Lead continued Nov 29, 2005

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Lead continued Nov 29, 2005 Lead Storage and
HalfLife Blood - 35 days Brain about 2
years Bone decades Blood lead reflects recent
exposure and mobilization from bone. Bone
demineralization is increased when Calcium
deficient.
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• The Special Case of Fetal and Early Childhood
  Exposure
• dual contributions to maternal blood lead levels
  Pb stored in bone and newly acquired
• bone demineralization common in pg
• maternal and umbilical cord blood levels are
  about equal
• exposure to fetus
• exposure through breast milk
• direct postnatal exposure via ingestion or
  respiration

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Childhood Symptoms Severe poisoning - gt 70
micrograms/dL 1st signs - lethargy, abdominal
cramps, anorexia and irritability After days
to weeks in infants lt 2 years - vomiting,
clumsiness and ataxia, then alternating periods
of hyperirritability and stupor, finally coma
and seizures.
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• Table 1. Summary of LOAELs for lead-induced
  health effects in adults
• LOAEL at given blood lead Effects
• (micrograms/l)
• --------------------------------------------------
  --------------------------------------------------
  --
• 10001200 Encephalopathic signs and symptoms
• 800 Frank anaemia
• 500 Reduced haemoglobin production Overt
  subencephalopathic neurological
  symptoms, cognition Impairment
• 400 Increased urinary ALA and elevated
  coproporphyrin
• 300 Peripherial nerve dysfunction(slowed
  nerve conduction velocities)
• 200300 FEP elevation in males
• 150200 FEP elevation in females

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• Table 2. Summary of LOAELs for lead-induced
  health effects in children
• LOAEL at given Blood lead level (µg/l) Effects
• (Micrograms/L)
• 8001000 Haem synthesis, haematological and
  other effects. Effects on the
  nervous system encephalopathic signs
  and symptoms
• 700 Frank anaemia
• 250300 Increased urinary ALA and elevated
  coproporphyrin Reduced haemoglobin
  synthesis
• 150200 FEP elevation
• 100150 Vitamin D3 reduction and Cognitive
  impairment
• ALAD inhibition Hearing impairment