California Code of Regulations › Title 27 - Environmental Protection › Division 4 - Office of Environmental Health Hazard Assessment › Chapter 1 - Safe Drinking Water and Toxic Enforcement Act of 1986 › Article 7 - NO Significant Risk Levels › Section 25703 - Quantitative Risk Assessment

Current through Register 2024 Notice Reg. No. 28, July 12, 2024
(a) A
				  quantitative risk assessment which conforms to this section shall be deemed to
				  determine the level of exposure to a listed chemical which, assuming daily
				  exposure at that level, poses no significant risk. The assessment shall be
				  based on evidence and standards of comparable scientific validity to the
				  evidence and standards which form the scientific basis for listing the chemical
				  as known to the state to cause cancer. In the absence of principles or
				  assumptions scientifically more appropriate, based upon the available data, the
				  following default principles and assumptions shall apply in any such
				  assessment:
(1) Animal bioassay studies for
				  quantitative risk assessment shall meet generally accepted scientific
				  principles, including the thoroughness of experimental protocol, the degree to
				  which dosing resembles the expected manner of human exposure, the temporal
				  exposure pattern, the duration of study, the purity of test material, the
				  number and size of exposed groups, the route of exposure, and the extent of
				  tumor occurrence.
(2) The quality
				  and suitability of available epidemiologic data shall be appraised to determine
				  whether the study is appropriate as the basis of a quantitative risk
				  assessment, considering such factors as the selection of the exposed and
				  reference groups, reliable ascertainment of exposure, and completeness of
				  follow-up. Biases and confounding factors shall be identified and
				  quantified.
(3) Risk analysis shall
				  be based on the most sensitive study deemed to be of sufficient
				  quality.
(4) The results obtained
				  for the most sensitive study deemed to be of sufficient quality shall be
				  applicable to all routes of exposure for which the results are
				  relevant.
(5) The absence of a
				  carcinogenic threshold dose shall be assumed and no-threshold models shall be
				  utilized. A linearized multistage model for extrapolation from high to low
				  doses, with the upper 95 percent confidence limit of the linear term expressing
				  the upper bound of potency shall be utilized. Time-to-tumor models may be
				  appropriate where data are available on the time of appearance of individual
				  tumors, and particularly when survival is poor due to competing
				  toxicity.
(6) Human cancer potency
				  shall be derived from data on human or animal cancer potency. Potency shall be
				  expressed in reciprocal milligrams of chemical per kilogram of bodyweight per
				  day. Interspecies conversion of animal cancer potency to human cancer potency
				  shall be determined by multiplying by a scaling factor equivalent to the ratio
				  of human to animal bodyweight, taken to the one-fourth power.
(7) When available data are of such quality
				  that physiologic, pharmacokinetic and metabolic considerations can be taken
				  into account with confidence, they may be used in the risk assessment for
				  inter-species, inter-dose, and inter-route extrapolations.
(8) When the cancer risk applies to the
				  general population, human body weight of 70 kilograms shall be assumed. When
				  the cancer risk applies to a certain subpopulation, the following assumptions
				  shall be made, as appropriate:
Subpopulation
Kilograms of Body
								Weight
Man (18+ years of age)
70
Woman (18+ years of age)
58
Woman with conceptus
58
Adolescent (11-18 years of age)
40
Child (2-10 years of age)
20
Infant (0-2 years of age)
10