Drinking water, maximum arsenic

For maximum protection of human health from the potential carcinogenic effects of exposure to arsenic through drinking water or contaminated aquatic organisms, the ambient water concentration should be zero, based on the nonthreshold assumption for arsenic. But a zero level may not be attainable. Accordingly, the levels established are those that are estimated to increase cancer risk over a lifetime to only one additional case per 100,000 population. These values are estimated at 0.022 pg As/L for drinking water and 0.175 pg As/L for water containing edible aquatic resources (USEPA 1980 Table 28.7). 

Although not as widespread as arsenic, barium also occurs naturally in the environment in some areas. It can also enter water supplies through hazardous industrial waste discharges or releases. Small doses of barium are not harmful. However, it is quite dangerous when consumed in large quantities. The maximum amount of barium allowed in drinking water by the standard is 1.0 mg/L of water. 

Maximum contaminant levels (MCLs) Drinking water standards for various contaminants that are enforced by the United States Environmental Protection Agency (US EPA) that take into account the risks of human health effects and the costs of cleaning the water (Appendix E). The current MCL for arsenic is 10 pg E 1 (40 Code of Federal Regulations 141.62). 

A Fischer assay simulates the conversion of oil shale to usable fuels in an above-ground retort. The results of an extensive program of chemical analysis of major and trace elements in spent shale, oil, and water collected from the Fischer assay of a standard oil shale are presented. The concentration of major elements in raw and spent shale can be determined only to 10% in this study. Two criteria show that fluorine and zinc may have been mobilized during the assays. The concentrations of arsenic and selenium in the Fischer assay retort water exceed the maximum permissible concentrations for drinking water. 

If the retort water is considered for domestic or irrigation uses, it would have to be treated to remove a number of contaminants. Of the major constituents in retort water, the NH4, HCOa", and organic compounds in the water clearly make it unsuitable for other uses (18). Of the trace constituents, the arsenic and selenium concentrations listed in Table IV are above the maximum permissible concentrations for drinking water (36). The boron concentration may make water unsuitable for irrigation (22). Other studies have found silver and lead concentrations in retort waters have exceeded the maximum permissible concentrations for drinking water (1,2,36). Numerous studies for the treatment of the retort water have been initiated (37). The objectives of these studies are usually to find a method to recover the ammonia and organic material from the water so that treatment costs will be lowered through by-product recovery. 

Arsenic contents measured in sediments are between 0.1 and 490 mg/kg while levels up to 1.5 g/kg were found in coals (average 13 mg/kg). The concentration of arsenic in seawater varies between 0.09 and 24 pg/L (average 1.5 pg/L), and in Ireshwater between 0.15 and 0.45 pg/L (maximum 1 mg/L). In mineral and thermal waters, arsenic was found in concentrations up to a factor of 300 higher than its mean concentration in groundwater [100]. The WHO recommends a maximum contaminant level for arsenic in drinking water 10 pg/L. 

In contrast to stream water, groundwater in the Warrior coalfield may have elevated arsenic concentrations. Waters produced during methane recovery from coal (n=28) were found to have a mean arsenic content of 25 ppb with a maximum of 475 ppb (O Neil et al., 1993). These production waters are typically saline and not potable. However, the presence of elevated arsenic in the deep groundwater samples indicates that arsenic may be mobilized from the coal into solution. Shallow drinking-water wells in the Warrior coalfield are lower in arsenic than the production waters, having a mean of 2 ppb and a maximum of 44 ppb (n=35)(0 Neil et al., 1993). The highest of these arsenic contents exceed the present drinking water standard and indicate the potential for at least isolated arsenic contamination. 

Trace amounts of arsenic occur in groundwater it may cause human cancers at concentrations in drinking water of about 300 ppb. The U.S. Environmental Protection Agency (EPA) has proposed lowering the maximum allowable arsenic concentration in U.S. drinking water from 50 to 5 ppb. The latter lower fimit is still controversial. 

The arsenic compounds are poisonous, especially As(III), causing chronical diseases. The maximum concentration of arsenic in drinking waters recommended by the World Health Organization is 0.05 mg 1 . ... 

The maximum permissible arsenic concentration in drinking water, ac-... 

REGULATORY STATUS Criterion to protect freshwater aquatic life 57 p/L/24 hr avg., concentration not to exceed 130 pg/L any time, total recoverable trivalent inorganic arsenic never to exceed 440 pg/L Criterion to protect saltwater aquatic life 29 pg/L/24 hr avg., concentration not to exceed 67 pg/L any time, 508 pg/L based on acute toxicity Criterion to protect human health maximum allowable level 50 pg/L, preferably concentrations calculated to keep the cancer nsk level below 10 10 ", and 10 are 0.02. 0.002, and 0.0002 pg/L respectively Maine has set a guideline in drinking water of 0.05 mg/L... 

Spurred by increasing concern about the adverse health effects from exposure to low levels of arsenic in drinking water (1), the U.S. Environmental Protection Agency (USEPA) has proposed lowering the Maximum Contaminant Level (MCL) for arsenic from 50 J,g/L down to 5 j,g/L (2). Total compliance costs for a regulation of 5 J,g/L have been estimated at 1.47 billion per year (3). 

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