Assessment of historical exposures in a nickel refinery in Norway

Objectives The aim of the study was, on the basis of new information on nickel species and exposure levels, to generate a specific exposure matrix for epidemiologie analyses in a cohort of Norwegian nickel-refinery workers with a known excess of respiratory cancer. Methods A department-time-exposure matrix was constructed with average exposure to total nickel estimated as the arithmetic mean of personal measurements for periods between 1973 and 1994. From 1972 back to the start of production in 1910, exposure concentrations were estimated through retrograde calculation with multiplication factors developed on the basis of reported changes in the metallurgical process and work environment. The relative distribution of water-soluble nickel salts (sulfates and chlorides), metallic nickel, and particulates with limited solubility (sulfides and oxides) was mainly derived from speciation analyses conducted in the 1990s. Results The average concentration of nickel in the breathing zone was < 0.7 mg/m³ for all workers after 1978. Exposure levels for smelter and roaster day workers were 2— 6 mg/m 3 before 1970, while workers in nickel electrolysis and electrolyte purification were exposed to concentrations in the range of 0.15— 1.2 mg/m³. The level of water-soluble nickel was of the same order for workers in the smelting and roasting departments as in some of the electrolyte purification departments. Conclusions Compared with earlier estimates, the present matrix probably offers a more reliable description of past exposures at the plant.