HEAVY METAL POISONING Flashcards
Specific gravity of heavy metals in their standard state
Above 5g/cm3
Which heavy metals are released into water by industrial and domestic waste
Pb
Hg
As
Cd
Long term use of fertilizers lead to accumulation of which heavy metal
Cd
Sewage or sludge application releases which heavy metals
Hg
Cd
Dust from smelters, industrial waste and bad agricultural watering practices contaminate agricultural lands with which heavy metals
Hg
Cd
As
Pb
How are plants contaminated by heavy metals
Fertilizers/Pesticides/Insecticides
Plants growing in soil contaminated area
Irrigation of crops with contaminated water
Plants method for detoxification of heavy metals is is mainly based on ————-//
Chelation subcellular compartmentalization
Five processes of phytoremediation
Rhizodegradation
Rhizofiltration
Phytoextraction/ Phytoaccumulation
Phytovolatilization
Phytostabilization
Examples of toxic metals that have no know beneficial effects in organisms
Plutonium
Lead
Most hazardous heavy metals that humans are exposed to
As, Pb, Hg, Cd, Fe and Al
Factors that affect toxicity of heavy metals
Dose absorbed
Exposure was acute or chronic
Age of the person
Why are young children more susceptible to effects of lead exposure
Their brains are more plastic and even brief exposures can influence developmental processes
Major sources of arsenic and mercury indoors
Pesticides and Fungicides
Methods for measuring trace metals
Atomic absorption spectrophotometry -destructive , sample should be in solution
X-ray fluorescence - nondestructive , sample can be in any state
Easiest screening process for heavy metal
Poisoning
Hair analysis
Steps involved in treating heavy metal poisoning
Decontamination
Resuscitation
Chelation
Toxicity of EDTA
Hypocalcémic tetany
Hydropic vacuolization of the proximal tubule
Loss of the brush border
Degeneration of proximal tubules
Why is mercury unavailable to EDTA
Tightly bound by sulfhydryl groups or sequestered in body compartments that are not penetrated by EDTA
Does EDTA penetrate cells
It does not significantly penetrate cells hence has a volume of distribution approximating ECF space
Disadvantage of DTPA
Depletes Zn
Teratogenic lime EDTA due to its Zn and Mn depletion effect
Limited access to intracellular sites
Which solvent is used for Dimercaprol
Peanut oil due to its instability in aqueous solutions
Why is Dimercaprol nephrotoxic
Sulfur-metal bond is unstable labile in acidic tubular urine increasing delivery of metal to renal tissue and increase toxicity
Another name for Dimercaprol
British Antilewisite BAL
Chelators used in Treatment of lead encephalopathy in due to lead poisoning
Dimercaprol + CaNa2EDTA
Route of administration of dimercaprol
Deep Intramuscular injection as 100mg/ml solution in peanut oil
Toxicity of dimercaprol
Hypertension
Tachycardia
Difference between succimer and dimercaprol
Succimer has two carboxylic groups hence has less lipid solubility
Desirable features of succimer
Does not significantly mobilise essential such as Zn, Cu and Fe
Difference between toxicity of dimercaprol and succimer
Succimer is less toxic due to its lower lipid solubility which minimizes cellular penetration
Why is n acetyloenicillamine more effective than penicillamine for mercury toxicity
More resistant to metabolism
Toxicity of penicillamine
Cutaneous lesions
Urticaria
Macular or papular reactions
Pemphigoid lesions
Lupus
Dermatomyositis
Adverse effects on collagen
Which chelator has prooxidant effects
DTPA
Aerobic bacteria involved in bioremediation
Mycobacterium
Sphingomonas
Alcaligenes
Rhodococcus
Pseudomonas
Examples of hyperaccumulator plant species
Avena spp
Brassica spp
Commonest source of acute metal poisoning
Arsenic
Least toxic form of arsenic
Elemental arsenic
Most popular homicidal poison
Arsenic
