1. Pathophysiology Unit 2-Factors of Disease Environmental Factors
Heavy Metal Toxicity
Pathophysiology
Unit 2-Factors of Disease
Environmental Factors
Arsenic
Lead
Mercury

2. Definitions
‘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

3. ‘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

4. Lead

5. 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

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

7. Toxicity 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

8. Clinical Manifestation
Acute toxicity
Acute encephalopathy, renal failure and severe GI symptoms

10. 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

11. 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

12. Childhood Lead Poisoning
Childhood lead poisoning is now defined as a blood lead level of 10 g/dl

13. The average lead level of American children is 2 g/dl
8.9% of American children have lead poisoning
Lead intoxication is more prevalent in minority groups and among those living in the northeast

14. 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

15. Diagnosis 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

16. Treatment Environmental inspection/hazard reduction
Nutritional supplementation
Chelation therapy

17. Arsenic

18. Introduction 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

19. Manifestations of acute arsenic poisoning
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
Hours
Hematopoietic system
Hemolysis
Hematuria
Lymphopenia
Pancytopenia
Several weeks
Pulmonary
(primarily in inhalational exposures)
Cough
Dyspnea
Chest Pain
Pulmonary edema
Liver
Jaundice
Fatty degeneration
Central necrosis
Days
Kidneys
Proteinuria
Acute renal failure
Hours to days
Manifestations of acute arsenic poisoning

20. Acute Arsenic Poinsoning

22. Mercury

23. Mercury
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.

24. Mercury - Exposure Elemental
liquid at room temperature that volatizes readily
rapid distribution in body by vapor, poor in GI tract
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 skin
can cross placenta and into breast milk

25. Elemental Mercury
At high concentrations, vapor inhalation produces acute necrotizing bronchitis, pneumonitis, and death.
Long term exposure affects CNS.
Early: insomnia, forgetfulness, anorexia, mild tremor
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.

26. 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.

27. 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 container
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.