25A C Hart and WR Wearmouth UK Patent 1476099 10 June 1977 Environmental Health and Safety Considerations

For practical purposes, the environmental, health, and safety considerations for these nickel-base alloys and their production are the same as those for nickel and nickel plating.

Environmental Considerations. Nickel is a naturally occurring constituent of our day-to-day environment. The soil worldwide contains 5 to 500 ppm Ni, with an average of 100 ppm. Food is grown and consumed in areas with higher levels still, without leading to any health problems for the inhabitants (e.g., 661 ppm in Hawaii) (Ref 26). Nickel has been determined to be an essential trace element for plant life, and some plants that accumulate nickel are regularly eaten by people with no harmful effects. Nickel is also present naturally in the atmosphere, rivers, seas, and oceans. Nonetheless, the desire to maintain the natural environment as it is has led to the establishment of maximum permitted levels for the discharge of nickel and other metals by industry. In nickel plating, the levels are attained by measures to reduce spray emission, process solution dragout, and effluent treatment. Details of all necessary techniques are available from suppliers to the metal finishing industry.

Health and Safety Considerations. Some 1.2% of men and 10 to 15% of women are sensitized to nickel and, when exposed to prolonged skin contact with nickel metal, certain nickel alloys, or nickel-containing solutions, may develop dermatitis at the point of contact. The occurrence of nickel contact dermatitis was first observed as a result of exposure to nickel-containing solutions in electrorefining of nickel. Today most electroplaters are aware of "nickel itch" but have never seen a case of it. The reason is that, despite increasing use of nickel-containing products, industry has adopted work practices that prevent occurrence of contact dermatitis. Today, nickel contact dermatitis occurs most frequently as a result of domestic exposures from close and persistent contact of the skin with nickel-plated articles or with certain nickel alloys. Accordingly, legislation in Europe will control the use of nickel metal, nickel alloys, and nickel-containing materials that come in contact with the skin. The main problem is with those articles that come into direct and prolonged contact, such as earrings, necklaces, bracelets, watch cases and straps, buttons, and rivets. It is important to note that nickel alloys that do not react with sweat do not cause dermatitis. Transient contact with nickel or nickel alloys is not damaging because there is insufficient time for reaction with sweat to form the soluble products that can penetrate the skin (Ref 27).

In nickel plating, plant design, exhaust ventilation, and methods of operation should be such as to avoid any risk of skin contact with the solutions. Protective clothing should be inspected regularly for leaks and tears. Where protective gloves are necessary it is recommended that cotton inner gloves be worn to reduce perspiration. The outer gloves should be rinsed off before removal to prevent process solution transfer to the hands or the inside of the gloves on removal (Ref 28).

A few cases of asthma, claimed to be nickel-induced, have reportedly arisen from aerosols of soluble nickel salts. The content of nickel in the atmosphere should be kept below the occupational exposure limit.

There is evidence that inhalation of some nickel compounds (nickel oxide, nickel subsulfide) occurring in the atmosphere associated with certain nickel refining operations may cause respiratory cancers in humans. There is no good evidence that occupational exposure to metallic nickel or nickel oxide, sulfate, or chloride during plating or polishing is associated with increased mortality due to cancer (Ref 29).

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