Microsoft Word - WaterChemistry

269

Radioactive metals have both radiological toxicity and chemical toxicity. Metals in an
oxidation state abnormal to the body may also become toxic: chromium (III) is an essential
trace element, but chromium (VI) is a carcinogen.

Toxicity is a function of solubility. Insoluble compounds as well as the metallic forms often
exhibit negligible toxicity. The toxicity of any metal depends on its ligands. In some cases,
organometallic forms, such as dimethyl mercury and tetraethyl lead, can be extremely
toxic. In other cases, organometallic derivatives are less toxic such as the cobaltocenium
cation.

Decontamination for toxic metals is different from organic toxins: because toxic metals are
elements, they cannot be destroyed. Toxic metals may be made insoluble or collected,
possibly by the aid of chelating agents. Toxic metals can bioaccumulate in the body and
in the food chain. Therefore, a common characteristic of toxic metals is the chronic nature
of their toxicity. This is particularly notable with radioactive heavy metals such as thorium,
which imitates calcium to the point of being incorporated into human bone, although similar
health implications are found in lead or mercury poisoning. The exceptions to this are
barium and aluminum, which can be removed efficiently by the kidneys.

Toxic Heavy Metals

 Antimony (a metalloid)

 Arsenic is a metalloid

 Barium

 Beryllium

 Cadmium - cadmium poisoning

 Lead - lead poisoning

 Mercury - mercury poisoning

 Osmium

 Thallium

 Vanadium

 Radioactive metals:

o Actinium

o Thorium

o Uranium

o Radium

o The transuraniums, such as plutonium, americium, etc.

o Polonium

o Radioactive isotopes of metallic elements not otherwise strongly toxic, e.g.

cobalt-60 and strontium-90.

Aluminum has no biological role and its classification into toxic metals is controversial.
Significant toxic effects and accumulation to tissues have been observed in renally
impaired patients. However, individuals with healthy kidneys can be exposed to large
amounts of aluminum with no ill effects. Thus, aluminum is not considered dangerous to
persons with normal elimination capacity.