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INTRODUCTION

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The diverse physical properties of metals have resulted in their extensive use in industry. These naturally occurring materials have long been recognized for their ability to impart a variety of valuable characteristics to finished goods. Metals are used in the construction, automotive, aerospace, electronics, glass, and other manufacturing industries. Metals are major sources of pigments and stabilizers for paints and plastics. Metals are also used as catalysts and intermediates in the chemical and pharmaceutical industries. Metals may be emitted as contaminants or by-products from industrial operations and power generation, and these have become the major sources of ongoing environmental contamination.

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Metals are used rarely in their pure form, usually being present in alloys. They also may be bound to organic materials, altering their physical characteristics and potential toxicity. Some compounds, such as hydrides and carbonyls, are highly toxic and may be formed accidentally when the parent metal reacts with acids. Metals may be altered by burning and smelting or after uptake by biologic systems. The chemical structure of the metal or organometallic compound alters absorption, distribution, and toxicity.

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Metals exert biologic effects chiefly through the formation of stable complexes with sulfhydryl groups, altering the structure and function of many proteins and enzyme systems. Certain metals, such as zinc, chromium, and manganese, are essential for normal metabolism. Others, such as lead, mercury, and arsenic, serve no recognized biologic purpose, raising public health concerns owing to their ubiquitous presence in living organisms. Understanding and eliminating health risks from low-level background exposures remains a top priority in environmental health.

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General population exposure to many metals is related primarily to air, water, and food contamination. Background exposures vary considerably around the world owing to natural occurrence in soil and groundwater, as well as pollution from industrial operations, automotive exhaust, and power generation. Familiarity with the potential health effects of metals in different settings is critical not only for the health and safety professional but also for the general medical practitioner.

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ACUTE METAL TOXICITY

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Acute toxicity usually occurs after ingestion of metal-­containing compounds or inhalation of high concentrations of metal dusts or fumes. These can arise from improperly ventilated burning or welding operations or from unexpected chemical reactions. Home ­remodeling activities can generate dust from paint pigments, ­particularly lead. This and ingestion of paint chips (pica) are important causes of childhood poisoning. Familiarity with the symptoms of acute heavy metal poisoning, along with an awareness of the potential sources of exposure, is critical for rapid detection and treatment. The levels of most metals can be measured in blood or urine to confirm the diagnosis and guide therapy.

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CHRONIC METAL TOXICITY

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Research into the health effects of low-level exposure to metals indicates that physiologic alterations occur at levels that have been considered safe previously. The evidence for neurotoxicity, circulatory effects, nephrotoxicity, reproductive toxicity, ...

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