Earlier work-related lung and
nasal cancer studies included estimates of exposures to different
nickel species in the refinery. Based on the metallurgy, only insoluble
nickel was believed to be present around the roasters but mixed exposure was assumed in most areas, including the tankhouse. Occasional leaching tests of samples from the roaster area have indicated the presence of soluble
nickel. This study reports on five parallel sets of dust samples collected from different floors with standard equipment and treated as follows. Two sets were leached with an
ammonium citrate buffer at pH 4.4. Undissolved material was treated with HClO4/HNO3, evaporated to dryness and dissolved in HCl, Ni, Cu, Co, Fe, Se, and As were determined in both fractions. Water soluble Ni was found in all samples, ranging from 5-35%.
Sulfate in the solutions correlated nearly stoichiometrically to the total
metal content. The three remaining sets were investigated by, respectively, differential leaching, X-ray diffraction and scanning electron microscopy. The percentage of soluble
nickel found by differential leaching corresponded well with those obtained by the simplified procedure. X-Ray diffraction analysis showed the presence of NiSO4.6H2O as well as
oxides of Ni and Cu. This study indicates mixed exposures also in the roaster area. It also clearly indicates that basing exposure on the metallurgy alone can lead to serious misjudgements. The impact of this new information on the interpretation of
cancer incidence at this refinery must await the analysis in an ongoing case-reference study.