Mercury estimating exposures

Studies assessing mercury vapor exposure have suggested various ratios relating the concentration of mercury in the air (in g/m3) to the levels of mercury in the urine (in g/L). Such estimates include 1 1 (Bell et al. 1973), 1 1.22 (Roels et al. 1987), and 1 2.5 (Lindstedt et al. 1979 Rosenman et al. 1986). Urinary metallic mercury levels ranging from 0.05 to 1.7 g/L were detected in the urine of workers exposed to mercury vapor (>0.1 mg/m3) this elemental mercury represented <1% of the inorganic mercury content of the urine (Y oshida and Yamamura 1982). With increased exposure to mercury vapor (0.47-0.67 mg/m3), the amount of elemental mercury in the urine increased. A "rough" correlation between levels of metallic mercury vapor in air and mercury levels in blood and urine was established by Rosenman et al. (1986). They associated levels of 50 g/100 mL in blood and 250 g/L in urine with a mercury level in air of approximately 0.1 mg/m3 (8-hour TWA), and 28 g/100 mL in blood and 100 g/L in urine with a TWA of 0.05 mg/m3. Roels et al. (1987) found a correlation between daily mercury vapor exposure and blood or urine mercury levels in 10 workers employed for at least 1 year at an alkaline battery plant. The mercury levels in the air and the pre- or post-workshift levels of blood and urinary mercury correlated well (r=0.79-0.86 [blood] and r=0.70-0.80 [urine]). Based on a ratio of... 

Shaw et al. 1986). Additional information on the biological monitoring of populations living in the vicinity of hazardous waste sites would be helpful in estimating exposure of these populations to mercury compounds. This information is useful for assessing the need to conduct health studies on these populations. 

Blood and hair samples are often analyzed in order to estimate exposure of humans to mercvny and its compounds. Blood should be taken by venipuncture. Since some commercial containers may contain mercury compounds added as preservatives it is advisable to check each commercial batch before use. The samples should be refrigerated but not frozen, as it is sometimes useful to measure mercvny in plasma and red blood cells separately. The separation of plasma and red blood cells should be performed as soon as possible to avoid hemolysis of the sample. If extensive hemolysis has occurred, the sample should be homogenized before an aliquot is taken for analysis. Blood samples may also be heparinized for total blood, serum, and red blood cell analyses. If unavoidable, samples may be stored deep frozen. However, repeatedly frozen and unfrozen blood samples showed a remarkable decrease in methylmercury concentrations. There is some evidence that methyl-mercvny may be destroyed during lyophilization of blood samples. 

Exposure. The exposure of humans and animals to mercury from the general environment occurs mainly by inhalation and ingestion of terrestrial and aquatic food chain items. Pish generally rank the highest (10—300 ng/g) in food chain concentrations of mercury. Swordfish and pike may frequently exceed 1 p.g/g (27). Most of the mercury in fish is methyl mercury [593-74-8]. Worldwide, the estimated average intake of total dietary mercury is 5—10 p-g/d in Europe, Russia, and Canada, 20 pg/d in the United States, and 40—80 pg/d in Japan (27). 

Fish are often the focal point of interest for methylmercury contamination, representing the main exposure pathway for humans and wildlife. Unfortunately, longterm data sets with records of both mercury deposition and fish mercury concentrations over time are limited. In Sweden, Johansson etal. (2001) estimated that... 

Human intake of total mercury from the diet normally ranges between 7 and 16 pg daily (Schumacher et al. 1994 Richardson et al. 1995). Fish consumption accounts for much of this exposure in the form of methylmercury 27% of the intake, and 40% of the absorbed dose. Intake of inorganic mercury arises primarily from foods other than fish, and is estimated at 1.8 pg daily with 0.18 pg absorbed daily (Richardson etal. 1995). In certain areas of India, blood mercury concentrations of people who ate fish were three to four times higher than non-fish eaters (Srinivasen and Mahajan 1989). In some countries, mercury in dental amalgams accounts for 2.8 pg daily, equivalent to as much as 36% of the total mercury intake and 42% of the absorbed dose (USPHS... 

Inhalation of mercury vapor may produce a metal fume fever-like syndrome, including chills, nausea, general malaise, tighmess in the chest, and respiratory symptoms. High concentrations cause corrosive bronchitis and interstitial pneumonitis. In the most severe cases, the patient will succumb because of respiratory insufficiency. In one episode involving four workers, it was estimated that mercurial pneumonitis resulted from exposure for several hours to concentrations ranging between 1 and 3mg/m. ... 

Although the sensor signal is changed during about 30-40 min after exposure to mercury vapor, an estimation of the concentration can be performed from the data measured within the first 5-10 min. 

Mercury Blood mercury Biomarker to toxic effect in humans, although this relationship is for cord blood biomarker to external dose in humans Biomarker results can be used directly for estimation of human risk exposure apportionment and intervention possible... 

Investigations into the presence of mercury in food have been carried out in a comparatively small number of foods in the UK since 1966. Mercury is included in the analytes measured in the samples of the Total Diet Study. The estimated dietary exposures to total mercury (organic and inorganic) for the general population as determined from the UK TDS (Table 7.5) have remained fairly constant between 0.002 and 0.005 mg/day. The dietary exposures of mean and 97.5th percentile consumers in the UK in 1997 were 0.0031 mg/day and 0.0064mg/day.10 These may be compared with the JECFA PTWI for mercury of 0.005 mg/kg bodyweight/week (of which no more than two-thirds should be methyl mercury),31 which is equivalent to 0.043 mg/day for a 60 kg adult. The dietary exposures are similar to those in the USA (0.008 mg/day)8 and the Netherlands (0.002 mg/day)7 but lower than New Zealand (0.013 mg/day).18... 

Analyses of methyl mercury in scalp hair can be used to make a retrospective estimation of maternal exposure during pregnancy. It has been found that children born to mothers, whose hair mercury concentrations ranged between 70 and 640 pg Hg/ g, show a considerably higher prevalence of developmental changes than controls. Scalp hair levels exceeding 6 pg/ g are considered elevated and should be confirmed by a 24-hour urine collection. 

Levels of exposure associated with carcinogenic effects (Cancer Effect Levels, CELs) of mercury are indicated in Tables 2-2 and 2-3 and Figures 2-2 and 2-3. Cancer effects could occur at lower exposure levels however, a range for the upper bound of estimated excess risks (ranging from a risk of 1 in 10,000 to 1 in 10,000,000 [10 4 to 10 7]) has not been developed by EPA. 

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