ABSTRACT
Both animal and human exposure–response data are used to estimate the incremental unit risks (IURs) of lung cancer for Ni3S2 and NiO, which are constituent compounds of nickel refinery dust. The animal experiments are used to determine relative lung cancer potencies for Ni3S2 and NiO, and the human epidemiological data are used as the best estimate of overall risk for refinery dust exposure. The animal data for Ni3S2 are fit with a linear model, while the nonlinear animal data for NiO are fit with a Weibull model. The lower 95% confidence limit at a 5% point of departure is used to calculate a tumorigenic potency ratio of Ni3S2 to NiO of 5.6. Analyses of actual nickel refinery dust indicate the weight% of Ni3S2 and NiO to be 82% and 9%, respectively. This information is used with the previously determined IUR for nickel refinery dust to calculate IURNiO = 5.1 × 10−5 (μg Ni/m3)−1 and IURNi3S2 = 2.9 × 10−4 (μg Ni/m3)−1.
ACKNOWLEDGMENTS
The authors thank Vale Inco for providing funding for writing this article.
Notes
2Model has many parameters as data points; goodness of fit statistic could not be calculated.
1Shaded row reflects point of departure selected for potency determination (see text).
2Benchmark dose.
3Point of departure (lower 95% confidence limit on BMD).