About this report

This Web page provides links to the final version of the five-volume report, Health & Environmental Assessment of the Use of Ethanol as a Fuel Oxygenate, an evaluation of the potential air, groundwater, and health impacts that may be associated with the use of ethanol as a fuel oxygenate in the state of California. This report has been prepared by the California Air Resources Board, the State Water Resources Control Board (SWRCB), and the California Environmental Protection Agency's Office of Environmental Health Hazard Assessment (CalEPA/OEHHA). The final version was published on December 30, 1999.

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Contents

• Volume I: Executive Summary

• Volume II: Background Information on the Use of Ethanol as a Fuel Oxygenate

• Volume III: Air Quality Impacts of the Use of Ethanol in California Reformulated Gasoline

• Volume IV: Potential Ground Water and Surface Water Impacts

• Volume V: Potential Health Risks of Ethanol in Gasoline

• Miscellaneous files

1.1 Scope of Report to the California Environmental Policy Council

1.2 Clean Air Act and the Use of Oxygenated Fuels

1.3 Requirement for a Multimedia Assessment of New Fuel Components

1.3.1 Regulatory and Legislative Requirements

1.3.2 Systems-Based Approach to Evaluating New Fuel Components

1.4 Use of Ethanol as a Transportation Fuel Oxygenate

1.5 Production of Ethanol

1.6 Chemical and Physical Properties of Ethanol in Gasoline

1.7 Increased Use of Alkylates as a Transportation Fuel Component

1.8 References

1. Introduction

1.1 Objectives

1.2 Scope

1.3 Study Approach

2. Review of Prior Studies

2.1 Atmospheric Chemistry of MTBE, Ethanol, and Alkylates

2.2 Recent Assessments of the Impact of Oxygenated Gasoline on the Environment

2.3 Ambient Air Quality Studies

3. Emission Issues

3.1 California Phase 3 Reformulated Gasoline Regulations

3.2 Fuel Additives

3.3 Emissions Associated with Transportation of Ethanol

3.4 Automotive Evaporative Emissions

3.5 Mileage Penalty for Gasolines With High Ethanol Content

4. Estimates of the Impact of MTBE-Free Gasolines on Future Emissions and Air Quality

4.1 Predicted Emissions for the South Coast Air Basin

4.2 Predicted Air Quality for the South Coast Air Basin

4.3 Air Quality Impacts for Other Areas of California

5. On-Going Efforts to Address Uncertainties

5.1 Emission Testing

5.2 Improvements in Photochemical Models

5.3 Ambient Air Quality Measurement Program

6. Refererences

Appendix A: Emissions [308-KB PDF]

Appendix B: Photochemical Modeling [518-KB PDF]

Appendix C: Baseline and Future Air Quality Concentrations [176-KB PDF]

Appendix D: Scientific Peer Review and Public Comments [186-KB PDF]

Attachment A1: Peer Review of Organic Gas Emission Profiles [1.26-MB PDF]

Attachment A2: Tables of Organic Gas Emission Profiles [120-KB PDF]

Attachment A3: Tables of Organic Gas Profiles from Emission Testing [158-KB PDF]

1. Potential Scenarios for Ethanol-Containing Gasoline Released into Surface and Subsurface Waters
[903-KB PDF | Read the abstract]

1.1 Introduction

1.2 Production

1.2.1 Trace Compounds Introduced during the Production of Fuel-Grade Ethanol

1.2.2 Additives

1.3 Distribution

1.3.1 Distribution of Bulk Fuel Ethanol

1.3.2 Blending of Ethanol with Gasoline

1.3.3 Transportation and Storage of Blended Gasohol

1.4 Use

1.4.1 Present Extent of Gasohol Use

1.4.2 Releases from Watercraft Exhaust Emissions into Surface Waters

1.4.3 Releases from Washout of Tailpipe Automotive Emissions and

1.5 Field Studies

1.5.1 Bulk Fuel Ethanol Releases with Fuel Hydrocarbons Absent

1.5.2 Bulk Fuel Ethanol Releases with Fuel Hydrocarbons Present

1.5.3 Releases of Gasohol from Tanker Truck

1.5.4 Gasohol Releases from Gas Station Underground Storage Tanks

1.5.5 Summary of Knowledge Gained from Field Studies

1.6 References

2. A Critical Review: The Effect of Ethanol in Gasoline on the Fate and Transport of BTEX in the Subsurface
[839-KB PDF | Read the abstract]

