Lead Poisoning ✅ Flashcards
How can childhood exposure to lead occur in developed countries?
- Environmental sources in the home, e.g. leaded paint
- Lead contaminated dust and soil
- Water contaminated by lead pipes
Is significant toxicity from lead common in developed countries?
No, it’s rare
Where is lead a much more significant problem?
In the developing world
What is the most common source of lead poisoning in the developing world?
Lead-glazed ceramics
Why is lead glazed ceramics a leading cause of lead poisoning in the developing world?
Their production is often a home-based industry in which children are actively employed
What are the other sources of lead in developing countries?
- Leaded petrol
- Groundwater contamination from mining, smelting, and battery factories
- Exposure to other occupational sources through parents
What are the toxic effects of lead related to?
Dose
What is a normal concentration of lead in the blood?
<0.5
What is the effect of blood lead concentrations of 0.5-1?
Developmental and growth delay
What is the effect of blood lead concentrations of 1-2?
Haemoglobin begins to fall
What is the effect of blood lead concentrations of 2-3?
Nerve conduction velocity impeded
What is the effect of blood lead concentrations of 3-4?
Overt anaemia
What is the effect of blood lead concentrations of 4-5?
Severe CNS toxicity
What is the effect of blood lead concentrations of 5-6?
Increasing risk of death
Why is the potential for adverse effects of environmental lead in children higher than in adults?
- Smaller body size leads to greater per unit body weight exposure
- Young children are orally exploratory, making them more likely to ingest lead-containing dust and soil
- Physiological update rates of lead are higher in children than adults
- Potential for adverse developmental effects
What are the pools of lead distribution in the body?
- Blood
- Skin and muscle
- Bone and dentine
What % of lead distributes into the blood?
2%
Where is lead mostly found within the blood?
Bound to the erythrocyte membrane
What % of lead distributes to the skin and muscles?
2-3%
What % of lead distributes to bone and dentine?
95%
What is the biological half life of lead distributed to bone and dentine?
20-30 years
What systems are affected by the toxic effects of lead?
- Haematological
- Neurological
- Renal
How does lead affect the haematological system?
By affecting enzymes essential for the production of haem
What enzymes essential for the production of haem are affected by lead?
- 5-aminolaevulinic acid dehydratase (ALAD)
- Ferrochelatase
What is the result of leads effect on enzymes essential for the production of haem?
- Anaemia
- Elevated plasma concentrations of 5-aminolaevulinic acid (ALA) and zinc protoporphyrin (ZPP)
What are the features of the anaemia caused by lead poisoning?
- Microcytic
- Hypochromic
How might lead poisoning manifest neurologically?
Cognitive impairment
When might lead poisoning manifest with cognitive impairment?
- As a result of chronic low-level lead exposure
- Acute encephalopathy
What is the mechanism of neurotoxicity in lead poisoning?
Unknown
How might lead poisoning affect the kidneys?
Acute severe lead exposure may give rise to proximal tubular dysfunction resulting in glycosuria and aminoaciduria
What kidney pathology might result from chronic lead exposure?
Interstitial nephritis
What is the most important initial aspect of the management of lead poisoning?
Removal of the child from the source of exposure
What is required in order to remove the child from the source of lead exposure?
A comprehensive environmental assessment
What is used in the treatment of lead poisoning?
Chelating agents
What is the purpose of chelating agents in lead poisoning?
To enhance the elimination of lead
How do chelating agents enhance the elimination of lead?
They form water-soluble complexes with lead, preventing its binding to cell components
What happens to complexes produced with lead by chelating agents?
They are excreted in the urine
What are the most widely used chelating agents in lead poisoning?
- IV sodium calcium edetate (EDTA)
- Oral succimer (2,3-dimercaptosuccinic acid, DMSA)
