Section 302.651  The Human Nonthreshold Criterion

The Human Nonthreshold Criterion (HNC) of a substance is that concentration or level of a substance at which humans are protected from an unreasonable risk of disease caused by a nonthreshold toxic mechanism as a result of incidental exposure to or ingestion of surface waters of the State and from ingestion of aquatic organisms taken from surface waters of the State.  HNCs are derived for those toxic substances for which any exposure, regardless of extent, carries some risk of damage as specified in subsections (a) and (b).

a)         For single substances, a risk level of one in one million (1 in 1,000,000) shall be allowed (i.e, considered acceptable) for the purposes of determination of an HNC.

b)         For mixtures of substances, an additive risk level of one in one hundred thousand (1 in 100,00) shall be allowed (i.e, considered acceptable) for the purposes of determination of an HNC.

(Source:  Added at 14 Ill. Reg. 2899, effective February 13, 1990)