Development of a unit risk factor for nickel and inorganic nickel compounds based on an updated carcinogenic toxicity assessment

Development of a unit risk factor for nickel and inorganic nickel compounds based on an updated carcinogenic toxicity assessment

► The two cohorts used for URF development had more environmentally-relevant exposure. ► Grimsrud et al. (2003) has not previously been used to derive URF estimates. ► The TCEQ URFs are more conservative than the USEPA URFs for the same cohorts. ► A confidence-based weighting procedure combined URFs...

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Bibliographic Details
Published in:Regulatory toxicology and pharmacology Vol. 62; no. 1; pp. 191 - 201
Main Authors: Haney, Joseph T., McCant, Darrell D., Sielken, Robert L., Valdez-Flores, Ciriaco, Grant, Roberta L.
Format: Journal Article
Language:English
Published: Netherlands Elsevier Inc 01-02-2012
Subjects:
Air Pollutants - toxicity
Animals
Cancer
Carcinogenesis
Carcinogenicity
Carcinogens - toxicity
Environmental Exposure - adverse effects
Humans
Incidence
Inhalation
Lung
Lung Neoplasms - chemically induced
Lung Neoplasms - epidemiology
Mortality
Nickel
Nickel - toxicity
Respiratory
Risk Assessment
Toxicity
Uncertainty
Toxicity
Lung
Mortality
Nickel
Respiratory
Carcinogenicity
Carcinogenesis
Cancer
Incidence
Inhalation
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Summary:► The two cohorts used for URF development had more environmentally-relevant exposure. ► Grimsrud et al. (2003) has not previously been used to derive URF estimates. ► The TCEQ URFs are more conservative than the USEPA URFs for the same cohorts. ► A confidence-based weighting procedure combined URFs into the final nickel URF. ► Extra lung cancer risk: 1.6-1.7E-4perμg/m3 with US/TX rates and life-table analysis. The TCEQ has developed a URF for nickel based on excess lung cancer in two epidemiological studies of nickel refinery workers with nickel species exposure profiles most similar to emissions expected in Texas (i.e., low in sulfidic nickel). One of the studies (Enterline and Marsh, 1982) was used in the 1986 USEPA assessment, while the other (Grimsrud et al., 2003) is an update to an earlier study (Magnus et al., 1982) used by USEPA. The linear multiplicative relative risk model with Poisson regression modeling was used to obtain maximum likelihood estimates and asymptotic variances for cancer potency factors (β) using cumulative nickel exposure levels versus observed and expected lung cancer mortality (Enterline and Marsh, 1982) or lung cancer incidence cases (Grimsrud et al., 2003). Life-table analyses were then used to develop URFs from these two studies, which were combined using weighting factors relevant to confidence to derive the final URF for nickel of 1.7E-04perμg/m3. The de minimis air concentration corresponding to a 1 in 100,000 extra lung cancer risk level is 0.059μg/m3. The TCEQ will use this conservative value to protect the general public in Texas against the potential carcinogenic effects from chronic exposure to nickel.
ISSN:0273-2300
1096-0295
DOI:10.1016/j.yrtph.2011.10.005