Mercury exposure in the population from Wuchuan mercury mining area, Guizhou, China

Mercury (Hg) exposure in the population from Wuchuan mercury mining area (WMMA), Guizhou, China, was evaluated by human hair Hg investigation. Total gaseous mercury (TGM) in the ambient air and Hg in rice were measured to assess human risk of Hg exposure. High TGM concentrations in the ambient air were found near smelting workshop. Rice not only contained high total mercury (T-Hg) which ranged from 6.0-113 ng/g, but also contained highly elevated methylmercury (Me-Hg) which ranged from 3.1-13.4 ng/g. The means of hair T-Hg concentrations were 33.9 microg/g and 21.5 microg/g at YQG and JXC sites, respectively. Residents from other sites also reflected a certain level of Hg exposure. Age had no significant effect on hair Hg levels, but male had higher hair T-Hg concentrations due to occupational exposure and also higher Me-Hg levels which might be related to larger amount of rice consumption. Hair may be a useful tool for monitoring human exposure of Hg vapor in Hg-mining areas. By a preliminary estimation, the inhalation of Hg polluted air was the main route of inorganic Hg exposure to the smelting workers and vicinal residents; but the population in the study area was also at a potential risk of Me-Hg exposure via rice intake.     

Fish consumption and bioindicators of inorganic mercury exposure

BACKGROUND: The direct and close relationship between fish consumption and blood and hair mercury (Hg) levels is well known, but the influence of fish consumption on inorganic mercury in blood (B-IHg) and in urine (U-Hg) is unclear. OBJECTIVE: Examine the relationship between fish consumption, total, inorganic and organic blood Hg levels and urinary Hg concentration. METHODS: A cross-sectional study was carried out on 171 persons from 7 riparian communities on the Tapajós River (Brazilian Amazon), with no history of inorganic Hg exposure from occupation or dental amalgams. During the rising water season in 2004, participants responded to a dietary survey, based on a seven-day recall of fish and fruit consumption frequency, and socio-demographic information was recorded. Blood and urine samples were collected. Total, organic and inorganic Hg in blood as well as U-Hg were determined by Atomic Absorption Spectrometry. RESULTS: On average, participants consumed 7.4 fish meals/week and 8.8 fruits/week. Blood total Hg averaged 38.6+/-21.7 microg/L, and the average percentage of B-IHg was 13.8%. Average organic Hg (MeHg) was 33.6+/-19.4 microg/L, B-IHg was 5.0+/-2.6 microg/L, while average U-Hg was 7.5+/-6.9 microg/L, with 19.9% of participants presenting U-Hg levels above 10 microg/L. B-IHg was highly significantly related to the number of meals of carnivorous fish, but no relation was observed with non-carnivorous fish; it was negatively related to fruit consumption, increased with age, was higher among those who were born in the Tapajós region, and varied with community. U-Hg was also significantly related to carnivorous but not non-carnivorous fish consumption, showed a tendency towards a negative relation with fruit consumption, was higher among men compared to women and higher among those born in the region. U-Hg was strongly related to I-Hg, blood methyl Hg (B-MeHg) and blood total Hg (B-THg). The Odds Ratio (OR) for U-Hg above 10 microg/L for those who ate >4 carnivorous fish meals/week was 4.00 [1.83-9.20]. CONCLUSION: This study adds further evidence to a positive relation between fish consumption and IHg in both blood and urine, which may result from absorption of IHg from fish or from demethylation of MeHg. The findings support the importance of assessing IHg exposure in fish-eating communities. Further studies should examine the potential toxicity of IHg in heavy fish consumers.     

Biological monitoring of mercury exposure in individuals referred to a toxicological center in Venezuela

