Lead, blood levels

Preventive Measures. The intake uptake biokinetic model (lUBK) projects the impact of lead in the environment on blood lead. This model assumes conservatively high levels of intake and cannot account for chemical speciation, thus over-predictions of blood lead levels often occur. Nonetheless, because of the allegations of the impact of blood lead and neurobehavioral development, blood lead levels in children are being reduced adrninistratively to below 10 //g/dL. In order to do so, soil leads are being reduced to a level of between 500—1000 ppm where remediation is required. 

The different forms of lead have different bioavailabiUty and this ultimately impacts cleanup levels. Mine tailings, slag, and other such residues have limited impact on blood lead levels because these materials contain lead in the form of lead sulfide, which has limited biological reactivity and uptake. 

In addition to limits on airborne lead, an OSHA regulation provides for biological monitoring and places limits on blood lead levels in workers of... 

Reviews on the occurrence, biochemical basis, and treatment of lead toxicity in children (11) and workers (3,12,13) have been pubhshed. Approximately 17% of all preschool children in the United States have blood lead levels >10 //g/dL. In inner city, low income minority children the prevalence of blood lead levels >10 //g/dL is 68%. It has been estimated that over two million American workers are at risk of exposure to lead as a result of their work. PubHc health surveillance data document that each year thousands of American workers occupationally exposed to lead develop signs and symptoms indicative of... 

Lead-induced anemia results from impairment of heme biosynthesis and acceleration of red blood cell destmction (10,13). Lead-induced inhibition of heme biosynthesis is caused by inhibition of S-aminolevulinic acid dehydratase and ferrochelatase which starts to occur at blood lead levels of 10 to 20 pu gjdL and 25 to 30 //g/dL, respectively (10,13). Anemia, however, is not manifested until higher levels are reached. 

Table X shows the percent of preschoolers having various blood-lead levels at the three sites.

Table X. Percentage Distribution of Blood-Lead Levels In Preschool Children...

Table XII shows the population estimate, sample size by stratum, and mean blood lead levels among black children In the reference area of 13.2 and 14.6 pg/dl In the low and high traffic density areas, respectively.

There are no children In the reference area who had lead toxicity or whose blood lead level exceeded 29 pg/dl (Table XIII). The term "lead toxicity" Is defined here as a child with a blood-lead level > 30 pg/dl and an EP pg/dl. The term "lead toxicity" Is not used In a toxicological sense. 

Table XVI shows that 17 percent of the black children living near the RSR site, were found to have a blood-lead level > 30 pg/dl In the high traffic density area and 8.3 percent In the low traffic density area. Only 1.6 percent of black children living beyond the 0.5 mile...

Table XII. Mean Blood Lead Levels by Race in Reference Area ...

Traffic Density Percent with Lead Toxicity Percent with Blood Lead Levels >30 g/dl ... 

The mean blood lead level of black children at the Dixie site was found to be only slightly higher (15.8 g/dl) for those living within 0.5 mile of the smelter as compared to those living within 0.5 - 1 mile (14.9 g/dl). The three non-black children whose blood-lead levels were 30 g/dl were siblings in a family where a parent worked at Dixie Metals (Tables XVIII and XIX). 

Table XVIII. Mean Blood-Lead Level by Race, Traffic, and Distance from Dixie Site...

Approximate Distance (miles) Sample Size Mean Blood Lead Level ( g/dl) ... 

Tables XXI and XXII show that for the RSR site the differences In mean blood-lead levels and proportion of children with lead toxicity remain evident even when other sources of potential exposure (as determined from the questionnaire) were taken Into consideration Tables XXIII and XXIV show this Is not the case for the Dixie site ...

A multivariate analysis (Table XXV) shows the increased blood-lead level caused by the RSR smelter contribution and the traffic contribution to be 5.5 and 1.0, respectively. ... 

At neither site is there evidence of absorption of lead to the degree usually associated with clinical symptoms of lead poisoning, and the reported blood-lead levels are not high enough to make this likely. However, a public health concern exists, particularly in the RSR area, since 5 percent of these black children were found to have lead toxicity. 

When the Dixie site is compared to the reference area, proximity to the smelter (within 0.5 mile) contributed 1.85 pg/dl to the mean blood-lead level. The potential contribution of traffic density could not be determined because of the configuration of the roadway and the distance of the roadway from the smelter site. Although an elevated mean blood-lead level was found for children living close to the Dixie site, the increase was not as great as observed in the RSR site and the few children found to have lead toxicity, as defined previously, appear to have lead exposure due to occupation of parents. 

Background measurements, soil samples, 119-20 Blood-lead levels In preschool... 

Studies carried out by the Center for Disease Control and Prevention (CDC) show that the levels of lead in the blood of U.S. children have been getting lower and lower. This is because lead is banned from gasoline, residential paint, and solder that is used for food cans and water pipes. Still, about 900,000 U.S. children between the ages of 1 and 5 years are believed to have blood lead levels equal or greater than 10 ig/dL, the CDC level of concern. 

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. 

CDC considers children to have an elevated level of lead if the amount of lead in the blood is at least 10 pg/dL. Medical evaluation and environmental investigation and remediation should be done for all children with blood lead levels equal or greater than 20 pg/dL. Medical treatment may be necessary in children if the lead concentration in blood is higher than 45 pg/dL. 

OSHA regulations limit the concentration of lead in workroom air to 50 ig/m3 for an 8-hour workday. If a worker has a blood lead level of 50 ig/dL, then OSHA requires that worker be removed from the workroom where lead exposure is occurring. 

Duration of exposure System Effect Blood lead levels at which effect was observed (ug/dL) Reference... 

NS (general population) Cardiovascular Increased systolic pressure by 1-2 mm Hg and increased diastolic pressure by 1.4 mm Hg with every doubling in blood lead level effect most prominent in middle-aged white men 7-38 Coate and Fowles 1989 Harlan 1988 Harlan et al. 1988 Landis and Flegal 1988 Pirkle et al. 1985 Schwartz 1988 Proctor et al. 1996... 

NS (general population) Cardiovascular No significant correlation between blood pressure and blood lead levels 6-13 (median) or NS Elwood et al. 1988 Grandjean et al. 1989 Neri et al. 1988 Staessen et al. 1990, 1991... 

NS (occup) Hematological Increased ALAS and/or decreased ALAD 87 or NS (correlation with blood lead level) Alessio et al. 1976 Meredith et al. 1978 Wada et al. 1973... 

NS (chronic) (general population) Other No association between blood lead levels and growth in children 10-47 (levels measured) Greene and Emhart 1991 Sachs and Moel 1989... 

NS (general population) Neurological No correlation between blood lead levels and permanent effects on neurobehavioral development in children 10-15 Bellinger et al. 1989a Cooney et al. 1989a Dietrich et al. 1987a Emhart and Greene 1990 Harvey et al. 1984,1988 Lansdown et al. 1986 McBride et al. 1982 McMichael et al. 1986 Pocock et al. 1989 Smith et al. 1983 Winneke et al. 1984... 

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