A team of 21CT and EpidStrategies scientists are authors on a manuscript being published in Regulatory Toxicology and Pharmacology. The study examines current practices for assessing risk associated with environmental exposure to hexavalent chromium, comparing approaches based on margin of exposure to those using linear extrapolation. The authors assert that regulatory lung cancer potency estimates for Cr(VI) are based on outdated research, whereas more current mechanistic data support an epigenetic role for Cr(VI) and a non-mutagenic mode of action. The article cites a need for new epidemiology data to inform risk assessment of low-intensity exposures, concluding, however, that Cr(VI) in ambient air poses little concern for human health.