People in developing countries are often considered at greater risk of mercury (Hg) poisoning due to a variety of factors including a lack of awareness regarding their occupational risks. Individuals requiring urine mercury (U-Hg) analysis at the Center for Toxicological Investigations of the University of Carabobo (CITUC), between 1998 and 2002 were studied to identify demographic characteristics associated to U-Hg levels. The studied population included individuals with a history of exposure (or related exposures) to Hg processes, and was comprised of 1159 individuals (65 children, 1094 adults) ages 0.58-79 years old, mean 36.63+/-12.4. Children's geometric mean U-Hg levels were 2.73 microg/g Creatinine (Ct) and in adults 2.55 microg/g Ct. The highest frequency of adults' occupations were shipyard workers (35.47%), dentists (23.5%), lab technicians (11.43%), dental employees 10.42% and miners (10.2%). Chemical laboratory technicians had the highest mean U-Hg (4.46 microg/g Ct). Mean U-Hg levels in female adults (3.45 microg/g Ct) were statistically superior to levels in male adults (2.15 microg/g Ct). Two of the 172 women in reproductive age, had U-Hg levels higher than 78 microg/g Ct. Individuals from Falcon State were found to have the highest mean U-Hg (4.53 microg/g Ct). U-Hg levels higher than permissible limits were found in only 2 states (Carabobo and Bolivar) with a total of 24 cases. Although the results of this investigation were highly variable, the findings can be used to examine circumstances which influence mercury toxicity trends, and possibly used in future studies working to identify Hg exposures.     

Mercury levels in fisherman and their household members in Zhoushan, China: Impact of public health

Zhoushan Island is situated in the coast of the East China Sea. In order to assess the potential health risks associated with dietary consumption of mercury, hair samples from 59 piscatorial households, thirteen species of fish, crops and poultry samples were collected from the fishing villagers of Zhoushan. Total mercury (T-Hg) and methylmercury (MeHg) concentrations in the fathers' hair (mean, 5.7 and 3.8 μg/g) were approximately 2.5 and 2.1 times greater and 2.6 and 2.0 times higher than those of their wives (2.3 and 1.8 μg/g) and their children (2.2 and 1.7 μg/g), respectively. However, the mean quantity of the fish consumed by the fathers was 2.5 and 2.4 times higher than those of the mothers and children, implying that there was a wide variation in hair Hg concentrations between the fathers and the mothers and children of the same household, which was probably related to the quantity, frequency and type of fish consumed. The average T-Hg and MeHg concentrations in all species of fish were 0.26 and 0.18 μg/g, respectively. Approximately, 15% and 19% of the samples showed T-Hg and MeHg levels which exceeded the limit established by the Chinese National Standard Agency (CNSA) (0.3 and 0.2 μg/g), respectively. However, T-Hg and MeHg levels in crops, poultry, milk, drinking water, food oil and salt samples were all below the corresponding CNSA limit. The estimated total daily dietary intakes of T-Hg and MeHg via different food types showed that fish intake was the major source (> 85%) of Hg exposure. The consumption advisories for the total quantity of thirteen species of fish were 69.3, 58.7 and 15.0 g per day for fathers, mothers and children, respectively.     

Health assessment for mercury exposure among schoolchildren residing near a gold processing and refining plant in Apokon, Tagum, Davao del Norte, Philippines

Artisanal gold-mining activities in the Philippines have proliferated since the early 1980s. Presently, environmental and health monitoring conducted by several governmental agencies is limited to the determination of total mercury only. Previous studies undertaken focused mainly on the exposure of adults and workers to mercury during mining/processing operations. However, in one area in Mindanao, mined ores are brought down and processed in the lowlands where residential communities are exposed to environmental pollutants resulting from gold processing/refining operations. The area of study is Apokon, Tagum, Davao del Norte, which has 29 gold processing and refining plants. Health complaints among schoolchildren in Apokon Elementary School were received by the Department of Health and were attributed to the mercury pollution in the environment. As part of a collaboration with the Health Department, UP-National Poisons Control and Information Service, the National Institute for Minamata Disease (NIMD), Japan, provided technical assistance in the analytical determination of mercury in biological and environmental samples. Elevated mercury concentrations were noted in some of the river systems up to 15 km from the mining areas. Environmental quality monitoring showed T-Hg sediment levels ranged from 0.553 to 66.471 microg/g dry wt. while water samples from river systems exhibited mercury levels from 72.8 to 78.4 ng/ml. Twenty-seven sediment samples from river systems near mining operations and seven water samples were also brought to the Institute for analysis. Fish samples collected showed levels ranging from 1.07 to 438.8 ng/g for total mercury and 0.71-377.18 ng/g for methylmercury. Methylmercury content in fish is predominant. All water and sediment samples collected from three sampling sites have elevated T-Hg level while three fish species have elevated T-Hg and methylmercury levels (WHO/CDC, 1994). Blood and hair samples from 162 schoolchildren aged 5-17 years were collected and analyzed at the NIMD for mercury analysis. Analytical procedures used in the NIMD for mercury testing were applied. Laboratory results showed that total mercury hair samples ranged from 0.278 to 20.393 microg/g while methylmercury hair results were from 0.191 to 18.469 microg/g. Methylmercury in hair showed levels from 45.96 to 99.81%. Total blood mercury levels ranged from 0.757 to 56.88 microg/l while Me-Hg blood levels ranged from 1.36 to 46.73 microg/l. It was determined that 10 children had elevated T-Hg blood levels while one child had high total and methylmercury levels in hair. A summary of physical examination results showed that the predominant findings include under-height, gingival discoloration, adenopathy, underweight and dermatologic abnormalities among children examined.     

