AFARI PALM VILLAGE PHASE 2 PLOT ASD.ppt

Lead goes down iron or calcium absorption pathway in GIT.
Children absorb lead well orally (~50%) cf adults poorly (~10%). Children also have more hand to mouth activity.
Lead absorption is enhanced if diet is poor in iron or calcium.
Pica is one of the worst risk factors.
Lead can be inhaled.
Tetraethyl lead can be absorbed via skin.

1. Lead Poisoning
Dr. Ben Balzer
Technical Advisory Board member
The LEAD group (general practice)
(Lead Education and Abatement Design Group)
1
6 September 2000

2. Lead Poisoning
Lead has no known biological function.
There is no proven safe lower limit for lead.
Lead Pb
++
, competes with Ca
++
, Fe
++
It is cheap, useful, easy to mine, therefore
Lead is ubiquitous- in air, food, water, soil, ceilings etc.
Leaded petrol means that all environmental dusts are
high in lead- contaminating ceiling dust, topsoil,
window wells etc.
2

3. Uses and Sources
of Lead
  Paint (until 1970)
  Petrol (tetraethyl lead)
 Household dust (via settlement of air pollution)
 Ceiling dust
 Occupational
 Solder
 Ceramic glazes
  Pesticides (lead arsenate)
 Cigarettes
  Mines, smelters
3

4. More Uses and
Sources of Lead
 TV's, Computer monitors
  Batteries, Bullets Sinkers
 Aviation
 X-ray shields
 Crystal-ware (high levels in
decanters)
 Explosives
 Non-stick linings of pots (in the past)
 Plastic colouring (wire, blinds)
 Pewter
4

5. Absorption of
Lead
 Lead goes down iron or calcium absorption pathway in
GIT.
 Children absorb lead well orally (~50%) cf adults poorly
(~10%). Children also have more hand to mouth activity.
Lead absorption is enhanced if diet is poor in iron or
calcium.
Pica is one of the worst risk factors.
Lead can be inhaled.
Tetraethyl lead can be absorbed via skin.
5

6. Absorption of Lead
6

7. Contribution of
Sources
S:\Leadgpc\BB Lead Poisoning.ppt 7

8. Reduction of Lead hazards in
the home
S:\Leadgpc\BB Lead Poisoning.ppt 8

9. Distribution of
Lead
95% long bones.
Binds into matrix.
Released during
osteolysis.
4% brain, liver, kidneys.
1% blood.
Crosses placenta, foetal
BBB is open
9

10. Release of lead during osteolysis
Pregnancy increases mobilization of lead from
maternal skeleton
Gulson BL, Jameson CW, Mahaffey KR, Mizon KJ, Korsch MJ, Vimpani G.. J Lab Clin Med
1997a;130:51-62
Mobilization of lead from the skeleton during the
post-natal period is larger than during pregnancy.
Gulson BL, Mahaffey KR, Jameson CW, Mizon KJ, Korsch MJ, Cameron MA, Eisman JA. J Lab Clin
Med 1998a;131:324-9
Lead is released in menopausal bone loss
Lead levels have second peak in middle age- more
in men than women (NHANES 3).
Lead follows calcium into and out of bone.
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11. Lead movement
In childhood, blood lead levels reflect the
environmental lead level ie exogenous lead.
Protection requires placing barriers between
the child and the lead.
In adults, lead levels reflect the release of
endogenous lead from bone, as well as the
intake of exogenous lead. Protection requires
prevention of exposure plus preservation of
bone density.
11

12. Data from the US NHANES 3 study showing the second
peak of lead levels in adulthood. Higher adult male levels
reflect occupation and hobby. High risk occupations would
be even higher. Women get a post-menopausal peak.
12

13. Lead and Race. Data from the US NHANES 3 study
showing differences with race –probably reflecting
differences in accommodation and occupation
13

