Transcript Environmental Chemical Exposures and Children: What You

Occupational and Environmental
Chemical Exposures
Heavy Metals: Lead and Mercury
Mary McDaniel, D.O., J.D., M.P.H.
McDaniel Lambert Inc.
[email protected]
UCLA
February 21, 2006
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Who’s at Risk?
Occupational Exposure
Household exposure
Ambient exposure
For many chemicals, fetuses, infants and/or
children are at greatest risk due to
susceptibility to toxic effects and/or increased
exposure
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Lead
Long history of human exposure (5000 yrs
plus).
Thought to have been responsible for downfall
of Greek and Roman civilizations.
Widespread environmental contaminant.
Childhood lead poisoning was first described in
Australia 100 years ago
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Sources of Lead Exposure –
Ingestion and Inhalation
Occupational – lead mines, smelters and refiners,
plumbers, auto repair, police officers, glass
manufacturers, battery manufacturers.
Hobbies – glazed ceramics, target shooting,
soldering (electronics, stained glass), painting,
home repair activities.
Environmental – leaded gasoline and paints, water
from corroded pipes, earthenware, contaminated
soil and dust, imported canned foods/candy
Substance use – folk remedies, health foods
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Nutrition and Lead
Ingestion of lead during a period of fasting
results in greater absorption
Dietary intake of calcium has a very significant
effect on lead uptake
 Rats on a low-calcium diet had four times higher
blood lead concentrations than rats on a normal diet
Intake of iron is also important with low levels
increasing the uptake of lead
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Lead Health Effects
Interferes with normal cell function and various
physiological process: peripheral and central
nervous systems, blood cell production,
metabolism of vitamin D and calcium, kidneys,
reproductive system
Probable human carcinogen (classified B2 by
USEPA)
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Lead Health Effects (cont.)
 Children and pregnant women at highest risk
 Children – higher exposures and postnatal
susceptibility
 For every 10 ug/dl increase in concentration
there is a one to three-point drop in IQ
 Pregnant women – lead crosses the placenta
and damages nervous system
 Lead in the fetus tends to equilibrate with
maternal lead
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Lead Health Effects (cont’d)
Symptoms of lead poisoning
Early symptoms are vague and
nonspecific
Pallor, vomiting, abdominal pain,
constipation, stupor, loss of appetite,
irritability, and loss of muscular
coordination
Classic signs include lead colic, lead
“lines” on the gums and wrist drop
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Lead Biological Fate
 Inorganic lead not metabolized – directly absorbed,
distributed and excreted
 Inhaled lead completely absorbed; typically 10-15% of
ingested lead absorbed from the GI tract
 Lead half lives in adults
 Blood – 25 days
 Soft tissue – 40 days
 Bone – 25+ years
 Lead poisoning does not require major acute exposure body accumulates over lifetime and releases slowly
 Under stress, body may metabolize lead stores, thus
increasing blood lead levels
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Health Effects at Various Blood
Lead Levels
Health Effect (ug/dl)
Level of concern for fetal effects
Blood enzyme changes
IQ deficiencies in children
Clinical anemia, children
Clinical anemia, adults
Reproductive effects in adults
Mental losses (writing/speech
problems, retardation)
Irreversible brain damage
Blood Lead
<10
15-20
<25
40
50
50
50-60
100
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Lead Standards and Regulations
Blood Levels
CDC Advisory – level of concern for children
OSHA – level of concern
OSHA Regulation – medical removal from exposure
10 ug/dL
40 ug/dL
50 ug/dL
Air Concentrations
OSHA Action level
OSHA Regulation – PEL
US EPA – ambient air quality standard (3 month average)
30 ug/m3
50 ug/m3
1.5 ug/m3
Food
EPA – drinking water action level
CalEPA – drinking water public health goal
CalEPA – drinking water maximum contaminant level
FDA – food advisory level
15 ug/L
2 ug/L
15 ug/L
100 ug/day
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Poverty and Lead Poisoning
Impact greatest among urban poor
 Older housing more lead based paints and lead
contaminated soils
 Older schools
4.5% of all 1 to 2 year-old children have blood
lead levels >10 ug/dl
21.6% of 1 to 2 year-old black children have blood
lead levels >10 ug/dl
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Blood Lead Levels
for Various Groups of People
Rural Children
Urban Children
Adults
Children near smelter
7-11
9-33
15-22
35-68
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Diagnosis
 Exposure Interviews
 Occupation, housing, lifestyle/hobbies, school exposures,
pica child
 Signs and Symptoms: most persons with lead toxicity
are not overly symptomatic
 Continuum includes increasing severity of fatigue, irritability,
lethargy, abdominal pain
 School
 Pica
 Blood lead level is best screening and diagnostic test
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Treatment
Depends on exposure level
Limit exposure
May be only therapy needed for asymptomatic patients
with blood levels below 25 ug/dL
Dietary changes
 Ca supplements
Chelation therapy (e.g. calcium disodium EDTA)
CDC recommends immediate chelation therapy for children
with blood levels of 45 ug/dL and above
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Mercury
0
Hg
Long history of use
 Metallic mercury used as a laxative
 Mad Hatters disease from use in felt manufacture
 Andrew Jackson thought to have died from mercuric
chloride treatment
 “Dancing Cat Disease”
Chemistry
 Exists in 3 forms: elemental, inorganic salts and organic
 Elemental (metallic) mercury (Hg0) can be converted to
organic methylmercury (MeHg) in the environment by the
action of bacteria
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Sources of Mercury Exposure
Highest exposures have been from industrial
or pesticide poisonings (Minamata, Japan –
Chlor-alkali; Iraq – Wheat fungicide)
General population mostly exposed by eating
contaminated fish (methylmercury)
Fish bioaccumulate methyl mercury with 99% of
mercury in fish in the the methylated form
Older and larger carnivorous fish have the highest
levels (swordfish, tuna, shark, king mackerel)
Can of tuna contains 0.20 ppm
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Sources of Mercury Exposure
(cont.)
