Establishing normal values for nickel in human lung disease

Abstract

People working in the nickel refining industry are known to have a higher concentration of nickel in lung tissue than the general population. To be able to evaluate a potential nickel exposure from other sources, e.g., welding, it is important to have sufficient data on what is normal for a local population. Several local factors such as the content of nickel in air and soil can have a significant impact on this so-called normal value. As almost all surgical equipment contains nickel, the sampling process can in itself be a source of contamination. The scope of this work was to investigate if there was any measurable contamination from the sampling instruments routinely used in hospitals, and if the presence of a nickel refinery had any effect on the nickel content in the lungs of the general population. Autopsy lung tissue samples were collected in situ from 50 people who had lived in the county of Vest Agder in Norway. Two samples were collected from each person; one with a regular scalpel (Swann–Norton) and forceps, and one with a titanium knife and plastic forceps. None of the persons had any known connection to the nickel refinery. The samples were collected at random and no special attention was given to age, sex and place of residence. The autopsies were performed according to Norwegian law and in understanding with the next of kin. The arithmetic mean value ±s of nickel was 0.64 ± 0.56 µg g^–1 and 0.29 ± 0.20 µg g^–1 dry weight, respectively, for samples collected with a regular scalpel and a titanium knife (P < 0.0001). For people who lived 8 km and closer to the refinery by the time of death, the nickel content was 0.41 ± 0.19 µg g^–1 and for those who had lived between 8 and 70 km away from the refinery it was 0.18 ± 0.13 µg g^–1 (P < 0.015). No statistical difference was established between results for males and females. Previous investigations have shown that the nickel content in lung tissue varies in the so-called normal population. This work has shown that factors such as sampling equipment and place of residence have an impact on the results. It thus demonstrates that reliable background values can presumably only be obtained by collecting samples from individuals not exposed to known environmental nickel sources and to use nickel-free instruments in the sampling process.