Biological effects of lead

The half-life of lead in humans is estimated to be about 6 years for the whole body burden and from 15 to 20 years for skeleton. Thus, an excretion from the skeleton is very slow. Lead, like mercury, is a cumulative poison. The skeletal burdens of lead increase almost linearly with age. This suggests that the Pb steady state is not 

like mercury, causes neurological diseases. The organolead compounds are more toxic than mineral lead salts, since they are non-polar, lipid-soluble, and more readily cross the blood-brain barrier. This disease is related to mental retardation is children, lower performance on I.Q. tests, and hyperactivity. Severe exposure in adults causes irritability, sleeplessness, and irrational behavior. Some have gone as far as to blame anti-social behavior and criminality on sub-clinical Pb poisoning. A correlation between Pb in blood and Pb in air, dust and soils has been observed in many studies. The U.S. Centers for Disease Control has proclaimed a goal of reducing blood lead contents in children below 10 jag/lOOmL. 

Lead is a well-known poison, but the effects of exposure to lower levels have been contentious. There is growing evidence of sub-clinical Pb poisoning, especially among young children who play in polluted parks, gardens and streets. Contaminated soil or dust particles may be transferred to children s hands and ingested accidentally. Humans are exposed to Pd from various sources and road dust and soils can contribute to the total lead exposure. Approximately one half of lead ingested in food is absorbed. 

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Alessio L, Bertazzi PA, Monelli O, et al. 1976. Free erythrocyte protoporphyrin as an indicator of the biological effect of lead in adult males II. Comparison between free erythrocyte protoporphyrin and other indicators of effect. Int Arch Occup Environ Health 37 89-105. 

Krasovskii GN, Vasukovich LY, Chariev OG. 1979. Experimental study of biological effects of lead and aluminum following oral administration. Environ Health Perspect 30 47-51. 

Odone P, Castoldi MR, Guercilena S, et al. 1979. Erythrocyte zinc protoporphyrin as an indicator of the biological effect of lead in adults and children. In International Conference on Management and Control of Heavy Metals in the Environment, London, United Kingdom, September. Edinburgh, UK CEP Consultants, Ltd., 66-69. 

Aronson, A.L. 1971. Biologic effects of lead in fish. Jour. Wash. Acad. Sci. 61 124-128. 

Young children are especially susceptible to the effects of environmental lead, first because their bodies accumulate lead more readily than do those of adults and, second, because they appear to be more vulnerable to certain of the biological effects of lead. In 1988 the US Public Health Service estimated that, in the United States alone, 12 million children were exposed to leaded paint, 5.6 million to leaded gasoline, 5.9-11 million to dusts and soils containing excessive lead, 10.4 million to lead in water (in part because of lead in pipe solders) and 1.0 million to lead in food. The Public Health Service also... 

Cohen D], Johnson WT, Capamlo BK Pica and elevated blood lead level in autistic and atypical children. American Journal of Diseases of Children 130 47-48, 1976 Committee on Biologic Effects of Atmospheric Pollutants Biologic effects of lead in man, in Lead Airborne Lead in Perspective. Edited by Committee on Biologic Effects of Atmospheric Pollutants. Washington, DC, National Academy of Sciences, 1972, pp 71-313... 

One form of biological poisoning mirrors the effect of lead on a catalytic converter. The activity of an enzyme is destroyed if an alien substrate attaches too strongly to the enzyme s active site, because then the site is blocked and made unavailable to the true substrate (Fig. 13.42). As a result, the chain of biochemical reactions in the cell stops, and the cell dies. The action of nerve gases is believed to stem from their ability to block the enzyme-controlled reactions that allow impulses to travel through nerves. Arsenic, that favorite of fictional poisoners, acts in a similar way. After ingestion as As(V) in the form of arsenate ions (As043 ), it is reduced to As(III), which binds to enzymes and inhibits their action. 

Berg S, Jonsson A. 1984. Analysis of airborne organic lead. In Grandjean P, ed. Biological effects of organolead compounds. Boca Raton, FL CRC Press, 33-42. 

NAS. 1972. Lead Airborne lead in perspective Biologic effects of atmospheric pollutants. Washington, DC National Academy of Sciences, 71-177, 281-313. 

Committee on Biologic Effects of Atmospheric Pollutants, Division of Medical Sciences, National Research Council Lead— Airborne Lead in Perspective. Washington, DC, National Academy of Sciences, 1972... 

These large differences in energy distribution, at the microscopic level, between radiation qualities at equal absorbed dose, produce different biological effects this leads to the concept of RBE. 

Chau, Y. K., Wong P. T. S. Organie lead in the aquatic Environment, in Biological Effects of Organolead Compounds (ed.) Grandjean, P., p. 22, Boca Raton, Florida, CRC Press, Inc. 1984... 

Tolerance is the modification of the biological effect of a chemical as a result of repeated dosing. For example, repeated dosing with phenobarbital leads to a decrease in the anesthetic effect of the drug as a result of enzyme induction. Giving animals a small dose of carbon tetrachloride renders a second larger dose less toxic. This may be a result of induction of repair processes and destruction of cytochrome P-450 caused by the small first dose. 

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