General Populations

The general population may be exposed to nickel in ambient air, food, and water. General populations may also be exposed through inhalation of cigarette smoke. Widespread exposure may occur through dermal contact with coins and jewelry containing nickel alloys or nickel plating. Occupational Populations Occupational exposure to nickel may occur by dermal contact or by inhalation of aerosols, dusts, fumes, or mists containing nickel. Dermal contact may also occur with nickel solutions, such as those used in electroplating. Occupational exposure to nickel will be highest for those involved in production, processing, and use of nickel. Operations with the highest airborne concentrations of nickel are those involved in grinding, welding, and handling powders. Toxicokinetics In humans, about 20–35 % of inhaled nickel deposited in the lungs is absorbed into the bloodstream. About 27 % of nickel in drinking water is absorbed in humans; much less nickel (about 1%) is absorbed from food. More soluble nickel compounds have higher absorption efficiencies. Nickel is poorly absorbed through the skin. Once absorbed, nickel is distributed throughout the body. Nickel is not metabolized and absorbed nickel is eliminated via the urine. The elimination half-time for absorbed nickel is 28 days for the oral route. Normal Human Levels The reference values for nickel in healthy adults are 0.2 μg/L in serum and 1–3 μg/L in urine. Biomarkers Serum and urine nickel levels are the most useful biomarkers of nickel exposure