OEHHA REPORT ON ETHANOL IN GASOLINE - 02/15/00

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## ADDENDUM

Estimating atmospheric concentrations and the resulting risks posed by the chemicals of concern for the South Coast Air Basin is a very complex and dynamic process. As more information is obtained on atmospheric chemistry fate and health effects of these chemicals, there is the expectation that the modeled atmospheric concentrations and health risk values will change. Ultimately, the goal is to provide a more accurate analysis and lower the uncertainty involved in the process. Thus, CARB performed a supplementary “upper-bound model” simulation on the five fuel scenarios that formed the original basis of the health impacts assessment. The additional model inputs included the effects of emission uncertainty and chlorine chemistry, uses updated MTBE and ethanol rate constants, and corrects boundary conditions for several substances. The resulting atmospheric concentration estimates are shown in Table A-1, and our conclusions are as follows:

• The “upper-bound model atmospheric concentrations” presented here are generally lower than the original atmospheric concentrations presented in Table 4. Thus, the cumulative hazard indices and cumulative cancer risks are predicted to be lower under this modified model simulation.

• The only increased atmospheric levels under the modified model simulation were for ethanol. In some cases these were nearly double the original predicted atmospheric concentrations. However, the increased ethanol concentrations are expected to haveno impact on health due to ethanol’s low anticipated health risk relative to other fuelrelated chemicals.

• Comparing the atmospheric concentrations among the year 2003 fuel scenarios under the modified model, there are higher concentrations of acetaldehyde in the scenario with ethanol (3.5% oxygen) fuel. This difference was less marked in the predictions of the previous version of the model. However, the health impact of the higher acetaldehyde concentrations is negligible due to its relatively low health risk compared to other chemicals of concern.

• Under the modified model, the upper range estimates of PAN concentrations are higher in the scenario with ethanol (3.5% oxygen) fuel. This difference also was less marked with the previous version of the model. If the atmospheric concentrations of PAN were in fact to be substantially increased, this would be of concern since PAN has a relatively high health impact for acute eye irritation. However, given the total range of the predicted PAN concentrations and the uncertainty in the model prediction, it is unclear whether PAN results in a greater health risk under the ethanol (3.5% oxygen) fuel scenario.

• It appears that the modified model simulations are more sensitive to fuel composition in the predictions of ethanol, acetaldehyde, and PAN concentrations (and therefore of the associated health impacts) compared to the other chemicals of concern.OEHHA REPORT ON ETHANOL IN GASOLINE - 02/15/00

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### • There are no indications of substantial differences between the 2003 fuel types in cancer or noncancer health impacts of airborne exposures, whether the original or modified model is used. Therefore, there are no grounds to recommend one fuel over another based on health impacts of air pollution. Similarly, there is no indication that any of those fuel choices would result in worse health impacts than the current situation. In addition to predicted values for PM10

### , CARB also included in their latest report predicted values for PM2.5

### . As with PM10

### , CARB states that they expect no difference among 2003 scenarios, and therefore only provided a maximum daily average (81 μg/m3

### ) and a maximum annual average (25.9 μg/m3

### ) for the 1997 MTBE fuel scenario for PM2.5

### . Currently, although U. S. EPA has proposed standards for PM2.5

### ,there are no state or federal standards in place for this material. However, it is commonly assumed that the ratio of PM2.5

### /PM10

### is 0.5. Use of the California PM10

### standards (30 μg/m3

### for the annual average; 50 μg/m3

### for the 24-hr average standard) results in values of 15 and 25 μg/m3



### , respectively, as guidance for interpreting the significance of the predicted PM2.5 

### concentrations. While it is known that these guidance values for particulates are frequently exceeded in California, according to CARB's report, there is no difference expected among the 2003 scenarios. Further discussion and analysis of the atmospheric concentration estimates based on the modified model simulations can be found in section 4.2.2 of CARB’s “Air Quality Impacts of the Use of Ethanol in California Reformulated Gasoline. Final Report to the California Environmental Policy Council. December, 1999”.OEHHA REPORT ON ETHANOL IN GASOLINE - 02/15/00

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### Table A-1. Atmospheric Concentration Estimates: Range of Predicted 1997 and 2003 Air Quality for the South Coast Air Basin Using “Upper-Bound Model Simulations” a

