lead symptoms and exposure route

Topics: Lead, Toxicity, Crime Pages: 9 (813 words) Published: September 26, 2013
Elemental Exposure-General
Truisms

Childhood Lead Poisoning
Why you might be smarter than your parents

• Most are not toxic
• Nutritional = less toxic (Zn, Cd)
Noel Stanton
WI State Lab of Hygiene
2601 Agriculture Drive
PO Box 7996
Madison WI 53707
(608) 224-6251
nvstox@mail.slh.wisc.edu

– Homeostasis

• Abundance

= toxicity

• Every truism has exceptions

Speciation Considerations
• Can greatly influence toxicity
• Ability to differentiate limited, improving
– Cr+3 = nutrient, Cr +6 = carcinogen
– Toxicity As+3 > As+5 >>organic As

or

Exposure Routes

?

Assessment
• Contamination biggest concern
– serum Al: 1970 = 1,000 µg/L, 2002 = 2 µg/L

• Ingestion—most common
• Inhalation—more dangerous

Mechanisms of Action
• Binding to SH groups
– alters protein shape

• Substitution for nutritional element

• Best sample will be element
and species dependent
– correlation w/disease often limited
– Blood, urine, serum typical
– Hair is generally NOT valid

• Analytical methods
– Atomic spectrometry (AA, ICP-MS)
– Electrochemical (ion-specific electrodes, ASV)
– XRF

1

Lead and Exposure
• Many uses-now~85% batteries
• Widely dispersed in environment
– U.S., huge reservoir in housing

• Well-characterized env. toxin
• Many toxic effects
• Young children most impacted
– Subclinical effects

Major Public Health Success
• Existing blood Pb threshold for action = 10 µg/dL
• 1976-80, mean blood Pb ~14.9 µg/dL (88%>10)
• 2002, mean blood Pb ~1.7 µg/dL (1.2%>10)

But…Still a Big Problem
• Nationally, 1.2% still >10, ~180,000 kids
• WI 4.7% entering school had Pb >10 (2006)
• 2111 kids (2.6% tested) >10, ~5/day (2006)

The Lead-Learning Link






Low-level Pb effect studies began 1970’s
Linked IQ, cognitive problems with Pb
Studies replicated worldwide
Early study populations still followed
Demonstrated links to delinquency,
violence, etc.
• IQ as Pb may be steepest at lower [ ]
Locations associated with Pb-poisoned children, 1996-2006 (WI DHFS)

2

Confounding Variables
• Studies control for many other influences
• Examples include:
Parental education level(s)
Maternal age at birth
Smoking during pregnancy
Birth weight
Birth order
Feeding style (breast or bottle)
HOME* score
Maternal IQ
Gender of child
Socio-economic status
Race of child
Immunization history
Parental occupation(s)
Alcohol consumption
*HOME = Home Observation for Measurement of the Environment

Lead Toxicokinetics
• Absorption
– Inhaled lead ~40% (not sig. for children)
– Ingested lead ~10-40% (children) ~32%% adults

• Distribution
– Blood & soft tissue, ½ life=30-40 days
– Tooth & bone, ½ life=25 years (>90% body burden)
– Equilibrium exists between the compartments

• Excretion primarily via bile/feces & urine, ~2:1

3

Treatment
• Identify & eliminate exposure source
• Chelating agents
– BAL--selective, IM injection
– EDTA--IV, broad chelater
– DMSA--selective, oral

Major Pb Exposure Sources
• Lead-based paint
– 38 million homes have LBP
– 24 million have lead hazards
– 1.2 of the 24 million w/young kids
Jacobs et al., Env Hlth Persp 2002:110 #10

• Soil, from paint and gasoline
• Industrial sources--restricted

4

Other Exposure Sources
• Ceramic glazes
• Traditional medicines & cosmetics

Recent Hazards
• Consumer products
– TOYS
– Jewelry
• CSPC moves to ban
• Death in MN 2006

– Sidewalk chalk 2003

Risk Factors/Predictors
• Housing age & condition
– 92% of WI poisoned kids live in pre-1950 housing

• Poverty
– 88% of poisoned kids in Medicaid/WIC






Housing renovation
Residency Status
Pica and developmental deficits
Fe and other dietary deficiences

5

Hg Health Effects, cont’

Pb Isotope Ratios

Housing age of WI Pb-poisoned kids when 1st diagnosed

• Inorganic Hg
– G.I. tract necrosis
• cramps, bloody diarrhea, circulatory collapse

– renal failure...
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