Exposure to which metal causes DIAPHORESIS (excessive sweating) as a characteristic feature of chronic toxicity?

Correct answer: D. Mercury

• A. ZINC is an essential trace element; excess mainly causes gastrointestinal upset and secondary copper deficiency.
• B. LEAD toxicity causes abdominal colic, peripheral motor neuropathy (wrist drop), microcytic anaemia with basophilic stippling, and a BURTONIAN blue-grey line along the gingival margin — but not prominent diaphoresis.
• C. SILVER causes ARGYRIA, an irreversible slate-blue-grey pigmentation of skin and mucosa. This is a cosmetic problem, not a systemic toxic syndrome with sweating.
• D. CORRECT. MERCURY toxicity characteristically produces profuse DIAPHORESIS along with a triad of TREMOR (intention tremor of hands, eyelids and tongue), GINGIVITIS with excessive salivation and a blue-grey gingival line, and ERETHISM — the neuropsychiatric syndrome of irritability, shyness, memory loss and emotional lability that gave us the 'mad hatter.' In children, ACRODYNIA (pink disease) features painful pink extremities with marked sweating.

Note: Directly relevant to dentistry through AMALGAM handling. The greatest occupational risk is inhalation of mercury VAPOUR from spills, from heating amalgam, or from removing old restorations without water spray and high-volume suction. Use a rubber dam and copious water when sectioning amalgam, store scrap under fixer solution, and never vacuum a mercury spill.