Chapter 95: Mercury

INTRODUCTION

HISTORY AND EPIDEMIOLOGY

Mercury is a metal that is widely toxic to multiple organ systems. Its toxicologic manifestations are well known as a result of thousands of years of medicinal applications, industrial use, and environmental disasters.^69,112 Mercury occurs naturally in small amounts as the elemental (Hg⁰) silver-colored liquid (quicksilver); as inorganic compounds such as mercuric (Hg²⁺) sulfide (cinnabar), mercurous (Hg⁺) chloride (calomel), mercuric chloride (corrosive sublimate), and mercuric oxide; and as organic compounds (methylmercury and dimethylmercury). Mercury’s gastroenteric irritant effects led to its use as a therapy for constipation. In recent (16th–19th), centuries, mercury-containing preparations, advocated for their potent diuretic and sialogogic properties, were widely used to treat syphilis to “flush” the “virus” out.⁸¹ The musician Paganini was one of several famous persons whose gingivitis, dental decay, ptyalism (excessive salivation), and erethism (pathologic irritability and emotional instability) were attributed to mercury therapy.⁸⁰ In the 1800s, the United States witnessed an epidemic of “hatters’ shakes” or “Danbury shakes” and “mercurial salivation” in hat industry workers.¹²³ Danbury, Connecticut, was a US center of felt hat manufacturing in which mercuric nitrate was used to mat animal furs into felt.^112,123

In the early 1900s, acrodynia, a painful dusky pink discoloration of the hands and feet, or “pink disease,” was described in children who received calomel for ascariasis or teething discomfort.¹⁶ Vividly described in a series of 41 children, the development of acrodynia was more common in younger children, did not seem to correlate with mercury dose, and was not necessarily related to urine concentrations of mercury.¹²²

One of the most devastating epidemics of mercury poisoning occurred as the result of a decade of contamination of Minamata Bay in Japan by a nearby vinyl chloride plant during the 1940s. Methylmercury accumulated in the bay’s marine life and poisoned the inhabitants of the local fishing community. Although officially only 121 victims were reported, thousands more are believed to have been affected by what has subsequently been named Minamata disease.^88,113 The largest outbreak of methylmercury poisoning to date occurred in Iraq in late 1971. Approximately 95,000 tons of seed grain intended for planting and treated with methylmercury as a fungicide were baked into bread for direct consumption, resulting in widespread neurologic symptoms, 6,530 hospital admissions, and more than 400 deaths.^5,23,96

In 1990, the US Environmental Protection Agency (EPA) banned mercury-containing compounds from interior paints.³ However, mercury-containing paints manufactured before that ruling may still be on interior walls, and mercury-containing paint can still be sold for outdoor use. In 1997, a scientist succumbed to delayed, progressive neurologic deterioration after a minute dermal exposure to dimethylmercury.⁷⁷ Contemporary exposures occur in the form of mercury-tainted seafood, mercury-based preservatives (thimerosal), and artisanal gold mining.³⁶

...