15a ncac 02b .0208 STANDARDS FOR TOXIC SUBSTANCES AND TEMPERATURE
(a) Toxic Substances: the concentration of toxic substances, either alone or in combination with other wastes, in surface waters shall not render waters injurious to aquatic life or wildlife, recreational activities, or public health, nor shall it impair the waters for any designated uses. Specific standards for toxic substances to protect freshwater and tidal saltwater uses are listed in Rules .0211 and .0220 of this Section, respectively. The narrative standard for toxic substances and numerical standards applicable to all waters shall be interpreted as follows:
(1) The concentration of toxic substances shall not result in chronic toxicity to aquatic life. Any levels in excess of the chronic value for aquatic life shall be considered to result in chronic toxicity. In the absence of direct measurements of chronic toxicity, the concentration of toxic substances shall not exceed the concentration specified by the fraction of the lowest LC50 value that predicts a no effect chronic level as determined by the use of an acceptable Acute to Chronic Ratio (ACR) in accordance with U.S. Environmental Protection Agency (EPA) "Guidelines for Deriving Numerical Water Quality Criteria for the Protection of Aquatic Life and its Uses." In the absence of an ACR, that toxic substance shall not exceed one‑one hundredth (0.01) of the lowest LC50 or, if it is demonstrated that a toxic substance has a half‑life of less than 96 hours, the maximum concentration shall not exceed one‑twentieth (0.05) of the lowest LC50.
(2) The concentration of toxic substances shall not exceed the level necessary to protect human health through exposure routes of fish tissue consumption, water consumption, recreation, or other route identified for the water body. Fish tissue consumption shall include the consumption of shellfish. These concentrations of toxic substances shall be determined as follows:
(A) For non‑carcinogens, these concentrations shall be determined using a Reference Dose (RfD) as published by the EPA pursuant to Section 304(a) of the Federal Water Pollution Control Act as amended, a RfD issued by the EPA as listed in the Integrated Risk Information System (IRIS) file, or a RfD approved by the Director after consultation with the State Health director. Water quality standards or criteria used to calculate water quality based effluent limitations to protect human health through the different exposure routes shall be determined as follows:
(i) Fish tissue consumption:
WQS = (RfD x RSC) x Body Weight / (FCR x BCF)
where:
WQS = water quality standard or criteria;
RfD = reference dose;
RSC = Relative Source Contribution;
FCR = fish consumption rate (based upon 17.5 gm/person‑day);
BCF = bioconcentration factor or bioaccumulation factor (BAF), as appropriate.
Pursuant to Section 304(a) of the Federal Water Pollution Control Act as amended, BCF or BAF values, literature values, or site specific bioconcentration data shall be based on EPA publications; FCR values shall be average consumption rates for a 70 Kg adult for the lifetime of the population; alternative FCR values may be used when it is considered necessary to protect localized populations that may be consuming fish at a higher rate; RSC values, when made available through EPA publications pursuant to Section 304(a) of the Federal Clean Water Pollution Control Act to account for non-water sources of exposure may be either a percentage (multiplied) or amount subtracted, depending on whether multiple criteria are relevant to the chemical;
(ii) Water consumption (including a correction for fish consumption):
WQS = (RfD x RSC) x Body Weight / [WCR+(FCRxBCF)]
where:
WQS = water quality standard or criteria;
RfD = reference dose;
RSC = Relative Source Contribution;
FCR = fish consumption rate (based upon 17.5 gm/person‑day);
BCF = bioconcentration factor or bioaccumulation factor (BAF), as appropriate;
WCR = water consumption rate (assumed to be two liters per day for adults).
To protect sensitive groups, exposure shall be based on a 10 Kg child drinking one liter of water per day. Standards may also be based on drinking water standards based on the requirements of the Federal Safe Drinking Water Act, 42 U.S.C. 300(f)(g)-1. For non‑carcinogens, specific numerical water quality standards have not been included in this Rule because water quality standards to protect aquatic life for all toxic substances for which standards have been considered are more stringent than numerical standards to protect human health from non‑carcinogens through consumption of fish. Standards to protect human health from non‑carcinogens through water consumption are listed under the water supply classification standards in Rule .0211 of this Section. The equations listed in this Subparagraph shall be used to develop water quality based effluent limitations on a case‑by‑case basis for toxic substances that are not presently included in the water quality standards. Alternative FCR values may be used when it is necessary to protect localized populations that may be consuming fish at a higher rate;
(B) For carcinogens, the concentrations of toxic substances shall not result in unacceptable health risks and shall be based on a Carcinogenic Potency Factor (CPF). An unacceptable health risk for cancer shall be more than one case of cancer per one million people exposed (10-6 risk level). The CPF is a measure of the cancer‑causing potency of a substance estimated by the upper 95 percent confidence limit of the slope of a straight line calculated by the Linearized Multistage Model or other appropriate model according to U.S. Environmental Protection Agency Guidelines, FR 51 (185): 33992‑34003; and FR 45 (231 Part V): 79318‑79379. Water quality standards or criteria for water quality based effluent limitations shall be calculated using the procedures given in this Part and in Part (A) of this Subparagraph. Standards to protect human health from carcinogens through water consumption are listed under the water supply classification standards in Rules .0212, .0214, .0215, .0216, and .0218 of this Section. Standards to protect human health from carcinogens through the consumption of fish (and shellfish) only shall be applicable to all waters as follows:
(i) Aldrin: 0.05 ng/l;
(ii) Arsenic: 10 ug/l;
(iii) Benzene: 51 ug/l;
(iv) Carbon tetrachloride: 1.6 ug/l;
(v) Chlordane: 0.8 ng/l;
(vi) DDT: 0.2 ng/l;
(vii) Dieldrin: 0.05 ng/l;
(viii) Dioxin: 0.000005 ng/l;
(ix) Heptachlor: 0.08 ng/l;
(x) Hexachlorobutadiene: 18 ug/l;
(xi) Polychlorinated biphenyls (total of all identified PCBs and congeners): 0.064 ng/l;
(xii) Polynuclear aromatic hydrocarbons (total of all PAHs): 31.1 ng/l;
(xiii) Tetrachloroethane (1,1,2,2): 4 ug/l;
(xiv) Tetrachloroethylene: 3.3 ug/L;
(xvi) Trichloroethylene: 30 ug/l;
(xvii) Vinyl chloride: 2.4 ug/l.
The values listed in Subparts (i) through (xvii) of this Part may be adjusted by the Commission or its designee on a case‑by‑case basis to account for site‑specific or chemical‑specific information pertaining to the assumed BCF, FCR, or CPF values or other data.
(b) Temperature: the Commission may establish a water quality standard for temperature for specific water bodies other than the standards specified in Rules .0211 and .0220 of this Section upon a case‑by‑case determination that thermal discharges to these waters that serve or may serve as a source or receptor of industrial cooling water provide for the maintenance of the designated best use throughout a portion of the water body. Such revisions of the temperature standard shall be consistent with the provisions of Section 316(a) of the Federal Water Pollution Control Act, as amended. A list of such revisions shall be maintained and made available to the public by the Division.
History Note: Authority G.S. 143‑214.1; 143‑215.3(a)(1);
Eff. February 1, 1976;
Amended Eff. May 1, 2007; April 1, 2003; February 1, 1993; October 1, 1989; January 1, 1985; September 9, 1979;
Readopted Eff. November 1, 2019.