Blood leads

Workers who produce or use lead should be aware of possible ha2ards. Symptoms of chronic lead poisoning include fatigue, headache, constipation, uneasy stomach, irritabiHty, poor appetite, metallic taste, weight loss, and loss of sleep. Most of these same symptoms also occur in many common illnesses, such as the flu, thus a physician must rely on tests, such as blood lead analysis, to determine chronic lead poisoning. 

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. 

Biological limits are also in force for lead and its compounds under the Control of Lead at Work Regulations 1998 different blood lead action, and suspension from work, levels apply to women of reproductive capacity, young persons and other employees. 

Warfarin and the second-generation superwarfarins are ARs that have a structural resemblance to dicoumarol and vitamin K. They act as vitamin K antagonists, thereby retarding or stopping the carboxylation of clotting proteins in the hepatic endoplasmic reticulum. The buildup of nonfunctional, undercarboxylated clotting proteins in the blood leads eventually to death by hemorrhaging. 

Kllroe-Smlth, T. A. "Linear Working Graphs In Blood Lead Determinations with the Beckman Flameless Atomic Absorption Cuvet . Clin. Chem. (1975), 21, 630-632. 

Rosen, J. F. and Trinidad, E. E. "The Mlcrodetermlnatlon of Blood Lead In Children by Flameless Atomic Absorption ... 

Blood Chemistry Data. All blood specimens were obtained by venipuncture. The erythrocyte protoporphyrin (EP) was measured by the extraction method. Blood lead determinations were done In quadruplicate and are presented as an arithmetic mean of the four replicates. 

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 XV shows that at the RSR site, the mean blood-lead was found to be 20.1 pg/dl for black children living within 0.5 mile of the smelter (near) as compared to 15.0 for those who live from 0.5 mile to 1 mile (far). Among those who live near the smelter, the mean blood-lead was higher (21.8 pg/dl) for those who also live within 1 block of the major roadways compared to those who live more than 1 block from the roadway (19.1 pg/dl).

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 ...

Table XXII Percent Blood Lead >30 pg/dl by Distance, ...

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. 

At the RSR site, proximity to the smelter and to high traffic density contribute to the lead in the soil and to the blood-lead... 

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. 

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