Mercury distribution and enrichment in coastal sediments from different geographical areas in the North Atlantic Ocean.

This study evaluated mercury (Hg) in three coastal areas in the North Atlantic Ocean (Azores archipelago, Northwest Portugal and Southeast Mexico) and calculated their enrichment factor and geoaccumulation index. Hg presented greater affinity with fine sediment fraction. In all sampling areas the sites with proximity to possible Hg hotspots presented increased [Hg] in fine sediments. However, this fraction only represents less than 1% of the whole sediment, resulting in a significantly lower [Hg] in the total sediment fraction. After comparing [Hg] in the fine fraction and the values established by the Sediment Quality Guidelines, two sites in the Azores exceeded these values. Nevertheless, when considering the total sediment fraction, adverse biological effects are not expected to occur. Finally, both enrichment factor and geoaccumulation index indicated that the Hg present in 86% comes from natural sources and only sampling sites close to potential hotspots showed some degree of enrichment and contamination.

Water temperature modulates mercury accumulation and oxidative stress status of common goby (Pomatoschistus microps).

Mercury (Hg) is a widespread pollutant across estuarine and coastal areas, raising concern on its potential impact on aquatic organisms. Hg may origin from natural and anthropogenic sources, being persistent and potentially toxic to biota, ultimately representing a serious risk to human health. Hg accumulation and toxicity may also induce reactive oxygen species (ROS) production in marine organisms, responsible for cell and tissue damage. Additionally, the temperature is undoubtedly an important environmental factor to consider regarding accumulation, due to its marked influence on the physiology and ecology of aquatic organisms. This study aimed to investigate the effect of different temperature scenarios (15, 20 and 25 °C) on the Hg accumulation in Pomatoschistus microps (Krøyer, 1838) liver and muscle, as well as on oxidative stress responses and energy metabolism, after short-term exposure to a naturally contaminated sediment with an environmentally relevant [Hg] (1.2 µg g-1). The results showed that Hg accumulation tends to increase along the temperature gradient with higher values of Hg accumulated in liver than in muscle tissue. The action of antioxidant enzymes and stress proteins seems to be effective in combating oxidative stress in the liver. Despite the action of antioxidant defences in the muscle, oxidative damage was observed at the protein level concomitantly with a decrease in aerobic energy production after exposure to Hg at higher temperatures. These findings are ecologically relevant and highlight the importance of further investigation of combined effects of Hg and other stressors, especially in a scenario of a changing climate where events leading to rapid alterations on water parameters are more frequent.

Mercury bioaccumulation in the long-fin squid Loligo forbesi near the Mid-Atlantic Ridge: Implications to human exposure.

Due to growing commercial interest as a fishing resource and its intermediate position in the marine trophic chains as both prey and predator, cephalopods can play an important role in mercury (Hg) transfer along the marine food webs, since they can bioaccumulate this metal in its tissues. Our study aims to analyze Hg accumulation in Loligo forbesi caught in the Azores Archipelago (Portugal) quantifying Hg in different tissues (mantle and stomach), as well in the squid stomach content, in order to evaluate the efficiency of Hg transfer from prey to predator. Hg data from the tissues was used to estimate the weekly tolerable Hg intake due to squid consumption. Overall data indicate that Hg measured in the stomach tissue (0.1 ± 0.01 µg g-1) was significantly higher than Hg levels found in the mantle (0.04 ± 0.001 µg g-1) and stomach contents (0.01 ± 0.001 µg g-1). BMF (bioaccumulation factor) was >1 for all the samples, indicating a biomagnification process from prey to predator. Hg concentration in the mantle tissue was correlated with mantle size; although females present higher Hg levels than males, the difference was found to be not related to gender but rather to the fact that females had larger bodies. Finally, considering the Hg concentration found in the mantle and the permitted Hg levels, it is advisable to consume up to 1050-1890g of squid per week, according to the regulatory agencies. Thus, our results indicate that, since these doses are respected, consumption of squids from the Azorean waters do not pose a risk to humans.

Fish consumption recommendations to conform to current advice in regard to mercury intake.

This article reviews fish consumption data, mercury tolerable intake values, and mercury (Hg) content in fish, based on several reports from the Food and Agriculture Organization and European Union. The study assumptions are valid based on the current established USEPA reference dose (RfD). Combining the number of meals (per week), amount of fish ingested (by meal), and levels of MeHg in fish, this study calculates and presents isocurves indicating the maximum number of fishmeal per week without exceeding the USEPA RfD for methylmercury (MeHg). RfD are assumed to be the "exposure dose that is likely to be without deleterious effect even if continued exposure occurs over a lifetime." The study points out that even considering a single 50-g fish meal per week, the USEPA RfD would be exceeded, triggered by values above 0.84 µg g(-1) of MeHg in fish, and this despite being allowed levels up to 1.0 µg g(-1) of MeHg in fish consumption!-Have we a health risk? Fish consumption is expected to be relatively stable, while anthropogenic mercury emissions are expected to stabilize or even to increase beyond current values. How many meals of fish per week can we have, combining the number of fish meals per week, amount of fish ingested by meal, and levels of MeHg in fish?