Methyl mercury exposure in Swedish women with high fish consumption

We studied the exposure to methyl mercury (MeHg) in 127 Swedish women of childbearing age with high consumption of various types of fish, using total mercury (T-Hg) in hair and MeHg in blood as biomarkers. Fish consumption was assessed using a food frequency questionnaire (FFQ), including detailed information about consumption of different fish species, reflecting average intake during 1 year. We also determined inorganic mercury (I-Hg) in blood, and selenium (Se) in serum. The average total fish consumption, as reported in the food frequency questionnaire, was approximately 4 times/week (range 1.6-19 times/week). Fish species potentially high in MeHg, included in the Swedish dietary advisories, was consumed by 79% of the women. About 10% consumed such species more than once a week, i.e., more than what is recommended. Other fish species potentially high in MeHg, not included in the Swedish dietary advisories, was consumed by 54% of the women. Eleven percent never consumed fish species potentially high in MeHg. T-Hg in hair (median 0.70 mg/kg; range 0.08-6.6 mg/kg) was associated with MeHg in blood (median 1.7 microg/L; range 0.30-14 microg/L; rs = 0.78; p < 0.001). Hair T-Hg, blood MeHg and serum Se (median 70 microg/L; range 46-154 microg/L) increased with increasing total fish consumption (rs = 0.32; p < 0.001, rs = 0.37; p < 0.001 and rs = 0.35; p = 0.002, respectively). I-Hg in blood (median 0.24 microg/L; range 0.01-1.6 microg/L) increased with increasing number of dental amalgam fillings. We found no statistical significant associations between the various mercury species measured and the Se concentration in serum. Hair mercury levels exceeded the levels corresponding to the EPA reference dose (RfD) of 0.1 microg MeHg/kg b.w. per day in 20% of the women. Thus, there seems to be no margin of safety for neurodevelopmental effects in fetus, for women with high fish consumption unless they decrease their intake of certain fish species.     

Human exposure to mercury due to small scale gold mining in northern Tanzania

In northern Tanzania large numbers of small scale miners use mercury in the gold extraction process causing contamination of the environment and risks to human health. Human exposure to Hg was assessed in populations in and around small scale gold mining camps by means of human hair and urine surveys. We also determined Hg concentration in fish in aquatic bodies close to these camps. Urinary Hg testing in three communities showed that 36% of the gold miners working with amalgam exceeded the WHO guideline concentration of 50 microg Hg/g creatinine. Data from a hair survey of fishermen and farmers confirm that at present, the fish-eating population close to the southern tip of Lake Victoria is at low risk with regard to Hg exposure. Concentrations in fish were low and > 90% of the hair samples from the fish-eating population were below 2 microg/g T-Hg. Highest Hg concentrations in fish caught along the southern shores of Lake Victoria and in rivers draining from gold processing sites were detected in lungfish species (Protopterus aethiopicus), and lowest Hg concentrations in tilapia (Oreochromis niloticus and Tilapia zilii).     

Total and organic Hg concentrations in cephalopods from the North Eastern Atlantic waters: influence of geographical origin and feeding ecology

Total (T-Hg) and organic (O-Hg) mercury concentrations and tissue distribution were examined in 20 species of cephalopods (n=278) from the north eastern Atlantic waters, i.e. from the Bay of Biscay to the Faroe Islands. Concentrations of T-Hg in whole cephalopods showed elevated variations among species, i.e. from 40 to 3560ng g(-1) dwt, but a low variability within each species (mean CV%=39%). With the exception of oceanic squids, the digestive gland globally displayed higher T-Hg concentrations than the remaining tissues. In contrast, O-Hg concentrations determined in selected species were generally higher in the remaining tissues. Despite higher T-Hg concentrations, the digestive gland weakly contributed to the total body burden of both T-Hg and O-Hg (<25% and <15%, respectively). In fact, from 75% to 95% of the T-Hg and O-Hg were contained in the muscular remaining tissues. Therefore, O-Hg may have a strong affinity to proteins in cephalopods. Sex and size only significantly influenced the bioaccumulation of Hg for the Loliginidae family. T-Hg and O-Hg concentrations were also influenced by geographical origin: Celtic Sea>Bay of Biscay>Faroe Islands, corresponding to the seawater Hg concentrations in these areas. In the Faroe Islands and the Celtic Sea, benthic cephalopods contained significant higher Hg concentrations compared to pelagic ones. This suggests that diet is not the main pathway of Hg uptake in cephalopods as pelagic species were expected to be more exposed to O-Hg through fish consumption than benthic ones.     

