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Heavy Metal Toxicity


Heavy Metal Toxicity PATHOPHYSIOLOGY UNIT 2-FACTORS OF DISEASE ENVIRONMENTAL FACTORS Arsenic Lead Mercury * Definitions Metals originally included only gold ... – PowerPoint PPT presentation

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Title: Heavy Metal Toxicity

Heavy Metal Toxicity
  • Pathophysiology
  • Unit 2-Factors of Disease
  • Environmental Factors

  • Metals originally included only gold, silver,
    copper, iron, lead, and tin.
  • Dense, malleable, lustrous
  • Conduct heat and electricity
  • Many other elements since added to the list with
    some of these characteristics
  • Metalloids are elements with features
    intermediate between metals and non-metals.
    Examples lead and arsenic

Heavy metal
  • A metal having an atomic weight greater than
    sodium, a density greater than 5 g/cm3
  • Some notion of toxicity
  • Includes cadmium, lead and mercury

Lead Paint
  • The use of lead in residential paint was banned
    in 1977
  • Lead-containing pigments still are used for
    outdoor paint products because of their bright
    colors and weather resistant properties
  • Tetraethyl and tetramethyl lead are still used as
    additives in gasoline in several countries

Sources of Exposure
  • Soil and dust
  • Paint chips
  • Contaminated water
  • Parents lead-related occupation
  • Folk remedies
  • Congenital exposure
  • Pica
  • Developmental delay

  • Absorption
  • Lungs depends on size particle
  • GI
  • Adults 20-30
  • Children as much as 50 of dietary lead
  • Inadequate intake of iron, calcium, and total
    calories are associated with higher lead levels
  • Skin
  • Inorganic lead is not absorbed
  • Organic lead is well absorbed
  • Lead is carried bound to the RBC

Clinical Manifestation
  • Acute toxicity
  • Acute encephalopathy, renal failure and severe GI

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General Signs and Symptoms of Lead Toxicity
  • Fatigue
  • Irritability
  • Lethargy
  • Paresthesis
  • Myalgias
  • Abdominal pain
  • Tremor
  • Headache
  • Vomiting
  • Weight loss
  • Constipation
  • Loss of libido
  • Motor neuropathy
  • Encephalopathy
  • Cerebral edema
  • Seizures
  • Coma
  • Severe abdominal cramping
  • Epiphyseal lead lines in children (growth arrest)
  • Renal failure

Range of Lead-induced Health Effects in Adults
and Children
Blood lead levels Adults Children
10 ?g/dL Hypertension may occur Crosses placenta Impairment IQ, growth Partial inhibition of heme synthesis
20 ?g/dL Inhibition of heme synthesis Increased erythrocyte protoporphyrin Beginning impairment of nerve conduction velocity
30 ?g/dL Systolic hypertension Impaired hearing(?) Impaired vitamin D metabolism
40 ?g/dL Infertility in males Renal effects Neuropathy Fatigue, headache, abd pain Hemoglobin synthesis inhibition
50 ?g/dL Anemia, GI sx, headache, tremor Colicky abd pain, neuropathy
100 ?g/dL Lethargy, seizures, encephalopathy Encephalopathy, anemia, nephropathy, seizures
Childhood Lead Poisoning
  • Childhood lead poisoning is now defined as a
    blood lead level of 10 ?g/dl

  • The average lead level of American children is 2
  • 8.9 of American children have lead poisoning
  • Lead intoxication is more prevalent in minority
    groups and among those living in the northeast

Neurotoxicity of Lead in Childhood
  • Mental retardation in severe lead intoxication
  • ? 5 points in IQ for every 10 ?g/dl ? in blood
    lead level- population based studies
  • Other adverse developmental outcomes
  • Aggression
  • Hyperactivity
  • Antisocial behaviors
  • Learning disability- impairment in memory,
    auditory processing, and visual-motor
    integration. The IQ is normal. These effects has
    been demonstrated with blood lead levels as low
    as 6 ?g/dl

