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 (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 (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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