"HAP or Hazardous air pollutant" means an air pollutant to which no ambient air standard is applicable and which in the judgment of the Board causes, or contributes to, air pollution which may reasonably be anticipated to result in an increase in mortality or an increase in serious irreversible, or incapacitating reversible, illness. This term shall include, but is not limited to, those pollutants for which EPA has adopted NESHAPS at 40 C. F. R. Part 61 and Part 63. For the purpose of Chapters 115 and 140, HAP means an air pollutant identified by the EPA in regulations pursuant to Section 112(b) of the CAA.
06-096 C.M.R. ch. 100, § 63