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LEAD POISONING

LEAD POISONING. Lead poisoning Absorption. Skin: little/no absorption Inhalation (<1µm) : dust or lead fumes absorb 50-70% Oral : adults absorb 10% children absorb 40-50% increased absorption if low Fe, Ca. Lead poisoning Storage & Distribution.

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LEAD POISONING

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  1. LEAD POISONING

  2. Lead poisoningAbsorption • Skin: • little/no absorption • Inhalation (<1µm): • dust or lead fumes • absorb 50-70% • Oral: • adults absorb 10% • children absorb 40-50% • increased absorption if low Fe, Ca

  3. 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 > 3.5 µg/kg/day accumulation will occur

  4. 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 Lead poisoningSources

  5. 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

  6. Environmental lead exposurePaint • Pre 1960’s up to 40% lead in paint • rapid drying, weather resistance, colouring • Domestic paint now <0.06% 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

  7. Ayurvedic Traditional Remedies • Numerous reports of lead, mercury, thallium, arsenic poisoning from Ayurvedic (& Chinese) remedies • 40% of the >6000 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

  8. 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

  9. 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

  10. Blood lead concentration (µg/L) Children: <400 Adults: <400 400-500 400-600 500-700 600-1000 >700 >1000 GI Tract Nil ±Abdominal pain ±Constipation Abdominal pain, constipation, weight loss, loss of appetite Abdominal colic, vomiting Blood Subclinical inhibition of RBC enzymes Subclinical inhibition of RBC enzymes Mild anaemia Severe anaemia CNS Effects on IQ in children? Mild fatigue, irritability, slowed motor neurone conduction Fatigue, poor concentration [Peripheral neuropathy] Encephalopathy - delirium - ataxia - fits - coma Other Nil Muscle pain Hypertension, nephrotoxicity, lowered Vit D metabolism Hypertension, nephrotoxicity, lowered Vit D metabolism

  11. Low level lead poisoning and children’s 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

  12. Diagnosis of Lead Poisoning • Blood lead is the best test (normal <100µg/l) • Other bloods • FBC (film), U&E, 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

  13. 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 >450µg/l (children)

  14. 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

  15. EDTA and DMSA • EDTA - Sodium Calcium Edetate • IV for severe toxicity, particularly encephalopathy • Well tolerated, <1% 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 !!

  16. Treatment guidelinesChildren 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 >700µg/l : Remove from source : Urgent EDTA chelation (with BAL if encephalopathy)

  17. Treatment guidelinesAdults 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 >700µg/l : Remove from source : DMSA chelation : EDTA if neurological features

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