Module 3: Toxicology - Section 10: Other Heavy Metals |
TOX 10.2: Mercury |
inorganic mercury is mined primarily as cinnabar (HgS) and in very rich ores as metallic mercury → heated by roasting to produce mercury vapour; secondary production from dental amalgams, scrap batteries, discarded instruments and electrical devices;
inorganic mercury mainly used for electrical apparatus, chemical industry(chlorine and caustic soda production), catalysts (polyurethane foams), dentistry, industrial and control instruments (thermometers, barometers, manometers), dry batteries, soldering;
1. Classical syndrome: inflammation of the mouth; muscle tremors and psychic irritability.
mouth inflammation: gingivitis, loosening of teeth, salivary gland swelling, excess salivation, stomatitis, blue-grey line along gum margins (individuals with poor oral hygiene);
muscle tremors: initially affects the eyelids, tongue, fingers ® difficulty in writing (jerky appearance); progress to arms and legs ® difficulty in walking; absent during sleep (similar to Parkinson’s disease); disappears on removal from exposure;
psychic irritability (erethism): workers become timid and anxious, lose self confidence, easily embarrassed, fearful of criticism and job loss, irritable, anger outbursts, insomnia, nightmares and excessive drowsiness (during waking hours).
2. Peripheral Nerves:
3. Skin:
a) Eczematous dermatitis:
b) Skin ulcers:
4. Kidney:
5. Enzymes:
a) Limiting exposure:
b) Industrial hygiene monitoring:
The occupational exposure limit (OEL) according to the Regulations for Hazardous Chemical Substances (HCS):
Mercury alkyls: (also skin absorption)
TWA - 0.01 mg/m3 (recommended limit)
TWA - 0.03 mg/m3 (STEL);
Mercury and compounds: (except alkyls)
TWA - 0.05 mg/m3 (recommended limit)
TWA - 0.15 mg/m3 (STEL).
ACGIH:
Mercury alkyls:
TWA - 0.01 mg/m3
TWA - 0.03 mg/m3 (STEL).
Mercury aryls:
TWA - 0.1 mg/m3 (recommended limit).
Inorganic and metallic mercury:
TWA - 0.025 mg/m3.
c) Biological monitoring:
blood mercury is a useful indicator of exposure and correlates better with exposure than urine mercury; levels reflect methyl mercury as well as inorganic and organic forms and is therefore affected by dietary fish intake; airborne inorganic mercury of 50 µg/m3 corresponds to 3-3.5 µg/100 ml; proteinuria associated with levels > 3 µg/100ml; persons with no occupational exposures have levels <2 µg/100ml; for alkyl mercury clinical signs of intoxication occur >20 µg/100ml;
urine mercury is a good indicator of recent exposure to inorganic Hg and aryl/alkyl Hg compounds (not methyl mercury); clinical signs of poisoning usually occur with urine levels >300 µg/g creatinine; persons with no occupational exposures have urine levels <5 µg/g creatinine; dietary fish intake (methyl mercury) does not appreciably influence levels;
hair determination not useful in industry since there is no way to differentiate between adsorbed and endogenous mercury;
biological exposure indices (BEI) for total inorganic mercury according to the Regulations for Hazardous Chemical Substances (HCS) and ACGIH:
d) Medical surveillance:
e) Treatment:
f) Compensation:
Any disease or pathological manifestation due to mercury is compensable under COIDA as it is listed as one of the substances in schedule 3 of the Act.
g) Notify the case to the Chief Inspector in DOL:
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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