PRINCIPLES OF TOXICOLOGY

326 PROPERTIES AND EFFECTS OF METALS
the general environment, brought about by their mining, processing, commerce, and disposal by
humans, has resulted in higher background levels of metals in some areas where the general population
may be exposed. In this chapter, properties and potential effects of both occupational and environmental
exposure to metals are discussed. Table 14.1 lists common uses and toxic effects of some selected
metals.
Essential and Nonessential Metals
A number of metals have important biological roles and thus are considered essential for good health.
Nevertheless, at sufficient concentrations, a number of these essential metals are potentially toxic. For
example, cobalt is a necessary component of vitamin B 12 and is required for the production of red
blood cells and the prevention of pernicious anemia. Copper is an essential component of several
enzymes and is necessary for the utilization of iron. Iron, in turn, is necessary for the production of
hemoglobin. Magnesium, manganese, and molybdenum are cofactors for a number of enzymatic
reactions. Selenium is a component of the enzyme glutathione peroxidase. Zinc is a cofactor for more
than 100 metalloenzymes.
Vanadium and tin are also considered essential in some animal species. Arsenic and chromium are
regarded as essential at low doses to animals and humans, respectively, but also are considered to be
major toxic concerns at higher exposure levels in some specific forms and are discussed in detail in
Section 14.6 of this chapter.
Nonessential metals are those metals that have no known beneficial role to play in biological
function. These metals include beryllium, cadmium, lead, mercury, thallium, titanium, and uranium.
TABLE 14.1 Common Uses and Principal Toxic Effects of Selected Metals
Metal Common Industrial Uses Principal Toxic Effects
Aluminum Alloys, sheetmetal, appliances, food Environmental exposures are relatively
packaging
nontoxic
Arsenic Pesticides, herbicides, agricultural products Lung cancer, skin diseases
Beryllium Electronics, alloys, spacecraft Lung disease
Cadmium Batteries, plastics, pigments, plating Kidney damage, lung cancer, bone disorders
Chromium Plating, alloys, dyes, tanning Lung cancer (Cr 6+ ), respiratory effects,
allergic dermatitis
Cobalt Alloys, paints, porcelain Environmental exposures are relatively
nontoxic
Copper Electrical wiring, water pipes, sheetmetal, Environmental exposures are relatively
alloys
nontoxic
Lead Batteries, wire and cable, alloys Neurological effects, hematopoietic system
damage, reproductive effects
Manganese Pesticides, ceramics, batteries, steel Central nervous system effects
Mercury Chloralkali industry, pesticides,
thermometers, batteries
Neurological effects, kidney damage
Nickel Coins, jewelry, alloys, plating, batteries Environmental exposures are relatively
nontoxic; dermatitis
Thallium Electronics, alloys Neurological, heart, lung, kidney, and liver
effects
Tin Plastics, food packaging, pesticides, wood Inorganic tin is relatively nontoxic; organic
preservatives
compounds—neurological
Titanium Paints, alloys, ceramics, plastics Environmental exposures are relatively
nontoxic
Zinc Batteries, alloys, galvanizing, dyes,
pharmaceuticals
Gastrointestinal effects, anemia