§ 250.307. Inhalation numeric values.
(a) For a regulated substance which is a systemic toxicant, the following applies:
(1) For a volatile compound, the numeric value for inhalation from soil shall be calculated using the appropriate residential or nonresidential exposure assumptions from subsection (d) according to the following equation using TF for volatiles:
(2) For a regulated substance attached to particulates, the numeric value for inhalation from soil was calculated using the appropriate residential or nonresidential exposure assumptions from subsection (d) according to the equation in paragraph (1) using TF for particulates.
(b) For a regulated substance which is a carcinogen, the following apply:
(1) For a volatile compound, the numeric value for inhalation from soil was calculated using the appropriate residential or nonresidential exposure assumptions from subsection (d) according to the following equation using TF for volatiles:
(2) For a regulated substance attached to particulates, the numeric value for inhalation from soil was calculated using the appropriate residential or nonresidential exposure assumptions from subsection (d) according to the equation in paragraph (1) using TF for particulates.
(3) For a regulated substance identified in § 250.301(b) (relating to scope) as a mutagen, except for vinyl chloride and trichloroethylene, the numeric value for inhalation from soil was calculated using the appropriate residential or nonresidential exposure assumptions from subsection (d) according to the following equation using the TF for volatiles or particulates:
(4) For vinyl chloride, the numeric value for inhalation from soil was calculated using the appropriate residential or nonresidential exposure assumptions from subsection (d) according to the following equation using the TF for volatiles or particulates:
(5) For trichloroethylene, the numeric value for inhalation from soil was calculated using the appropriate residential or nonresidential exposure assumptions from subsection (d) according to the following equation using the TF for volatiles:
(c) For a regulated substance which is both a systemic toxicant and a carcinogen, the inhalation 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 inhalation numeric values for soil are as follows:
Residential Nonresidential Term Systemic1 Carcinogens2 (Onsite Worker) THQ Target Hazard Quotient 1 N/A 1 RfCi Inhal. Reference Concentration (mg/m3) Chemical-specific N/A Chemical-specific ATnc Averaging Time for systemic toxicants (yr) 30 N/A 25 TF Transport Factor (mg/kg)/(mg/m3) Volatilization3 Chemical-specific Chemical-specific Chemical-specific Particulate4 1 x 1010 1 x 1010 1 x 1010 ET Exposure Time (hr/day) 24 24 8 EF Exposure Frequency5 (d/yr) 250 250 180 ED Exposure Duration (yr) 30 30 25 CF Conversion Factor N/A 1000 µg/mg 1000 µg/mg TR Target Risk N/A 1 x 10-5 1 x 10-5 IUR Inhalation Unit Risk (µg/m3)-1 N/A Chemical-specific Chemical-specific ATc Averaging Time for carcinogens (yr) N/A 70 70 AED Combined Age-Dependent Adjustment Factor and Exposure Duration (yr)6 N/A 76 N/A IURk TCE inhalation unit risk for kidney cancer (ug/m3)-1 1 x 10-6 IURl TCE inhalation unit risk for both non-Hodgkin lymphoma and liver cancer (ug/m3)-1 3 x 10-6 Notes: Modified from USEPA Region III Risk-based Concentration Table, dated October 20, 1995.
N/A = Not Applicable
1 Residential exposure to systemic toxicants is based on adult exposure, consistent with USEPA (1991).
2 Residential exposure to carcinogens is based on combined child and adult exposure.
3 Volatilization transport factor is calculated using TF = (ER x DF)-1, where DF = 12 (mg/m3)/(m2-sec). See soil depth-specific algorithm for the calculation of ER.
4 Particulate transfer factor was calculated using TF = (ER x DF)-1, where ER = 8.25 x 10-12 (mg/m2-sec)/(mg/kg) and DF = 12(mg/m3)/(mg/m2-sec).
5 Assumes approximately 100 days/yr with the ground being frozen. Exposure to surficial soils when the ground is frozen is considered de minimis. The nonresidential exposure frequency is defined as 5/7 x 250 days/yr.
6 The Combined Age-Dependent Adjustment Factor and Exposure Duration (AED) is calculated using the equation AED = ADAF‹2 x ED‹2 + ADAF2-16 x ED2-16 + ADAF›16 x ED›16, where ADAF‹2 = 10, ED‹2 = 2 yr, ADAF2-16 = 3, ED2-16 = 14 yr, ADAF›16 = 1, ED›16 = 14 yr.