Occupational (primarily elemental mercury
vapor) – chlor-alkalai plants, laboratory
personnel, miners and processors of cinnabar,
gold, silver, copper, and zinc, metallurgists,
ectroplaters, explosive manufacturers
Hobbies – fishing
Environmental – atmospheric deposition from
coal-fired power plants, incineration of
municipal and solid waste, latex paints, fish
consumptions
Substance use – folk medicines, cosmetic;
dental amalgams have not been proven to
cause adverse effects.
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Mercury Health Effects
Effects depend on duration, intensity, and route of
exposure, and chemical form
Central nervous system and kidneys are key
targets
Elemental mercury: nervous system
Mercury salts: respiratory or GI (acute exposure);
kidneys (chronic exposure)
Organic mercury: nervous system; developmental
effects
Elemental mercury not classified with respect to
carcinogenicity (USEPA Class D)
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Observed Effects of Methylmercury
Toxicity
 Iraq and Minamata (Japan)
 Effects in utero quite different from childhood or adult
exposures
 Fetus is the most sensitive
 Methylmercury exposed women have delivered infants with
severe behavioral and sensory deficits, including deafness
and blindness without maternal toxicity
 Prenatal exposure results in a widespread pattern of
adverse effects on brain development and organization
 Alters the normal migration of neurons to cerebellar and
cerebral cortices during brain development
 Reduced brain size
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Mercury Controversy
 Two recent studies of predominately fish eating
populations:
 Faroese Islands
Dose dependent relationship seen (delayed
language, reduced memory and attention
spans)
 Seychelle Islands
No health effects observed
 Many experts strongly advise pregnant women and
women of child bearing age to limit exposure
 However, fish is a significant source of protein
throughout the world, some argue that the benefits
outweigh the potential risk from low-level exposure
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Mercury Biological Fate
Chemical and physical form of mercury determine
absorption, metabolism, distribution, and excretion
pathways
 Elemental mercury: nearly completely absorbed when
inhaled; poorly absorbed when ingested or via dermal
contact; readily crosses blood-brain barrier
 Mercury salts: Mercuric Hg2+) salts are generally more
soluble, and therefore more toxic than mercurous
(Hg1+) salts; on average, less than 10% of ingested salts
absorbed in GI tract; do not cross blood-brain barrier as
readily
Organic mercury: readily absorbed by inhalation, dermal,
contact, and ingestion; distributed uniformly to all tissues,
although concentrated mostly in blood and brain.
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Mercury Standards and
Regulations
Air Concentrations
OSHA – organic mercury PEL
metallic mercury vapor PEL
0.1 mg/m3
0.05 mg/m3
Water (inorganic mercury)
EPA – drinking water maximum contaminant level
CAlEPA – drinking water public health goal
CAlEPA – drinking water maximum contaminant level
2 ug/L
1.2 ug/L
2 ug/L
Food
FDA – Fish action level
USEPA – fish action level
Japan – fish action level
Australia – fish action level
1 ppm
0.3 ppm
0.3 ppm
0.5 ppm
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California Proposition 65 Fish
Lawsuit
 Filed by Attorney General/TI January 2003
 USFDA listed fish: swordfish, mackerel, tile fish, and
shark
 Safeway, Kroger, Albertsons, Trader Joe’s and Whole
Foods
 Dr. Katherine Mahaffey who wrote USEPA Mercury report
to Congress and helped developed RfD says “ . . . other
states are going to pick up the idea. Clearly it’s an
important step.”
 Red Lobster is next . . .
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Diagnosis
 Exposure Interviews
Occupation, housing (recent move), lifestyle/hobbies (fish
consumption), school laboratory
 Signs and Symptoms
Elemental mercury: pulmonary and CNS effects (cough, chest
pain, colitis, pulmonary edema); chronic exposure may result in
tremor and personality disorders
Mercury salts: affects GI tract and kidneys
Organic mercury: typically nonspecific and delayed (ataxia,
malaise, blurred vision); chronic exposure may result in
permanent CNS damage
 Blood lead level typical test for acute exposure; urine
test for chronic exposure
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Signs and Symptoms at Various
Urine Mercury Levels
Sign and Symptoms
Urine (ug/L)
Decreased response on tests for nerve condition, brain
wave activity and verbal skills; early indication of tremor
2-100
Irritability, depression, memory loss, minor tremor, other
nervous system disturbances; disturbed kidney function
100-500
Kidney inflammation, swollen gums, significant tremor and
nervous system disturbances
500-1000
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Treatment
Depends on form of mercury exposure
Elemental mercury of mercury salts
Limit exposure
Chelation therapy
Organic mercury
No antidote; supportive care recommended
Chelating agent BAL contraindicated, as it has been
shown to increase methylmercury concentrations in
the brain
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Toxicology
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