About Water Quality
Inorganic ContaminantsArsenicAntimonyAsbestosBariumBeryllium232CadmiumChromiumCopper CyanideFluorideLeadlead
Organic Contaminants (VOCS)BenzeneCarbon
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IN DRINKING WATER
may be found in water which has flowed through arsenic-rich rocks. Severe health
effects have been observed in populations drinking arsenic-rich water over long
periods in countries world-wide.
- Arsenic is
widely distributed throughout the earth's crust.
is introduced into water through the dissolution of minerals and ores, and concentrations
in groundwater in some areas are elevated as a result of erosion from local rocks.
effluents also contribute arsenic to water in some areas.
is also used commercially e.g. in alloying agents and wood preservatives.
of fossil fuels is a source of arsenic in the environment through disperse atmospheric
arsenic can occur in the environment in several forms but in natural waters, and
thus in drinking-water, it is mostly found as trivalent arsenite (As(III)) or
pentavalent arsenate (As (V)). Organic arsenic species, abundant in seafood, are
very much less harmful to health, and are readily eliminated by the body.
poses the greatest threat to public health from arsenic. Exposure at work and
mining and industrial emissions may also be significant locally.
- Chronic arsenic
poisoning, as occurs after long-term exposure through drinking- water is very
different to acute poisoning. Immediate symptoms on an acute poisoning typically
include vomiting, oesophageal and abdominal pain, and bloody "rice water" diarrhoea.
Chelation therapy may be effective in acute poisoning but should not be used against
symptoms and signs that arsenic causes, appear to differ between individuals,
population groups and geographic areas. Thus, there is no universal definition
of the disease caused by arsenic. This complicates the assessment of the burden
on health of arsenic. Similarly, there is no method to identify those cases of
internal cancer that were caused by arsenic from cancers induced by other factors.
exposure to arsenic via drinking-water causes cancer of the skin, lungs, urinary
bladder, and kidney, as well as other skin changes such as pigmentation changes
and thickening (hyperkeratosis).
risks of lung and bladder cancer and of arsenic-associated skin lesions have been
observed at drinking-water arsenic concentrations of less than 0.05 mg/L.
of arsenic through the skin is minimal and thus hand-washing, bathing, laundry,
etc. with water containing arsenic do not pose human health risk.
long-term exposure, the first changes are usually observed in the skin: pigmentation
changes, and then hyperkeratosis. Cancer is a late phenomenon, and usually takes
more than 10 years to develop.
relationship between arsenic exposure and other health effects is not clear-cut.
For example, some studies have reported hypertensive and cardiovascular disease,
diabetes and reproductive effects.
to arsenic via drinking-water has been shown to cause a severe disease of blood
vessels leading to gangrene in China (Province of Taiwan), known as ‘black foot
disease? This disease has not been observed in other parts of the world, and
it is possible that malnutrition contributes to its development. However, studies
in several countries have demonstrated that arsenic causes other, less severe
forms of peripheral vascular disease.
to some estimates, arsenic in drinking-water will cause 200,000 ?270,000 deaths
from cancer in Bangladesh alone (NRC, 1998; Smith, et al, 2000).
for drinking-water quality, 2nd
World Health Organization, 1996.