415 ILCS 5/3.215
"Hazardous substance" means: (A) any substance designated pursuant to Section 311(b)(2)(A) of the Federal Water Pollution Control Act ( P.L. 92-500), as amended, (B) any element, compound, mixture, solution, or substance designated pursuant to Section 102 of the Comprehensive Environmental Response, Compensation, and Liability Act of 1980 ( P.L. 96-510), as amended, (C) any hazardous waste, (D) any toxic pollutant listed under Section 307(a) of the Federal Water Pollution Control Act ( P.L. 92-500), as amended, (E) any hazardous air pollutant listed under Section 112 of the Clean Air Act ( P.L. 95-95), as amended, (F) any imminently hazardous chemical substance or mixture with respect to which the Administrator of the U.S. Environmental Protection Agency has taken action pursuant to Section 7 of the Toxic Substances Control Act ( P.L. 94-469), as amended. The term does not include petroleum, including crude oil or any fraction thereof which is not otherwise specifically listed or designated as a hazardous substance under subparagraphs (A) through (F) of this paragraph, and the term does not include natural gas, natural gas liquids, liquefied natural gas, or synthetic gas usable for fuel or mixtures of natural gas and such synthetic gas.
415 ILCS 5/3.215