title: Development of an inhalation unit risk factor for hexavalent chromium.
abstract: A unit risk factor (URF) was developed for hexavalent chromium (CrVI). The URF is based on excess lung cancer mortality in two key epidemiological studies of chromate production workers. The Crump et al. (2003) study concerns the Painesville, OH worker cohort, while Gibb et al. (2000) regards the Baltimore, MD cohort. A supporting assessment was also performed for a cohort from four low-dose chromate plants (Leverkusen and Uerdingen, Germany, Corpus Christi, TX, Castle Hayne, NC). For the Crump et al. (2003) study, grouped observed and expected number of lung cancer mortalities along with cumulative CrVI exposures were used to obtain the maximum likelihood estimate and asymptotic variance of the slope (β) for the linear multiplicative relative risk model using Poisson regression modeling. For the Gibb et al. (2000) study, Cox proportional hazards modeling was performed with optimal exposure lag and adjusting for the effect of covariates (e.g., smoking) to estimate β values. Life-table analyses were used to develop URFs for each of the two key studies, as well as for supporting and related studies. The two key study URFs were combined using weighting factors relevant to confidence to derive the final URF for CrVI of 2.3E-03 per μgCrVI/m(3).
authors.affiliation: Texas Commission on Environmental Quality (TCEQ), Toxicology Division, MC-168, P.O. Box 13087, Austin, TX 78711-3087, United States. Electronic address: Joseph.Haney@tceq.texas.gov.
authors.forename: Joseph T
authors.initials: JT
authors.lastname: Haney
authors.affiliation: Texas Commission on Environmental Quality (TCEQ), Toxicology Division, MC-168, P.O. Box 13087, Austin, TX 78711-3087, United States. Electronic address: Neeraja.Erraguntla@tceq.texas.gov.
authors.forename: Neeraja
authors.initials: N
authors.lastname: Erraguntla
authors.affiliation: Sielken & Associates Consulting Inc., 3833 Texas Avenue, Bryan, TX 77802, United States. Electronic address: SielkenAssoc@aol.com.
authors.forename: Robert L
authors.initials: RL
authors.lastname: Sielken
authors.affiliation: Sielken & Associates Consulting Inc., 3833 Texas Avenue, Bryan, TX 77802, United States. Electronic address: SielkenAssoc@aol.com.
authors.forename: Ciriaco
authors.initials: C
authors.lastname: Valdez-Flores
mesh_terms: D000395:Air Pollutants, Occupational / Q000633:toxicity; D000818:Animals; D002617:Chemical Industry; D002840:Chromates / Q000737:chemistry / Q000633:toxicity; D002857:Chromium / Q000633:toxicity*; D015331:Cohort Studies; D005260:Female; D006801:Humans; D016014:Linear Models; D008175:Lung Neoplasms / Q000139:chemically induced* / Q000453:epidemiology; D008297:Male; D009784:Occupational Diseases / Q000453:epidemiology* / Q000209:etiology; D016273:Occupational Exposure / Q000009:adverse effects*; D016012:Poisson Distribution; D016016:Proportional Hazards Models; D012044:Regression Analysis; D012306:Risk; D018570:Risk Assessment / Q000379:methods; D012307:Risk Factors
chemical_list: D000395:Air Pollutants, Occupational; D002840:Chromates; D002857:Chromium; C074702:chromium hexavalent ion
keywords: Cancer; Carcinogenicity; Chromium; Hexavalent; Inhalation; Lung; Mortality; Regulatory; Respiratory; Toxicity