Lead in teeth

The amount of total lead in the blood can be measured to determine if exposure to lead has occurred. This test can tell if you have been recently exposed to lead. Lead can be measured lead in teeth or bones by X-ray techniques, but these methods are not widely available. These tests tell about long-term exposures to lead. Exposure to lead can be evaluated by measuring erythrocyte protoporphyrin (EP) in blood samples. EP is a part of red blood cells known to increase when the amount of lead in the blood is high. However, the EP level is not sensitive enough to identify children with elevated blood lead levels below about 25 micrograms per deciliter ( ig/dL). For this reason, the primary screening method is measurement of blood lead. For more information on tests to measure lead in the body, see Chapters 2 and 6. 

Purchase NG, Fergusson JE. 1986. Lead in teeth The influence of the tooth type and the sample within a tooth on lead levels. Sci Total Environ 52 239-250. 

Shapiro, I.M., Burke, A., Mitchell, G. and Bloch, P. (1978). X-ray fluorescence analysis of lead in teeth of urban children in situ Correlation between the tooth lead level and the concentration of blood lead and free erythroporphyrins. Environ. Res., 17. 46-52. 

It is generally understood that PbB reflects a shorter exposure time than, say, lead in teeth, but it is not widely known just what this means in quantitative terms. Hence, it is of interest to examine the response of PbB with changes in exposure, particularly reduction in lead uptake as occurs when children grow older, and the relative stability of PbB as a function of time and/or development. 

The use of lead in mineralizing tissue, especially in teeth, as a biological indicator of lead exposure is based on the accumulation of the toxicant in these matrices as a function of both age and level of exposure. Hence, lead in teeth or bone provides a cumulative index of exposure over very extended time frames. Lead levels in shed teeth as an exposure indicator have been employed in a number of studies of the effects of lead on paediatric populations (e.g., Needleman et al, 1979 Delves et al, 1982 Ewers et al, 1982 Grandjean et al, 1984). Elevated levels of the element have been reported in whole teeth or their constituents as a function of poisoning history, point source proximity, or geographical location (Shapiro et al, 1973 Needleman et al, 1979 Steenhout and Pourtois, 1981 Ewers et al, 1982 Delves et al, 1982 Grandjean et al, 1984). 

In summary, the use of shed dentition as a biological indicator of cumulative exposure to lead in children would appear to be appropriate under certain conditions. These conditions include rigorous steps to minimize variance in the measure multiple tooth sampling restricted to the same type (and location if possible), or use of concordance criteria for acceptance or rejection of lead levels in replicate sampling. By its nature, measurement of lead in teeth is a retrospective index of exposure to lead, and this measure is not as inherently useful for regulatory policy or clinical intervention/management of lead exposure and intoxication as is PbB. The various prospective studies currently under way in different countries for lead exposure/effects in children include some that utilize serial measurement of PbB in the paediatric subjects as they develop. Comparison of these multiple measurements with lead in shed dentition in the future would be valuable in establishing blood lead-tooth lead relationships. 

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. 

The degree of association found between lead in teeth and scores of Toulouse-Pieron (T and T2) was greater in children with PbT levels higher than 8.61 flgg (> 75th percentile) (r = 0.393 r = 0.395, respectively). 

For the total and verbal IQ, the variance accountable to lead in teeth is increased (4.80% and 5.29%, respectively). The relationship between ALA-D and total IQ reached statistical significance (explained variance 1.80% p = 0.05). 

With respect to neuropsychological effects of the metal exposure, lead was found to be associated with impairments on the cognitive functions evaluated by WISC-R. After regressing out the variance attributable to confounding factors, the total and verbal scale of IQ was related to lead in teeth, in agreement with findings of other workers (Bellinger et al, 1984 Hansen et al, 1985). Furthermore, the two verbal subtests of WISC (vocabulary and comprehension) were associated with ALA-D and PbH, respectively. 

Steenhout A, Pourtois M. 1981. Lead accumulation in teeth as a function of age with different exposures. Br J Ind Med 38 297-303. 

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