Civil Engineering Reference
In-Depth Information
100 mg have been demonstrated to be lethal. Acute exposures at elevated concentra-
tions may cause nausea, vomiting, and diarrhea, whereas long-term exposure may
cause decreased longevity, decreased growth, or altered blood levels of glucose and
chlorestorol. There is inadequate evidence to define whether antimony has the potential
to cause cancer from lifetime exposures in drinking water.
Arsenic
Sources
Natural sources, such as the erosion of rocks, are thought to account for
most of the arsenic in surface and ground waters. Arsenic is present in the earth's
crust in concentrations averaging 2 mg / L. Erosion of arsenic-containing surface rocks
probably accounts for a significant amount of the arsenic in water supplies. It is con-
centrated in shales, clays, phosphorites, coals, sedimentary iron ore, and manganese
ores.
6
Industrial uses of arsenic include semiconductor manufacturing, petroleum re-
fining, wood preservatives, animal feed additives, and herbicides.
Occurrence
Arsenic is widely distributed across the United States in low concen-
trations in surface waters, as shown in Table 2-2. Except for local exceptions where
arsenic concentrations could be traced to specific causes, there are only minor regional
differences in the average values in surface waters or in the percentage of contaminated
samples.
Arsenic occurrence is highest in groundwater systems in the western United States
In 1985, EPA conducted a survey collecting 982 samples of groundwater. With
a detection level of 5
g / L, the survey found detectable concentration of arsenic
in 7 percent of 982 samples. Data collected from the 64 samples ranged from 5 to
48
g / L, with a mean of 13
g / L and a median of 9
g/L.
2
Health Effects
Arsenic can combine with other elements to form water-soluble ar-
senicals that are readily absorbed through the gastrointestinal tract, lungs, and skin.
Pentavalent arsenic, both organic and inorganic, is absorbed more readily than the
trivalent form. Arsenic primarily enters the liver, kidneys, intestinal wall, spleen, and
lungs.
Human exposure to arsenic of a sufficient concentration to cause poisoning is usu-
ally a result of ingestion of contaminated food or drink. Inorganic arsenite produces
rapid collapse, shock, and death. The major characteristics of acute poisoning are
TABLE 2-2. Regional Summary of Arsenic in U.S. Surface Waters
Maximum
g/L
Minimum
g/L
Median
g/L
Proportion,
10
g/L %
Proportion
10
g/L %
Region
New England
and Northeast
60
10
10
80
20
Southeast 1,110
10
10 70 30
Central 140
10
10 75 25
Southwest 10
10
10 87 13
Northwest 30
10
10 86 14
Source:
Durum, W. H., Hem, J. D., and Heidel, S. G. ''Reconnaissance of Selected Minor Elements in Surface
Waters of the United States,'' October 1970, U.S. Geological Survey Circular 643, Washington, DC, 1971.