14. Health Effects
of Lead
Concentration
related
IQ/ delinquency
related to total
dosage in childhood
14

15. Recommended Lead level
<0.48 µmol/L (10 µg/dL)
< 0.48µmol/L (10µg/dL)
= NHMRC Goal.
>0.48µmol/L (10µg/dL)
= elevated.
>0.72µmol/L (15µg/dL)
=substantially elevated. Notifiable
level.
1.20µmol/L (25µg/dL)
= dangerously elevated.
>2.20µmol/L (45µg/dL)= Symptomatic.
15

16. Symptoms from lead are rare!
16

17. Lead and
Neurodevelopment
Each 0.48 µmol/L(10µg/dL) in children.
 = 4 to 7 IQ points (US Acad. Pediatrics).
Industry/ Australian government consensus
of 3-5 IQ points.
Effects on behaviour are FAR WORSE.
Delinquency rates are 8 times higher in the top
30% of bone lead. Needleman 1996.
Needleman, Herbert L. et al, "Bone Lead Levels and Delinquent Behavior," JOURNAL OF THE AMERICAN
MEDICAL ASSOCIATION Vol. 275, No. 5 (February 7, 1996), pgs.363-369.
Measurable adverse behaviour changes in 2 year
olds Mendelsohn 1999. Alan L. Mendelsohn, Benard P. Dreyer, Arthur H.
Fierman, Carolyn M. Rosen, Lori A. Legano, Hillary A. Kruger, Sylvia W. Lim, and Cheryl D.
Courtlandt "Low-Level Lead Exposure and Behavior in Early Childhood“ Pediatrics 1998; 101: e10
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18. Lead and IQ
18

19. Toxicology of Lead 1
Lead disrupts the main structural components of
the blood-brain barrier by primary injury to
astrocytes with a secondary damage to the
endothelial microvasculature. Within the brain,
lead-induced damage occurs preferentially in the
prefrontal cerebral cortex, hippocampus and
cerebellum. Some characteristic clinical features of
lead poisoning may be attributed to this specific
anatomical pattern.
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20. Toxicology of Lead contd
Although the molecular targets for lead are unknown, a vast
amount of evidence accumulated over many years has
shown that lead disrupts processes that are regulated by
calcium.
Picomolar concentrations of lead can replace micromolar
concentrations of calcium in a protein kinase C enzyme
assay. Furthermore, lead activates protein kinase C in intact
cells and induces the expression of new genes by a
mechanism dependent on protein kinase C. We propose that
the learning deficits caused by lead are due to events
regulated by protein kinase C that most likely occur at the
synapse.
Bressler J, Kim KA, Chakraborti T, Goldstein GMolecular mechanisms of lead
neurotoxicity. Neurochem Res 1999 Apr;24(4):595-600
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21. Toxicology of Lead 3
The cellular, intracellular and molecular
mechanisms of lead neurotoxicity are numerous,
as lead impacts many biological activities at
different levels of control: at the voltage-gated
channels and on the first, second and third
messenger systems. These effects could be related
to lead's ability to interfere with the regulatory
action of calcium in cell functions.
Finkelstein Y, Markowitz ME, Rosen JF Low-level lead-induced
neurotoxicity in children: an update on central nervous system effects
Brain Res Brain Res Rev 1998 Jul;27(2):168-76
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22. Toxicology of Lead 4
At a neuronal level, exposure to lead alters the release of
neurotransmitter from presynaptic nerve endings.
Spontaneous release is enhanced and evoked release is
inhibited. The former may be due to activation of protein
kinases in the nerve endings and the latter to blockade of
voltage-dependent calcium channels. This disruption of
neuronal activity may, in turn, alter the developmental
processes of synapse formation and result in a less efficient
brain with cognitive deficits. Bressler JP, Goldstein GW
Mechanisms of lead neurotoxicity. Biochem Pharmacol 1991 Feb
15;41(4):479-84