1997 MTBE 2003

MTBE 2003

Et2% 2003

Et3.5% 2003

Non-Oxy Acetaldehyde (ppb) Population-Weighted Annual Exposure Upper 1.8 1.5 1.5 1.8 1.5 Lower 1.8 1.4 1.5 1.7 1.4 Maximum Daily Average Upper 11.0 7.9 8.1 8.5 8.0 Lower 5.1 3.7 3.8 4.0 3.7 Maximum 1 Hour AverageUpper 17.7 12.4 12.7 13.6 12.3 Lower 13.8 9.7 9.9 10.6 9.6 Benzene (ppb) Population-Weighted Annual Average Upper 1.19 0.68 0.67 0.69 0.63 Lower 1.07 0.61 0.60 0.62 0.57 Maximum Daily Average Upper 9.5 5.6 5.6 5.7 5.2 Lower 7.4 4.4 4.3 4.4 4.1 Maximum 1 Hour AverageUpper 22.4 13.1 13.1 13.1 12.1 Lower 11.6 6.8 6.8 6.8 6.3 Butadiene (ppb) Population-Weighted Annual Average Upper 0.36 0.20 0.19 0.20 0.20 Lower 0.34 0.19 0.18 0.19 0.18 Maximum Daily Average Upper 2.9 1.5 1.5 1.5 1.5 Lower 2.0 1.1 1.1 1.1 1.1 Maximum 1 Hour AverageUpper 6.7 4.0 4.0 4.0 4.0 Lower 3.1 1.9 1.9 1.9 1.9 Ethanol (ppb) Population-Weighted Annual Average Upper 5.4 5.1 10.9 14.2 5.1

Maximum Daily Average Upper 51 48 98 125 48 Lower 47 45 93 121 44 Maximum 1 Hour AverageUpper 108 101 213 268 101 Lower 78 74 191 267 74OEHHA REPORT ON ETHANOL IN GASOLINE - 02/15/00

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### Table A-1 (continued). Atmospheric Concentration Estimates: Range of Predicted 1997 and 2003 Air Quality for the South Coast Air Basin Using “Upper-Bound Model Simulations”a

1997 MTBE 2003

MTBE 2003

Et2% 2003

Et3.5% 2003

Non-Oxy Formaldehyde (ppb) Population-Weighted Annual Average Upper 4.7 3.7 3.4 3.5 3.4 Lower 4.7 3.6 3.4 3.5 3.4 Maximum Daily Average Best 14.0 9.8 9.2 9.6 9.1

Maximum 1 Hour AverageUpper 37.8 26.5 25.1 25.9 24.9 Lower 20.3 14.2 13.5 13.9 13.4 MTBE (ppb) Population-Weighted Annual Average Upper 3.9 2.4 0 0 0 Lower 3.6 2.2 0 0 0 Maximum Daily Average Upper 29 18 0 0 0 Lower 13 8 0 0 0 Maximum 1 Hour AverageUpper 67 41 0 0 0 Lower 19 12 0 0 0 PAN (ppb)b Maximum Daily Average Upper Lower 5.0

2.5 3.3

1.7 3.2

1.6 3.4

1.7 3.1

1.6 Maximum 1 Hour AverageUpper Lower 10.0

5.0 6.3

3.1 6.0

3.0 6.5

3.2 5.7

2.9OEHHA REPORT ON ETHANOL IN GASOLINE - 02/15/00

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### Table A-1 (continued). Atmospheric Concentration Estimates: Range of Predicted 1997 and 2003 Air Quality for the South Coast Air Basin Using “Upper-Bound Model Simulations”a

1997 MTBE 2003

MTBE 2003

Et2% 2003

Et3.5% 2003

Non-Oxy Carbon Monoxide (ppm) Maximum 8 Hour AverageBest 17.5 12.7 12.7 12.1 13.1c Maximum 1 Hour AverageBest 22.5 16.1 16.1 15.3 16.6 c Nitrogen Dioxide (ppm) Maximum Annual Average Best 0.043 CARB reported, “No difference expected among 2003 scenarios” d Maximum Daily Average Best 0.117 0.095 0.095 0.095 0.095 Maximum 1 Hour AverageBest 0.255 0.207 0.207 0.207 0.207 Ozone (ppm) Maximum 8 Hour AverageBest 0.206 0.165 0.159 0.162 0.159 Maximum 1 Hour AverageBest 0.244 0.190 0.182 0.186 0.182 Particulate Matter (10 microns or less) ( m g/m 3 )
Maximum Annual Geometric Mean Best 56 CARB reported, “No difference expected among 2003 scenarios” d Maximum Daily Average Best 227 CARB reported, “No difference expected among 2003 scenarios” d

a Source: Table 4.9 of “Air Quality Impacts of the Use of Ethanol in California Reformulated Gasoline. Final Report to the California Environmental Policy Council. December, 1999. California Air Resources Board, Cal/EPA”

b A population-weighted annual average for PAN was not determined because consistent long-term measurements of atmospheric PAN have not been performed. See CARB report for details.

cThis apparent increase is a function of the emission assumptions. Due to the wintertime oxygenate requirement for the SoCAB, CO concentrations within the nonattainment area of Los Angeles County will not differ from the 2003 MTBE baseline.

d No significant change compared to 1997 MTBE-fuel scenario. See CARB report for details.OEHHA REPORT ON ETHANOL IN GASOLINE - 02/15/00