Monocyte-macrophage system and polymorphonuclear leukocytes in workers exposed to low levels of metallic mercury

Our previous research (Soleo L, Vacca A, Vimercati L et al. Occup Environ Med 1997;54:437-442) showed a reduction in tumor necrosis factor-alpha (TNF-alpha) serum levels in workers with prolonged exposure to low doses of inorganic mercury, suggesting an in vivo functional defect of the monocyte-macrophage system. On this basis, here we wondered whether workers exposed to lower doses of metallic mercury displayed possible changes in the monocyte-macrophage system. In this particular cohort of workers, we also sought for the effects of the exposure on the polymorphonuclear leukocytes (PMNL) chemotaxis. The monocyte-macrophage system and the natural killer (NK) cells were examined in 19 exposed workers and in 25 unexposed workers, as the control group (controls). Specifically, the circulating monocyte-macrophage cells and their CD13, CD15 and CD33 subsets, serum cytokines (IL-8, GM-CSF and TNF-alpha) and the NK cells were analyzed. In seven exposed and seven controls randomly chosen workers the PMNL chemotaxis was also assessed. The selected indicator of mercury exposure were the levels of mercury in the urine (U-Hg), that was significantly higher in exposed workers than the controls (9.7 +/- 5.5 microg/l and 2.4 +/- 1.2 microg/l, respectively). None of the exposed workers had shown signs of either acute or chronic inorganic mercury toxicity or any form of hypersensitivity. Several immunological variables tested, monocyte-macrophage cells and their subsets, NK cells and serum cytokines overlapped between the exposed and the control workers. When the workers were considered as a whole (exposed plus controls), no correlation was found between current U-Hg and all immunological parameters. However, when exposed workers were studied separately, an inverse correlation was disclosed between cumulative U-Hg and cells (as percentage) expressing the CD13 (r = -0.599; P = 0.007) and CD15 (r = -0.614; P = 0.005) molecules, and NK cells (r = -0.455; P = 0.05). Moreover, a significant impairment in the PMNL chemotaxis (t = 3.70; P = 0.003) was observed in the exposed workers. The results of our study suggest that the exposure to very low levels of metallic mercury led to subtle impairment of circulating monocyte and NK cells (as percentages) according to the increase in U-Hg levels, as well as of the PMNL chemotactic function in this particular group of workers, even though they remain clinically asymptomatic. Therefore, we suggest that impairment of these parameters provide a sensitive indicator of metallic mercury and other chemical contaminants present in the environment.     

Urinary mercury in adults in Poland living near a chloralkali plant

We conducted a study within the framework of the interdisciplinary European Mercury Emission from Chloralkali Plants (EMECAP) project to assess exposure to mercury (Hg) and the contribution of Hg emissions from a mercury cell chloralkali plant to urinary mercury (U-Hg) in adults living near the plant. We collected data from questionnaires and first morning urine samples from 75 subjects living near the Tarnow plant in Poland and 100 subjects living in a reference area. Median U-Hg was 0.32 mug/g creatinine (microg/gC) and 0.20 microg/gC, respectively. The median U-Hg was also higher in the amalgam-free subjects living near the plant (0.26 microg/gC) than in the reference group (0.18 microg/gC), but no such association was found in a multivariate analysis. There was a statistically significant positive association between U-Hg and number of teeth with amalgams, a negative association with age and a tendency towards higher U-Hg in female subjects. In the amalgam-free subjects there were statistically significant effects of female sex and fish consumption, and a negative association with age. The additional long-term average air Hg concentration from the plant, based on EMECAP environmental measurements and modelling, was estimated to be 1-3.5 ng/m(3) for the residential study area and should have a very small effect on U-Hg. The other Hg emission sources such as coal combustion facilities located nearby should be taken into account in assessing the overall impact of air Hg on U-Hg in this area.     

