Test code links throughout this Guide refer to the corresponding test in the User's Guide. Its toxic properties, both acute and chronic, have been understood for a long time. Common sources include dirt, paint, leaded gasoline, ceramics, and water pipes.
Lead inhibits aminolevulinic acid dehydratase, necessary for the synthesis of heme from porphyrin.
As a result, erythrocyte protoporphyrin levels are increased, and heme-deficient anemia may then ensue. Lead also binds to most proteins, resulting in a variety of effects. Due to rapid growth, children are particularly susceptible to the toxic effects of lead. Lead passes the blood-brain barrier more easily in children than adults, leading to lead encephalopathy at lower blood levels. The toxic effects of lead are especially evidenced in the developing nervous system of the fetus and young child.