Real and potential mercury accumulation in human scalp of adolescents: a case study.

Mercury (Hg) concentration in human hair is used to estimate methylmercury (MeHg) exposure and establish a reference dose for MeHg intake. In this study, Hg accumulation and MeHg intake were evaluated in relation to fish consumption habits in adolescents from two coastal areas: Angra do Heroísmo (Azores archipelago) and Murtosa (Portuguese mainland). Results showed that Hg concentration and MeHg intake increased with increasing fish consumption. In spite of that, Hg concentrations remained relatively low when compared with World Health Organization "no observed adversary effect level"; therefore, risk for mercury exposure should not be considered. Adolescents revealed a similar range of Hg concentrations (0.03-2.60 µg g(-1)) in scalp hair, apart from being exposed to natural or anthropogenic Hg source (Azores and Mainland, respectively). Nevertheless, Mainland volunteers generally exhibited higher values of Hg accumulation, being approximately 50 % of the results above 1 µg g(-1). Hg concentrations increased in both adolescent groups according to the weekly rate of fish meals, however, not linearly in the highest fish consumption rates. In fact, considering the adolescents' group having over one fish meal per week, the Hg bioaccumulation pattern found in the respective scalp hair suggests the ability of the human body to induce a self-protection response, probably mitigating Hg levels in the blood when experiencing increasing Hg exposure due to fish uptake. Actual and potential mercury levels in human scalp of adolescents probably diverge as fish consumption increases, the effective Hg uptake being lower than the expected, reducing risk to human health.

Mercury in scalp hair near the Mid-Atlantic Ridge (MAR) in relation to high fish consumption.

The aim of this study was to evaluate the potential risk of mercury contamination near the Mid-Atlantic Ridge relating total mercury (THg) concentrations in the human scalp hair (n = 110) and high fish consumption levels. THg was quantified in human scalp hair, and volunteers were questioned about age, gender, and smoking habits being subsequently grouped in categories based on the individual average intake of fish meals per week. THg concentrations ([THg]) in hair samples ranged from 0.05 to 2.24 µg g(-1), and significant differences were found according to age (p < 0.05) and also among volunteers presenting different fish consumption rates (p < 0.001) being the highest [THg] observed on the adult population and also on volunteers that indicated consuming five or more meals of fish per week. Results indicate a pattern of increased mercury accumulation with increasing fish consumption. Despite mercury availability and a potential mercury intake of up to seven times, the WHO provisional tolerable weekly intake of mercury value, in consequence of high fish consumption, mercury concentrations in scalp hair are comparatively low regarding recommended levels by WHO.

Tree rings, Populus nigra L., as mercury data logger in aquatic environments: case study of an historically contaminated environment.

In this study, a tree (Populus nigra L.) has been presented as data logger of mercury release in aquatic environments using tree rings chemistry to provide chronological historical monitoring of mercury discharge from a chlor-alkali industrial effluent to a coastal lagoon. Tree rings (Populus nigra L.) as mercury data logger is suggested by mercury accumulation trends in the tree rings reflecting the industrial plant capacity increments in the early stages of mercury discharges and enhancing industrial plant controls to minimize mercury discharges in the last two decades after imposed global regulations on mercury emissions.

Seasonal fluctuations of tissue mercury contents in the European shore crab Carcinus maenas from low and high contamination areas (Ria de Aveiro, Portugal).

The main objective was to study the seasonal variation of mercury concentrations in different tissues (muscle, hepatopancreas and gills) of Carcinus maenas from low and high Hg contaminated areas, a valuable resource in temperate estuaries and a possible pathway for human uptake. Individuals of two size classes (around 35 and 55 mm cephalothorax wide) were captured monthly between March 1999 and May 2000 in two areas of Ria de Aveiro: in the main navigation channel that connects the lagoon to the sea, and in the inner lagoon area heavily contaminated by mercury (maximum Hg in sediments of 5.4 microg g(-1)). Pronounced decreases in salinity and temperature and reduced food availability in winter seemed to be the responsible for the decline of the crab condition index (0.75-0.45) in larger individuals. Muscle and hepatopancreas exhibited higher mercury concentrations than gills, with concentrations in the contaminated site ranging from 0.03 to 0.63 microg g(-1) and 0.02 to 0.34 microg g(-1), respectively. Linear regressions between muscle and hepatopancreas (r=0.94, p<0.001) and muscle and gills (r=0.97, p<0.001) suggested a rapid redistribution of mercury inside the organism. During winter, a rapid elimination of mercury was found in the three analysed tissues followed by uptake. Larger crabs presented elimination rates from 18 to 34 ng g(-1) per week, while the smaller crabs showed lower elimination rates (10-24 ng g(-1) per week). The uptake was similar in both size classes (11-15 ng g(-1) and 8.1-15 ng g(-1) per week, respectively for large and small crabs). Our results suggest that C. maenas harvested in the contaminated areas must be considered with caution, since Hg concentrations were found to exceed the threshold concentration allowed for human consumption (0.5 microg g(-1)).