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Development of updated RfD and RfC values for medium carbon range aromatic and aliphatic total petroleum hydrocarbon
Chad M Thompson1, Virunya S Bhat2, Gregory P Brorby3
1ToxStrategies, Inc, Katy, Texas, USA.
Journal of the Air & Waste Management Association (1995)
|September 1, 2021
Summary
Updated toxicity criteria for petroleum hydrocarbon fractions suggest current health risk assessments are overly conservative. Reevaluating these criteria can ensure adequate protection while potentially revising cleanup levels for environmental contaminants.
Area of Science:
- Environmental Science and Health Risk Assessment
- Toxicology and Ecotoxicology
- Petroleum Chemistry and Environmental Remediation
Background:
- Total petroleum hydrocarbon (TPH) measurements are challenging for human health risk assessment due to the complex mixtures of chemicals in petroleum products.
- Current risk assessment practices rely on U.S. Environmental Protection Agency (USEPA) provisional toxicity criteria for TPH fractions, established over a decade ago.
- These criteria inform risk-based cleanup levels for soil and groundwater contaminated with petroleum hydrocarbons.
Purpose of the Study:
- To evaluate and update oral and inhalation toxicity criteria for medium-carbon-range aromatic and aliphatic hydrocarbon fractions.
- To incorporate newer data, advanced modeling techniques, and alternative analyses to refine toxicity assessments.
- To provide updated criteria for regulatory agencies and risk managers involved in environmental cleanup.
Main Methods:
- Re-analysis of existing toxicity data for medium-carbon-range aromatics and aliphatics.
- Application of updated modeling techniques and consideration of human relevance and uncertainty factors.
- Inclusion of new study data where applicable for both oral and inhalation endpoints.
Main Results:
- Inhalation reference concentrations (p-RfC) for both fractions could be increased approximately 10-fold (from 0.1 to 1 mg/m³).
- Oral reference doses (p-RfD) for medium-carbon-range aromatics suggest an increase of over 6.6-fold (from 0.03 to 0.2 mg/kg-day).
- Oral reference doses (p-RfD) for medium-carbon-range aliphatics suggest an approximate 20-fold increase (from 0.01 to 0.2 mg/kg-day).
Conclusions:
- The current provisional toxicity criteria for medium-carbon-range aromatic and aliphatic hydrocarbon fractions are likely overly conservative.
- Updated toxicity criteria support a significant increase in acceptable exposure levels for these TPH fractions.
- Revised criteria can inform more accurate risk-based screening and cleanup levels, ensuring continued health protection.
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