PRINCIPLES OF TOXICOLOGY - Biology East Borneo

326 PROPERTIES AND EFFECTS OF METALSthe general environment, brought about by their mining, processing, commerce, and disposal byhumans, has resulted in higher background levels of metals in some areas where the general populationmay be exposed. In this chapter, properties and potential effects of both occupational and environmentalexposure to metals are discussed. Table 14.1 lists common uses and toxic effects of some selectedmetals.Essential and Nonessential MetalsA 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. Forexample, cobalt is a necessary component of vitamin B 12and is required for the production of redblood cells and the prevention of pernicious anemia. Copper is an essential component of severalenzymes and is necessary for the utilization of iron. Iron, in turn, is necessary for the production ofhemoglobin. Magnesium, manganese, and molybdenum are cofactors for a number of enzymaticreactions. Selenium is a component of the enzyme glutathione peroxidase. Zinc is a cofactor for morethan 100 metalloenzymes.Vanadium and tin are also considered essential in some animal species. Arsenic and chromium areregarded as essential at low doses to animals and humans, respectively, but also are considered to bemajor toxic concerns at higher exposure levels in some specific forms and are discussed in detail inSection 14.6 of this chapter.Nonessential metals are those metals that have no known beneficial role to play in biologicalfunction. These metals include beryllium, cadmium, lead, mercury, thallium, titanium, and uranium.TABLE 14.1 Common Uses and Principal Toxic Effects of Selected MetalsMetal Common Industrial Uses Principal Toxic EffectsAluminum Alloys, sheetmetal, appliances, foodpackagingEnvironmental exposures are relativelynontoxicArsenic Pesticides, herbicides, agricultural products Lung cancer, skin diseasesBeryllium Electronics, alloys, spacecraft Lung diseaseCadmium Batteries, plastics, pigments, plating Kidney damage, lung cancer, bone disordersChromium Plating, alloys, dyes, tanning Lung cancer (Cr 6+ ), respiratory effects,allergic dermatitisCobalt Alloys, paints, porcelain Environmental exposures are relativelynontoxicCopperElectrical wiring, water pipes, sheetmetal,alloysEnvironmental exposures are relativelynontoxicLead Batteries, wire and cable, alloys Neurological effects, hematopoietic systemdamage, reproductive effectsManganese Pesticides, ceramics, batteries, steel Central nervous system effectsMercury Chloralkali industry, pesticides,Neurological effects, kidney damagethermometers, batteriesNickel Coins, jewelry, alloys, plating, batteries Environmental exposures are relativelynontoxic; dermatitisThallium Electronics, alloys Neurological, heart, lung, kidney, and livereffectsTinPlastics, food packaging, pesticides, woodpreservativesInorganic tin is relatively nontoxic; organiccompounds—neurologicalTitanium Paints, alloys, ceramics, plastics Environmental exposures are relativelynontoxicZincBatteries, alloys, galvanizing, dyes,pharmaceuticalsGastrointestinal effects, anemia