Lead toxicity causes paralysis and pain in the extremities due to effects on demyelinization, axonal degeneration, and presynaptic block.
Lead toxicity commonly affects sensory, visual, auditory, and cerebellar (coordination) functions, reflecting its impact on the nervous system. Normocytic, sideroblastic anemia is the consequence of lead’s inhibiting effects on enzymes in the heme biosynthesis pathway.
Other clinical signs associated with lead toxicity are kidney damage, epigastric pain and nausea, and male and female reproductive failure. Hyperactivity, anorexia, decreased play activity, low intelligence quotient and poor school performance have been observed in children with high lead levels.
Sources of lead include lead pipes, painted toys, some red lipsticks, lead paint or its dust, soil around old cars, old homes, or highways (past leaded gasoline contamination).
Hair lead is a sensitive measure of lead exposure. For those in apparent steady-state lead balance, hair levels were well correlated with blood lead. Normally, hair lead content is < 5 μg/g. Lead levels > 25 μg/g indicate severe lead exposure. Some hair darkening products contain lead acetate and may elevate lead levels in hair.
Whole blood is concentrated about 75-fold greater than that of serum or plasma and it has the highest correlation with toxicity. For this reason, whole blood lead is defined by the CDC as the preferred test for detecting lead exposure. The World Health Organization has defined high whole-blood lead levels as > 20 μg/dL in adults and > 10 μg/dL in children. As of 2007, the CDC acceptable level of whole blood lead was 10 μg/dL. Some have proposed to lower reference values for whole blood lead.
Urinary lead concentrations increase with lead poisoning, although urinary elimination of lead is a process that occurs for many days after a single exposure.
References:
– Lead Fact Sheet, Center for Disease Control and Prevention [L]
– Biomonitoring Summary, Center for Disease Control and Prevention [L]
– Chelation Medical Center, Comprehensive Digestive Stool Analysis [L]
Lead (Genova)
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