  • Evaluation of clinical symptoms and signs
  • CBC
  • Serum iron levelsAbdominal radiographs (for
    recent ingestion of lead-containing material)
  • Whole blood lead level
  • X-ray fluorescence (XRF)- to asses body burden

  • Environmental inspection/hazard reduction
  • Nutritional supplementation
  • Chelation therapy

  • Arsenic is common in the environment
  • Sources
  • Groundwater
  • Arsenic containing mineral ores
  • Industrial processes
  • Semiconductor manufacturing (gallium arsenide)
  • Fossil fuels
  • Wood treated with arsenic preservatives
  • Metallurgy
  • Smelting (copper, zinc, lead) and refining of
    metals and ores
  • Glass manufacturing

Bodily system affected Symptoms or signs Time of onset
Systemic Thirst Hypovolemia, Hypotension Minutes Minutes to hours
Gastrointestinal Garlic or metallic taste Burning mucosa Nausea and vomiting Diarrhea Abdominal pain Hematemesis Hematochezia, melena Rice-water stools Immediate Immediate Minutes Minutes to hours Minutes to hours Minutes to hours Hours Hours
Hematopoietic system Hemolysis Hematuria Lymphopenia Pancytopenia Minutes to hours Minutes to hours Several weeks Several weeks
Pulmonary (primarily in inhalational exposures) Cough Dyspnea Chest Pain Pulmonary edema Immediate Minutes to hours Minutes to hours Minutes to hours
Liver Jaundice Fatty degeneration Central necrosis Days Days Days
Kidneys Proteinuria Hematuria Acute renal failure Hours to days Hours to days Hours to days
Manifestations of acute arsenic poisoning
Acute Arsenic Poinsoning
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  • Occurs in three forms (elemental, inorganic
    salts, and organic compounds)
  • Contamination results from mining, smelting, and
    industrial discharges. Mercury in water can be
    converted by bacteria to organic mercury (more
    toxic) in fish.
  • Can also be found in thermometers, dental
    amalgams, fluorescent light bulbs, disc
    batteries, electrical switches, folk remedies,
    chemistry sets and vaccines.

Mercury - Exposure
  • Elemental
  • liquid at room temperature that volatizes readily
  • rapid distribution in body by vapor, poor in GI
  • Inorganic
  • poorly absorbed in GI tract, but can be caustic
  • dermal exposure has resulted in toxicity
  • Organic
  • lipid soluble and well absorbed via GI, lungs and
  • can cross placenta and into breast milk

Elemental Mercury
  • At high concentrations, vapor inhalation produces
    acute necrotizing bronchitis, pneumonitis, and
  • Long term exposure affects CNS.
  • Early insomnia, forgetfulness, anorexia, mild
  • Late progressive tremor and erethism (red
    palms, emotional lability, and memory impairment)
  • Salivation, excessive sweating, renal toxicity
    (proteinuria, or nephrotic syndrome)
  • Dental amalgams do not pose a health risk.

Diagnosis and Treatment
  • Dx made by history and physical and lab analysis.
    Inorganic mercury can be measured in 24 hour
    urine collection organic mercury is measured in
    whole blood.
  • The most important and effective treatment is to
    identify the source and end the exposure
  • Chelating agents (DMSA) may enhance inorganic
    mercury elimination. Dimercaprol may increase
    mercury concentration in the brain.

Mercury - Prevention
  • Many mercury compounds are no longer sold in the
    United States.
  • Elemental mercury spills
  • Roll onto a sheet of paper and place in airtight
  • Use of a vacuum cleaner should be avoided
    because it causes mercury to vaporize (unless it
    is a Hg Vac)
  • Consultation with environmental cleaning company
    is advised with large spills.
  • State advisories on public limit or avoid
    consumption of certain fish from specific bodies
    of water.
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