Some results on Hg content in hair in different populations in Albania

The mercury content in hair, for exposed dental workers and unexposed groups of people living in Albania was studied. The influence of factors such as age, sex, body weight, fish consumption in the diet, number of dental amalgam fillings and time exposed to mercury, was determined. The mean value of mercury content in hair for the subjects under study (0.705 microg/g) was found to be lower than the value referred from the World Health Organization (WHO) for people who do not consume fish with a high methylmercury content (1-2 microg/g). A significant positive correlation of Hg content with the number of dental amalgam fillings, time under exposure and frequency of fish consumption in the diet was found. These correlations became stronger when exposed and unexposed groups of people were evaluated separately.     

Human exposure to heavy metals in East Greenland I mercury

The concentration of mercury in 178 blood samples and 32 hair samples from the Angmagssalik district in East Greenland has been determined.For Greenlanders mercury concentrations are highly dependent on the amount of seal eaten. In the most heavily exposed group (eating more than six meals of seal per week), a significant positive correlation between blood mercury and age was demonstrated. No differences according to sex were demonstrated when the mean values were corrected for influence of age. In the most heavily exposed group, a mean value of 62.5 μg Hg/l was found, while in the group eating 1 meal of seal or less per week, the mean value was 22.2 μg Hg/l. In the control group consisting of Danes living temporarily in the district, the mean blood mercury concentration was 5.8 corresponding to the fact that they eat seal only occasionally.Hair mercury concentrations were found to correlate well with blood mercury concentrations (r = 0.9222). The hair/blood ratio was estimated to 289.It is concluded that the present relatively high mercury exposure in Greenland does not excert any immediate risk of intoxication to the adult population, but supplementary investigation on fetal exposure is needed.     

Hair mercury levels in pregnant women in Mahshahr, Iran: Fish consumption as a determinant of exposure

MeHg is a well-documented neurotoxicant even at low levels of exposure. Developing brain, in particular, is vulnerable to that. Through bioaccumulating to differing degrees in various fish species, it can have serious adverse effects on the development and functioning of the human central nervous system, especially during prenatal exposure. Therefore, the purpose of this study was to investigate mercury concentration in hair samples of pregnant women living in Mahshahr located in Khuzestan province, Iran. It assessed the association between fish consumption and specific characteristics that can influence exposure. From April to June 2008, 149 pregnant women were invited to participate in this study. An interview administered questionnaire was used to collect information about age, body weight, height, fish (fresh, canned and shrimp) consumption, pregnancy stage, residence duration, education level, family income and number of dental amalgam fillings. The obtained results showed that the geometric mean and range for hair total Hg concentration was 3.52 μg/g (0.44-53.56 μg/g). About 5.4% of mothers had hair total Hg levels in excess of 10 μg/g. Maternal hair mercury level was less than threshold level of WHO (5 μg/g). As expected, there was a clear increase in hair Hg with reported fresh marine fish consumption (p = 0.04). The highest mean for hair mercury level in a group who consumed fish several times per week, was 4.93 μg/g. Moreover, a significant effect of age and residential time on Hg concentration in the hair of the women was found. Pregnant women in Mahshahr consumed large amounts of fish; consequently, most of their offspring were prenatally exposed to moderately high levels of mercury. The results found suggest that pregnant women should decrease their fish consumption.     

Health assessment of artisanal gold miners in Tanzania

In 2003 UNIDO (United Nations Industrial Development Organization) conducted an environmental and health assessment in a small-scale mining area in Tanzania. BGS (British Geological Survey) performed the environmental assessment. The Institute of Forensic Medicine - University of Munich performed the health assessment. The results of the medical, neurological and neuro-psychological examination of 180 participants from the affected area of Rwamagasa and 31 controls were analyzed. Urine, blood and hair samples were analyzed to detect the level of mercury body burden. Mercury concentrations in the bio-monitors urine, blood and hair were statistically significantly higher in the exposed population from Rwamagasa compared to the control group from Katoro. Only amalgam burners showed mercury levels above the toxicological threshold limits. A speciation of mercury in hair indicated that mainly elemental mercury vapor contributed to the high body burden of the artisanal miners. 104 amalgam-burners, the most exposed population group, were examined. 25 of these workers were found to be intoxicated. Small-scale mining is a serious health hazard for amalgam burners. Reduction of the exposure is essential to prevent further damage.     

