The principal route of exposure to arsenic for the general population
is likely to be the oral route, and exposure to arsenic from
other pathways is generally small, but may be significant for areas
with high levels of arsenic contamination particularly in occupational
settings. Increased risk of lung cancer, respiratory irritation,
nausea, skin effects, and neurological effects have been reported
following inhalation exposure [39]. Human data suggest that
dermal or respiratory effects may be the most prevalent [40,41];
respiratory or immunological effects appeared to be the most
common following inhalation exposure to inorganic arsenic in
animals [42]. In occupational settings, only small amounts of
arsenic will be absorbed through the dermal route, so this is usually
not a source of concern. However, typical dermal effects that may
follow both oral and dermal exposure include hyperkeratinization
of the skin (especially on the palms and soles), formation of multiple
hyperkeratinized corns or warts, and hyperpigmentation of
the skin with interspersed spots of hypopigmentation. Arsenic is a
known human carcinogen by both inhalation and oral exposure
routes [39]. By the inhalation route, the primary tumor types are
respiratory system cancers, although a few reports have noted
increased incidence of tumors at other sites, including the liver,
skin, and digestive tract [39]. The mean arsenic urine concentration
of 40 mg/L detected in urine samples from paint factory workers
was 20 times higher than that found in nonfactory workers (2 mg/L).
The urinary excretion of arsenic appears to account for 30e60% of
the inhaled dose [42]; this suggests that nearly all arsenic that is
deposited in the lung is excreted in the urine.We can thus infer that
paint factory workers may be exposed to as high as 20 times more
arsenic than the general population. The time course of excretion in
humans exposed by inhalation has not been thoroughly investigated,
but urinary arsenic levels in workers in a smelter rose within
hours after they came to work on Monday and then fell over the