2.1 Overview of Processes Affecting Ethanol and Gasoline in the Subsurface

2.2 Subsurface Transport of Fuel Hydrocarbons in the Presence of Ethanol

2.2.1 Overall Phase Partitioning Behavior

2.2.2 Unsaturated Zone: Infiltration and Spreading at the Water Table

2.2.3 Gasoline-water Interface: Interphase Mass Transfer

2.2.4 Transport with the Aqueous Phase

2.2.5 Special Considerations

2.2.6 Examples of Modeling Efforts

2.3 Acknowledgements

2.4 References

3. The Effect of Ethanol on BTEX Biodegradation and Natural Attenuation
[323-KB PDF | Read the abstract]

3.1. Introduction and Objectives

3.1.1 Problem Statement

3.1.2 General Scope and Purpose of this Literature Review

3.2 Requirements for Biodegradation of Organic Pollutants

3.2.1 Occurrence of Microorganisms with Potential to Degrade the Target Compounds

3.2.2 Bioavailability of Target Pollutants

3.2.3 Induction of Appropriate Degradative Enzymes

3.2.4 Environmental Conditions Conducive to Microbiological Growth

3.3 Biodegradation of Ethanol

3.3.1 Ethanol Degradation Pathways

3.3.2 Summary of Metabolic Intermediates of Importance in Ethanol Degradation

3.3.3 Aerobic and Anaerobic Biodegradation Kinetics

3.4 Potential Effects of Ethanol on BTEX Biodegradation

3.4.1 Direct (Intracellular) Effects

3.4.2 Indirect (Environmental) Effects

3.5 References

4. Screening Model Evaluation of the Effects of Ethanol on Benzene Plume Lengths
[258-KB PDF | Read the abstract]

4.1 Introduction

4.2 Methodology

4.2.1 Overview

4.2.2 Model Construction

4.3 Results and Discussion

4.3.1 Uncorrelated Biotransformation Rates

4.3.2 Correlated Biotransformation Rates

4.4 References

5. Potential Impact of Ethanol-Containing Gasoline on Surface Water Resources
[194K PDF | Read the abstract]

5.1 Introduction

5.2 Background

5.3 Washout of Ethanol and MTBE from the Atmosphere

5.4 Releases to Rivers and Streams

5.4.1 Volatilization and Biodegradation of Ethanol in Rivers and Streams

5.4.2 Accidental Releases of Ethanol to Rivers and Streams

5.5 Releases to Reservoirs and Lakes

5.5.1 Background: Watercraft Releases of Fuel Compounds

5.5.2 Water Quality Impacts of MTBE and Ethanol Due to Recreational Boating

5.6 Summary

5.7 References

6. Environmental Transport and Fate of Fuel Hydrocarbon Alkylates
[129K PDF | Read the abstract]

6.1 Introduction

6.2 Background

6.3 Production of Alkylates

6.4 Chemical Composition and Properties of Alkylates

6.5 Environmental Behavior and Fate of Alkylates

6.5.1 Air

6.5.2 Water

6.5.3 Soil and Groundwater

6.5.4 Biodegradation

6.6 Summary

6.7 Reference

7. Evaluation of Analytical Methods for the Detection of Ethanol in Surface and Ground Waters
[129K PDF | Read the abstract]

7.1 Analytical Requirements

7.1.1 Routine Detection of Trace Amounts of Ethanol in Environmental Waters

7.1.2 Regulatory Requirements Versus Detection Limits for Fate and Transport Studies

7.2 Evaluation of Current Analytical Methods for Ethanol Detection

7.2.1 Ethanol Analysis Methods Used by Food and Biomedical Industries

7.2.2 Ethanol Analysis Methods Used by the Environmental Community

7.3 Handling and Preservation of Ethanol Samples

7.4 Recommendations to Improve Sampling and Analysis of Ethanol in Ground and Surface Water

7.4.1 Rigorous Study of Sample Preservation

7.4.2 Improved Extraction of Ethanol from Aqueous Samples

7.4.3 Improved Strategies for Ethanol Detection

7.4.4 Minor Modifications to Improve Existing Methods

7.5 Summary

7.6 References

8. Comparison of Groundwater Resource Impacts from Gasoline Containing Ethanol or MTBE
[1.5-MB PDF | Read the abstract]

8.1 Introduction

8.1.1 Methodology

8.2 Forecasting Benzene (Degrading) and MTBE (Nondegrading) Fuel Hydrocarbon Plume Behavior

8.2.1 Introduction

8.2.2 Conceptual Model of a Plume

8.2.3 Monte Carlo Analysis

8.2.4 Results of Plume Length Forecasts

8.3 Comparison of Potential Future Impacts Associated with Benzene Either in the Presence of Ethanol or the Presence of MTBE

