US EPA

2,2,4-Trimethylpentane (CASRN 540-84-1; iso-octane) is a constituent of petroleum and gasoline. It is released into the environment by the petroleum industries during refining processes and during the use of gasoline. Automotive evaporative emissions and exhaust are the most important sources of release into the environment. The most important route of human exposure is via inhalation. EPA is undertaking an update of the Integrated Risk Information System (IRIS) health assessment for 2,2,4-trimethylpentane. The outcome of this project will be an updated Toxicological Review and IRIS Summary of 2,2,4-trimethylpentane that will be entered on the IRIS data base. IRIS is an EPA data base containing Agency scientific positions on potential adverse human health effects that my result from chronic (or lifetime) exposure to chemicals in the environment. IRIS contains chemical-specific summaries of qualitative and quantitative health information in support of two steps of the risk assessment process, i.e., hazard identification and dose-response evaluation. The IRIS assessment is a critical review of the physiochemical and toxicokinetic properties of a chemical, and its toxicity in humans and experimental systems. The assessment will present reference values for the noncancer effects of 2,2,4-trimethylpentane (RfD and RfC), where supported by available data, and a cancer assessment. The Toxicological Review and IRIS Summary will be subject to internal peer consultation, Agency review, and external scientific peer review. The final product will reflect the Agency opinion on the toxicity of 2,2,4-trimethylpentane.