Lead in hair

Bonithon-Kopp et al. (1986b) investigated another potential marker for lead exposure. Maternal and infant hair lead levels, determined from hair samples taken at birth, were found to be correlated inversely with results on neurobehavioral tests (McCarthy Scales of Children s Abilities) when the children were tested at 6 years of age. Other studies have also reported associations between hair lead levels and behavioral or cognitive test scores, but measures of lead in hair may not accurately reflect internal body burden of lead, and such data should not be used to evaluate internal dose-response relationships (EPA 1986a). 

Raymond, R.B. and R.B. Forbes. 1975. Lead in hair of urban and rural small mammals. Bull. Environ. Contam. Toxicol. 13 551-553. 

Radioactivation analysis is used for the analysis of trace amounts of suitable elements. It is a technique that is not generally applicable to biological material although it has been used for the measurement of lead in hair and nails. 

Lansdown, Alan B. G. (2000). Leads in Hair Dyes Short Term Appeal vs. Long Term Risk. International Journal of Cosmetic Science 22 167-168. 

Past exposure to lead, which is not necessarily reflected by elevated PbB levels, can be estimated by measuring the amount of lead excreted in urine after provocation with a chelating agent, e.g. EDTA (Alessio et al., 1979). If, after administration of 1 g EDTA, the amount of lead in urine exceeds 1 mg in 24 h, the test usually Is considered positive (Lauwerys, 1983). Measurement of lead in hair allows the estimation of exposure during the previous months. Although hair is an easily available material, this method may not be reliable because It is highly difficult to distinguish between lead Incorporated into the hair and that simply adsorbed on its surface. 

HI. Hasegawa, N., Hiroi, A., Shibata, T., Sugino, H., and Kashiwagi, T., Determination of lead in hair by atomic absorption spectroscopy for simple screening of lead intoxication. Annii. Rep. Res. Inst. Environ. Med., Nagoya Univ. 18, 1-5 (1970). 

Despite the importance of activities related to lead for the economy of these cities, the large population potentially exposed and the fact that the Torreon refinery is generally considered one of the largest in Latin America, no studies have been carried out on air lead levels in the areas surrounding the smelters, only one study has been carried out on lead levels in blood and dust at Ciudad Juarez and two on lead in hair in Torreon. Their results will be presented in the relevant sections. In both cases, the need for further studies and the urgency for the strengthening of regulations to control lead emissions by these sources is evident from the data. 

Albert and Garcia (1977) carried out a study on the content of lead in hair of Mexican children. Samples were obtained from five different regions of the country. This included a small town (Matamoros, Coah.) which served as a control, one small town near a major highway Torredn, where the largest smelter in the country is located and its twin city (Gomez Palacio, Dgo.), the north of Mexico City and Puebla, Pue. Twenty samples were obtained from each zone and carefully... 

The lead concentrations in the samples from the control zone and the small town were the lowest in the study and, those for the control zone, were also lower than those reported earlier in the literature (Hammer et al. 1971, Roberts et al. 1974). The concentrations of lead in hair found for the samples from the urban areas of Mexico City, Puebla, Pue., and Gomez Palacio, Dgo., were in the range of those reported in the literature for urban areas. In contrast, in those from Tor-reon, Coah., the maximum was 220 pg/g, with a mean of 55.1 pg/g this was more than 10 times the mean for the control zone most of the samples from this area exceeded the value of 13 pg/g described by Roberts et al. (1974) as acceptable, while two-thirds of them exceeded also the value of 30 pg/g considered by the same authors as indicative of excessive exposure to lead. This study was later discussed extensively by Albert et al. (1986). 

In another study carried out at Torreon, Coah., with hair samples from university students living from 1-6 km from the smelter, the mean hair lead concentration was 15.3 + 7.9 pg/g (Albores et al. 1981). The authors also analyzed blood lead and ALA in urine and concluded that these values could not be correlated with those from lead in hair. 

For a review of the relevant evidence on lead s ability to penetrate the placental barrier, see Tourmaa (1995). One of the few studies to report evidence that the placental barrier is impermeable to lead is Black et al. (2002). This study is based on the comparison of lead levels in hair samples of newborn children and their mothers. It is not at all clear, however, that one should view the amount of lead in hair as the most relevant biochemical marker of undue lead exposure. See also Klein et al. (1994). 

In theory, lead in hair would appear to be an ideal biological indicator. The sampling is noninvasive, the medium is indefinitely stable in storage, and a temporal profile of exposure along the hair length is available. Hair has been used in a number of surveys of lead exposure in children (e.g., Marlow and Errera, 1982 Thatcher et al, 1982). 

Venous blood samples (approximately 5 ml) were collected in heparinized tubes and analysed in duplicate by atomic absorption spectometry (Stoeppler ei al, 1978) in Dusseldorf University, Institute of Environmental Hygiene. The mean lead values from the duplicate samples have been used in the statistical analyses. The lead in hair and nails are not as yet determined. 

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. 

For WISC-R total and verbal IQ, 3.73% and 3.49% of total variance, respectively, is explained by teeth lead levels. In the vocabulary subtest, 5.88% of total variance is explained by ALA-D, and 4.58% of the variance in the comprehension subtest is explained by lead in hair, respectively (Figure 5). 

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