89: Arsenic

HISTORY AND EPIDEMIOLOGY

Arsenic poisoning can be unintentional, suicidal, homicidal, occupational, environmental, or iatrogenic.^{108,109,141,165} Mass poisonings have occurred. Nearly 400 residents of Hong Kong fell ill after eating contaminated bread from the Esing Bakery in 1857; two bakery foremen were thought to have tampered with the recipe.⁸⁹ The 1900 Staffordshire beer epidemic in England saw 6000 beer drinkers fall ill and 70 die from beer brewed with sugar made with arsenic-contaminated sulfuric acid.¹⁰⁸ In Wakayama, Japan, 67 people were poisoned by eating intentionally contaminated curry at a festival in 1998.²²³ In 2003, the largest recent outbreak of arsenic poisoning in the United States occurred in New Sweden, Maine, when intentionally adulterated church coffee resulted in the death of one parishioner and the hospitalization of an additional 15 victims.¹⁹ Arsenic trioxide (As₂O₃) reemerged as a treatment for acute promyelocytic leukemia (APML) in the 1990s after physicians in Harbin, China, found a high remission rate in patients given, a crude As₂O₃ infusion.^126,259

Contaminated soil, water, and food are the primary sources of arsenic for the general population. Pentavalent arsenic (As⁵⁺) is the most common inorganic form in the environment.⁵⁷ Inorganic arsenic exposure from food is generally low and usually occurs from soil-derived foods such as rice and produce.^{32,199,250,258} Exposure to organic arsenic compounds of low toxicity occurs from consumption of algae, fish, and shellfish. In the past two decades, consumption of contaminated water has emerged as the primary cause of large-scale outbreaks of chronic arsenic toxicity. Arsenic leaches from certain minerals and ores, as well as from industrial waste.¹⁴⁸ In Ban­gla­desh, millions of people have been poisoned by drinking water from wells contam­inated with arsenic leached from ground minerals.¹⁷⁰ Ironically, the wells were dug to obtain safer groundwater. Hydroarsenicism is also reported in Chile, Taiwan, Brazil, India, Mexico, and Argentina.^{35,51,57,102,148,170,239} In 2001, the US Environmental Protection Agency decreased the maximum contaminant concentration of arsenic in drinking water to 10 parts per billion (ppb), or10 μg/L, after statistical modeling indicated an increased risk of lung and bladder cancer from water contaminated with arsenic at the formerly acceptable concentration of 50 ppb.⁶⁶ The World Health Organization also recommends a maximum concentration of 10 ppb.

CHEMISTRY

Arsenic is a metalloid that exists in multiple forms: elemental, gaseous (arsine), organic, and inorganic [As³⁺ (trivalent, or arsenite) and As⁵⁺ (pentavalent, or arsenate)]. Tables 89–1 and 89–2 list sources of arsenic and regulatory standards about arsenic, respectively. Arsenic metal is considered nonpoisonous because of its insolubility in water and, therefore, bodily fluids.¹⁹⁸ Arsine, which is highly toxic, is discussed in Chap. 124. Trivalent arsenicals include ...