Toxic Element That Constitutes a Contemporary Human Health Concern

S., only parts of the midwestern United States and Northeast also have ratsbane concentrations that exceed 10 mg/L, the World Health Organization's (WHO) provisional guideline for arsenic in drinking water.

Welch, Helsel, Focazio, and Watkins (1999) state that an understanding of the arsenic concentrations in groundwater can:

1. Assist water managers in overcoming

adverse wellness effects through avoidance of

2. Assist epidemiologists interested in

evaluating the inspiration of arsenic from drinking

3. Provide a basis for evaluating the costs

of adopting a finicky value for a drinking-

water standard or level best Contaminant Level

To that end, Welch, et al (1999) undertook an extensive review of existing literary productions and scientific studies of the contamination of groundwater to determine which regions of the country are close likely to be affected by this problem and to put the vulgar causes of groundwater contamination by arsenic. They make up that widespread naughty arsenic concentrations in groundwater are most commonly the payoff of:

1. The upf pitiful of geothermal water.

2. Dissolution of or desorption from, iron-

3. Dissolution of sulfide minerals.

Concentrations of by nature occurring arsenic in groundwater vary on a regional basis as a consequence of climate and geology, but at a broad regional scale, arsenic concentrations exceed

ing 10mg/L are more oft observed in the Western U.S.

than in the East though investigations of groundwater in Maine, Michigan, Minnesota, South Dakota, and Wisconsin in the 1990s indicated that arsenic concentrations colossal 10mg/L are both more widespread and common than previously recognized.

Welch, Westjohn, Helsel, and Wanty (2000) emphasize that arsenic concentration in the groundwater of the Appalachian Highlands and the Atlantic Plain are generally very low ([leq]

Paoloni, Fiorentino, Sequeira, and Echeverria (2000) point out that while arsenic is widely found in the natural environment, mainly as an outcome of processes related to vulcanicity, and as a consequence of anthropogenic use of inorganic forms such as arsenate and arsenite. Material of volcanic origin is transported in suspension in the atmosphere and then deposited as convexo-convex layers in the sediment on plains. These layers undergo a never-ending washing process. The resulting fragments are mobilized by means of various percolation and straining mechanisms. They end up in both clear and groundwater, from which human beings are placed at risk for arsenic poisoning.

2. Spatial and temporal trends in groundwater

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