Toxicity of Cadmium

Two hazardous consequences attend the use of cadmium in contact with food products: acute poisoning resulting from the ingestion of cadmium dissolved from containers or from food-handling equipment; and poisoning from the inhalation of fumes of cadmium oxide, if cadmium-plated vessels or food-handling equipment is heated.

Acute poisoning has resulted from the ingestion of cadmium salts derived from cadmium-plated vessels in which any acid foods have been stored for even short periods of time; therefore, cadmium should not be used on food containers of any kind. Fatal poisoning is more apt to result from the inhalation of dust or fumes of cadmium salts and cadmium oxide. These are the kinds of exposure encountered in industrial operations when cadmium-plated parts are heated or soldered. Exposure to dust or fumes of cadmium should be avoided and safety / OSHA regulations should be followed. The complete regulatory text of the cadmium rule and appendixes is published in the Federal Register 57 (178): 42102-42463, 14 September 1992. Among its provisions, the rule requires employers to adhere to a new personal exposure limit (5 g/ pm3), provide medical surveillance, monitor exposure level, and maintain proper records.

Deposits of cadmium on the sides or bottom of a tank previously used for cadmium plating should not be burned off, because the fumes from this operation are highly toxic. These deposits should be removed mechanically or deplated. For high-efficiency deplating, the solution used contains 45 to 60 g/L (6 to 8 oz/gal) of sodium cyanide and 23 to 30 g/L (3 to 4 oz/gal) of sodium hydroxide in water; the tank is the anode, and steel sheets or scrap steel parts are the cathodes. Just like the production solutions presented in Table 1(a), the resulting solution must be treated with the utmost care. The proper handling of cyanide solutions should be discussed with the proper vendors, and internal safety departments must train operators in the safe use of these solutions. Disposal issues must be part of waste treatment management practices. Additional information is available in the article "Cadmium Elimination" in this Volume.

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