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.
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Notes
Mich. Admin. Code
R. 336.1231
1992 AACS;
1998-2000 AACS; 2016
MR
24, Eff. 12/20/2016
