Occupational and Environmental Chemical Exposures Heavy Metals: Lead and Mercury

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Occupational and Environmental Chemical
Exposures Heavy Metals Lead and Mercury

• Mary McDaniel, D.O., J.D., M.P.H.
• McDaniel Lambert Inc.
• mfmcdaniel_at_mclam.com
• UCLA
• February 21, 2006

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Whos 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 (contd)

• 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) Blood Lead
• Level of concern for fetal effects lt10
• Blood enzyme changes 15-20
• IQ deficiencies in children lt25
• Clinical anemia, children 40
• Clinical anemia, adults 50
• Reproductive effects in adults 50
• Mental losses (writing/speech 50-60
• problems, retardation)
• Irreversible brain damage 100

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Lead Standards and Regulations

• Blood Levels
• CDC Advisory level of concern for children 10
  ug/dL
• OSHA level of concern 40 ug/dL
• OSHA Regulation medical removal from
  exposure 50 ug/dL
• Air Concentrations
• OSHA Action level 30 ug/m3
• OSHA Regulation PEL 50 ug/m3
• US EPA ambient air quality standard (3 month
  average) 1.5 ug/m3
• Food
• EPA drinking water action level 15 ug/L
• CalEPA drinking water public health goal 2
  ug/L
• CalEPA drinking water maximum contaminant
  level 15 ug/L
• FDA food advisory level
  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 gt10 ug/dl
• 21.6 of 1 to 2 year-old black children have
  blood lead levels gt10 ug/dl

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Blood Lead Levels for Various Groups of People

• Rural Children 7-11
• Urban Children 9-33
• Adults 15-22
• Children near smelter 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
Hg0

• 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 0.1 mg/m3
• metallic mercury vapor PEL 0.05 mg/m3
• Water (inorganic mercury)
• EPA drinking water maximum contaminant level 2
  ug/L
• CAlEPA drinking water public health goal 1.2
  ug/L
• CAlEPA drinking water maximum contaminant
  level 2 ug/L
• Food
• FDA Fish action level 1 ppm
• USEPA fish action level 0.3 ppm
• Japan fish action level 0.3 ppm
• Australia fish action level 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 Joes 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 its 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