Biomagnification of mercury through the benthic food webs of a temperate estuary: Masan Bay, Korea

The authors examined food web magnification factors of total mercury (THg) and methylmercury (MeHg) for the benthic organisms in Masan Bay, a semiclosed, temperate estuary located on the southeastern coast of Korea. For benthic invertebrates, concentrations of THg and MeHg (%MeHg) ranged from 9.57 to 195 and 2.56 to 111 ng/g dry weight (12.2-85.6%), respectively. Benthic fish THg and MeHg (%MeHg) concentrations ranged widely from 10.8 to 618 and 2.90 to 529 ng/g dry weight (22.9-93.9%), respectively. The linear regression slopes of log [Hg] relative to δ(15)N (i.e., food web magnification factors) found for the Masan Bay benthic organisms were 0.119 for THg and 0.168 for MeHg. These values are similar to the food web magnification factors of benthic organisms and lower than those of pelagic organisms of various coastal marine environments. It suggests that pelagic organisms might be at greater risk of THg and MeHg accumulation than benthic biota.     

Biomarkers of low-level mercury exposure through fish consumption in pregnant and lactating Slovenian women

In order to assess the mercury exposure of pregnant and lactating women in Slovenia, levels of total mercury (THg) and methylmercury (MeHg) were determined in hair, cord blood and breast milk. In addition, the frequency of fish consumption was estimated, because fish is generally the main pathway for human exposure to MeHg. Hair samples were collected from 574 women participating in this study, while cord blood and breast milk samples were collected from 446 and 284 women, respectively. As expected, the levels of THg in hair (median (Med)=297 ng/g, 10th percentile (P10)=73 ng/g, 90th percentile (P90)=781 ng/g), cord blood (Med=1.5 ng/g, P10=0.5 ng/g, P90=4.2 ng/g) and breast milk (Med=0.2 ng/g, P10=0.06 ng/g, P90=0.6 ng/g) were low, due to low consumption of fish (X=25 g/day). A significant linear correlation was found between levels of ln THg in hair and ln THg in cord blood (r=0.87, 95% confidence interval (CI): 0.84–0.89), between levels of ln THg in hair and ln MeHg in cord blood (r=0.94, 95% CI: 0.90–0.96) and between ln THg levels in cord blood and ln THg levels in breast milk (r=0.36, 95% CI: 0.25–0.47). Spearman's rank correlations between the frequency of fish consumption and THg in hair (r_s=0.35, 95% CI: 0.28–0.42), and between the frequency of fish consumption and THg in cord blood (r_s=0.43, 95% CI: 0.36–0.51) or MeHg in cord blood (r_s=0.31, 95% CI: 0.06–0.52) were weak. This could be due to the approximate information on fish consumption obtained from the questionnaires, the high variability of MeHg concentrations in fish and a relatively high proportion of inorganic mercury in the biomarkers which originates from sources other than fish. In conclusion, THg levels in cord blood, THg levels in hair and MeHg levels in cord blood are suitable biomarkers of low-level Hg exposure through fish consumption. Compared to cord blood, hair samples are easy to collect, store and analyse.     

Comparison of hair with nail as index media for biological monitoring of mercury

Mercury in hair and nails was determined with speciation of chemical forms of mercury. Scalp hair and toenails were sampled once and fingernails were sampled three times from the subjects (18 males and 5 females) whose age ranged from 23 to 56 yr. Total mercury (THg) and inorganic mercury (IHg) were determined by Magos' method with modifications. No sex-related differences were found in mercury levels in hair and nails. In the fingernail samples of three different formation periods, THg and IHg concentrations remained almost constant. Among the three kinds of index media, the highest THg concentration was found in scalp hair followed by fingernails and toenails in the order given, whereas IHg concentrations in scalp hair were similar as those in fingernails but were lowest in toenails. The percent inorganic to total mercury was higher in fingernails than in hair and toenails, which is likely to reflect a possible external contamination with IHg in fingernails. The higher THg concentration in scalp hair than in nails may be attributable to the difference in the chemical composition, in particular sulphur content, and in the blood flow during the formation of hair and nails.     

