Elemental beryllium and its salts are highly toxic, and immunotoxicity represents the greatest risk factor in industrial exposure. In beryllium-using industries (metal extraction, refining and machining, electronics, nuclear weapons manufacture, aerospace, and high-tech ceramics), inhalation of dust containing the metal triggers an immune reaction, potentially resulting in a condition termed chronic beryllium disease (CBD), with a prevalence of 2-5% in beryllium-exposed individuals (1,2).
Having a small atomic and ionic radius (1.11/0.31 A for Be/Be2+, respectively), beryllium can fit into positions on the surface of macromolecules too small for most other atoms; and its capacity for forming strong covalent bonds that displace other divalent cations may be the basis for its toxicity. Highly reactive with protein substrate, it is strongly retained by tissues and difficult to remo-bilize as its cytotoxicity interdicts normal phagocyte action (3-5). Albeit an alkaline earth element, beryllium can exist in the form of positive or negative ions depending on the pH of the environment (existing, respectively, as Be2+ or Be(OH)42~ in acidic and basic conditions). Over the pH range 4-8, Be compounds contacting the skin, lungs or lower GI tract typically decompose to form the poorly soluble, amorphous oxide BeO or hydroxide Be(OH)2, both of which are involved in granuloma formation. Once lodged in tissue, these amorphous beryllium precipitates are very slowly excreted, with granulomas persisting as long as the metal remains present. As a rule, removal is only accomplished by excision.
Major areas of concern regarding beryllium-related diseases and the ques- o tions still to be answered were the object of a conference in 1994 (6). From the |
review of several longitudinal data and population-based studies it became evident that, following exposure, beryllium disease progresses in discrete stages that in turn seem to depend on individual predisposition. Sensitization in individuals |
suspected of beryllium exposure, not necessarily showing symptoms or prog-
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