NR 105.09(4)(b)(b) For surface waters classified as public water supplies, if the human cancer criterion for a toxic substance as calculated in par. (a) exceeds the maximum contaminant level (MCL) for that substance as specified in ch. NR 809 or the July 8, 1987 Federal Register (52 FR 25690), the MCL shall be used as the human cancer criterion.

NR 105.09(5)(5) The risk associated dose (RAD) referenced in sub. (4) represents the maximum amount of a substance which if ingested daily for a lifetime of 70 years has an incremental cancer risk equal to one case of human cancer in a population of 100,000. Methods for deriving the risk associated dose are specified in pars. (a) to (d).

NR 105.09(5)(a)(a) The department shall review available references for acceptable human and animal studies from which the risk associated dose can be derived. The department shall use sound scientific judgment when determining the acceptability of a study and may use the U.S. environmental protection agency’s “Guidelines for Carcinogen Risk Assessment” (FR 51 33992, September 24, 1986) as guidance for judging acceptability. Suitable references for review include, but are not limited to, those presented in s. NR 105.04 (5).

NR 105.09(5)(b)(b) If an acceptable human epidemiologic study is available, contains usable exposure data, and indicates a carcinogenic effect, the risk associated dose shall be set equal to the lifetime average exposure which would produce an incremental cancer risk of one in 100,000 based on the exposure information from the study and assuming the excess cancer risk is proportional to the lifetime average exposure. If more than one human epidemiologic study is judged to be acceptable, the most protective risk associated dose derived from the studies is generally used to calculate the human cancer criterion. If the risk associated dose values differ significantly, the department may consult with experts outside of the department for guidance in the selection of the more appropriate value.

NR 105.09(5)(c)(c) In the absence of an acceptable human epidemiologic study, the risk associated dose shall be derived from available studies which use mammalian test species and which are judged acceptable. Methods for deriving the risk associated dose are specified in subds. 1. to 4.

NR 105.09(5)(c)1.1. A linear, non-threshold dose-response relationship as applied by the U.S. environmental protection agency in “Water Quality Criteria Documents; Availability” (45 FR 79318, November 28, 1980) shall be assumed unless a more appropriate dose-response relationship or extrapolation model is supported by credible scientific evidence.

NR 105.09 NoteNote: The linear non-threshold dose-response model used by the U.S. environmental protection agency provides an upper-bound estimate (i.e., the one-sided 95% upper confidence limit) of incremental cancer risk. The true cancer risk is unknown. While the true cancer risk is not likely to be greater than the upper bound estimate, it may be lower.

NR 105.09(5)(c)2.2. When a linear, non-threshold dose-response relationship is assumed, the risk associated dose shall be calculated using the following equation:

NR 105.09(5)(c)3.3. The department shall adhere to the following guidance for deriving carcinogenic potency factors, or corresponding values if an alternate dose-response relationship or extrapolation model is used, unless more appropriate procedures are supported by credible scientific evidence:

NR 105.09(5)(c)3.a.a. If 2 or more mammalian studies are judged acceptable, but vary in either species, strain or sex of the test animals, or in tumor type or site, the study giving the greatest carcinogenic potency factor shall be used. Studies which produce a spuriously high carcinogenic potency factor due to the use of a small number of test animals may be excluded.

NR 105.09(5)(c)3.b.b. If 2 or more mammalian studies are judged acceptable, are comparable in size and are identical in regard to species, strain and sex of the test animals and to tumor sites, the geometric mean of the carcinogenic potency factors derived from each study shall be used.

NR 105.09(5)(c)3.c.c. If in an acceptable study, tumors were induced at more than one site, the number of animals with tumors at one or more of the sites shall be used as incidence data when deriving the cancer potency factor.

NR 105.09(5)(c)3.e.e. Calculation of an equivalent dose between animal species and humans using a surface area conversion, and conversion of units of exposure to milligrams of toxicant per day (mg/d) shall be performed as specified by the U.S. environmental protection agency in “Water Quality Criteria Documents; Availability” (45 FR 79318, November 28, 1980).

NR 105.09(5)(c)3.f.f. If the duration of the mammalian study (D) is less than the natural life span of the test animal (LS), the carcinogenicity potency factor is multiplied by the factor (D/LS)3.

NR 105.09(5)(c)4.4. When available mammalian studies contain conflicting information, the department shall consult with the department of health services and may consult with experts outside of the department for guidance in the selection of the appropriate study.

NR 105.09(5)(d)(d) If both a human epidemiologic study and a study of mammalian test species are judged reliable but only the animal study indicates a carcinogenic effect, it is assumed that a risk of cancer to humans exists but that it is less than could have been detected in the epidemiologic study. An upper limit of cancer incidence may be calculated assuming that the true incidence is just below the level of detection in the cohort of the epidemiologic study. The department may consult with experts outside of the department for guidance in the selection of the appropriate study.

NR 105.09 HistoryHistory: Cr. Register, February, 1989, No. 398, eff. 3-1-89; am. table 9 and (6), Register, July, 1991, No. 427, eff. 8-1-91; correction in (4) (b) made under s. 13.93 (2m) (b) 7., Stats., Register, September, 1995, No. 477; am. (1), (3), r. and recr. Table 9, am. (4) (a), (b), (5) (intro.), (a) (b), (c) (intro.) and 2., r. (6), Register, August, 1997, No. 500, eff. 9-1-97; CR 03-050: am. Table 9 Register February 2004 No. 578, eff. 3-1-04; CR 07-110: am. Table 9 Register November 2008 No. 635, eff. 12-1-08; CR 09-123: am. Table 9 Register July 2010 No. 655, eff. 8-1-10; correction in (5) (c) 4. made under s. 13.92 (4) (b) 6., Stats., Register April 2023 No. 808.

NR 105.10(1)(1) The bioaccumulation factor used to derive wildlife, human threshold, human cancer and taste and odor criteria or secondary values is determined from a baseline BAF using the methodology provided in Appendix B to 40 CFR part 132. 40 CFR part 132, Appendix B as stated on September 1, 1997, is incorporated by reference. BAFs shall be used to calculate criteria and secondary values for human health and wildlife. Use of a BAF greater than 1000, as determined from either of the methods referred to in sub. (2) (c) or (d) for organic substances, will result in the calculation of a secondary value. The baseline BAF is based on the concentration of freely dissolved substances in the ambient water to facilitate extrapolation from one water to another.

NR 105.10(2)(a)(a) A measured baseline BAF for an organic or inorganic substance derived from a field study of acceptable quality;

NR 105.10(2)(b)(b) A predicted baseline BAF for an organic substance derived using field-measured BSAFs of acceptable quality;

NR 105.10(2)(c)(c) A predicted baseline BAF for an organic or inorganic substance derived from a BCF measured in a laboratory study of acceptable quality and a food-chain multiplier. Food-chain multipliers are provided in 40 CFR part 132, Appendix B; or