Total and Methyl Mercury Concentrations in Antarctic Toothfish (<Emphasis Type="Italic">Dissostichus mawsoni</Emphasis>): Health Risk Assessment

The concentrations of total mercury (THg) in different organs of the Antarctic toothfish (Dissostichus mawsoni) collected from CCAMLR research blocks in Subarea 88.3 and Division 58.4.1 off the coast of Antarctica were determined. The results revealed THg concentrations of 0.165?±?0.095 mg/kg (0.023–0.454 mg/kg, wet weight) in the Antarctic toothfish. In muscle, methyl mercury (MeHg) accounted for approximately 40% of the THg. In a comparison analysis, muscle and liver tended to bioaccumulate the highest levels of THg, and both THg and MeHg contents showed correlations with fish length and weight. Compared with international guidelines, fish contained 2.5–6.4% and 4.0–10.3% of the provisional tolerable weekly intake for THg recommended by the Joint FAO/WHO Expert Committee on Food Additives and the tolerable weekly intake for MeHg proposed by the European Food Safety Authority, respectively. These results suggest that consumption of the Antarctic toothfish presents no health risk to humans.     

Mercury, selenium, and cadmium in human autopsy samples from Idrija residents and mercury mine workers

Total Hg and Se concentrations were determined in autopsy samples of retired Idrija mercury mine workers, Idrija residents living in a Hg-contaminated environment, and a control group with no known Hg exposure from the environment. In selected samples we also checked the presence of MeHg. The highest Hg concentrations were found in endocrine glands and kidney cortex, regardless of the group. MeHg contributed only to a negligible degree to the total mercury concentrations in all analyzed samples. In the Hg-exposed groups the coaccumulation and retention of mercury and selenium was confirmed. Selenium coaccumulation with a Hg/Se molar ratio near 1 or higher was notable only in those tissue samples (thyroid, pituitary, kidney cortex, nucleus dentatus) where the mercury concentrations were >1 microg/g. After tissue separation of such samples the majority of these elements were found in the cell pellet. Because the general population is continuously exposed to Cd and possibly also to Pb from water, food, and/or air, in some samples the levels of these elements were also followed. In all examined control tissue samples the average values of Cd (kidney cortex, thyroid, hippocampus, cortex cerebellum, nucleus dentatus) and Pb (thyroid, hippocampus) exceeded the average values of Hg. Cd concentrations were the highest, particularly in kidney cortex and thyroids (microg/g), but no relationship between Cd and Se concentration was evident at the tissue level. Regarding the results in the control group, it is debatable which element is the more hazardous for the general population as concerns neurotoxicity.     

Monitoring and Mass Budget for Mercury in the Everglades Nutrient Removal Project

The Everglades Nutrient Removal Project (ENRP) is a 1,545-ha prototype wetland constructed to test a larger system of stormwater-treatment areas that is being used to remove agricultural nutrients and help restore the remnant Everglades. Concerns that the ENRP may lead to mercury bioaccumulation as observed in other newly created reservoirs resulted in an effort to construct a mercury mass budget and measure bioaccumulation in aquatic organisms. For the first 2 years of operation, total mercury (THg) and methylmercury (MeHg) concentrations in water decreased significantly a short distance into the ENRP, probably through particle settling. During both years, THg concentrations in largemouth bass were about 0.1 μg/g throughout the ENRP while the adjacent Water Conservation Area bass were at or above the state health advisory level of 0.5 μg/g. THg levels in mosquitofish were lower than levels found in bass, and mosquitofish mercury concentrations in the interior of the ENRP were significantly lower than the inflow and outflow sites. The major THg pool was the sediment while less than 1% the total mass was stored in vegetation, water, and fish. The major MeHg pool also was the sediment but vegetation, water, and fish were significant fractions. Mass budget estimates showed the inflow pump and rainfall to be the major sources of THg, while the outflow pump was the major output. The inflow pump was the major source of MeHg while the outflow pump was the major output. Evasion of elemental mercury estimated by the stagnant-film model indicated a minor loss, but field measurements over cattails suggested that evasion may be the major pathway. When all inputs and outputs were considered, the ENRP removed about 70% of the THg and MeHg masses in the first 2 years of operation. Received: 27 March 1998/Accepted: 6 July 1998     

