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COMMONWEALTH OF PENNSYLVANIA

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The Pennsylvania Code website reflects the Pennsylvania Code changes effective through 53 Pa.B. 8238 (December 30, 2023).

25 Pa. Code § 250.307. Inhalation numeric values.

§ 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:

 

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:

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ParameterDefinition
UnitRecommended Value(1)
ERChemical vapor emission rate from surface soil or subsurface soilmg/m2-sec per mg/kgChemical-specific
CoChemical concentration in soil, Co = CSρbg/m31.8
CSChemical concentration in soilmg/kg (ppm)1
DEEffective diffusion coefficientm2/secChemical-specific
DaiAir diffusivity for chemical im2/secChemical-specific
DLiWater diffusivity for chemical im2/secChemical-specific
tTimesecN/A
TEmission averaging timesecEqual to exposure duration
θTotal soil porosity, θ = θa + θmcm3/cm30.32(2)
θaAir-filled soil porositycm3/cm30.12(2)
θmMoisture-filled soil porosity, θm = wρbcm3/cm30.20(2)
wMoisture content for soilg water/g soil0.11
ρbDry bulk density of soil, ρb = (1-θ) ρg/cm31.8(2)
(Footnotes on next page)
ρSoil particle densityg/cm32.65
KdPartition coefficient, Kd = Kocfoccm3/gChemical-specific
HHenry’s Law constant dimensionlessChemical-specific
DGEffective gas-phase diffusion coefficientm2/secChemical-specific
DLeffective liquid-phase diffusion coefficientm2/secChemical-specific
LDepth of the contaminated surface soilm0.6(3)
lDepth of the clean soil coverm0.6(3)
WThickness of the contaminated subsurface soilm4.0(3)
KOCOrganic carbon partition coefficient for chemical icm3/gChemical-specific
fOCFraction of organic carbon in soildimensionless0.005(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:

 

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).



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