Why is arsenate less toxic than arsénite
It is has less water solubility
Most toxic form of arsenic
Arsine gas ( 25-30ppm) can be lethal in 30mins
Toxic dose of arsenic trioxide
200-300mg
Routes of absorption of arsenic
All routes
Effect of arsenic on bone
Replaces phosphorus in bone
Does arsenic cross the BBB
No
Teratogenic effects of arsenic
Intrauterine death of the fœtus
Or
Respiratory distress in less severe cases
How does arsenic cause respiratory distress in the fœtus
Pulmonary hemorrhage and hyaline membrane formation
Three clinical forms of arsenic poisoning
Acute fulminating type
Subacute type( gastroenteritis type)
Chronic type
Effects of acute arsenic toxicity
Capillary dilatation
Myocardial failure
Shock
Death
Mechanism of acute arsenic toxicity
Acts on sulfhydryl groups of enzymes and capillaries and inhibit cellular metabolism
Symptoms of sub acute type arsenic poisoning
Resembles cause of food poisoning or cholera
Five manifestations of chronic type arsenic toxicity
Gastrointestinal
Catarrhal
Raindrop pigmentation
Mees lines
Arsenic neuritis
Gastrointestinal symptoms of arsenic toxicity
Gradual weight loss
Malnutrition
Fatigue
Loss of appetite
Catarrhal symptoms of chronic arsenic toxicity
Running nose
Headache
Conjunctivitis
Bronchial catarrh
Raindrop pigmentation
Milk and roses pigmentation followed by brown patchy pigmentation of the skin
Mees lines
Whitish lines across the nails of the fingers and toes
Symptoms of arsenic neuritis
Polyneuritis
Optic neuritis
Paraesthesias
Atrophy of extensors regulating in wrist and food drop
Diagnosis of chronic arsenic toxicity
Urinary As level > 100mg/24 hours
Which metal poisoning causes garlic steel to breath and tissue fluids
Arsenic
Manifestations of arsine gas exposure
Acute hemolytic anemia and striking chills
Most common neurological effect of chronic arsenic intoxication
Sensory predominant peripheral neuropathy in a stocking glove pattern
Types of skin reactions caused by arsenic dust
Toxic
Eczematous
Combined toxic and eczematous
Follicular lesions
Describe the classical dermatitis caused by chronic arsenic toxicity
Hyperkeratosis with a classical dew drops on a dusty road appearance
Diagnosis of arsenic toxicity
Urine level
Blood level
Hair level
Radiography
Levels of arsenic in urine which indicate toxicity
24hr excretion more than 100mcg/L
Metabolites of arsenic
Methylarsonic acid
Dimerhyarsenic acid
Chelation therapy for arsenic
Dimercaprol
Penicillamine
DMPS and DMSA are superior
Which urine urine level of arsenic in an asymptomatic patient prompts chelation
200mcg/L
Most commonest metal involved in chronic poisoning
Lead
Forms of lead and uses
Lead acetate - therapeutics
Lead carbonate(white lead)- paints
Lead oxide (litharge)- glazing of pottery and enamel ware
Tetraethy lead - mixed with petrol as an antiknock
Lead tetraoxide - vermillion
Lead sulfide- collyrium (surma)
Routes of absorption of lead
All portals of entry
Which form of lead can be absorbed directly through the skin
Tetraethyl lead
Route of Occupational exposure to lead
Inhalation
Routes of excretion lead
Urine and Bile
Mode of action lead
Inhibits sulfhydryl enzymes
Decreases heme synthesis
Increases hemolysis
Edema in CNS
Affects CVS
Enzymes Involved in heme synthesis that are affected by lead
Aminolaevulinic acid synthetase
Aminolaevulinic acid dehydrase
Ferrochelatase
Corporphyrinogen oxidase
Effects of lead on CVS
Hypertension and Myocarditis
In what forms is lead stored in bones
As phosphate and carbonate
Effect of lead on kidney
Nephritis
What is plumbism
Lead toxicity
What is the burton line or gingival lead line
Dark blue line along the gums that signify lead poisoning
Management of cerebral edema in lead poisoning
Mannitol Or Glycerol
Dexamethasone
Management of seizures in lead encephalopathy
Diazepam