Mercury Speciation in Fish Tissues from a Mediterranean River Basin: The Tagus River (Central Spain) as a Case Study

An assessment of mercury (Hg) accumulation in fish from the Tagus River aquatic system (central Spain), which has been influenced by pollution from industrial and urban development, was performed. Total Hg (THg), inorganic Hg (IHg), and monomethylmercury (MMHg) were determined in muscle and liver of different fish species, including Cyprinus carpio, Ameiurus melas, and Chondrostoma miegii, sampled from three locations. Although concentrations of THg and Hg species showed wide variability among the fish species, they were also found to be considerably dependent on location and fish tissue. Relative contents of MMHg to THg in muscle varied from 60 to 88%, whereas those found in liver ranged from 7 to 59%. Mean THg concentrations ranged from 126 to 810 ng/g (dry weight [dw]) in liver and from 159 to 1057 ng/g dw in muscle. Therefore, the mean THg concentration in all fish muscle samples was far lower than the maximum residue level recommended by the European Union for fishery products. Nevertheless, the concentrations of Hg in fish muscle reported in this study were somewhat increased compared with other areas geographically distant from most major anthropogenic Hg sources and, in some cases, even greater than those previously reported elsewhere in more polluted areas. In contrast, Hg contents in liver were lower than those found in Hg-contaminated areas, but they were within the range found in other areas exposed to diffuse sources of pollution by Hg. Thus, this article provides an overview of the concentration and distribution of Hg species in fish muscle and liver tissues samples taken from a freshwater system in the Mediterranean River basin.     

Correlations between mercury concentrations in umbilical cord tissue and other biomarkers of fetal exposure to methylmercury in the Japanese population

Methylmercury (MeHg) is one of the most risky substances to affect humans through fish consumption, and the fetus is known to be in the most susceptible group. Our objective in this study is to examine the relationships of total mercury (THg) and MeHg concentrations between umbilical cord tissue and other tissues as biomarkers of fetal exposure to MeHg in the Japanese population. In total, 116 paired samples were collected in three Japanese districts, the Tsushima Islands, Fukuoka City, and Katsushika ward of metropolitan Tokyo. THg was measured for hair and THg and MeHg were measured in cord tissues, maternal blood, and cord blood. The relationships among tissues in Hg concentrations were similar among districts. Therefore, we analyzed the relationships using all the samples. More than 90% of Hg in cord tissue, cord blood, and maternal blood was MeHg. THg and MeHg in cord blood was about two times higher than in maternal blood. A strong correlation was found between THg and MeHg in cord tissue. The cord tissue THg and MeHg showed a strong correlation with cord blood Hg, which is recognized as the best biomarker for fetal exposure to MeHg. The findings of this study indicate the significance of cord tissue THg and MeHg as biomarkers for fetal exposure to MeHg at parturition.     

High exposure of Chinese mercury mine workers to elemental mercury vapor and increased methylmercury levels in their hair

