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 into the final nickel URF. ► Extra lung cancer risk: 1.6-1.7E-4 per μg/m3 with US/TX rates and life-table analysis.