Teeth, lead distribution

Mahler, D.T., Scott, A.S., Walsh. J.R. and Haynic, G. (1970). A study of trace metals in finger nails and hair using neutron activation analysis. J.Nucl. Med. 11,739-742 Malik. S.R. and Fremlin, J.H. (1974). A study of lead distribution in human teeth using charged particle activation analysis. Caries Res. 8, 283-292 Manly, R.S. and Hodge, H.G. (1939). Density and refractive index studies of dental hard tissue, J. Dent. Res. 18,133-141... 

Figures 1 and 2 show the frequency distributions of ALA-D and other lead exposures parameters. As expected, lead distributions in blood, hair and teeth are skewed. 12.2% of blood lead measures, 33.7% of hair lead measures, and 33.3% of tooth lead measures show values higher than 15 /igdl 15 Hgg and 5 fig g, respectively. ALA-D and PbT values are significantly affected when the influence of sex and parents status was investigated by analysis of covariance. However, as shown in Figure 3, the influence of parents status on mean values of ALA-D and PbT exists only for males.

Alloys are metallic materials prepared by mixing two or more molten metals. They are used for many purposes, such as construction, and are central to the transportation and electronics industries. Some common alloys are listed in Table 5.5. In homogeneous alloys, atoms of the different elements are distributed uniformly. Examples include brass, bronze, and the coinage alloys. Heterogeneous alloys, such as tin-lead solder and the mercury amalgam sometimes used to fill teeth, consist of a mixture of crystalline phases with different compositions. 

The isotopic distribution of lead (IDMS) in shed teeth from children has been shown to be useful in studies of the history of exposure to lead, including the definition of the source of the exposure, e.g., mine dust vs. food (Gulson and Wilson 1994), so IDMS certainly has important applicability, if not for routine determinations. ICP/MS, however, is easier, more sensitive, allows for multi-element analysis, and provides isotopic data. 

The total body burden of lead is a function of the balance between the amount being taken in (all routes combined), the amount distributed throughout the tissues, and the amount being excreted. Most of the body burden of lead is sequestered in the bones and teeth over 70% in children and over 90% in adults. The remainder of the body burden is distributed between soft tissue and the blood. Lead is stored in the bone for the greatest length of time. The estimated half-lives of lead range from 10 to 30 years in bone, are 40 days in soft tissues, and range from 28 to 36 days in blood (in adults). Children tend to retain approximately five times more absorbed lead than adults. 

The levels of lead and the distribution of lead in normal adult human tissues are shown in Table 1 (B9, K3, T2, T3). Certain tissues, notably the aorta and liver, and especially the adrenal and thyroid glands and the jejunum portion of the small intestine, appear to contain higher portions of lead than others. Kehoe et al. (K3) have shown the accumulation of lead in the bones. Sognnaes (S5) has shown that lead in the bulk enamel of teeth is 30 ppm in young teeth to 90 ppm in old teeth. Up to 500 ppm is reported in the peripheral enamel. 

From the blood plasma absorbed lead is distributed to the soft tissues, teeth, and the skeleton. The distribution of lead in soft tissues is subject to both between-tissue and within-tissue variation [6]. Indicative values of lead in liver, kidney, and brain are 0.29-0.77, 0.17-0,47, and 0.02-0.07 i.mol/g ash, respectively [6]. Lead is accumulated in the nervous system, where the lead... 

Once absorbed, lead is deposited in mineral tissue such as bones and teeth, in some soft tissues such as the liver, kidneys and brain, and some is retained in the blood stream. The distribution of total body lead to the bones is about 70 per cent, increasing to 90 per cent with age. 

Mineralizing tissue in humans consists of bone and teeth. These biominerals differ in a number of ways with respect to lead deposition and lead toxicokinetics. By and large, bone is the larger repository of lead in humans and is the more complex mineralizing tissue in terms of deposited Pb. Bone Pb can be readily resorbed and serve as a source of endogenous Pb exposure long after initial transport to and deposition in the various bone subcompartments. Table 8.9 presents illustrative summaries of Pb distributions and accumulations in human mineralizing tissues. 

Grandjean, P., 1978. Regional distribution of lead in human brains. Toxicol. Lett. 2, 65—69. Grandjean, P., Hansen, O.N., Lyngbye, K., 1986. Lead concentration in deciduous teeth variation related to tooth type and analytical technique. J. Toxicol. Environ. Health 19,... 

Edmonds, M.I., Al-Naimi, T. and Fremlin, J.H. (1978) The distribution of lead in human teeth, using charged particle activation analysis. Paper read at Fifth Symposium on Developments in Activation Analysis, Oxford, July... 

Al-Naimi, T., Edmonds, M.I. and Fremlin, J.H. (1980) The distribution of lead in human teeth, using charged particle activation analysis. Phys. Med. Biol, 25, 719-726 Araki, S. (1973) On the behaviour of active deposit of lead (Teisinger) in the Japanese free from occupational exposure to lead. Ind Health, 11, 203-224 Araki, S. and Ushio, K. (1982) Assessment of the body burden of chelatable lead a model for application to workers. Br. ]. Ind. Med., 39, 157-160 Brudevold, F., Aasenden, R., Srinivasien, B.N. and Bakhos, Y. (1977) Lead in enamel and saliva, dental caries and the use of enamel biopsis for measuring past exposure to lead. ]. Dental Res., 56, 1165-1171... 

Carroll, K.G., Needleman, H.L., Tuncay, O.C. and Shapiro, I.M. (1972) The distribution of lead in human deciduous teeth. Experientia, 28, 434-445 Chamberlain, A.C. (1985) Prediction of response of blood lead to airborne and dietary lead from volunteer experiments with lead isotopes. Proc. R. Soc. Lond., B, 224, 149-182 Chamberlain, A.C., Heard, M.J., Newton, D., Wells, A.C. and Wiffen, R.D. (1978) Investigations into Lead from Motor Vehicles. AERE Report 9198 (London HMSO)... 

In Table 5, the linear correlation coefficients between the biological parameters are reported. Overall the correlation coefficients obtained are low, but blood lead levels are significantly related to ALA-D and lead in hair, although not with teeth. Furthermore, lead in teeth is significantly correlated with lead in hair and ALA-D. In order to determine whether the degree of association is increased at different levels, we computed the linear correlations dividing the values of biochemical parameters according to percentile distribution. 

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