Objective The aim of this study was to determine the level of exposure of mercury (Hg) miners and smelter workers to elemental mercury (Hg⁰) vapor in China, who work in Hg mines without using protective equipment against Hg⁰ vapor. In addition, the level of methylmercury (MeHg) intake by the workers was estimated from the MeHg concentration in their hair. Methods Urinary total mercury (THg) and hair THg and MeHg concentrations were measured in 26 Hg miners and smelter workers (i.e., exposed group), and 48 unexposed people (unexposed group). Results The exposed group showed high geometric mean THg concentrations in urine (258 ng/ml, 226 μg/g creatinine) and hair (20.0 μg/g). The urinary THg concentration of the smelter workers in particular was extremely high (338 μg/g creatinine in urine). The highest urine THg concentration reached 4577 μg/g creatinine. THg concentrations in urine and hair showed a significant correlation in the exposed group (r=0.62), indicating the adhesion of Hg⁰ vapor to hair. However, no such significant correlation was found in the unexposed group. Hair MeHg concentration in the exposed group (1.97 μg/g) was about threefold higher than that in the unexposed group (0.60 μg/g). Conclusions This study shows that smelter workers in a Chinese Hg mine are exposed to extremely high levels of Hg⁰ vapor, and that Hg miners are exposed to higher levels of MeHg than the unexposed subjects. Further study is needed to determine the cause of the higher hair MeHg concentration in the exposed group.     

Spatial and temporal variations of total and methylmercury concentrations in plankton from a mercury-contaminated and eutrophic reservoir in Guizhou Province, China

Total mercury (THg) and methylmercury (MeHg) concentrations in four size fractions of plankton from three sampling stations in the Hg-contaminated and eutrophic Baihua Reservoir, Guizhou, China, were investigated for biomagnification and trophic transfer of Hg at different sites with various proximity to the major point sources of nutrients and metals. Total Hg concentrations in plankton of the various size fractions varied from 49 to 5,504 ng g(-1) and MeHg concentrations ranged from 3 to 101 ng g(-1). The percentage of Hg as MeHg varied from 0.16 to 70%. Total Hg and MeHg concentrations in plankton samples differed among the three sampling stations with different proximities from the major point sources. The plankton from the site closest to the dam contained the highest concentrations of MeHg. The successive increase of the ratios of MeHg to Hg from seston to macroplankton at all sites indicated that biomagnification is occurring along the plankton food web. However, biomagnification factors (BMF) for MeHg were low (1.5-2.0) between trophic levels. Concentrations of THg in seston decreased with an increase of chlorophyll concentrations, suggesting a significant dilution effect by the algae bloom for Hg. Eutrophication dilution may be a reason for lower MeHg accumulation by the four size classes of plankton in this Hg-contaminated reservoir.     

Mercury demethylation in waterbird livers: dose-response thresholds and differences among species

We assessed methylmercury (MeHg) demethylation in the livers of adults and chicks of four waterbird species that commonly breed in San Francisco Bay: American avocets, black-necked stilts, Caspian terns, and Forster's terns. In adults (all species combined), we found strong evidence for a threshold model where MeHg demethylation occurred above a hepatic total mercury concentration threshold of 8.51 +/- 0.93 microg/g dry weight, and there was a strong decline in %MeHg values as total mercury (THg) concentrations increased above 8.51 microg/g dry weight. Conversely, there was no evidence for a demethylation threshold in chicks, and we found that %MeHg values declined linearly with increasing THg concentrations. For adults, we also found taxonomic differences in the demethylation responses, with avocets and stilts showing a higher demethylation rate than that of terns when concentrations exceeded the threshold, whereas terns had a lower demethylation threshold (7.48 +/- 1.48 microg/g dry wt) than that of avocets and stilts (9.91 +/- 1.29 microg/g dry wt). Finally, we assessed the role of selenium (Se) in the demethylation process. Selenium concentrations were positively correlated with inorganic Hg in livers of birds above the demethylation threshold but not below. This suggests that Se may act as a binding site for demethylated Hg and may reduce the potential for secondary toxicity. Our findings indicate that waterbirds demethylate mercury in their livers if exposure exceeds a threshold value and suggest that taxonomic differences in demethylation ability may be an important factor in evaluating species-specific risk to MeHg exposure. Further, we provide strong evidence for a threshold of approximately 8.5 microg/g dry weight of THg in the liver where demethylation is initiated.     

