Toxicokinetics - trdoer40161

cancer was observed in Taiwanese and Chilean populations exposed to arsenic

in drinking water (IRIS 1999).

Toxicokinetics

Arsenic (trivalent or pentavalent insoluble forms) is well absorbed from the

gastrointestinal tract. Limited data suggest nearly complete absorption of soluble

forms of trivalent and pentavalent arsenic. Deposition of arsenic in the airway is

dependent on particle size and chemical form. Excretion of absorbed arsenic is

mainly via the urine. Arsenic has a predilection for the skin and is excreted by

desquamation of skin and in sweat, particularly during periods of profuse

sweating. It also concentrates in nails and hair. Dimethyl arsenic is the principal

detoxication product (Klaassen, Amdur, and Doull 1995).

Ecological effects

Bioaccumulation. Arsenic is neither a major contaminant of aquatic plants

nor does it normally concentrate in either freshwater or marine fish. Only in

extreme cases of ambient pollution does it contaminate aquatic plants and there

are few reports of tissue residues exceeding health guidelines in fish. However,

some reports do demonstrate rather high levels in invertebrates, for example,

exceeding 30 mg/kg.

Toxic effects to aquatic organisms. Although insufficient data exist to

determine the definitive acute toxicity to organisms, fresh or marine, work on the

topic indicates that large doses of arsenic (greater than 1 mg As/L) are required

to induce acute toxic effects in both plants and invertebrates. Chronic effects for

both invertebrates and fish exposed to inorganic arsenic have been reported and

require a relatively large dose, typically > 5 mg As/L.

Toxic effects to wildlife (tertiary). To be absorbed by terrestrial plants,

arsenic compounds must be in a mobile form in the soil. Unless located in an

area where arsenic concentrations are exceptionally high, plants will distribute

accumulated arsenic in nontoxic amounts throughout the plant body. Most plants

will yield significantly less of a crop when concentrations become 3 to 28 mg/L

of water soluble arsenic and 25 to 85 mg/kg of total arsenic. Air concentrations

up to 3.9 Fg As/m3 have also been seen to have adverse effects on vegetation.

Effects on soil biota and insects remain limited, but generally it is believed

that soil microorganisms are capable of tolerating relatively high concentrations

of arsenic.

In birds, signs of inorganic trivalent arsenite poisoning include muscular

uncoordination, debility, slowness, jerkiness, falling hyperactivity, fluffed

feathers, drooped eyelid, huddled position, immobility, and seizures. Studies

suggest that lethal acute inorganic arsenic poisoning results in the destruction of

blood vessels lining the gut, thereby causing decreased blood pressure and

subsequent shock.

Appendix D Toxicological Profiles