Lead and public health

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Feb 4, 2015 - Needleman, Herbert L. et al, "Bone Lead Levels and Delinquent Behavior," JOURNAL OF THE AMERICAN. MEDICAL ASSOCIATION Vol. 275 ...

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The 3rd International Public Health Conference & The 20th National Public Health Colloquium, 27-29 August 2013 Kuching, Sarawak

Prof. Madya Dr Shamsul BS Centre of Occupational Safety & Health Universiti Malaysia Sabah

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.

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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

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 coloring (wire, blinds) Pewter

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Environmental Sources of Childhood Lead Exposure

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.

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Contribution of Sources

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Distribution of Lead      

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

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;130:5162



Mobilization of lead from the skeleton during the postnatal 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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Risk groups   

Children Pregnant women and developing fetus. Specific occupational exposure

Why are Children at High Risk? 

Children’s nervous systems are still developing



Young children have more hand-to-mouth activity than older children



Children absorb more lead than adults

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Effects of lead exposure on young children 

Lowered IQ



Learning disabilities



Attention deficit and hyperactivity



Other behavioral issues



Impaired hearing



Anemia



Decreased growth

Children blood lead data (Malaysia 1996-2013)

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Children Blood Lead Levels in the U.S.

Blood Lead Levels (µg/dL)

population 1976-2002 (NHANES)

Year

CDC US “Blood lead level of concerns” (1991) Groups

Blood lead (µg/dL)

Measures must be taken Not considered to be suffering from lead poisoning. No treatment is needed for this group.

A

Less than 10

B

10 - 14

This group is noteworthy. Impairment of intelligence levels can occur, even if the child does not show any signs of toxicity.

C

15 - 19

Children in this group should be given special action such as a balanced diet and an education program to reduce lead concentrations. Follow-up testing is required. Although treatment may not be necessary, but children must be separated from the source of lead.

D

20 - 44

Children in this group require a medical evaluation and to be separated from the source of exposure.

E

45 - 69

Children in this group require medical attention, including treatment cure and environmental assessment to determine the cause of lead.

Lead concentrations at the level of danger. Medical treatment and isolation of lead sources are urgently needed. Source: Center for Disease Control (CDC) USA, 1991 F

More than 70

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New Recommendations to Define Elevated Blood Lead Levels (CDC, 2012)  In January 2012, a committee of experts recommended that the CDC change its “blood lead level of concern.”  The recommendation was based on a growing number of scientific studies that show that even low blood lead levels can cause lifelong health effects.  Currently, the new value is 5 µg/dL of lead in blood.  The new value means that more children will be identified as having lead exposure earlier.  Suggested parents, doctors, public health officials, and communities can take action earlier and the expert committee also said, that the best way to protect children is to prevent lead exposure in the first place.

Health Effects of Lead

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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

Lead and IQ

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Programs Awareness & Educations

Legislative & Policy

National Public Health Programs

Research

Consultancy

Reduction of Lead hazards in the home

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