Uptake of lead

Loaec M, Olier R, Guezennec J (1997) Uptake of lead, cadmium and zinc by a novel bacterial expolysaccharide. Wat Res 31 1171... 

The Leggett Model simulates lead biokinetics in liver with two compartments the first simulates rapid uptake of lead from plasma and a relatively short removal half-life (days) for transfers to plasma and to the small intestine by biliary secretion a second compartment simulates a more gradual transfer to plasma of approximately 10% of lead uptake in liver. Different transfer rates associated with each compartment are calibrated to reproduce patterns of uptake and retention of lead observed in humans, baboons, and beagles following intravenous injection, as well as blood-to-liver concentration ratios from data on chronically exposed humans. Similarly, the Leggett Model simulates lead biokinetics in three compartments of soft tissues, representing rapid, intermediate, and slow turnover rates (without specific physiologic correlates). 

Dietary copper also appears to be antagonistic to the adverse effects of lead on the hematopoietic system, growth depression, and tissue hypertrophy (Klauder and Peterini 1975). The reduction in uptake of lead and decrease of lead-induced ALAD inhibition upon administration of copper may be achieved through a competition between the two metals for binding to proteins (Underwood 1977). 

Other factors such as absorption of lead from cooking water and cookware can influence the amount of lead in cooked vegetables. The degree to which lead is released from plant tissue once the vegetable or fruit is consumed also influences a person s uptake of lead. 

Clarkson TW, Kench JE. 1958. Uptake of lead by human erythrocytes in vitro. Biochem J 69 432-439. 

Heard MJ, Chamberlain AC. 1982. Effect of minerals and food on uptake of lead from the gastrointe stinal tract in humans. Hum Toxicol 1 411-416. 

Heard MJ, Chamberlain AC. 1983. Uptake of lead by humans and effects of minerals and food. Sci Total Environ 30 245-253. 

James HM, Milbum ME, Blair JA. 1985. Effects of meals and meal times on uptake of lead from the gastrointestinal tract of humans. Human Toxicol 4 401-407. 

Mistry P, Mastri C, Fowler BA. 1986. Influence of metal ions on renal cytosolic lead-binding proteins and nuclear uptake of lead in the kidney. Biochem Pharmacol 35 711-713. 

Morton AP, Partridge S, Blair JA. 1985. The intestinal uptake of lead. Chem Br 21 926-927. 

EPA. 1990. Uptake of lead from formula and food by infants Reanalysis of the Ryu et al. data. Draft final report. US Environmental Protection Agency, Office of Pesticides and Toxic Substances Exposure Evaluation Division, Office of Toxic Substances. 

Han, D.H. and J.H. Lee. 1996. Effects of liming on uptake of lead and cadmium by Raphanus sativa. Arch. Environ. Contam. Toxicol. 31 488-493. 

The effect of diet on vulnerability to lead makes interpretation of published information on experimental lead poisoning in waterfowl extremely difficult (Chasko et al. 1984). For example, many mallards on a diet of com die within 10 to 14 days after ingesting a single lead shot, whereas similar birds on a balanced commercial duck ration appear outwardly normal after ingesting as many as 32 pellets of the same size (Wobeser 1981). Also, multiple nutritional deficiencies may have additional effects in potentiating the toxicity of lead in mallards (Carlson and Nielsen 1985). Under conditions of reduced dietary calcium availability, such as can occur in acid-impacted environments, birds risk increased uptake of lead (and other metals) and may accumulate toxic concentrations more rapidly (Scheuhammer 1996). Enhanced accumulation of lead was accompanied by an increased synthesis of metallothioneins and a greater inhibition of ALAD activity (Scheuhammer 1996). 

Knowlton, M.F., T.P. Boyle, and J.R. Jones. 1983. Uptake of lead from aquatic sediment by submersed macrophytes and crayfish. Arch. Environ. Contam. Toxicol. 12 535-541. 

