25 Pa. Code § 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:

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(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:

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(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:

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(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:

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(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:

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(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:

Term Residential Nonresidential (Onsite Worker)
Systemic1 Carcinogens2
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 Particulate4 Chemical-specific 1 × 1010 Chemical-specific 1 × 1010 Chemical-specific 1 × 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 Ã- 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 × 10-6
IURl TCE inhalation unit risk for both non-Hodgkin lymphoma and liver cancer (ug/m3)-1 3 × 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 - 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 - DF)-1, where ER = 8.25 - 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 - 250 days/yr.

6The Combined Age-Dependent Adjustment Factor and Exposure Duration (AED) is calculated using the equation AED = ADAF > 2 - ED > 2 + ADAF2-16 - ED2-16 + ADAF > 16 - 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):

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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 = CS[rho ]b 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
[thgr ] Total soil porosity, [thgr ] = [thgr ]a + [thgr ]m cm3/cm3 0.32(2)
[thgr ]a Air-filled soil porosity cm3/cm3 0.12(2)
[thgr ]m Moisture-filled soil porosity, [thgr ]m = w[rho ]b cm3/cm3 0.20(2)
w Moisture content for soil g water/g soil 0.11
[rho ]b Dry bulk density of soil, [rho ]b = (1-[thgr ]) [rho ] g/cm3 1.8(2)
(Footnotes on next page)
[rho ] 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:

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(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):

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

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(3) For vinyl chloride:

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(4) For trichloroethylene:

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(h) The default exposure assumptions used to calculate the inhalation numeric values for the inhalation of volatiles from groundwater are as follows:

Term Residential Nonresidential (Onsite Worker)
Systemic1 Carcinogens2
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 × 10-5 1 × 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 × 10-6
IURl TCE inhalation unit risk for both non-Hodgkin lymphoma and liver cancer (ug/m3)1 3 × 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.

4 The Combined Age-Dependent Adjustment Factor and Exposure Duration (AED) is calculated using the equation AED = ADAF > 2 - ED > 2 + ADAF2 16 - ED2 16 + ADAF > 16 - ED > 16 where ADAF > 2 = 10, ED > 2 = 2 yr, ADAF2 16 = 3, ED2 16 = 14 yr, ADAF > 16 = 1, ED > 16 = 14 yr.

Notes

25 Pa. Code § 250.307
The provisions of this § 250.307 amended January 7, 2011, effective 1/8/2011, 41 Pa.B. 230; corrected March 19, 2011, effective 3/5/2011, 41 Pa.B. 1458; corrected May 16, 2014, effective 3/5/2011, 44 Pa.B. 2975; amended August 26, 2016, effective 8/27/2016, 46 Pa.B. 5655; amended November 19, 2021, effective 11/20/2021, 51 Pa.B. 7173.

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).

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).

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