Mercury Biomagnification in the Aquaculture Pond Ecosystem in the Pearl River Delta

This is the first study to investigate the rate of mercury (Hg) biomagnification in the aquaculture pond ecosystem of the Pearl River Delta (PRD), China, by analyzing total mercury (THg) and methyl mercury (MeHg) concentrations in various species of fish at different trophic levels (TLs). Species representing a gradient of trophic positions in the aquaculture pond food chains were chosen for analyzing THg and MeHg concentrations. In this study, there were two kinds of the aquaculture pond food chains: (1) omnivorous (fish feeds, zooplankton, grass carp [Ctenopharyngodon idellus], and bighead carp [Aristichthys nobilis]) and (2) predatory (zooplankton, mud carp [Cirrhina molitorella], and mandarin fish [Siniperca kneri]). Bighead carp and mandarin fish had the highest MeHg and THg concentrations, i.e., an order of magnitude higher than other species, in their respective food chains. More than 90% of the THg concentrations detected in bighead carp, mandarin fish, and mud carp were in the methylated form. In this study, %MeHg increased with TLs and MeHg concentrations, reflecting that MeHg is the dominant chemical species of Hg accumulated in higher concentrations in biota, especially biota associated with higher TLs in the food chains. The trophic magnification factors were 2.32 and 2.60 for MeHg and 1.94 and 2.03 for THg in omnivorous and predatory food chains, respectively, in PRD. Hg concentrations in fish tissue correlated to Hg levels in the ambient environment, and sediment seemed to be the major source for Hg accumulated in fish. In addition, feeding habit also affected Hg accumulation in different fish species. Four significant linear relationships were obtained between log-THg and δ¹⁵N and between log-MeHg and δ¹⁵N. The slope of the regression equations, as biomagnification power, was smaller in magnitude compared with those reported for temperate and arctic marine and freshwater ecosystems, indicating that THg and MeHg biomagnifications were lower in this PRD subtropical aquaculture pond ecosystem. This was probably due to low Hg bioavailability at lower TLs as well as individual feeding behavior of fish.     

Mercury in eggs and feathers of great egrets (Ardea albus) from the Florida Everglades

Great egret (Ardea albus) eggs and nestling feathers were collected for total mercury (THg) and methylmercury (MeHg) analysis from two colonies in the Florida Everglades in 1999 and 2000. THg was present in all eggs at a mean concentration of 0.39 ± 0.19 μg/g fresh weight (n = 33, range = 0.08–0.86 μg/g). Egg-THg levels did not differ significantly between colonies or years. MeHg concentration in eggs was 0.35 ± 0.18 μg/g fresh weight (n = 20, range = 0.05–0.82 μg/g,), and on average represented 85% of the THg found in the egg. Concentration of THg in feathers from egret nestlings, age 11–31 days, ranged from 1.4 to 8.6 μg/g dry weight. Feather-THg levels also did not differ significantly between colonies or years. THg concentrations in feathers, normalized based on bill length, were positively correlated to THg concentrations in eggs from the same clutch. Levels of THg in both eggs and feathers were lower in 1999 and 2000 than values reported for similar samples collected in 1993–95, indicating that MeHg exposure has decreased in the southern Everglades since the mid-1990s. THg levels in eggs and nestling feathers for the period of this study were below levels associated with toxic reproductive effects. Clutch size, fledging success, and brood size observed in this study were consistent for this species in the Everglades. Collectively, these results suggest that MeHg was not adversely affecting the reproductive performance of this population during the study. Received: 20 December 2000/Accepted: 30 August 2001     

Mercury and Methylmercury Accumulation and Excretion in Prairie Voles (<Emphasis Type="Italic">Microtus ochrogaster</Emphasis>) Receiving Chronic Doses of Methylmercury