Pools and uptake of lead in vegetation at Hubbard Brook were insignificant. Lead is not a plant essential nutrient and therefore it is not surprising that uptake was low. 

Coughtrey, P. J. and Martin, M. H. (1977). The uptake of lead, cadmium and copper by the pulmonate mollusc, Helix aspersa Muller and its relevance to the monitoring of heavy metal contamination of the environment, Oecologica, 27, 65-74. 

Alarmingly, higher uptake of lead and cadmium (when compared to PTWI) has been observed in children, especially in industrial areas, and in... 

Laperche, V., Logan, T. J., Gaddam, P. Traina, S. J. 1997. Effect of apatite amendments on plant uptake of lead from contaminated soil. Environmental Science Technology, 31, 2745-2753. 

As early as 1937, R.A. Kehoe began to investigate the human uptake of lead at the Kettering Laboratory, Cincinnati. A full account of the work, with statistical analysis, has been published by Gross (1981). In this and later work by Griffin et al. (1975), lead aerosol was produced by burning tetra-ethyl lead in propane and was passed into chambers. Volunteers were exposed in the chambers to the lead aerosol daily over periods of several months. The concentration of lead in the air (PbA) was monitored continuously, and samples of venous blood were taken from the volunteers at intervals for measurement of blood lead (PbB). It was found that PbB increased during the first month or two and then reached a quasi-equilibrium in which the intake from inhalation was balanced by excretion. 

If PbB is measured in fig kg-1 and PbA in /ug m-3, a has units m3 kg-1. In cases where the volunteer was exposed for a certain number of hours per day, PbA is taken as the equivalent 24-h average. In principle, estimates of a can also be made by comparing PbB in populations exposed to differing PbA in the ambient air, on the assumption, rarely fulfilled in practice, that uptakes of lead from dietary and other sources are the same. As the uptake of lead from all sources increases, PbB is found to increase non-linearly (references in Chamberlain, 1985), so the hypothetical relation between PbB and PbA, with a constant level of dietary lead, is as shown in Fig. 7.7. The tangent AP has slope a, and a is expected to decrease as PbB increases. 

A comparison of the results with other data on the deposition of submicrometre aerosols, all related to a tidal volume of 11, is shown in Fig. 1.14. Although the density of the lead particles was greater than that of the other particles, the fractional deposition was similar, except possibly for the 0.5 pm size, because deposition was by Brownian motion. The percentage deposition increases for particles of diameter less than 0.1 /urn, and this means increased uptake of lead, relative to a given PbA, for persons exposed to non-aggregated aerosol, as found alongside major roads. 

In the pyranose ring, the true cis orientation is encountered in boat forms (for example, XIX) or in the half-chair forms (for example, XX) and again, as illustrated by the very rapid uptake of lead tetraacetate by methyl 2,6-anhydro-a-D-altropyranoside,84 which is known to have a boat conformation,... 

In these catalyzed oxidations, formic acid production did not parallel the uptake of lead tetraacetate49 and, particularly with the D-mannopyrano-side and D-galactopyranoside, fell far short of the theoretical value of one mole per mole (see Fig. 2). Methyl a-D-mannoside yielded only one third of a mole of free acid per mole, a result which agreed well with the earlier formulation97 of the ester (XLVII) as the reaction product to be expected. The almost equally low yield of formic acid from methyl a-D-galactopyrano-... 

The above calculations estimate that for a typical adult in a developed country, daily uptake of lead from air, diet, and drinking water is, respectively 1.4 pg, 6 pg, and 1.1 pg. Exposure to lead from all of these sources has fallen rapidly over the past 20-30 years. Figure 12 contrasts the temporal trends in use of lead in petrol (gasoline) and blood leads in the general population of the UK over the period when much of this decline took place. It is interesting to note that from 1971 to 1985 use of lead in petrol was relatively steady, but blood leads declined by a factor of more than two over this period mainly as a response to reductions in dietary exposure, particularly associated with the cessation of use of... 

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