Human exposure to mercury in San Jorge river basin,Colombia (South America)

During May-September 1999 human hair samples were collected from the village of Caimito, a fishing community of the state of Sucre (Colombia), in the San Jorge River basin area, and analyzed for total mercury (t-Hg) by cold vapor atomic absorption spectroscopy. T-Hg was measured in both male and female people aged 15-65 years, whose diet mainly consists of fish collected in nearby marshes. Average hair t-Hg concentration in people from Caimito was 4.91 +/- 0.55 microg/g (n = 94), similar to the value previously detected in fishermen living in the gold mining area, 50 km east. Males had similar t-Hg concentrations (4.31 +/- 0.42 microg/g; n = 56) to females (5.78 +/- 1.21 microg/g; n = 38) and there was no difference in t-Hg levels between groups of different age. Mercury content in hair was weakly but significantly associated (R = 0.20, P = 0.05) with fish consumption.     

Prenatal exposure to mercury in a prospective mother-infant cohort study in a Mediterranean area, Valencia, Spain

BACKGROUND: Mercury (Hg) is a ubiquitous pollutant that negatively affects fetal and child neurodevelopment at accidental high-dose exposure. Some studies indicate that Mediterranean populations could be at risk of prenatal exposure to mercury through fish consumption. OBJECTIVES: To assess the prenatal exposure to total mercury (T-Hg), both inorganic and organic, in newborns by analyzing the T-Hg concentration in cord blood, and to evaluate the role of maternal fish consumption in this exposure. METHODS: In the context of a multi-center project (INMA project), a prospective birth cohort was set up in Valencia, Spain, from 2005 to 2006. A total of 253 newborns were included in this study. We compared cord blood T-Hg concentration by levels of fish intake assessed by a food frequency questionnaire completed at 28-32 weeks of gestation. Maternal covariates were obtained through a questionnaire. RESULTS: The geometric mean of T-Hg at birth was 9.9 microg/L (95% CI: 9.0, 10.8). Seventy five percent of cord blood samples were above the estimated level assumed to be without appreciable harm (5.8 microg/L). Women who consumed a portion of large oily fish, lean fish, or mixed fried fish two or more times per week had mean cord blood levels 1.6, 1.4 and 1.3 times higher, respectively, than those who rarely or never consumed fish. Other factors such as the mother's age, country of origin, smoking and season of delivery were also significantly and independently associated with cord blood T-Hg concentrations. CONCLUSIONS: Newborns from a Mediterranean area presented elevated levels of T-Hg in cord blood. Higher concentrations of T-Hg were related to maternal fish intake, particularly in the case of large oily fish species.     

Mercury and selenium concentrations in the internal organs of toothed whales and dolphins marketed for human consumption in Japan

Small cetaceans (toothed whales odontoceti and dolphins delphinidae) have been traditionally hunted along the coast of Japan and fresh red meat and blubber, as well as boiled internal organs such as liver, kidney, lung and small intestine, are still being sold for human consumption. We surveyed mercury contamination in boiled liver, kidney and lung products marketed in Japan between 1999-2001. The average +/- S.D. of total mercury (T-Hg) was 370 +/- 525 (range: 7.60 approximately 1980, n = 26) microg/g in liver, 40.5 +/- 48.5 (7.30-95.1, n = 15) microg/g in kidney and 42.8 +/- 43.8 (2.10-79.6, n = 23) microg/g in lung. A high correlation was observed between T-Hg and selenium (Se) concentrations in these organs, supporting the formation of a Hg-Se complex. The formation of a Hg-Se complex probably contribute to the detoxification of Hg for cetaceans and allows a very large accumulation of Hg in livers. The provisional permitted level of T-Hg in marine foods set by the Japanese Ministry of Health and Welfare is 0.4 microg/ g, and the provisional permitted weekly intake (PTWI) set by WHO is 5 microg/kg bw/week. The maximal T-Hg detected in boiled liver (1,980 microg/g) exceeds the permitted level by approximately 5,000 times and the consumption of only 0.15 g of liver exceeds the PTWI of 60 kg of body weight of the consumer, suggesting the possibility of an acute intoxication by T-Hg even after a single consumption of the product.     

