LEAD POISONING Lead poisoning Absorption Skin littleno absorption
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 1 Rapid turnover soft tissue pool: T 1/2 30 40 days; blood, liver, kidney, CNS 2 Slow turnover skeletal pool: T 1/2 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
Lead poisoning Occupational – – – Sources Environmental Lead smelters – paint (walls, furniture, toys) Painter/decorators – water Battery manufacturers – food Stain glass workers – air (petrol, industry), dust/soil Jewellery makers Other Bronze workers etc. . . – traditional remedies (Ayruvedic) – surma & kohl cosmetics – lead shot – lead glazed ceramics – foreign body ingestion e. g. curtain/fishing weight, snooker chalk
Environmental lead exposure Water • Lead in water: 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
Environmental lead exposure Paint • Pre 1960’s up to 40% lead in paint rapid drying, weather resistance, colouring • Domestic paint now <0. 06% lead (600 ppm) • BUT leaded paint remains in many homes walls, furniture, toys • Lead exposure from paint: sanding, heat stripping, flaking, pica contamination of carpets/curtains, dust
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
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
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
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 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
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
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, d. ALA
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)
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
EDTA and DMSA • EDTA Sodium Calcium Edetate IV for severe toxicity, particularly encephalopathy Well tolerated, <1% nephrotoxicity • DMSA 2, 3 dimercaptosuccinic 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 !!
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 >700µg/l : Remove from source : Urgent EDTA chelation (with BAL if encephalopathy)
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 >700µg/l : Remove from source : DMSA chelation : EDTA if neurological features
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