Maximum allowable concentrations, mercury

To circumvent some of the above-mentioned drawbacks of sulfur-based mercury chemodosimeters, a system based on the alkyne oxymercuration of 58 has been developed (Fig. 22) [146]. 58 shows high selectivity, a limit of detection of ca. 8 ppm, resistance against strong oxidants, and a positive reaction even in the presence of cysteine, which is known to form stable mercury complexes and is used for the extraction of mercury from tissue samples. Another metal that is well-known for its catalytic ability is palladium, catalyzing different reactions depending on its oxidation state. Since this metal is toxic, assessment of the maximum allowable concentration of Pd in consumer products such as pharmaceuticals requires highly sensitive and selective detection schemes. For this purpose, indicator 60 was conceived to undergo allylic oxidative insertion to the fluorescein... 

Anoni Maximum allowable concentrations of mercury compounds. Arch Environ Health 19(6) 891-905, 1969... 

The toxic metals are present in water in the foimn of ions or complexes (organic or inorganic). Lead, cadmium, and mercury are most important they can be accumulated in sediments. Their maximum allowable concentrations in water supplies for water works in Czechoslovakia were determined by an official regulation in 1975 as 0.05, 0.0001, and 0.01 mg/1 for lead, mercury, and cadmium, respectively, and in other surface waters as 0.5, 0.005, and 0.3 mg/1, respectively [9]. The three metals are especially dangerous for fish their acute letal concentrations are indicated in Table 1. 

TABLE 7.7. Maximum Allowable Concentrations of Metallic Impurities in Mercury Cells... 

National or European directives regulate the presence of metallic cations in drinking water. The maximum allowed concentration of chromium and mercury within the European Union is... 

Man can also obtain mercury from the water he drinks. In 1970 the suggested maximum allowable amount of mercury in drinking water was 5 ppb.10 This posed a problem at that time because there was no simple quantitative method capable of determining concentrations that low. However, by the end of 1970 a new method that could measure down to 1 ppb was announced. ... 

Table 2 The maximum permissible concentration of mercury allowed in waste discharges to the environment for Mauritius (From Ministry of Environment of Mauritius)...

Calculation yields that in these experiments the stationary concentration of radicals [ 4] for the maximum intensity of light of a mercury lamp SVDSh-500 was no more than 10 radicals/cm, the stationary conductivity of a ZnO film at 300 C changing by 300 to 400% compared to its initial pre-adsorption value. Thus, in accordance with the above formula (3.21), concentrations of radicals equal to 10 -10 radicals/cm may be detected by means of semiconductor sensors which is 7 magnitudes lower than existing methods would allow. 

Tokuyama Bay, Japan, received 6.6 metric tons of mercury wastes between 1952 and 1975 in wastewater from two chloralkali plants, although sediment analysis suggests that as much as 380 tons of mercury were released (Nakanishi et al. 1989). Unlike Minamata Bay, however, there were no human sicknesses reported, and the hair of residents contained 0 to 5 mg Hg/kg FW vs. 15 to 100 mg Hg/kg FW in Minamata residents. In 1970, a maximum concentration of 3.3 mg total Hg/kg FW was reported in tissues of Squilla, a crustacean. In 1973, a health safety limit was set of 0.4 mg total Hg/kg FW in edible fish and shellfish tissues with a maximum of 0.3 mg methyl-mercury/kg FW permitted at least five species of fish had more than 0.4 mg total Hg/kg FW, and fishing was prohibited. Contaminated sediments (>15 mg total Hg/kg) were removed by dredging and reclamation between 1974 and 1977. By 1979, the mercury content of all fish, except one species, was less than 0.4 mg total Hg/kg FW fishing was prohibited. By 1983, all fish and shellfish contained less than 0.4 mg Hg/kg FW and fishing was allowed (Nakanishi et al. 1989). 

The ROHS Directive would impose substitution on the use of lead, mercury, cadmium, hexavalent chromium, and brominated substances polybrominated diphenyl ethers (PBDE), and polybrominated biphenyls (PBB) in electrical and electronic equipment. The Directive would allow the Commission to establish maximum concentration values, where the presence of specific materials or components is tolerated. Industry welcomes this option because heavy metals covered by the Directive are present in most materials as naturally occurring substances. As for the economic implications, the Commission recognized that substantial costs would be incurred for replacing lead in solders and estimated the additional operating costs of using tin-based solders or other alternatives would be about 150 million Euros per year. 

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