LEAD POISONING

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LEAD POISONING
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Lead poisoningAbsorption

• Skin
• little/no absorption
• Inhalation (lt1µm)
• dust or lead fumes
• absorb 50-70
• Oral
• adults absorb 10
• children absorb 40-50
• increased absorption if low Fe, Ca

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Lead poisoningStorage Distribution

• Rapid turnover soft tissue pool
• T1/2 30-40 days blood, liver, kidney, CNS
• Slow turnover skeletal pool
• T1/2 10-20 years 75 - 90 in skeletal pool
• Chronic exposure results in a steady state
  distribution between bone and blood
• Excretion Renal (90) and biliary (10)
• Maximum excretion is 3.5µg/kg/day
• If intake gt 3.5 µg/kg/day accumulation will occur

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Lead poisoningSources

• Occupational
• Lead smelters
• Painter/decorators
• Battery manufacturers
• Stain-glass workers
• Jewellery makers
• Bronze workers etc...

• Environmental
• paint (walls, furniture, toys)
• water
• food
• air (petrol, industry), dust/soil
• Other
• traditional remedies (Ayruvedic)
• surma kohl cosmetics
• lead shot
• lead glazed ceramics
• foreign body ingestion
• e.g. curtain/fishing weight, snooker chalk

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Environmental lead exposureWater

• Lead in water
• Largely from lead pipes/solderings/fittings
• Water lead contamination from ground lead has
  occurred in Nepal
• WHO max water lead content 10µg/l
• 20-30 UK homes exceed this limit

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Environmental lead exposurePaint

• Pre 1960s up to 40 lead in paint
• rapid drying, weather resistance, colouring
• Domestic paint now lt0.06 lead (600ppm)
• BUT leaded paint remains in many homes
• walls, furniture, toys
• Lead exposure from paint
• sanding, heat stripping, flaking, pica
• contamination of carpets/curtains, dust

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Ayurvedic Traditional Remedies

• Numerous reports of lead, mercury, thallium,
  arsenic poisoning from Ayurvedic ( Chinese)
  remedies
• 40 of the gt6000 medicines in Ayurveda contain at
  least one heavy metal
• Thought by practitioners to have therapeutic
  properties and/or to increase the efficacy of
  other herbal contents
• Used most commonly for chronic disorders and so
  there is a greater risk of heavy metal
  accumulation

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Ayurvedic Traditional Remedies

• Case 1 68 mg/g lead i.e. 6.8
• 76 mg/g mercury i.e. 7.6
• 12 mg/g arsenic i.e. 1.2
• i.e. 15.5 heavy metals

• Case 2 50 mg/g lead i.e. 5.0
• 39 mg/g mercury i.e. 3.9
• i.e. 8.9 heavy metals

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Clinical features of lead poisoning

• Results in variable effects on many systems
• The effects are well established at high levels
• Infants/children get symptoms at lower levels
• Treatable, but can cause chronic sequelae

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Low level lead poisoning and childrens IQ

• There have been many studies
• 5 prospective, 14 cross-sectional
• The problem is allowing for multiple confounders
• Three published metanalyses
• ?100µg/l blood lead
• ? ? IQ 2.5 points

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Diagnosis of Lead Poisoning

• Blood lead is the best test (normal lt100µg/l)
• Other bloods
• FBC (film), UE, LFT, Ca, Vit D, Ferritin
• Radiology
• AXR ?lead in gut
• Long bone XR in children
• Other tests much less reliable
• Urine lead - variable, more useful for organic
  lead
• RBC Zn protoporphyrin, Urine coproporphyrin, dALA

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Management of Lead Poisoning

• IDENTIFY REMOVE from SOURCE
• Treat coexisting iron ( calcium) deficiency
• Consider the use of chelation therapy
• - Good data for benefit with blood lead gt450µg/l
  (children)

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Chelating agents for lead poisoning

• 1. EDTA - Sodium calcium edetate
• 2. DMSA - Dimercaptosuccinic acid
• 3. BAL - Dimercaprol
• - IM for severe toxicity only, particularly
  encephalopathy
• 4. Penicillamine - no longer recommended

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EDTA and DMSA

• EDTA - Sodium Calcium Edetate
• IV for severe toxicity, particularly
  encephalopathy
• Well tolerated, lt1 nephrotoxicity
• DMSA - 2,3dimercaptosuccinic acid
• The oral agent of choice for lead poisoning
• Given as a 19 day course
• Well tolerated
• The main problem is foul taste and smell !!

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Treatment guidelines Children

• 100-240µg/l Remove from source, repeat level 1
  month
• 250-440µg/l Remove from source
• DMSA only if persists at
  this level

450-690µg/l Remove from source DMSA
chelation gt700µg/l Remove from source
Urgent EDTA chelation (with
BAL if encephalopathy)
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Treatment guidelines Adults

• 100-400µg/l Remove from source (??)
• Repeat level 3-6 mths
• 400-500µg/l Remove from source (?)
• Repeat level 1-2 mths

450-690µg/l Remove from source DMSA
chelation IF symptomatic gt700µg/l Remove
from source DMSA
chelation EDTA if neurological features