LEAD POISONING
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LEAD POISONING
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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
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1 Rapid turnover soft tissue pool: T1/2 30-40 days; blood, liver, kidney, CNS
2 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
Lead poisoningStorage & Distribution
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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
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• Lead in waterLead 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
Environmental lead exposureWater
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• 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
Environmental lead exposurePaint
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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
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• Case 1: 68 g/g lead i.e. 6.8 %
76 g/g mercury i.e. 7.6 %
12 g/g arsenic i.e. 1.2 %
i.e. 15.5 % heavy metals
• Case 2: 50 g/g lead i.e. 5.0 %
39 g/g mercury i.e. 3.9 %
i.e. 8.9 % heavy metals
Ayurvedic Traditional Remedies
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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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Blood lead concentration (µg/L)
Children: <400Adults: <400
400-500400-600
500-700600-1000
>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
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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
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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, ALA
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• 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)
Management of Lead Poisoning
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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, <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 !!
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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
>700µg/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
>700µg/l : Remove from source : DMSA chelation
: EDTA if neurological features