Blood-lead concentration

Most of the studies on lead in Mexico have been carried out on this subject. As was mentioned earlier, the first was reported by Viniegra et al. (1960). Later, Molina et al. carried out many more similar studies, (1979, 1980, 1981, 1982, 

In Mexico, blood lead concentrations have been traditionally analyzed according to the classification mentioned by Mills (1971), with 40 pg/100 mL as the maximum concentration to be considered as normal (Table 22). This classification has recently been challenged, since adverse effects have been demonstrated at lower blood lead concentrations (US-EPA 1986) however, it is still accepted in Mexico and has been used by all the authors to discuss their results. 

The importance of traditional pottery glazing as a source of lead exposure for people working in this trade and their families has been demonstrated by Molina et al. (1980, 1981, 1982) in several studies. 

Class Blood lead (lig/100 mL) Affected populations and symptoms 

Excessive 80-120 Excessive occupational exposure with slight symptoms 

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Delves HT, Diaper SJ. Oppert 5, Peescott-Ciarke P, Periam J, Dong W, Golhoun H, Gom-PERTZ D (1996) Blood lead concentrations in United Kingdom have fallen substantially since 1984. Brit Med J 313 883-884. 

In most of these studies, prenatal exposure was generally estimated through maternal and/or cord blood lead concentrations. Exposure of the mothers can be assumed to have been primarily through the oral route, but with contribution from the inhalation route as well. The most relevant studies are discussed below, along with results from a few investigations of different markers for lead exposure. 

Dietary calcium intake appears to affect lead absorption. An inverse relationship has been observed between dietary calcium intake and blood lead concentration in children, suggesting that children who are calcium deficient may absorb more lead than calcium replete children (Mahaffey et al. 1986 Ziegler et al. 1978). An effect of calcium on lead absorption is also evident in adults. In experimental studies of adults, absorption of a single dose of lead (100-300 ig lead chloride) was lower when the lead was... 

Bioavailability was assessed from measurement of the area under the curve (AUC) of whole blood lead concentration vs time (Blood AUC) or from measurements of the lead concentrations in bone, kidney or liver (the arithmetic mean of the three tissues is shown in the table). Data are from Casteel et al. (1997) and EPA (1996a, 1996b, 1996c). 

Using this analytical technique, a curvilinear relationship between plasma and blood lead concentrations has been demonstrated in adults (118 active lead industry workers and 25 retired workers) whose PbB concentrations were 1- 93 pg/dL log plasma (pg/L)= 0.00225 x blood ( pg/L) - 0.58 this relationship describes a plasma/blood lead concentration ratio of approximately 0.4 at PbB concentrations between 10 and 30 pg/dL, and ratios increasing to 3.5% at PbB concentrations between 30 and 90 pg/dL (Berdahl et al. 1997 Berdahl and SkerfVing 1997). Similar ratios have been reported for serum and blood serum... 

Target tissues. Output from the O Flaherty Model is an estimate of age-specific blood lead concentrations. The O Flaherty Model has also been used to predict lead concentrations in bone and other tissue compartments (O Flaherty 1995a), in order to evaluate correspondence between predicted tissue concentrations and observed concentrations in different populations of children and adults. 

Validation of the model. Output from the Leggett Model has been compared with data in children and adult subjects exposed to lead in order to calibrate model parameters. The model appears to predict blood lead concentrations in adults exposed to relatively low levels of lead however, no information could be found describing efforts to compare predicted blood lead concentrations with observations in children. 

Studies in rodents, dogs, and non-human primates have demonstrated all of the major types of health effects of lead that have been observed in humans, including cardiovascular, hematological, neurodevelopmental, and renal effects (EPA 1986a). These studies also provide support for the concept of blood lead concentration as a metric of internal dose for use in dose-response assessments in humans. 

Zheng W Columbia University, New York, NY The effects of DMSA on blood lead concentrations and urinary Pb excretion National Institute of Environmental Health Sciences... 

Campara P, D Andrea F, Micciolo R, et al. 1984. Psychological performance of workers with blood-lead concentration below the current threshold limit value. Int Arch Occup Environ Health 53 233-246. 

Chiaradia M, Gulson BL, MacDonald K. 1997. Contamination of houses by workers occupationally exposed in a lead-zinc-copper mine and impact on blood lead concentrations in the families. Occup Environ Med 54(2) 117-124. 

Frisancho AR, Ryan AS. 1991. Decreased stature associated with moderate blood lead concentrations in Mexican-American children. Am J Clin Nutr 54 16-19. 

Froom P, Kristal-Boneh E, Benbassat J, et al. 1998. Predictive values of determinations of zinc protoporphyrin for increase blood lead concentrations. Clin Chem 44 1283-1288. 

Ito Y, Niiya Y, Otani M, et al. 1987. Effect of food intake on blood lead concentration in workers occupationally exposed to lead. Toxicol Lett 37 105-114. 

Lansdown R, Yule W, Urbanowicz MA. et al. 1986. The relationship between blood lead concentrations, intelligence, attainment and behavior in a school population The second London study. Int Arch Occup Environ Health 57 225-235. 

Mahaffey KR, Rosen JF, Chesney RW, et al. 1982. Association between age, blood lead concentration, and serum 1,25-dihydroxycholecalciferol levels in children. Am J Clin Nutr 35 1327-1331. 

Orssaud G, Claude JR, Moreau T, et al. 1985. Blood lead concentration and blood pressure. BrMedJ 290 244. 

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