?Effect of lead on omega 3 and 6 fats.
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23. Lead and the Elderly
Risk of dementia increases with lead
burden
Risk of accidental lead ingestion
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24. Dementia and lead 1
The relationship between performance on cognitive
tasks and circulating levels of lead in blood and
accumulated levels of lead in bone was examined in 141
middle-aged and elderly men. Men with higher levels of
blood and bone (tibia) lead copied spatial figures less
accurately; men with higher levels of bone (tibia) lead
had slower responses for pattern memory. These
findings suggest that low levels of lead contribute to
impairments in cognitive function among elderly men.
Payton M, Riggs KM, Spiro A 3rd, Weiss ST, Hu H Relations of bone and blood lead to
cognitive function: the VA Normative Aging Study.
Neurotoxicol Teratol 1998 Jan-Feb;20(1):19-27
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25. Dementia and Lead 2
/~/ the cross-sectional relationship between blood lead
levels and a variety of measures of neuropsychological
function in a large cohort of elderly women /~/ This
study / demonstrates that blood lead levels as low as 8
micrograms/dl were significantly associated with
poorer cognitive function as measured by certain
neuropsychological tests. Even a slight decrement in
cognition would have a large public health impact due
to the large number of elderly at risk.
Muldoon SB, Cauley JA, Kuller LH, Morrow L, Needleman HL, Scott J, Hooper FJ
Neuroepidemiology 1996;15(2):62-72Effects of blood lead levels on cognitive function of
older women.
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26. Niklowitz WJ Neurofibrillary changes after acute
experimental lead poisoning.
Neurology 1975 Oct;25(10):927-34
Following acute tetraethyl lead intoxication in
rabbits classic neurofibrillary tangles develop. As
studied by electron microscopy, such tangles develop
in hydropic degenerating neurons and consist
primarily of bundles of 200 A diameter smooth
tubules of enormous length. In two of 16 animals a
few twisted tubules (periodicity of 800 A) also could
be found. The significance of these lead-induced
twisted tubules, so characteristic of Alzheimer's pre-
senile dementia in man, is discussed.
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27. Unresolved Questions
How much does lead contribute to cognitive
decline and Alzheimer’s disease?
Do bone preserving therapies or calcium
supplements reduce cognitive decline?
Is lead a modifiable risk factor for dementia?
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28. Incidence of Elevated Blood
Leads Sydney 1996 Mira Et Al.
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29. Does Your Child…
Have a brother or sister, housemate or playmate
with an elevated blood lead level?
Sometimes eat non-food items such as soil or paint?
Have any of the following conditions sometimes
associated with lead poisoning, eg iron deficiency
anaemia, behaviour problem, learning problem or
developmental delay?

30. If your child is aged between 9 and 48 months, does he or
she:
     Live in, or frequently visit, a house* built before 1970
with peeling or chipping paint?
     Live in, or frequently visit, a house* built before 1970
with or ongoing renovation where old paint (interior or
exterior) has been burnt or sanded off, or where ceilings,
walls or floors demolished?
     Live in, or frequently visit, a house near a lead releasing
industry, eg lead mine, lead smelter, battery-recycling plant?
Live with an adult whose job or hobby uses lead? (eg lead
mining or smelting, automotive repair, panel-beating,
leadlighting, fishing sinker making, electronics, shooting
instruction, car-battery service/ repair or manufacture).  

31. U.S. Lead Situation 1
1. 
  
1978 Lead banned from paint
2. 
  
1980's- Levels higher than Australia
3. 
  
Late 1980's Removal of lead from gasoline
4. 
  
1980's Universal questionnaire screening
5. 
  
1991 Universal blood testing
6. 
  
1990's Public housing program
7. 
  
1990's Private housing program
8. 
  
1990's Massive EPA environmental program
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32. U.S. Lead Situation 2
9. 
  
~1995 Title X regulations for sale of properties built
before 1978.
10. 
  
~1997 Lead litigation compensation approaches
asbestos in some states.
11. 
  
1998 Builders, tradesmen required to issue
documents warning clients of risk when they
renovate properties built before 1978.
12. 
  
1998 Successful reduction in community levels
leads to reintroduction of questionnaire screening in
some areas.
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