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Chapter: Basic & Clinical Pharmacology - Introduction to Toxicology: Occupational & Environmental

Metals - Specific Chemicals

Occupational and environmental poisoning with metals, metalloids, and metal compounds is a major health problem.

METALS

Occupational and environmental poisoning with metals, metalloids, and metal compounds is a major health problem. Exposure in the workplace is found in many industries, and exposure in the home and elsewhere in the nonoccupational environment is wide-spread. The classic metal poisons (arsenic, lead, and mercury) continue to be widely used. Occupational exposure and poisoning due to beryllium, cadmium, manganese, and uranium are relatively new occupational problems, which present new and previously unaddressed problems.

Beryllium

Beryllium (Be) is a light alkaline metal that confers special proper-ties on the alloys and ceramics in which it is incorporated. One attractive property of beryllium is its nonsparking quality, which makes it useful in such diverse applications as the manufacture of dental appliances and of nuclear weapons. Beryllium-copper alloys find use as components of computers, in the encasement of the first stage of nuclear weapons, in devices that require hardening such as missile ceramic nose cones, and in the space shuttle heat shield tiles. Because of the use of beryllium in dental appliances, dentists and dental appliance makers are often exposed to beryl-lium dust in toxic concentrations.

Beryllium is highly toxic by inhalation and is classified by IARC as a class 1, known human carcinogen. Inhalation of beryllium particles produces progressive pulmonary fibrosis and may lead to cancer. Skin disease also develops in workers over-exposed to beryllium. The pulmonary disease is called chronic beryllium disease (CBD) and is a chronic granulomatous pul-monary fibrosis. In the 5–15% of the population that is sensi-tive to beryllium, chronic beryllium disease is the result of activation of an autoimmune attack on the skin and lungs. The disease is progressive and may lead to severe disability and death. Although some treatment approaches to the manage-ment of chronic beryllium disease show promise, the prognosis is poor in most cases.

The current permissible exposure levels for beryllium of 0.01 mcg/m3 averaged over a 30-day period or 2 mcg/m3 over an 8-hour period are insufficiently protective to prevent chronic beryllium disease. Both NIOSH and the ACGIH have recom-mended that the PEL and TLV be reduced to 0.05 mcg/m3. These recommendations have not yet been implemented.

Environmental beryllium exposure is not generally thought to be a hazard to human health except in the vicinity of industrial sites where air, water and soil pollution have occurred.

Cadmium

Cadmium (Cd) is a transition metal widely used in industry. Workers are exposed to cadmium in the manufacture of nickel cadmium batteries, pigments, low-melting-point eutectic materi-als; in solder; in television phosphors; and in plating operations. It is also used extensively in semiconductors and in plastics as a sta-bilizer. Cadmium smelting is often done from residual dust fromlead smelting operations, and cadmium smelter workers often face both lead and cadmium toxicity.

Cadmium is toxic by inhalation and by ingestion. When met-als that have been plated with cadmium or welded with cadmium-containing materials are vaporized by the heat of torches or cutting implements, the fine dust and fumes released produce an acute respiratory disorder called cadmium fume fever. This disor-der, common in welders, is usually characterized by shaking chills, cough, fever, and malaise. Although it may produce pneumonia, it is usually transient. However, chronic exposure to cadmium dust produces a far more serious progressive pulmonary fibrosis. Cadmium also causes severe kidney damage, including renal fail-ure if exposure continues. Cadmium is a human carcinogen and is listed as a group 1, known human carcinogen by the IARC.The current OSHA PEL for cadmium is 5 mcg/m3. This PEL, considered by OSHA to be the lowest feasible limit for the dust, is insufficiently protective of worker health.


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