb did not exceed maximum limits for human consumption. Based on the current trend of fish consumption in Tanzania (7.7 kg/person/year), the measured elements (As, Cd, Co, Cu, Mn, Pb and Zn) are not likely to present health risks to shellfish consumers. Nevertheless, potential risks of As and Cu cannot be ruled out if the average per capita consumption is exceeded. This calls for strengthened waste management systems and pollution control measures.

Diffusive Gradients in Thin-films technique for uranium monitoring along a salinity gradient: A comparative study on the performance of Chelex-100, Dow-PIWBA, Diphonix, and Lewatit FO 36 resin gels in the Scheldt estuary.

Monitoring of uranium in the environment using the Diffusive Gradients in Thin-films (DGT) technique gains in importance as it can provide unique information about the bioavailability of the element and allows its long-term in-situ measurement. Hence, in this study, four DGT binding phases (Chelex-100, Dow-PIWBA, Diphonix, and Lewatit FO 36 resins) were evaluated for uranium monitoring to assess the robustness of their performance in estuarine and marine environments. These DGTs were deployed along the Scheldt estuary (Belgium and the Netherlands) over four campaigns between 2014 and 2021. The DGT performance (ratio of the DGT-determined vs. dissolved U concentration in grab water sample) varied with the water salinity. The Chelex-100 DGTs generally provided good performance in freshwater (median ratios close to 1.0), but an inverse correlation with the increasing salinity was observed (median ratios 0.7 at the stations with salinity >5). The Lewatit FO 36 DGTs provided good performance in the salinity range 0-18 (median ratios 1.0). However, a strong negative influence was observed at stations with high salinity levels (>18, ratio 0.6) and during the long-term deployment in seawater (ratios <0.5 over deployment periods ≥2 days). The Dow-PIWBA and Diphonix DGTs provided overall similar results with excellent performances along the whole salinity gradient (median ratios 1.1 and 1.0, respectively). Nevertheless, the long-term deployment trial in seawater (salinity ∼27) revealed the robustness of Diphonix DGTs that provided outstanding results even after 28 days of deployment (ratio 1.0). The differences in the performance of tested DGT resins were mostly given by the changes of U speciation along the salinity gradient. The speciation modelling of U showed that calcium uranyl carbonate complexes dominate along the Scheldt estuary (from 97 to 86% seawards) with increasing fraction of UO2(CO3)34- (from 2 to 14%) towards the mouth.

A multimethodological evaluation of arsenic in the Zenne River, Belgium: Sources, distribution, geochemistry, and bioavailability.

The distribution and geochemistry of arsenic (As) in water and sediments of the Zenne River, a small urban river flowing through Brussels (Belgium), were assessed based on the results of 18 sampling campaigns performed between 2010 and 2021. In general, concentrations of As sharply increase between Vilvoorde and Eppegem and are up to 6-8 times higher in the section downstream of Eppegem in comparison to the upstream part of the Zenne. The monitoring surveys in which the grab water samples were taken at a 1-hour sampling frequency revealed that the large temporal variability in As concentrations found in the downstream part of the river is driven by the tidal cycle. The diffusive gradients in thin films (DGT) technique was used to assess the DGT labile As species in surface water and sediment porewater. Three DGT sorbents (Metsorb, Lewatit FO 36, and ZrO2) for the determination of total As were applied to compare their performance, and the 3-mercaptopropyl-functionalized silica (3-MFS) was used for the speciation of As(III) in porewater. Arsenic species are fully labile in surface waters as the DGT time-integrated concentrations of As were in good agreement with the average concentrations calculated from the grab samplings. In sediment porewaters, As is predominantly present as non-DGT labile species (66-93 %), and the DGT labile As fraction is dominated by As(III). Flux calculations evaluating the relative importance of different As sources to the Zenne River revealed the presence of a point source on the tributary Tangebeek, which contributes to 87 % of the As load carried by the Zenne River.

Trace metal concentrations measured in blood and urine of adolescents in Flanders, Belgium: reference population and case studies Genk-Zuid and Menen.

In the Flemish human biomonitoring programme FLEHS II (2007-2011) trace metals (Cd, Pb, Cr, Ni, Cu, Mn, Tl, Sb, As and toxic relevant arsenic) were analysed in the blood and urine of adolescents (14-15 years old) in the reference population in Flanders and in areas of important industrial activities: Genk-Zuid and Menen. After adjustment of the results for confounding factors, the adolescents living in Genk-Zuid had higher levels of Cr, Cu and Tl in blood, higher levels of Cd and toxic relevant arsenic (TRA) in urine, but lower levels of Ni in blood and Sb in urine compared to the reference population. In Menen higher levels of Cd and Cu in urine, higher concentrations of Tl in blood but lower concentrations of Pb in blood and lower Ni, Sb and As in urine were found compared to the reference population. For both the reference population and the hot spots the concentrations are within the ranges found in other countries. Compared to the previous biomonitoring programme FLEHS I (2002-2006) a decrease in the concentrations of Cd and especially of Pb in blood was observed. However, it cannot be excluded that differences between the two campaigns are partially due to different sampling strategies.

Trace metals in blood and urine of newborn/mother pairs, adolescents and adults of the Flemish population (2007-2011).

The Flemish Centre for Environment and Health started with human biomonitoring in 2002 (FLEHS I: 2002-2006). The main goal of the second human biomonitoring cycle (FLEHS II: 2007-2011), was to determine mean values for a large number of pollutants in a representative sample of the general Flemish population. Values for Cd and Pb were updated, and a group of previously undetermined metals and metalloids (As, Mn, Cu and Tl) were included in some of the age groups. In this human biomonitoring program, three different age groups of the general Flemish population were monitored: 255 newborns and their mothers, 210 adolescents aged 14-15, and 204 adults between 20 and 40 years old. Trace elements were determined in cord blood and maternal blood of the mothers, in blood and urine of adolescents and in urine of adults. Determinants of life-style and personal factors were taken into account. The levels of trace elements in cord blood and maternal blood were for most elements at the lower end of the range found in literature. For Pb, As and Tl, a strong correlation (respectively r=0.43, 0.55 and 0.33; p<0.05) was found between levels in cord blood (respectively 8.6, 0.54 and 0.017 µg/L) and maternal blood (11.1, 0.64 and 0.028 µg/L), indicating that they are transported via the placenta from mother to fetus. The levels found in the adolescents and adults were compared with results from international biomonitoring studies, and were found to be in the same ranges. With the exception of Pb, all trace elements increased with increasing age group population. Finally, the results also showed that the levels of Cd and Pb in blood for this campaign (e.g. for Pb 8.6 and 14.8 µg/L in neonates and adolescents respectively) were lower compared to the first campaign (e.g. for Pb 14.7 and 21.7 µg/L in neonates and adolescents respectively), indicating a decrease over time. However, differences in sampling strategies might partially explain this observed trend.