(a) For the purposes of this chapter, a hazardous substance is present in any mixture or product if it is present in any of the following concentrations:

1. (1) One percent or more of the mixture or product.
2. (2) Two percent of the mixture or product if the hazardous substance exists as an impurity in the mixture.

3. (3) One-tenth of 1 percent of the mixture or product if the hazardous substance in the mixture or product is designated as a carcinogen pursuant to the Occupational Carcinogens Control Act of 1976 (Ch. 2 (commencing with Section 24200), Div. 20, H.& S.C.) or the federal Hazard Communication Standard (29 C.F.R. Sec. 1910.1200).

   The director may, by regulation, raise the concentration requirement for a hazardous substance which the director finds is not hazardous at the threshold levels; and, lower the concentration requirement for a hazardous substance for which there is valid and substantial evidence that the substance is extraordinarily hazardous.