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, public health, or 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.  Procedures for interpreting the narrative standard for toxic substances and numerical standards applicable to all waters are as follows:

(1)           Aquatic life standards: the concentration of toxic substances shall not result in chronic toxicity.  Any levels in excess of the chronic value 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 acceptable acute/chronic ratios).  If an acceptable acute/chronic ratio is not available, then that toxic substance shall not exceed one‑one hundredth (0.01) of the lowest LC50 or if it is affirmatively 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)           Human health standards: the concentration of toxic substances shall not exceed the level necessary to protect human health through exposure routes of fish tissue consumption, water consumption, or other route identified as appropriate for the water body. Fish tissue consumption includes the consumption of shellfish;

(A)          For non‑carcinogens, these concentrations shall be determined using a Reference Dose (RfD) as published by the U.S. Environmental Protection Agency pursuant to Section 304(a) of the Federal Water Pollution Control Act as amended or a RfD issued by the U.S. Environmental Protection Agency 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 are 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  approved by the Commission or its designee are based on U.S. Environmental Protection Agency publications; FCR values are 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 U.S. Environmental Protection Agency 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 is 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 considered 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 considered to 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 are calculated using the procedures given in Subparagraphs (A) and (B) of this Rule.  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 are 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) 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 reasonable portion of the water body.  Such revisions of the temperature standard must be consistent with the provisions of Section 316(a) of the Federal Water Pollution Control Act as amended.  A listing of existing thermal 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.