Lead poisoning mechanisms

Labbe RF. Lead poisoning mechanisms. Clin Chem 1990 36 1870-1. 

Lead is a toxic metal and rigid precautions against lead poisoning are essential. Sprayed lead is, like other sprayed metals, porous, and the sprayed layers will not as a rule withstand attack by strong acids. On the other hand, lead from 0-13 to 0-25 mm (0-005 to 0-01 in) in thickness has proved extremely useful in atmospheres containing sulphuric acid. In this case the pores in the lead become blocked with lead sulphate, with the result that complete protection is assured. In the event of mechanical breakdown, lead does not exhibit any sacrificial action and therefore corrosion may lift the lead layer. 

Goldman RH, Baker EL, Hannan M, et al. 1987. Lead poisoning in automobile radiator mechanics. N Engl J Med 317 214-218. 

Cooper, B. J., Renny, L. V., and White, R. J., Lead Poisoning of Automobile Emission Control Catalysts—Influence of Emission System and Catalyst Design Characteristics on the Poisoning Mechanism, Am. Chem. Soc.. Symp. Automot. Catal., Chicago Meet., 1975. 

Lead-Poisoned Pd-CaCQs (Lindlar Catalyst))82 Palladium chloride (1.48 g, 0.0083 mol) is placed in a 10-ml Erlenmeyer flask, and 3.6 ml (0.043 mol) of 37% hydrochloric acid is added. The flask is shaken at about 30°C until the palladium chloride is dissolved. The chloropalladic acid solution is transferred to a 150-ml beaker with 45 ml of distilled water. The pH of the solution is brought to 4.0-4.5 by slow addition of aqueous 3M sodium hydroxide. The solution is diluted to approximately 100 ml and placed in a 200- or 250-ml three-necked, round-bottomed flask equipped with a mechanical stirrer and a thermometer. Precipitated calcium carbonate (18 g) is added. The well-stirred suspension is heated to 75-85°C and held... 

The tris(mercaptoimidazolyl) ligand TmAr has been employed to emulate the coordination environment of 5-aminolevulinate dehydratase (ALAD). Several ZnX(TmAr) have been described145-147 that also have helped in the knowledge of the mechanism of action of ALAD. To study the lead poisoning that is associated with lead interaction with ALAD, PbX(TmAr) complexes have been also reported.148... 

Lead poisoning can be treated by chelation therapy using CaNa2(EDTA) (acute) or penicillamine (chronic). Although both Cd(II) and Pb(II) bind to sulfhydryl groups in thionein, we have little information at the molecular level on the mechanisms by which these elements induce toxicity. 

The well known toxic effects of alcohol appear to be ameliorated by the administration of vitamin C which plays a role in hepatic detoxification mechanisms by contributing to the oxidising cytochrome P450 system. Perhaps the gin and tonic imbibers should be advised to resume the now outmoded gin and orange in order that the latter may help to counter the after effects of the former The vitamin has also been used in treating lead poisoning but carefully controlled trials showed no effect of ascorbate in reducing heavy metals in hair. 

Catalyst deactivation from a poisoning mechanism was most severe when lead alone was present in the fuel. Hence lead in the fuel may be... 

The result common to aU the studies discussed above, both the historical sediment records and the studies examined by Thomas et al. (20), is the dramatic decrease in lead deposition in the past 15 years (7, 8, 15, 33, 417, 419 30). Whether the drop is attributable mainly to decreased gasoline emissions or to a combination of decreases in automobile, industrial, and other emissions, the existence of the trend is unambiguous. The large quantities of anthropogenic lead already in the environment, though, require continued attention. The remediation of contaminated soil and water, the treatment of lead poisoning, and the elucidation of the mechanisms of lead toxicity are all areas in which a firm understanding of the fundamental chemistry of lead complexes can contribute dramatically. 

Despite the prevalence of lead poisoning and the seriousness of the health problems associated with lead poisoning, many fundamental questions about the mechanism of lead poisoning still remain unanswered (29). These include... 

Thus, it is clear that the impairment of heme synthesis by lead exposure occurs at relatively low BLLs and that increased concentrations of ALA and protoporphyrin are associated with lead exposure. However, it is not widely recognized that the inhibition of heme synthesis cannot fully explain the anemia of lead poisoning. The elegant work of Piomelli et al. (1975) has demonstrated that even in patients with BBLs over 90 pg/dL, erythrocytes contain roughly 300 molecules of heme for every molecule of free protoporphyrin. Thus, other molecular mechanisms must play more important roles in the etiology of the anemia. 

Lead is often associated with an iron deficiency. When lead poisoning patients are iron deficient, they absorb more lead. Also, there may be similar mechanisms by which iron deficiency and lead affect growing cells, including brain cells. ... 

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