99: Nickel

HISTORY AND EPIDEMIOLOGY

Nickel is a ubiquitous metal commonly found in both home and industry. It exists in a variety of chemical forms, from naturally occurring ores to synthetically produced nickel carbonyl. Elemental nickel is a white, lustrous metal whose name is derived from the German word “kupfernickel” or “devil’s copper.” Swedish chemist Baron Axel Fredrik first identified nickel in 1751 in a mineral known as niccolite. Nickel comprises 0.008% of the Earth’s crust and is found in diverse locations, ranging from meteorites and soil to bodies of fresh and saltwater.

First produced by the Chinese, nickel has been used as a component in a variety of metal alloys for more than 1700 years. The first malleable nickel was produced by Joseph Wharton following the American Civil War. Wharton went on to sell bulk quantities of nickel to the US government for the minting of 3-cent coins, and later donated the equivalent of 3.3 million of these coins to help fund what is today known as the Wharton School of Business.⁶⁵ The modern US 5-cent piece, the “nickel,” is actually only approximately 25% nickel by weight, and all US coins except the penny are made of nickel-containing alloys.¹⁰

Nickel ores typically consist of accumulations of nickel sulfide minerals of relatively low nickel content. Although a variety of technical methods for extracting nickel from ore have been developed, one method of special note was developed in 1890 by Ludwig Mond, who is credited with the discovery of nickel carbonyl. The Mond process for the extraction of nickel involves passing carbon monoxide over smelted ore. This creates nickel carbonyl, which then decomposes at high temperatures to produce purified nickel and carbon monoxide.⁶⁵ Nickel mining ceased 30 years ago in the United States, and despite an increasing worldwide demand, as of 2011 there were still no active domestic nickel mines.¹⁰ Nickel is imported into the United States from other nickel-rich countries, such as Canada, Russia, and Australia, while domestic production of nickel in the United States is essentially limited to the recycling of nickel-containing metals.

Nickel is a siderophoric material that forms naturally occurring alloys with iron, a property that has made it useful for many centuries in the production of coins, tools, and weapons. Today, most nickel is used in the production of stainless steel, a highly corrosion-resistant alloy containing 8% to 15% nickel by weight.

Occupational exposure to nickel and nickel containing compounds occurs in a variety of industries, including nickel mining, refining, reclaiming, and smelting. Chemists, magnet makers, jewelry makers, oil hydrogenator workers, battery manufacturers, petroleum refinery workers, electroplaters, stainless steel and alloy workers, and welders are at increased risk for exposure to nickel and nickel-containing compounds. Most nonindustrial human exposures to nickel are usually from dietary and environmental sources, although cigarette smoking is an important nickel exposure and elevates urinary nickel concentrations.^63...