R 336.1231 Cancer risk assessment screening methodology.

Rule 231. (1) The initial risk screening level (IRSL) and the secondary risk screening level (SRSL) shall be determined as follows: Where: Inhalation unit risk = Additional lifetime cancer risk occurring in a population in which all individuals are exposed continuously for life to a concentration of 1 microgram per cubic meter of the chemical in the air they breathe. 1 x 10-6 = An upper bound lifetime cancer risk of 1 in 1,000,000. 1 x 10-5 =An upper bound lifetime cancer risk of 1 in 100,000. (2) The following provisions apply to derivation of the inhalation unit risk: (a) The inhalation unit risk value determined by the United States environmental protection agency (b) If the inhalation unit risk value has not been determined by the United States environmental protection agency, then the inhalation unit risk value shall be determined by the department according to the United States environmental protection agency guidelines for carcinogen risk assessment and supplemental guidance for assessing susceptibility from early-life exposure to carcinogens, adopted by reference in R 336.1902. (c) Equivalence between tissue doses in animals and humans, yielding equal lifetime risks, shall be based on dosimetric adjustment factors to determine toxicokinetic or toxicodynamic equivalence, according to the United States environmental protection agency advances in inhalation gas dosimetry for derivation of a reference concentration (RfC) and use in risk assessment, adopted by reference in R 336.1902. (3) An annual average time period shall be used for the IRSL and SRSL. IRSL = 1 x 10-6 Inhalation unit risk SRSL = 1 x 10-5 Inhalation unit risk