Chelation therapy in workers exposed to lead. A critical review

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Abstract
Oral prophylactic treatment with chelating agents such as edetate disodium calcium or penicillamine is contraindicated for the prevention of Pb poisoning in workers exposed to Pb. Among the reasons are the poor absorption of edetate disodium calcium from the gastrointestinal tract, the concomitant possible increased absorption of ingested Pb, and the unsatisfactory effect of oral administration of edetate disodium calcium on blood Pb, urinary coproporphyrin and .delta.-amino levulinic acid indicating a failure to prevent adverse metabolic effects. These constraints explain the repeated failures of oral chelation therapy with symptomatic Pb poisoning developing in some workers despite the prophylactic treatment. The effect of long-term chelation therapy on serum Fe, Cu, Mg and Zn levels and the probable interference with metal-dependent enzymatic activity adds to the disadvantage of this treatment, as do the side effects of penicillamine, such as renal damage, leukopenia, agranulocytosis, eosinophilia and decreased serum Fe levels. Alteration of bilogical measurements used to estimate the current extent of absorption of Pb by individuals occupationally exposed occurs and is bound to make the clinical management of Pb disease more difficult and confused. Adequate control of occupational Pb exposure cannot and should not be replaced by inappropriate and potentially hazardous attempts at prophylactic treatment.