Module 3: Toxicology - Section 10: Other Heavy Metals |
TOX 10.3: Arsenic |
produced as byproduct of mining/smelting of copper and other non-ferrous metal ores viz. Pb, Zn, gold from which arsenic is removed as an impurity;
various arsenic compounds produced, the most common being inorganic arsenic trioxide (As2O3);
other arsenic compounds include inorganic eg. arsenic pentoxide (As2O5), arsine (AsH3) and organoarsenicals eg. arsenobetaine present in seafood;
mainly used for agricultural purposes (insecticides, herbicides) but also used in wood preservatives, pharmaceutical, chemical, smelting, mining and microelectronic industries.
a) Absorption:
b) Distribution:
c) Excretion:
toxic effects depend on the type of arsenic exposure. The trivalent compounds viz. arsenic trioxide and arsine are regarded as more toxic than the pentavalent form;
all arsenic compounds (except arsine) act by inhibiting sulfhydryl enzyme systems required for cell metabolism.
INORGANIC ARSENIC (ARSENIC TRIOXIDE):
1. Skin: most common:
Eczematous dermatitis:
red, itchy and painful swelling of the skin;
Follicular dermatitis:
Patchy hyperpigmentation pronounced around the eyelids, neck, armpits and groin.
Hyperkeratosis (thickening) of palms and soles of feet.
Transverse white lines (Mees' lines) on the nails.
Skin cancer: Bowen's disease, basal cell carcinoma and squamous cell carcinoma.
2. Eyes:
Conjunctivitis (red, itchy and painful eyes).
3. Nose:
4. Peripheral Nerves:
5. Liver:
6. Lung:
ARSINE (ASH3):
The occupational exposure limit (OEL) according to the Regulations for Hazardous Chemical Substances:
ACGIH:
Urine arsenic is a good indicator of current exposure (1-2 days).
Due to the presence of organic arsenic present in diet (seafood), measurement of inorganic arsenic acid and its metabolites viz. cacodylic acid, monomethylarsonic acid better indicators of occupational arsenic absorption.
While hair arsenic determinations are a good indicator of past exposure to arsenic it does not distinguish between ingested/inhaled arsenic and that deposited on the hair due to bathing or working in arsenic-contaminated environments. Their use is therefore limited.
Biological exposure indices (BEI) for arsenic and arsine metabolitites according to the Regulations for Hazardous Chemical Substances and ACGIH is an end of workweek urine specimen with arsenic metabolites not exceeding 50 µg/g creatinine (includes background levels - important to abstain from seafood for 2 days).
Any disease or pathological manifestation due to arsenic is compensable under COIDA as it is listed as one of the substances in schedule 3 of the Act.
EXERCISES AND INTERACTIVE EXAMPLES ABOUT TOXIC METALS | |
Exercise 1 Exercise 2 |
Example 1 Example 2 Example 3 |
Postgraduate Diploma in Occupational Health (DOH) - Modules 3: Occupational Medicine & Toxicology (Basic) by Profs Mohamed Jeebhay and Rodney Ehrlich, Health Sciences UCT is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.5 South Africa License. Major contributors: Mohamed Jeebhay, Rodney Ehrlich, Jonny Myers, Leslie London, Sophie Kisting, Rajen Naidoo, Saloshni Naidoo. Source available from here. For any updates to the material, or more permissions beyond the scope of this license, please email healthoer@uct.ac.za or visit www.healthedu.uct.ac.za.
Last updated Jan 2007.
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