(e) For the inhalation numeric values in subsections (a) and (b), the TF was calculated by the following equation:
TF = (ER x DF)-1
The Dispersion Factor (DF) value of 12 (mg/m3)/(mg/m2/sec) is taken from the default value in the EPA Draft Soil Screening Guidance (U. S. EPA, 1994. Technical Background Document for Soil Screening Guidance. Review Draft. Office of Emergency and Remedial Response. EPA-540/R-94/106) and the Emission Rate (ER) is calculated by the following equations (from Jury et al. 1990. Water Resources Research, Vol. 26. No. 1. pp. 13-20):
(i) For surficial soils:
Parameter Definition Unit Recommended Value(1) ER Chemical vapor emission rate from surface soil or subsurface soil mg/m2-sec per mg/kg Chemical-specific Co Chemical concentration in soil, Co = CSρb g/m3 1.8 CS Chemical concentration in soil mg/kg (ppm) 1 DE Effective diffusion coefficient m2/sec Chemical-specific Dai Air diffusivity for chemical i m2/sec Chemical-specific DLi Water diffusivity for chemical i m2/sec Chemical-specific t Time sec N/A T Emission averaging time sec Equal to exposure duration θ Total soil porosity, θ = θa + θm cm3/cm3 0.32(2) θa Air-filled soil porosity cm3/cm3 0.12(2) θm Moisture-filled soil porosity, θm = wρb cm3/cm3 0.20(2) w Moisture content for soil g water/g soil 0.11 ρb Dry bulk density of soil, ρb = (1-θ) ρ g/cm3 1.8(2) (Footnotes on next page) ρ Soil particle density g/cm3 2.65 Kd Partition coefficient, Kd = Kocfoc cm3/g Chemical-specific H Henry’s Law constant dimensionless Chemical-specific DG Effective gas-phase diffusion coefficient m2/sec Chemical-specific DL effective liquid-phase diffusion coefficient m2/sec Chemical-specific L Depth of the contaminated surface soil m 0.6(3) l Depth of the clean soil cover m 0.6(3) W Thickness of the contaminated subsurface soil m 4.0(3) KOC Organic carbon partition coefficient for chemical i cm3/g Chemical-specific fOC Fraction of organic carbon in soil dimensionless 0.005(4) (1)All default values from USEPA (1994) Draft Soil Screening Guidance, EPA-540/R-94/106, except as noted. (2)Consistent with Standards Subcommittee recommendation. (3)Based on Act 2 SAB-agreed depths. (4)The Risk Assessment Subcommittee selected a foc of 0.005, which falls between foc’s of 0.006 for surface soil and 0.002 for subsurface soil.
(f) For a regulated substance which is a systemic toxicant and is a volatile compound, the numeric value for the inhalation of volatiles from groundwater was calculated by using the appropriate residential or nonresidential exposure assumptions from subsection (h) according to the following equation:
(g) For a regulated substance which is a carcinogen and is a volatile compound, the numeric value for the inhalation of volatiles from groundwater shall be calculated by using the appropriate residential or nonresidential exposure assumptions from subsection (h) according to the following equations:
(1) For regulated substances not identified as a mutagen in § 250.301(b):
(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:
(h) The default exposure assumptions used to calculate the inhalation numeric values for the inhalation of volatiles from groundwater are as follows:
Residential Nonresidential Term Systemic1 Carcinogens2 (Onsite Worker) THQ Target Hazard Quotient 1 N/A 1 RfCi Inhal. Reference Concentration (mg/m3) Chemical-specific N/A Chemical-specific ATnc Averaging Time for systemic toxicants (yr) 30 N/A 25 ET Exposure Time (hr/day) 24 24 8 EF Exposure Frequency (d/yr) 350 350 250 ED Exposure Duration (yr) 30 30 25 TF Transfer Factor (L/m3)3 0.5 0.5 0.5 CF Conversion Factor N/A 1,000 µg/mg 1,000 µg/mg TR Target Risk N/A 1 x 10-5 1 x 10-5 IUR Inhalation Unit Risk (ug/m3)-1 N/A Chemical-specific Chemical-specific ATc Averaging Time for carcinogens (yr) N/A 70 70 AED Combined Age-Dependent adjustment Factor and Exposure Duration (yr)4 N/A 76 N/A IURk TCE inhalation unit risk for kidney cancer (ug/m3)-1 1 x 10-6 IURl TCE inhalation unit risk for both non-Hodgkin lymphoma and liver cancer (ug/m3)1 3 x 10-6 Notes: Modified from USEPA Region III Risk-based Concentration Table, dated October 20, 1995.
N/A = Not Applicable
1 Residential exposure to systemic toxicants is based on adult exposure, consistent with USEPA (1991).
2 Residential exposure to carcinogens is based on combined child and adult exposure.
3 Default Transfer Factor is as presented in USEPA’s RAGS, Part B.
4 The Combined Age-Dependent Adjustment Factor and Exposure Duration (AED) is calculated using the equation AED = ADAF‹2 x ED‹2 + ADAF2-16 x ED2-16 + ADAF›16 x ED›16 where ADAF‹2 = 10, ED‹2 = 2 yr, ADAF2-16 = 3, ED2-16 = 14 yr, ADAF›16 = 1, ED›16 = 14 yr.
Authority The provisions of this § 250.307 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 § 250.307 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 (382773) to (382780) and (383329) to (383331).
Cross References This section cited in 25 Pa. Code § 250.301 (relating to scope); 25 Pa. Code § 250.304 (relating to MSCs for groundwater); and 25 Pa. Code § 250.305 (relating to MSCs for soil).
No part of the information on this site may be reproduced for profit or sold for profit.
This material has been drawn directly from the official Pennsylvania Code full text database. Due to the limitations of HTML or differences in display capabilities of different browsers, this version may differ slightly from the official printed version.