Methylmercury cation (MeHg) and divalent mercury (Hg⁺⁺) accumulation in liver, kidney, and brain were quantified in prairie voles (Microtus ochrogaster) at 0, 3, 6, and 12 weeks during chronic exposure to aqueous MeHg. Dose groups received deionized water or aqueous solutions containing 9, 103, or 920 ng MeHg/ml. Our study presents temporal patterns of Hg⁺⁺ and MeHg concentrations in organ tissues and makes inter-tissue comparisons at each time point to illustrate the accumulation and distribution of Hg species during the study. MeHg was accumulated in tissues for 3 weeks and then concentrations plateaued. Mercury accumulated in brain, liver, and kidney to average concentrations of 510 ng/g, 180 ng/g, and 3400 ng/g, respectively. MeHg and Hg⁺⁺ concentrations were roughly equivalent in liver, kidney, and urine. MeHg concentrations in brain tissue were 2 to 20 times the concentrations of Hg⁺⁺. Regression analysis was also used to demonstrate the utility of urinalysis as an indicator of Hg⁺⁺ and MeHg concentrations in organ tissue (p < 0.001).     

Risk assessment of methylmercury based on internal exposure and fish and seafood consumption estimates in Taiwanese children

Fish and seafood consumption is a major source of human exposure to methylmercury (MeHg). This study evaluated the potential health risk of MeHg in Taiwanese children from fish and seafood consumption using a toxicokinetic model, hazard quotients and hazard indices (HIs). Two biomonitoring programs provided an important resource for blood specimens for assessing MeHg exposure in human populations. For internal exposures, total mercury (THg) was measured as a biomarker of MeHg in whole blood (WB) and red blood cells using inductively coupled plasma mass spectrometry and cold-vapor atomic absorption spectroscopy, respectively. The THg concentrations were used to estimate MeHg concentrations. Consumption of fish and seafood was assessed using the National Food Consumption database in Taiwan, while mercury concentrations in edible fish and seafood were collected from published studies in Taiwan. Our results indicated that 1) the highest median THg (representing estimated MeHg) daily intakes were found to decrease with increasing age in children consuming saltwater fish for age groups 0–3, 4–6, 7–12, and 13–18 years: 0.03?>?0.02?>?0.017?>?0.007 (μg?kg-BW^?1?day^?1); 2) HI greater than one, based on WB-THg, was found in 28% of 4–6-year-old children and 3) internal exposure estimates based on WB-THg, though slightly higher, were comparable to those based on fish and seafood consumption. The results support the use of dietary intake estimates as surrogates for internal blood MeHg levels in Taiwanese children to assess their exposure.     

High Levels of Methylmercury in Guano and Ornithogenic Coral Sand Sediments on Xisha Islands, South China Sea

This study determined the distribution and main source of methylmercury in ornithogenic coral sand sediments and pure guano collected from Guangjin and Jinqing islets of the South China Sea. Results showed that the levels of methylmercury (MeHg) and total mercury (THg), as well as the percentage of MeHg relative to THg (%MeHg), are high in both fresh and ancient guano samples. %MeHg in ancient guano exceeded 70 %, much greater than that in fresh seabird droppings (~45 %). These results suggest that excretion through feces likely plays an important role in the cycling of MeHg by seabirds. Guano has been identified as the major source of MeHg in the ornithogenic coral sand sediments in the Xisha Islands. The close relationship between MeHg and guano-derived phosphorus has weakened considerably since 1840 AD. This is probably caused by a significant increase in THg and MeHg in modern guano samples due to the recent increase of Hg pollution. %MeHg in the ornithogenic coral sand sediments is extremely high, ranging from 10 to 30 % (average 20 %).     

甲基汞对大鼠脂质过氧化及信使分子一氧化氮的影响

研究了氯化甲基汞(MeHgCl)对大鼠脑不同区域(大脑皮层、小脑、海巴和/或纹状体)、肝脏及肾脏中脂质过氧化产物(LPO)、信使分子一氧化氮(NO)及其效应分子环磷鸟苷(cGMP)的影响。结果表明:试验组与对照组相比,小脑、肝脏、肾脏中3个指标均显著升高;大脑中LPO升高,而NO和cGMP变化没有显著性意义;纹状体中cGMP显著升高;海巴中NO和cGMP均无显著性变化。本研究提示;甲基汞(MeHg)对大鼠不同组织中LPO、NO及cGMP的不同影响,可能与各脏器对MeHg的敏感性不同和/或与一氧化氮合成酶(NOS)阳性神经元分布不均一有关。     

