1. (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:

   

2. (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. (1) For regulated substances not identified as a mutagen in § 250.301(b) (relating to scope):

      

   2. (2) For regulated substances identified as a mutagen, except for vinyl chloride and trichloroethylene, in § 250.301(b):

      

   3. (3) For vinyl chloride:

      

   4. (4) For trichloroethylene:

      

3. (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).

4. (d) The default exposure assumptions used to calculate the ingestion numeric values are as follows:

   Term		Residential Systemic1	Carcinogens2,6	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 80	N/A	80 80
   ATnc	Averaging Time for systemic toxicants (yr) Soil Groundwater	6 30	N/A N/A	25 25
   Abs	Absorption (unitless)3	1	1	1
   EF	Exposure Frequency (d/yr) Soil Groundwater	250 350	250 350	180 250
   ED	Exposure Duration (yr) Soil Groundwater	6 30	N/A N/A	25 25
   IngR	Ingestion Rate Soil (mg/day) GW (L/day)	100 2.4	N/A N/A	50 1.2
   CF	Conversion Factor Soil (kg/mg) GW (unitless)	1 x 10-6 1	1 x 10-6 1	1 x 10-6 1
   TR	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 1.2	15.6 0.38
   AIFadj5	Combined Age-Dependent Adjustment Factor and Ingestion Factor Soil (mg-yr/kg-day) GW (L-yr/kg-day)	N/A	241 3.45	N/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 1—6) 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 = ED_c x IR_c/BW_c + ED_a x IR_a/BW_a, where ED_c = 6 yr, IR_c = 100 mg/day for soils and 1 L/day for groundwater, BW_c = 15 kg, ED_a = 24 yr, IR_a = 50 mg/day for soils and 2.4 L/day for groundwater, and BW_a = 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 = [(ADAF_‹2 x ED_‹2) + (ADAF_2-6 x ED_2-6)] x IR_c / BW_c + [(ADAF_›6-16 x ED_›6-16 + (ADAF_›16 x ED_›16)] x IR_a / BW_a, where ADAF_‹2 = 10, ED_‹2 = 2 yr, ADAF_2-6 = 3, ED_2-6 = 4 yr, IR_c = 100mg/day for soils and 1 L/day for groundwater, BW_c = 15 kg, ADAF_›6-16 = 3, ED_›6-16 = 10 yr, ADAF_›16 = 1, ED_›16 = 14 yr, IR_a = 50 mg/day for soils and 2.4 L/day for groundwater, and BW_a = 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.

5. (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).