Nickel Carcinogenicity in Relation to the Health Risks from Residual Oil Fly Ash

ABSTRACT

Epidemiological studies of workers in the nickel industry, animal exposure studies, and reports on the potential mechanisms of nickel-induced toxicity and carcinogenicity indicate that only crystalline sulfidic nickel compounds have been clearly established as carcinogenic or potentially carcinogenic in humans. This observation indicates the need to modify and update regulatory approaches for nickel to reflect noncancer toxicity values for some individual nickel species. Analysis of nickel compounds in residual oil fly ash (ROFA) indicates that sulfidic nickel compounds (e.g., nickel subsulfide, nickel sulfide) are not present. Thus, the potential for emission of carcinogenic nickel compounds from residual oil fly ash appears to be low. Preliminary reference concentrations (RfCs) for a number of nickel compounds, based on non-carcinogenic endpoints, are proposed on the basis of the benchmark dose approach in conjunction with NTP data for nickel species.

Keywords:

• nickel
• residual oil fly ash
• ROFA
• cancer
• reference concentration
• RfC
• benchmark dose.

ACKNOWLEDGMENT

The authors acknowledge the financial support of the Oil-fired Generators Group in preparation of this article.

Notes

¹Based on data from NTP (1996c). ²Aggregate of a factor of 3 for the extrapolation from animals to humans and a factor of 10 for the protection of sensitive subpopulations. Source: ENVIRON (2002).

¹Based on data from NTP (1996a).

²Aggregate of a factor of 3 for the extrapolation from animals to humans and a factor of 10 for the protection of sensitive subpopulations. ³BMDL₁₀ obtained after dropping the high dose.