Development of a mercury speciation, fate, and biotic uptake (BIOTRANSPEC) model: application to Lahontan Reservoir (Nevada, USA)

A mathematically linked mercury transport, speciation, kinetic, and simple biotic uptake (BIOTRANSPEC) model has been developed. An extension of the metal transport and speciation (TRANSPEC) model, BIOTRANSPEC estimates the fate and biotic uptake of inorganic (Hg(II)), elemental (Hg(0)) and organic (MeHg) forms of mercury and their species in the dissolved, colloidal (e.g., dissolved organic matter [DOM]), and particulate phases of surface aquatic systems. A pseudo-steady state version of the model was used to describe mercury dynamics in Lahontan Reservoir (near Carson City, NV, USA), where internal loading of the historically deposited mercury is remobilized, thereby maintaining elevated water concentrations. The Carson River is the main source of total mercury (THg), of which more than 90% is tightly bound in a gold-silver-mercury amalgam, to the system through loadings in the spring, with negligible input from the atmospheric deposition. The speciation results suggest that aqueous species are dominated by Hg-DOM, Hg(OH)(2), and HgClOH. Sediment-to-water diffusion of MeHg and Hg-DOM accounts for approximately 10% of total loadings to the water column. The water column acts as a net sink for MeHg by reducing its levels through two competitive processes: Uptake by fish, and net MeHg demethylation. Although reservoir sediments produce significant amounts of MeHg (4 g/d), its transport from sediment to water is limited (1.6 g/d), possibly because of its adsorption on metal oxides of iron and manganese at the sediment-water interface. Fish accumulate approximately 45% of the total MeHg mass in the water column, and 9% of total MeHg uptake by fish leaves the system because of fishing. Results from this new model reiterate the previous conclusion that more than 90% of THg input is retained in sediment, which perpetuates elevated water concentrations.     

Demethylation and excretion of methyl mercury by the guinea pig

Female guinea pigs were dosed po with 1.0 mg CH₃²⁰³Hg/kg as methylmercuric chloride, 10 times over a 3-week period. Tissue distribution, excretion, and accumulation of inorganic and organic mercury were studied. The highest concentration of mercury was found in the kidney. The greatest decreases of mercury levels were observed in the small bowel, red blood cells, liver, and cerebrum. The half-life of whole body clearance, based on a single compartment model, was 31.6 days. Mercury in the kidney, liver, and cerebrum was bound mainly by nuclear and soluble fractions. The highest ratio of inorganic to total mercury was seen in the kidney, 60% of this being as inorganic mercury. Excretion of mercury in the feces was measured throughout the experiment. The relationship of organic to inorganic mercury was relatively constant at about 1:3. Data on the effects of methyl mercury on tissue concentrations of zinc and copper show that the only change in the copper content was a marked increase in the kidney.     

Methylmercury Monitoring Study in Karakuwacho Peninsula Area in Japan

Methylmercury (MeHg) is a worldwide concern owing to its adverse health effects. To explore MeHg exposure burdens and the potential contributing factors in different subpopulations in a peninsula area (Karakuwacho) in Japan, a cross-sectional survey was performed. This study included 189 individuals from 102 families. The geometric means of total hair mercury (THg) were 5.74, 3.78 and 2.37 μg/g for adult males, females and children, respectively, of which 56.5 %, 30.9 % and 12.9 % had hair THg exceeding 5 μg/g, respectively. Tuna and mackerel were the common fish species that were positively correlated with hair THg levels in different subpopulations (standardized coefficient ranged from 0.20 to 0.58, p < 0.05). Frequent consumption of these fish species and a large amount of fish intake are likely major contributors of MeHg exposure in this area. Local-scale risk evaluation and risk communication should be highlighted in future studies.