Mercury Cas No. 7439-97-6

Mercury

Cas No. 7439-97-6

Potential sources and exposure

Mercury (Hg) is an element that can occur naturally in the environment in

several forms. Elemental Hg is used in barometers, thermometers, batteries, and

paints. Mercury can combine with other chemicals in the environment, such as

chlorine, carbon, or oxygen to form "inorganic" or "organic" mercury

compounds. Compounds of Hg have been used as fungicides and preservatives.

Most human and ecological receptors are exposed to mercuric compounds that

have been produced by industrial sources. Human exposure is generally through

occupational exposure via inhalation of Hg vapors, dermal contact with mercuric

compounds, or nonoccupational ingestion of mercuric compounds in foods such

as fish that have high levels of methylmercury in their systems.

Physical and chemical properties

Property

Value

Molecular weight

200.59 g/mol (metallic)

0.002 mmHg at 25 oC

Vapor pressure

Toxicity

The route of exposure and the type of mercuric compound to which the

individual is exposed will determine the toxicity. The central nervous system is

the target system for Hg toxicity. Following acute exposures, several adverse

neurological effects have been noted in humans, including tremors, decreases in

motor function, and headaches. These acute effects may be reversible. Elemental

mercury is not highly toxic as an acute poison, although inhalation of high

concentrations of mercury vapor for relatively short duration can cause

bronchitis, chest pains, dyspnea, coughing, salivation, and diarrhea. Mercury

compounds are primary skin irritants and may cause dermatitis on contact.

Exposures to chronic low doses of the Hg vapor can result in short-term memory

deficits, decreased nerve conduction, and visual disturbances. Long-term effects

may also include memory loss, hallucination, and mental deterioration.

The reference dose for inhalation of elemental Hg is based on subchronic

human studies in which a NOAEL of 0.009 was observed for neurological

effects. The oral RfD is based upon a subchronic exposure to rats in which

immunological effects were observed at the lowest LOAEL.

The USEPA has classified mercury as a Class D carcinogen based upon the

lack of human data and inadequate animal data.

D48

Appendix D Toxicological Profiles