| (a) General. (1) Due to the unique nature of the toxicity and/or exposure, the person shall use the COC-specific approaches described in this section for the following COCs: (A) cadmium; (B) lead; (C) polychlorinated biphenyls; (D) polychlorinated dibenzodioxins and dibenzofurans; (E) polycyclic aromatic hydrocarbons; and (F) total petroleum hydrocarbons. (2) Except for the specific provisions contained in this section, the person shall establish RBELs and PCLs in accordance with the standard procedures outlined in the previous sections of this subchapter. (3) This section addresses only those exposure pathways for which PCL equations are provided in this subchapter. When dealing with other exposure pathways as required in §350.71(c) of this title (relating to General Requirements), the executive director will specify how those pathways should be addressed for these COCs using the best available science. (4) The person shall use the figures as required in subsections (b) - (g) of this section. (b) Cadmium. (1) In calculating residential soil PCLs that are protective for noncarcinogenic effects for all tiers, the person shall incorporate age-adjusted exposure assumptions for the soil ingestion, vegetable ingestion, and dermal soil exposure pathways. Accordingly, 30 years of cadmium exposure shall be partitioned into three specific exposure periods: <1 - 6 years, 6 - 18 years, and 18 - 30 years. Cadmium intake shall be calculated for each of these periods, based on the period-specific exposure assumptions. The soil PCL for cadmium shall be a function of the final integrated intake estimate, which shall be determined by time-weighting intake from each of the three exposure periods. The age-adjusted RBEL equations and default parameters to be used for cadmium are provided in the following figure. The soil PCL for cadmium shall be calculated by combining the pathway-specific PCLs as outlined in §350.75(i)(6) of this title (relating to Tiered Human Health Protective Concentration Level Evaluation). Attached Graphic (2) In calculating residential and commercial/industrial soil PCLs for all tiers, the person shall use the reference dose values for cadmium in food in evaluating exposures to cadmium through the soil ingestion, vegetable ingestion, and dermal soil exposure pathways. (c) Lead. (1) The Tier 1 residential soil PCL ( Tot SoilComb ) for lead is 500 mg/kg. (2) Subject to prior approval by the executive director, the person may use property-specific data in conjunction with a lead model approved by the executive director (e.g., EPA Integrated Exposure Uptake Biokinetic model for lead in children (version 1.0 from 2005)) to calculate a Tier 3 residential soil PCL (Tot Soil Comb ) for lead. The person shall submit information to the executive director which demonstrates that variance from default model inputs is supported by property-specific information (e.g., data from a scientifically valid bioavailability study using property-specific soils). Property-specific model input values must be approved by the executive director. Consistent with the development of residential RBELs for COCs without chemical-specific approaches in accordance with §350.74 of this title (Development of Risk-Based Exposure Limits), variance from certain model default exposure factors such as soil/dust ingestion rates and exposure frequency to less conservative (i.e., lower) numerical values shall not be allowed. (3) The commercial/industrial soil PCL ( Tot SoilComb ) is based only on the soil ingestion pathway (Soil Soil Ing ). The person shall use the exposure algorithm and default exposure factors in the following figure for calculating the Tier 1 commercial/industrial Soil RBELIng value. Attached Graphic (4) The person may use a different exposure algorithm as presented in the following figure that considers soil and dust separately for calculating the Tier 2 and 3 commercial/industrial Soil RBELIng value in cases where the person has adequate direct measurement data on the concentrations of lead in both soil and dust at the affected property. In addition, in calculating Tier 2 or 3 Soil RBELIng values, the person may deviate from the default exposure factors as shown in the figure in paragraph (3) of this subsection and the following figure if property-specific or defensible alternative data (e.g., from open literature or privately funded studies) adequately support such an approach. The specific exposure factors for which the person may use property-specific or scientifically defensible alternative values are the following: Attached Graphic (A) individual geometric standard deviation (GSD i ); (B) baseline blood lead (PbBO); (C) absolute absorption fraction of lead in soil/dust (Afsd); (D) absolute absorption fraction of lead in soil (AFs); and (E) absolute absorption fraction of lead in dust (Afd). (d) Polychlorinated Biphenyls. (1) In calculating Tier 1 residential and commercial/industrial soil and groundwater PCLs, the person shall use the upper-reference point of the upper-bound slope factors (2 (mg/kg-day)-1 ) for the soil ingestion, dermal contact with soil, vegetable ingestion, and inhalation (both vapor and particulate phases) exposure pathways. (2) For Tiers 2 and 3, the person may use alternative slope factors when the following conditions are met: (A) The person may use the lower reference point of the upper bound slope factors (0.4 (mg/kg-day)-1 ) to calculate an inhalation unit risk factor when evaluating inhalation exposures to volatilized polychlorinated biphenyls. The person must still use the upper reference point of the upper bound slope factors (2 (mg/kg-day)-1 ) to evaluate inhalation exposures to particulate phase polychlorinated biphenyls. (B) The person may conduct congener or isomer analyses. The person may use the lowest reference point of the upper-bound slope factors (0.07 (mg/kg-day)-1 ) for the soil ingestion, dermal contact with soil, and inhalation exposure pathways if congener or isomer analyses verify that congeners with more than four chlorines comprise less than one-half percent of total polychlorinated biphenyls in a given exposure medium. The upper reference point of the upper-bound slope factors (2 (mg/kg-day)-1 ) shall be used for all other exposure pathways regardless of the results of the congener- or isomer-specific analyses. If congener or isomer analyses indicate that congeners with more than four chlorines comprise greater than one-half percent of total polychlorinated biphenyls in a given exposure medium, then the person shall use the upper-reference point of the upper-bound slope factors (2 (mg/kg-day)-1 ) for all pathways for that specific exposure medium. Further, when congener concentrations are available, the contribution of dioxin-like polychlorinated biphenyls to total dioxin equivalents shall be considered. The person shall apply the toxicity equivalency factors specified in the following figure to the measured concentrations for each of the dioxin-like polychlorinated biphenyls. These values shall then be summed to obtain a 2,3,7,8-TCDD toxicity equivalency quotient. Toxicity equivalency quotients for dioxin-like polychlorinated biphenyls shall then be added to those for other dioxin-like compounds as specified in subsection (e) of this section to yield a total toxicity equivalency quotient concentration. This total toxicity equivalency quotients concentration shall then be compared with the critical PCL for TCDD, 2,3,7,8-(dioxin). When addressing dioxin-like polychlorinated biphenyls in this manner, the person shall subtract the concentration of dioxin-like polychlorinated biphenyls from the total polychlorinated biphenyls concentration to avoid overestimating dioxin-like polychlorinated biphenyls by evaluating them twice. Attached Graphic (3) In evaluating inhalation exposures under Tiers 2 or 3, the person shall convert the appropriate slope factor to an inhalation unit risk factor, based on the following equation: Inhalation Unit Risk Factor (risk per µg/m3 )= oral slope factor x 20 m3 /day divided by 70 kg x 10 -3 mg/µg. (4) In Tiers 2 and 3, and only when applicable for a specific site, the person may set soil PCLs based on the requirements of the Toxic Substances Control Act, 40 Code of Federal Regulations Parts 750 and 761, as amended. Sites must comply fully with all applicable Toxic Substances Control Act, as amended, requirements when establishing the soil PCL for polychlorinated biphenyls in this manner. (e) Polychlorinated Dibenzo-p-Dioxins and Dibenzofurans. Cont'd... |
