Arsenic - Toxicology of Metals - page 359

coupled to ICP (Sheppard et al ., 1992). In this tech-
nique, the IC separates the species of arsenic before
the introduction into the ICP-MS (or other detection
method). This allows for the automation of the specia-
tion method(s) for the different matrices. The method
most used for speciation of the various arsenic species
is high-performance liquid chromatography (HPLC)
in various forms. Arsenic(III), As(V), monomethylar-
sonic acid (MMAA), dimethylarsinic acid (DMAA),
and arsenobetaine (AsB) are separated by HPLC and
determined on-line by inductively coupled plasma
mass spectrometry (ICP-MS). Two forms of HPLC may
be used: ion pairing and ion exchange, with absolute
detection limits for arsenic ranging between 50 and
300 pg (Beauchemin et al ., 1989). An ICP-MS detector in
combination with HPLC has been used for the analysis
of six arsenic compounds with detection limits for
arsenic species in the range from 10-30 pg. (Demesmay
et al ., 1994).
Methods and problems of arsenic analysis, includ-
ing speciation in various matrices, have been reviewed
by Braman (1977, 1983), Brinckman et al . (1977), Hung
et al . (2004), Munoz and Palmero (2005), Gong et al .
(2002), and Rose et al . (2001).

3.2 Uses
Arsenic was known as a therapeutic agent as early
as 400 BC and has since been widely used as such. From
the 19th century onward, an inorganic arsenic com-
pound known as Fowler's solution (liquor arsenicalis
B.P. 1963, arsenite solution containing 7.6 g As/L) has
been used for the treatment of leukemia, psoriasis, and
chronic bronchial asthma, and organic arsenic com-
pounds have been extensively used in the treatment
of spirochetal and protozoal disease (Martindale, 1977;
NRC, 1999). Many countries have now banned the use
of Fowler's solution. Recently, there has been reported
use of arsenic trioxide in the treatment of acute promy-
elocytic leukemia (APL) (Gallagher, 1998; Wang, 2001).
The major current uses of arsenic are in pesticides
(e.g., lead arsenate, calcium arsenate, and sodium
arsenite), herbicides (e.g., monosodium arsenate and
cacodylic acid [dimethylarsinic acid]); cotton desic-
cants (e.g., arsenic acid); and wood preservatives
(e.g., copper chromium arsenate). Arsenic is also used
as a bronzing or decolorizing agent in the manufacture
of glass and in the fabrication of opal glass and enam-
els. It has also been used in the manufacture of dye-
stuffs and chemical warfare gases and is still used in
the purifi cation of industrial gases (removal of sulfur).
Elemental arsenic is used as an additive in the produc-
tion of several alloys to increase hardness and heat
resistance. In the livestock industry, organic arseni-
cal is sometimes added to swine and poultry feed as
antimicrobial medicine. In 1999-2000, approximately
70% of the broiler industry added roxarsone to broiler
poultry feed (Garbarino et al ., 2003). Recently, gallium
arsenide and indium arsenide, artifi cial crystals, have
become important materials in semiconductors, solar
cells, and space research (Brooks, 2005; IARC, 2006;
Yamauchi et al ., 1992).

3 PRODUCTION AND USES

3.1 Production
Arsenic is widely distributed in the earth's crust,
which contains about 3.4 ppm arsenic (Wedepohl, 1991).
It usually exists in nature in sulfi de ores. Arsenopyrite
is by far the most common arsenic-containing mineral.
There are more than 150 arsenic-bearing minerals
(Budavari et al ., 2001; Carapella, 1992). Arsenic tri-
oxide (white arsenic) is principally obtained as a by-
product in the smelting of copper, lead, or gold ores.
When these ores are smelted, the arsenic becomes
gaseous and is trapped by electrostatic precipita-
tors as a crude dust that is then roasted, whereby the
arsenic trioxide is driven off. The purifi ed arsenic
trioxide is collected in a cooling chamber. The prin-
cipal impurity is Sb 2 O 3 (Pinto and McGill, 1953).
Most commercially available arsenic compounds are
produced from arsenic trioxide. The average annual
world production of arsenic on the basis of limited
data (1975-1977) was approximately 60,000 tons, and
this production seems to be stable (WHO, 1981). In
2003, China was the world leader in the production
of commercial-grade arsenic, followed by Chile and
Peru (Brooks, 2003). The United States is the world's
leading consumer of arsenic; however, the United
States ceased production in 1985.

4 ENVIRONMENTAL LEVELS
AND EXPOSURES

4.1 Food and Daily Intake
With the exception of some kinds of fi sh, crusta-
ceans, and seaweed, most food contains low levels
of arsenic, normally below 0.25 mg/kg (Jelinek and
Corneliussen, 1977). The degree of arsenic uptake in
plants is apparently related to the concentration of
soluble arsenic in the soil, the chemical composition
of the soil, and plant species (Walsh et al ., 1977). Sur-
face contamination with insecticides may increase the
concentrations of arsenic in plants. Extensive lists of
arsenic concentrations in foodstuffs have been pub-
lished by the National Academy of Sciences (NRC,