430 ILCS 35/2-6
"Highly Toxic" means any substance which produces death within 14 days in at least half of a group of 10 or more laboratory white rats each weighing between 200 and 300 grams, when a single dose of 50 milligrams or less per kilogram of body weight, is orally administered or when inhaled continuously for a period of one hour or less at an atmospheric concentration of 200 parts per million by volume or less of gas or vapor or two milligrams per liter by volume or less of mist or dust, provided such concentration is likely to be encountered by man when the substance is used in any reasonably foreseeable manner, or which produces death within 14 days in at least half of a group of 10 or more rabbits tested in a dosage of 200 milligrams or less per kilogram of body weight, when administered by continuous contact with the bare skin for 24 hours or less.
If the Director finds that available data on human experience with any substance indicate results different from those obtained on animals in the above named dosages or concentrations, the human data shall take precedence.
430 ILCS 35/2-6