§ 250.306. Ingestion numeric values.
(a) For a regulated substance which is a systemic toxicant, the ingestion numeric value for that substance was calculated using the appropriate residential or nonresidential exposure assumptions from subsection (d) according to the following equation:
(b) For a regulated substance which is a carcinogen, the ingestion numeric value for that substance was calculated using the appropriate residential or nonresidential exposure assumptions from subsection (d) according to the following equations:
(1) For regulated substances not identified as a mutagen in § 250.301(b) (relating to scope):
(2) For regulated substances identified as a mutagen, except for vinyl chloride and trichloroethylene, in § 250.301(b):
(3) For vinyl chloride:
(4) For trichloroethylene:
(c) For a regulated substance that has both an oral reference dose and an oral cancer slope factor, the ingestion numeric value is the lower of the two numbers as calculated by the equations in subsections (a) and (b).
(d) The default exposure assumptions used to calculate the ingestion numeric values are as follows:
Term Residential
Systemic1Carcinogens2,6 Nonresidential
(Onsite Worker)THQ Target Hazard Quotient 1 N/A 1 RfDo Oral Reference Dose (mg/kg-day) Chemical-specific N/A Chemical-specific BW Body Weight (kg) Soil Groundwater 15
80N/A 80
80ATnc Averaging Time for systemic toxicants (yr) Soil Groundwater 6
30N/A
N/A25
25Abs Absorption (unitless)3 1 1 1 EF Exposure Frequency (d/yr) Soil Groundwater 250
350250
350180
250ED Exposure Duration (yr) Soil Groundwater 6
30N/A
N/A25
25IngR Ingestion Rate Soil (mg/day) GW (L/day) 100
2.4N/A
N/A50
1.2CF Conversion Factor Soil (kg/mg) GW (unitless) 1 x 10-6
11 x 10-6
11 x 10-6
1TR Target Risk N/A 1 x10-5 1 x 10-5 CSFo Oral Cancer Slope Factor (mg/kg-day)-1 N/A Chemical-specific Chemical-specific ATc Averaging Time for carcinogens (yr) N/A 70 70 IFadj4 Ingestion Factor Soil (mg-yr/kg-day) GW (L-yr/kg day) N/A 55
1.215.6
0.38AIFadj5 Combined Age-Dependent Adjustment Factor and Ingestion Factor Soil (mg-yr/kg-day) GW (L-yr/kg-day) N/A 241
3.45N/A CSFok TCE oral cancer slope factor for kidney cancer (mg/kg/day)-1 9.3 x 10-3 CSFol TCE oral cancer slope factor for non-Hodgkin lymphoma and liver cancer (mg/kg/day)-1 3.7 x 10-2 Notes:
1 Residential exposure to noncarcinogens is based on childhood (ages 16) exposure for soil, and adult exposure for groundwater, consistent with USEPA (1991).
2 Residential exposure to carcinogens is based on combined childhood and adult exposure.
3 The oral absorption factor takes into account absorption and bioavailability. In cases where the oral RfD or CSF is based on administered oral dose, the absorption factor would be limited to bioavailability. The default value is 1.
4 The Ingestion Factor for the residential scenario is calculated using the equation If adj = EDc x IRc/BWc + EDa x IRa/BWa, where EDc = 6 yr, IRc = 100 mg/day for soils and 1 L/day for groundwater, BWc = 15 kg, EDa = 24 yr, IRa = 50 mg/day for soils and 2.4 L/day for groundwater, and BWa = 80 kg. The ingestion factor for the nonresidential scenario is calculated using the equation If adj = ED x IR/BW, where ED = 25 yr, IR = 50 mg/day for soils and 1.2 L/day for groundwater, and BW = 80 kg.
5 The Combined Age-Dependent Adjustment Factor and Ingestion Factor (AIFadj) for the residential scenario is calculated using the equation AIFadj = [(ADAF2 x ED2) + (ADAF2-6 x ED2-6)] x IRc / BWc + [(ADAF6-16 x ED6-16 + (ADAF16 x ED16)] x IRa / BWa, where ADAF2 = 10, ED2 = 2 yr, ADAF2-6 = 3, ED2-6 = 4 yr, IRc = 100mg/day for soils and 1 L/day for groundwater, BWc = 15 kg, ADAF6-16 = 3, ED6-16 = 10 yr, ADAF16 = 1, ED16 = 14 yr, IRa = 50 mg/day for soils and 2.4 L/day for groundwater, and BWa = 80 kg.
6 For the equation to calculate the vinyl chloride residential MSC based on the carcinogenic effect, IRc = 100 mg/day for soils and 1 L/day for groundwater, BWc = 15 kg.
(e) The residential ingestion numeric value for lead in soil was developed using the Uptake Biokinetic (UBK) Model for Lead (version 0.4) developed by the EPA (U.S. Environmental Protection Agency. (1990) Uptake Biokinetic (UBK) Model for Lead (version 0.4). U.S. EPA/ECAO. August 1990, in lieu of the algorithms presented in subsections (a) and (b). Default input values are identified in Appendix A, Table 7. Because the UBK model is applicable only to children, the nonresidential ingestion numeric value was calculated according to the method developed by the Society for Environmental Geochemistry and Health (Wixson, B. G. (1991)). The Society for Environmental Geochemistry and Health (SEGH) Task Force Approach to the Assessment of Lead in Soil. Trace Substances in Environmental Health. (11-20), using the following equations:
Table 7 identifies each of the variables in this equation.
Authority The provisions of this § 250.306 amended under sections 104(a) and 303(a) of the Land Recycling and Environmental Remediation Standards Act (35 P.S. § § 6026.104(a) and 6026.303(a)); and section 1920-A of The Administrative Code of 1929 (71 P.S. § 510-20).
Source The provisions of this § 250.306 amended January 7, 2011, effective January 8, 2011, 41 Pa.B. 230; corrected March 19, 2011, effective March 5, 2011, 41 Pa.B. 1458; corrected May 16, 2014, effective March 5, 2011, 44 Pa.B. 2975; amended August 26, 2016, effective August 27, 2016, 46 Pa.B. 5655; amended November 19, 2021, effective November 20, 2021, 51 Pa.B. 7173. Immediately preceding text appears at serial pages (382769) to (382773).
Cross References This section cited in 25 Pa. Code § 250.301 (relating to scope); 25 Pa. Code § 250.304 (relating to MSCs for groundwater); 25 Pa. Code § 250.305 (relating to MSCs for soil); and 25 Pa. Code § 250.310 (relating to minimum threshold MSCs).
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