Assessment of reference values for mercury in urine: the results of an Italian polycentric study

The results of a polycentric study to assess the reference values of urinary mercury (U-Hg) in four Italian cities are presented. A total of 383 subjects were selected on the basis of standardised criteria by a questionnaire on personal habits, lifestyle, occupational or non-occupational exposure to Hg, medical history, number and area of dental amalgams. U-Hg was determined by hydride generation atomic absorption method (HG-AAS), with a detection limit of 0.5 microg/l and by flow injection (FI) inductively coupled plasma mass spectrometry (ICP-MS), with a detection limit of 0.03 microg/l. The median value of U-Hg, determined by HG-AAS, was 0.78 microg/g creatinine (0.75 for males and 0.83 for females), with 5 degrees and 95 degrees percentiles, respectively, of 0.17 and 3.66 microg/g creatinine. When determined by FI ICP-MS, the median value was 0.79 microg/g creatinine (0.77 for males and 0.79 for females) with 5 degrees and 95 degrees percentiles of, respectively, 0.12 and 5.02 microg/g creatinine. Among the independent variables, city of origin, area of dental amalgams, fish intake and tobacco smoking significantly influenced the U-Hg levels. The U-Hg reference values from this survey are lower than those from other recent investigations, probably due to characteristics and selection of the examined individuals and to the strict control of pre-analytical and analytical factors of variability.     

Urinary mercury in people living near point sources of mercury emissions

As part of the European Mercury Emissions from Chlor Alkali Plants (EMECAP) project, we tested the hypothesis that contamination of ambient air with mercury around chlor alkali plants using mercury cells would increase the internal dose of mercury in people living close to the plants. Mercury in urine (U-Hg) was determined in 225 individuals living near a Swedish or an Italian chlor alkali plant, and in 256 age- and sex-matched individuals from two reference areas. Other factors possibly affecting mercury exposure were examined. Emissions and concentrations of total gaseous mercury (TGM) around the plants were measured and modeled. No increase in U-Hg could be demonstrated in the populations living close to the plants. This was the case also when the comparison was restricted to subjects with no dental amalgam and low fish consumption. The emissions of mercury to air doubled the background level, but contributed only about 2 ng/m(3) to long-term averages in the residential areas. The median U-Hg levels in subjects with dental amalgam were 1.2 microg/g creatinine (micro/gC) in Italy and 0.6 microg/gC in Sweden. In individuals without dental amalgam, the medians were 0.9 microg/gC and 0.2 microg/gC, respectively. The number of amalgam fillings, as well as chewing, fish consumption, and female sex were associated with higher U-Hg. The difference between the countries is probably due to higher fish consumption in Italy, demethylated methyl mercury (MeHg) being partly excreted in urine. Post hoc power calculations showed that if the background mercury exposure is low it may be possible to demonstrate an increase in U-Hg of as little as about 10 ng/m(3) as a contribution to ambient mercury from a point source.     

Burdens of mercury in residents of Temirtau, Kazakhstan: I: Hair mercury concentrations and factors of elevated hair mercury levels

Mercury (Hg) is released either naturally in the environment or by anthropogenic activities. During its global circulation, Hg presents in a diversity of chemical forms and transforms between each other. Among Hg species, methylmercury (MeHg) is readily absorbed by humans via the aquatic food chain and thus it is very neurotoxic to exposed populations including fetuses due to perinatal exposure. In 2005, a survey was carried out in Temirtau, an Hg-contaminated site in North Central Kazakhstan, to investigate Hg concentrations in the hair samples of the residents and the relationship between Hg exposure levels and the related factors. Among the 289 hair samples, Hg concentrations ranged from 0.009 to 5.184 µg/g with a mean of 0.577 µg/g. Nearly 17% of the population exceeded 1 µg/g for hair Hg, which corresponds to the reference of dose (RfD) 0.1 µg/kg body weight/day developed by the United States Environmental Protection Agency (USEPA). Subgroups of males, people aged over 45 and fishermen or anglers were found to have elevated Hg exposure levels in their hair. A positive correlation was found between Hg concentrations in hair and frequencies of river fish consumption. As a result, the finding that people were exposed to high levels of Hg was expected due to the frequent consumption of fish caught from the polluted River Nura or the neighbouring lakes. A regression model showed that approximately 41% of variance of Hg concentrations in the study population's hair was attributed to the variables of gender, residential location, age and fishery occupation. The model implied that demographic characteristics together with dietary behaviour should be taken into account in studies associated with Hg exposure risk, in order to clearly define the group potentially sensitive to Hg exposure.