This is from the Wikipedia entry on rubbing alcohol. Obviously this won't apply to 99.98% industrial purposed ISO.
Legislation
In the USA, rubbing alcohol, USP and all preparations coming under the classification of Rubbing Alcohols (defined as those containing ethanol) must be manufactured in accordance with the requirements of the US Treasury Department, Bureau of Alcohol, Tobacco, and Firearms, using Formula 23-H (8 parts by volume of acetone, 1.5 parts by volume of methyl isobutyl ketone, and 100 parts by volume of ethyl alcohol). It contains 97.5-100% by volume of absolute ethyl alcohol. The rest consists of water and the denaturants, with or without color additives, and perfume oils. Rubbing Alcohol contains in each 100 mL not less than 355 mg of sucrose octaacetate or not less than 1.40 mg of denatonium benzoate. The preparation may be colored with one or more color additives. A suitable stabilizer may also be added.[4]
Also note that 99.0% Iso doesn't contain ethanol and isn't classified as rubbing alcohol.