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|Title||Nickel Beyond Environmental Exposure: Stainless Steel Cookware's Contribution to Nickel Exposure from Cooked Foods|
|Year of Publication||2012|
|Authors||Kamerud KL, Hobbie KA, Anderson KA|
|Conference/Meeting/Venue||SETAC North America 33rd Annual Meeting|
Environmental and occupational exposure to nickel is generally well characterized, however other potential routes of exposure,such as leaching from stainless steel cookware are not well known. Nickel occurs naturally in plants and animals, and humans are exposed to it from these dietary sources. Humans are estimated to ingest an average of 150 to 900μg of nickel per day. In 2001, the Tolerable Upper Intake Level (UL) of nickel was decreased to 1000μg per day. The toxicological studies of nickel indicate that single oral doses as low as 3000μg causes allergic dermatitis. It is recommended that individuals sensitive to nickel lower their exposure. However, nickel may be introduced to the diet via leaching from stainless steel cookware into foods during cooking processes, contributing to flare-ups of allergic contact dermatitis. We tested three variables, grade of stainless steel, cook time, and repeated usage or cooking cycles, for their effects on nickel leaching from stainless steel during the process of cooking tomato sauce. Sampling involved simulated home cooking procedures with stainless steel grades equivalent to those found in cookware. After the cooking procedure samples underwent acid digestion, and analysis using Inductively Coupled Plasma-Mass Spectrometry (ICP-MS). Results show significant differences in nickel leaching between grades of stainless steel, indicative of the reported protective properties of the chromium oxide film in stainless steel. The amount of nickel in tomato sauce increased from 4.99mg/kg after a cook time of two hours to 7.63mg/kg after a cook time of twenty hours. The first cooking cycle showed the highest nickel concentration of 5.76mg/kg. Sequential cooking cycles with the sample stainless steel resulted in decreasing amounts nickel leached with each subsequent cooking cycle. From this set of experiments we can conclude that in addition to dietary exposures, stainless steel comparable to cookware is a source of nickel. Nickel exposure from stainless steel is variable, and dependent on grade of steel,cook time, and number of cooking cycles.