8.3.1 Location Relationship between LUFT Sites and Public Drinking Water Wells

8.3.2 Screening Model Estimate of the Probability of Future Impacts to Public Drinking Water Wells from LUFT Sites

8.4 Important Uncertainty Considerations

8.4.1 Location Accuracy of Drinking Water Wells and LUFT Sites

8.4.2 Sampling Frequency and Impact Rates of Public Drinking Water Wells and LUFT Sites

8.4.3 Comparisons of Well BTEX/MTBE Detection Levels, Well Construction, Well Yield, and Groundwater Levels

8.4.4 Vulnerability of Private Drinking Water Wells

8.5 Conclusions

8.6 Acknowledgements

8.7 References

9. Knowledge Gaps Regarding the Surface Water and Groundwater Impacts of Ethanol-containing Gasoline and Recommendations for Future Research
[129-KB PDF | Read the abstract]

9.1 Introduction

9.2 Knowledge Gaps in the Life-cycle Analysis of Ethanol and Nonoxygenated Fuel Compounds

9.3 Knowledge Gaps in Fate-and-transport Processes Associated with the Use of Ethanol as a Fuel Oxygenate

9.3.1 Subsurface Abiotic Processes

9.3.2 Subsurface Biodegradation Processes

9.3.3 Historical-case Studies

9.3.4 Modeling Uncertainties

9.3.5 Extracting Ethanol from Aqueous Samples

9.4 Recommendations to Address Knowledge Gaps

9.4.1 Expanded Life-cycle Analysis of the Use of Ethanol and Nonoxygenated Fuel Compounds

9.4.2 Additional Field and Laboratory Research

9.5 References

10. Response to Comments
[129-KB PDF | Read the abstract]

10.1 Peer Review Comments

10.1.1 Peer Review Comments from Dr. Patricia Holden, Donald Bren School of Environmental Science and Management, University of California, Santa Barbara

10.1.2 Dr. Michael K. Stenstrom, Civil and Environmental Engineering Department, University of California, Los Angeles

10.1.3 Dr. Michael R. Hoffman, Executive Officer of Environmental Engineering Science, James Irvine Professor of Environmental Science, California Institute of Technology

10.2 Public Review Comments

10.2.1 Michael C. Kavanaugh, Ph.D., P.E., and Andrew Stocking, P.E., Malcolm Pirnie, Inc.: Comments and LLNL Responses

10.2.2 Western States Petroleum Association (WSPA): Comments and LLNL Responses

1. Introduction

1.1 Objective

2. Hazard Identification: Chemicals of Concern

3. Dose-Response Assessment

3.1 Values for Assessing Potential Health Impacts from Inhalation Exposures

3.1.1 Carcinogenic Endpoints

3.1.2 Noncancer Endpoints

3.1.2.1 Acute, One-Hour Inhalation Exposures

3.1.2.2 Annual Average Inhalation Exposure Concentrations

3.2 Values for Assessing Potential Health Impacts from Exposure via Drinking Water

3.2.1 Public Health Goals (PHGs)

4. Exposure Assessment: Sources of Exposure Data

5. Methodology Used for Quantifying Cancer and Noncancer Risks

5.1 Estimating Cancer Risk

5.2 Estimating Noncancer Risk

6. Risk Characterization

6.1 Inhalation--Cancer and Noncancer Effects

6.1.1 Acetaldehyde

6.1.2 Benzene

6.1.3 Butadiene

6.1.4 Ethanol

6.1.5 Formaldehyde

6.1.6 Methyl t-Butyl Ether (MTBE)

6.1.7 Peroxyacetyl Nitrate (PAN)

6.2 Risk Characterization for Other Compounds of Concern: Toluene, Xylenes, Isobutene, n-Hexane

6.3 Cumulative Cancer Impact of Multiple Chemical Exposures

6.4 Cumulative Noncancer Impact of Multiple Chemical Exposures

6.5 Health Impacts of Drinking Water Contamination by Gasoline Components

Appendix A: Toxicity Summaries [152-KB PDF]

Appendix B: Response to Comments [154-KB PDF]

Addendum [37-KB PDF]

Miscellaneous files

Cover [305-KB PDF]

Contents [310-KB PDF]

Volume 1 Cover [318-KB PDF]

Volume 2 Cover [318-KB PDF]

Volume 3 Cover [267-KB PDF]

Volume 4 Cover [311-KB PDF]

Volume 5 Cover [270-KB PDF]