EPA Regional Screening Level Calculator Updated to Incorporate New IRIS Toxicity values for Benzo(a)pyrene and the Trimethylbenzene isomers
The need to find a balance between risk and cost when remediating contaminated land has led to more research about appropriate levels of specific chemicals.
On January 19, 2017 the United States Environmental Protection Agency (EPA) Integrated Risk Information System (IRIS) program released its final assessment of benzo(a)pyrene (BaP). The final toxicity values from EPA's IRIS have the potential to reduce the need for remediation of BaP and other carcinogenic polycyclic aromatic hydrocarbons (PAHs).
EPA's IRIS program identifies and characterizes the health hazards of chemicals found in the environment. Each IRIS assessment can cover a chemical, a group of related chemicals, or a complex mixture. BaP is released into the atmosphere as a component of smoke from forest fires, industrial processes, vehicle exhaust, cigarettes, and through the burning of fuel (such as wood, coal, and petroleum products).
The EPA has not updated its Regional Screening Levels (RSLs) tables since May 2016, which has effectively delayed the implementation of these toxicity values in site assessments and remediation. However, EPA has updated its RSL calculator, which is used to generate the RSL tables, to incorporate these final toxicity values. The updated BaP RSLs for EPA's default exposure media and scenarios are as follows:
| Benzo(a)pyrene RSLs | ||||
|
Exposure Media and Scenario |
Previous RSLs |
Updated RSLs
|
||
| Cancer (TCR = 1E-6) |
Noncancer (THQ = 1) |
Cancer (TCR = 1E-6) |
Noncancer (THQ = 1) |
|
| Resident Soil | 0.016 mg/kg | NA | 0.115 mg/kg | 17.8 mg/kg |
| Industrial Soil | 0.29 mg/kg | NA | 2.11 mg/kg | 222 mg/kg |
| Resident Air | 0.00092 ug/m3 | NA | 0.00169 ug/m3 | 0.00209 ug/m3 |
| Industrial Air | 0.011 ug/m3 | NA | 0.0204 ug/m3 | 0.00876 ug/m3 |
| Tapwater | 0.0034 ug/L | NA | 0.0251 ug/L | 6.02 ug/L |
EPA's RSL calculator also includes the final IRIS assessment for Trimethylbenzenes (TMB) from September 9, 2016. EPA's final assessment evaluated the toxicity for the 1,2,3-TMB, 1,2,4-TMB, and 1,3,5-TMB isomers and concluded that all three isomers should use the same toxicity values. The updated TMB RSLs for EPA's default exposure media and scenarios are as follows:
| Chemical | Exposure Media and Scenario |
Previous RSLs Noncancer |
Updated RSLs Noncancer |
| 1,2,3-TMB | Resident Soil | 49 mg/kg | 336 mg/kg |
| Industrial Soil | 210 mg/kg | 2,050 mg/kg | |
| Resident Air | 5.2 ug/m3 | 62.6 ug/m3 | |
| Industrial Air | 22 ug/m3 | 263 ug/m3 | |
| Tapwater | 10 ug/L | 55 ug/L | |
| 1,2,4-TMB | Resident Soil | 58 mg/kg | 303 mg/kg |
| Industrial Soil | 240 mg/kg | 1,770 mg/kg | |
| Resident Air | 7.3 ug/m3 | 62.6 ug/m3 | |
| Industrial Air | 31 ug/m3 | 263 ug/m3 | |
| Tapwater | 15 ug/L | 55.7 ug/L | |
| 1,3,5-TMB | Resident Soil | 780 mg/kg | 271 mg/kg |
| Industrial Soil | 12,000 mg/kg | 1,510 mg/kg | |
| Resident Air | NA | 62.6 ug/m3 | |
| Industrial Air | NA | 263 ug/m3 | |
| Tapwater | 120 ug/L | 60.3 ug/L |
The RSLs for BaP and the TMBs that use EPA's default exposure factors and updated IRIS toxicity values can be found here.
How can GHD help?
Contact a GHD Risk Assessor for more information. We can help determine the most appropriate path to optimize environmental investigation or cleanup at your site.
Francis C. Ramacciotti | Associate, Risk Assessment Services
1140 Welsh Road, Suite 120, North Wales, PA 19454
E: francis.ramacciotti@ghd.com | T: +1 215 853 3281
Steven Harris | Principal, Risk Assessment Services
651 Colby Drive, Waterloo, ON N2V 1C2
E: steve.harris@ghd.com | T: +1 519 884 0510 ext 3513