Lead Dr Mark Little Clinical Toxicologist and Emergency Physician - - PowerPoint PPT Presentation
Lead Dr Mark Little Clinical Toxicologist and Emergency Physician NSW Qld WA Poisons Information Centre March 2011 Aim Discuss Toxicology of lead Symptomatic childhood poisoning Asymptomatic childhood poisoning - why the concern
Clinical Toxicologist and Emergency Physician NSW Qld WA Poisons Information Centre March 2011
Discuss
Toxicology of lead Symptomatic childhood poisoning Asymptomatic childhood poisoning - why the concern Medical management My recommendations
One of first metals smelted & used Lead based ochre paints Neanderthal era (40 000BC) Lead artifacts found in sites from Turkey 6200 BC Ancient Hebrews and Egyptians used lead Romans used lead for pipes, ceramic glazes, cooking utensils.
Most widely used non ferrous metal Global production 9 million tons pa Uses:
Waterproofing, electrical & radiation shielding Batteries Telephone cables Solder Ammunition Paint Fuel additive
Greek physicians 2BC
CNS effects “mind gave way”
Pliny warned of the danger of inhaled lead fumes from smelting Benjamin Franklin (1763) described “dry gripes” = abdominal colic “dangles” = wrist drop In tinkers, painters and typesetters
Absorption:
Inhalation: <1mcm in alveoli Ingestion:
Transplacental: readily crosses
Distribution:
99% bound to RBC Deposited Bone Teeth Soft tissue CNS prefers grey matter
Excretion:
Mainly urine (65%) and bile (35%) Miniscule amount in hair Vit C may enhance excretion
Lead binds to sulfhydryl groups effecting numerous enzymatic, receptors and structural proteins Similar to calcium so interfers with multiple metabolic pathways
No known physiological role for lead Any lead found in the body fluids represents environmental contamination
BLL (mcg/dL) Effect in adults 100 Life threatening encephalopathy 80 Anaemia Impaired kidney function 60 Reduced fertility females 40 Impaired conduction peripheral nerves 30 Hypertension Reduced testicular function
Children - especially under 4 Pregnant women - unborn baby Breast feeding mothers Those working with lead
Measure of body lead load Blood lead level used as primary biomarker
Urine is insensitive Hair in unreliable Shed teeth is used in research
BLL > 10 mcg/dL Recommended by NHMRC, CDC, WHO, AAP However we should aim for a BLL as low as possible
Age Mean BLL mcg/dL 6 months 3.4 24 months 9.7 61 months 5.8
Canfield et al NEJM 03
Mt Isa Blood Lead Survey July 2007: children 1 - 4 years
10 20 30 40 50 60 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 Rounded Blood Lead mcg/dl Number (n = 328)
Mean 5.8 mcg/dL Median 5 mcg/dL
Everyone
Lead paint poisoning recognised in Brisbane (Aust Med
Gaz 1897)
Law passed banning lead paint for houses 1914 USA only passed similar law 1961!
Children recovering from symptomatic lead poisoning frequently left with neurological sequelae and intellectual impairment (Am J Dis Child 1943)
Symptomatic paediatric lead poisoning commonly seen in 1950/60’s in USA and effective chelation protocols developed (Paeds 1957, J Paed 1966) Recognition & quantification of more subtle neurocognitive impairment due to subclinical poisoning in 1970/80’s (NEJM 1972)
1. Acute lead encephalopathy [SEVERE] (BLL>70mcg/dL)
behaviour, ataxia, change in developmental skills, CN palsies
2. Subencephalopathic [MODERATE] (BLL>50mcg/dL)
Often difficult to diagnose 1-5 yo “terrible two’s” Irritable, intermittent lethargy, constipation, intermittent vomiting, abdominal pain & anorexia Often not recognised until after chelation
Children with elevated lead burden but without overt symptoms the largest group of persons at risk from chronic lead toxicity Numerous studies demonstrate a correlation between elevated lead levels and:-
Increased rate learning disabilities Lower IQ Lower class rank
Goldfrank’s Clinical Toxicology 7th ED
Blood lead level (mcg/dL) ?
Succimer = 2,3dimercaptosuccinic acid [DMSA] Oral agent SAS drug
Adults Symptomatic BLL >60 mcg/dL Children Symptomatic BLL > 45 mcg/dL [Has been used to chelate mercury, arsenic, bismuth, antimony, copper - limited experience]
780 children with BLL 20 - 45 mcg/dL Randomised double blind placebo controlled trial 3 x 25 days of succimer
Those treated with succimer reduced BLL No improvement in cognition, behaviour or neuropsychiatric testing Succimer is NOT indicated in these children
“…Suggests that as there is no effective treatment for children with moderate lead levels the collective evidence argues for shift toward primary prevention of lead exposure…”
Genetic Prenatal factors Socioeconomic factors Nutrition Smoking/drugs Parent and family nuturing
172 children BLL measured 6,12,18,24,36 mo Stanford Binet intelligence scale at 3 and 5 yrs Regression modelling
For 101 children with BLL < 10mcg/dL IQ dropped by 7.4 pts for lifetime average BLL <10 mcg/dL
Effects of early childhood lead exposure on academic performance and behaviour of school aged children Arch Dis Child 2009
582 children at 30 months had BLL Developmental behavioural and standardised educational outcomes at 7 - 8 yrs
488 cases had all data on confounders Regression analysis
Exposure to lead early in childhood even at low levels is harmful on behaviour and school performance Reduce level of concern to 5 mcg/dL
To determine the effectiveness of household interventions in reducing lead exposure Only 12 studies All in the USA
No evidence of effectiness of household interventions for education or dust controls Insufficient evidence for soil abatement Further trials required to establish the most effective intervention for the prevention of lead exposure
Lead is here in Mt Isa Children absorb more lead that adults Children around 2 years seem to have the highest BLL Children probably absorb most of the lead through ingestion
Dust Lead paint and home renovations Contaminated people, clothes cars or items Rain water
Wash hands (especially children) before eating Wet wipe and mop Those working with lead shower and change before coming home Shoes/work gear outside Reduce exposure to potentially contaminated soil
Regular meals Diet high in iron, zinc, calcium and vit C
Aim for BLL < 10 mcg/dL The lower the better Everyone should be tested Opportunity to explain lead and its toxicity/reduction of exposure
CDC
Test entire family Involve Public Health Unit
BLL is best measure of lead body load BLL < 45 mcg/dL
Not use chelating drug Seek enviromental source and limit
Asymptomatic child BLL > 45mcg/dL Seek source Chelate with succimer dw toxicologist/PIC Symptomatic or BLL > 70 mcg/dL Admit Immediate chelate - dw Toxicologist/PIC
Lead poisoning humans for centuries Elevated BLL indicates environmental contamination Main concern is in children and the risk of cognitive development Major management [BLL < 45 mcg/dL] is removal from the lead source
Will have an ongoing lead exposure Need to have an ongoing process of education of community to reduce exposure to children Need to test the entire population
Clinical Toxicologists available through the Poisons Information Centre system Ph 13 11 26 any time and ask for a toxicologist