LEAD POISONING

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

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

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

• 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

• 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

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

• 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

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: <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

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, ALA

• 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

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 - 2,3dimercaptosuccinic 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 !!

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