Lead in the Americas A Call for Action (1996) / Chapter Skim
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3 Session B: Health Effects of Lead
3 Session B: Health Effects of Lead
Pages 57-74
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From page 57... ...
SESSION B Health Effects of Lead
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From page 59... ...
Control and prevention strategies to address domestic sources of lead exposure are more complex than those for confined occupational sources, because of the former's varied, heterogeneous nature (Landrigan, 1988~. The major domestic sources contributing to increased blood lead levels in children in most countries of the Americas are vehicular traffic and air pollution caused by use of leaded gasoline (Romieu et al., 19921.
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The sources of lead ingested by children differ according to the time, region, and group of children studied. For example, principal sources of lead poisoning in children were reported to include ingested household dust contaminated with lead brought home by parents who are industrial workers in Memphis, Tennessee (Baker et al., 1977~; contaminated soil in an area near a lead smelter in Santo Amaro, Brazil (Silvany-Neto et al., ~L9891; household leaded paints and lead-containing tap water in Boston, Massachusetts (Shannon and Graef, 1992~; and contaminated dust from factories producing lead-containing ceramics in the Umbria region of central Italy (Abbritti et al., 1992~.
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These advancements changed the clinical and public health paradigm of lead poisoning to one of widespread acceptance that no level of lead exposure could be considered safe. Figure 3-2 reflects current understanding of the adverse health affects associated with increasing blood lead levels.
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Effects of inorganic lead on children and adults—lowest observable adverse health effects. Source: ATSDR, 1992.
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Groups of children at high risk of lead exposure have been shown to have Tower intelligence scores, depending on the type of evaluative test used. Although these findings continue to be challenged by an increasing minority of clinicians and researchers, there is a rapidly accumulating base of evidence that suggests that blood lead levels are inversely related to cognitive function and ability (Bentou-Maranditou et al., 1988; Hansen et al., 1989; Landrigan, 1989; Needleman and Gatsonis, 1990; NRC, 1993;
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For example, Bellinger and colleagues (1984, 1986) reported neurobehavioral deficits on the Bayley Scale of Infant Development associated with higher prenatal exposures (cord blood lead levels of 10-25 ~g/611.
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To move toward this end, there is a need for more extensive identification and monitoring of lead levels in high-risk children and for the strengthening of medical education to alert pediatricians and other clinical practitioners to the signs, symptoms, and effects of lead poisoning. Blood lead levels should be measured at least once in high-risk children in the first year of life, and clinic personnel should be prepared to provide basic counseling to parents on how to reduce infant and child exposure to lead.
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Correct diagnosis of a lead-poisoned individual, therefore, requires adequate clinical training, the execution of a complete occupational and environmental history, laboratory facilities for lead determination, and awareness of the problem by health care professionals. An understanding of the problem of lead poisoning in adults requires that specific factors that predispose or aggravate {ead's effects be taken into account.
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As a rule, in the adult, between 30 and 50 percent of lead is absorbed. Lead ingestion also results from consuming food and beverages contaminated with lead and from swallowing lead particulates cleared by the upper respiratory tract.
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68 LEAD IN THE AMERICAS: A CALL FOR ACTION CO ._ ._ I Z AY o ._ x LL ._ ._ in o Q a' ~5 ._ o m _ .
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Bones serve as a long-term repository of approximately 75 percent and 95 percent of lead in children and adults, respectively (Barry and Mossman, 19701. Studies have demonstrated that bone lead levels remain elevated despite declines in blood [Lead, suggesting that bone lead may be a better biological marker of chronic toxicity (Steenhout, 19821.
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Subclinical states have also been described in asymptomatic adults with lead levels between 80-120 ~g/~l and have been characterized by diminished conductor velocity, muscular fibrillation, and loss of motor neurons. Renal Elects Acute renal effects include reversible loss of renal function~amage to the proximal tubules, which produces a Fanconi Syndrome manifested by aminoaciduria, glucosuria, and phosphaturia.
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Gastrointestinal symptoms are aggravated when blood lead levels reach 100 ~g/~1 or higher and can include severe abdominal colic and constipation. Severe symptoms occur at blood lead levels of 150 ~g/61 or higher and can include "lead colic" (severe abdominal spasms that resemble acute abdominal pain requiring surgery)
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Tests that are useful in the diagnosis of lead poisoning are: TABLE 3-2 Levels of ZPP and Blood Lead Level Equivalents ZPP (mg/100 ml) Interpretation Blood Lead Level Equivalents < 80 Normal for adults 80-250 Typical labor exposure 20~40 mg/lOOml 251-500 High range of exposure 40-55 > 500 Extreme exposure > 55 Source: Adapted from Saryan and Zenz, 1994.
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, and, recently, X-Ray Fluorescence, have been found useful in determining levels of sequestered lead in bone. Clinical Examination Clinical examination of cases of suspected lead poisoning should include a detailed history of possible environmental and occupational exposure to lead; a complete physical examination, especially of blood pressure; laboratory tests of blood lead, hematic cytology, hemoglobin, BUN, and creatine; and urinalysis.
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From page 74... ...
74 LEAD IN THE AMERICAS: A CALL FOR ACTION occupational sources. The responsibility of controlling lead exposures and guaranteeing healthy working and living conditions must be shared by everyone, including government, workers, unions, scientists, health providers, and the general public.
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