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### Tables A-2 and A-3 display the non-cancer Hazard Quotients (HQs) generated from the modeled atmospheric concentrations in Table A-1. The relatively marginal increase in the acute atmospheric acetaldehyde concentrations under the 3.5% ethanol fuel scenario relative to the other fuel scenarios did not translate into a proportionally higher HQ. This was primarily due to acetaldehyde’s relatively low HQ. In contrast, the upper range atmospheric PAN concentrations under the 3.5% fuel scenario exhibited a proportionally increased HQ compared to the other fuel scenarios. Although the proportional increases in upper range PAN and acetaldehyde concentrations were similar under this fuel scenario, there is likely greater concern for PAN’s acute effects because of its relatively high HQ. However, it is not clear how real this difference is because the lower range PAN HQ is proportionally similar to the lower range PAN HQs in the other fuel scenarios. Given the total range of the PAN HQs and the uncertainty in the model prediction, it is unclear whether PAN results in a greater health risk under the 3.5% ethanol fuel scenario.OEHHA REPORT ON ETHANOL IN GASOLINE - 02/15/00

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### Table A-2. Range of Estimated Maximum Noncancer Hazard Quotients (HQ) for Various Scenarios in the South Coast Air Basin Based onARB’s “Upper-Bound Model Simulations”

1997 MTBE 2003

MTBE 2003

Et2% 2003

Et3.5% 2003

NonOxy Acetaldehyde Upper 0.4 0.3 0.3 0.4 0.3 Chronic HQ Lower 0.4 0.3 0.3 0.3 0.3

Upper 0.3 0.2 0.2 0.2 0.2 Acute HQ Lower 0.2 0.1 0.2 0.2 0.1

Benzene Upper 0.06 0.03 0.03 0.03 0.03 Chronic HQ Lower 0.05 0.03 0.03 0.03 0.03

Upper 0.06 0.03 0.03 0.03 0.03 Acute HQ Lower 0.03 0.02 0.02 0.02 0.02
Butadiene Upper 0.09 0.05 0.05 0.05 0.05 Chronic HQ Lower 0.09 0.05 0.05 0.05 0.05

Upper 0.05 0.03 0.03 0.03 0.03 Acute HQ Lower 0.02 0.01 0.01 0.01 0.01

Ethanol
Best 0.0001 0.0001 0.0002 0.0003 0.0001 Chronic HQ Upper 0.002 0.002 0.004 0.005 0.002 Acute HQ Lower 0.001 0.001 0.004 0.005 0.001 Formaldehyde Upper 2.4 1.9 1.7 1.8 1.7 Chronic HQ Lower 2.4 1.8 1.7 1.8 1.7

Upper 0.5 0.3 0.3 0.3 0.3 Acute HQ Lower 0.3 0.2 0.2 0.2 0.2

MTBE Upper 0.005 0.003 0.0 0.0 0.0 Chronic HQ Lower 0.005 0.003 0.0 0.0 0.0

Upper 0.01 0.006 0.0 0.0 0.0 Acute HQ Lower 0.003 0.002 0.0 0.0 0.0

PAN* Upper 5.5 3.5 3.3 3.6 3.2 Acute HQ Lower 2.7 1.7 1.7 1.8 1.6 * A population-weighted annual average for PAN was not determined because consistent long-term measurements of atmospheric PAN have not been performed. See CARB report for details.OEHHA REPORT ON ETHANOL IN GASOLINE - 02/15/00

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### Table A-3. Range of Estimated Maximum Noncancer Hazard Quotients (HQ) for Various Scenarios in the South Coast Air Basin Based onARB’s “Upper-Bound Model Simulations” – Criteria Air Pollutants

1997 MTBE 2003

MTBE 2003

Et2% 2003

Et3.5% 2003

NonOxy

Carbon Monoxide
Acute 8 hour HQ 1.9 1.4 1.4 1.3 1.5 Acute 1 hour HQ 1.1 0.8 0.8 0.8 0.8

Nitrogen Dioxide
Chronic HQ 0.8 concentrations not estimated by CARB since no significant change in Maximum 1-Hour* Acute 1 hour HQ 1.0 0.8 0.8 0.8 0.8

Ozone
Acute 8 hour HQ 2.6 2.1 2.0 2.0 2.0 Acute 1 hour HQ 2.7 2.1 2.0 2.1 2.0 Particulate Matter (PM10)
Chronic HQ 1.9 Acute 24 hour HQ 4.5 CARB reported, “No significant change expected among 2003 scenarios” for both annual and daily concentrations*

*compared to exposure estimates for the 1997 MTBE-fuel scenario (see CARB report for details)



### With regard to the chemicals that are predicted to pose a cancer risk (Table A-4), the modified model simulation does not change the existing conclusions that, (1) we have more confidence in the relative risks estimates than the absolute values of concentrations and risk, and (2) there are no substantial differences between the 2003 fuel types with regard to the cumulative lifetime cancer risk estimates. As expected, the marginal increase in atmospheric acetaldehyde concentrations under the 3.5% ethanol fuel scenario relative to the other fuel scenarios did not result in a significant increase in cumulative cancer risk. This is primarily due to acetaldehyde’s considerably lower cancer risk relative to other carcinogens such as benzene.OEHHA REPORT ON ETHANOL IN GASOLINE - 02/15/00

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### Table A-4. Lifetime Cancer Risk from Individual Chemicals and Cumulative Lifetime Cancer Risk for Each of the Five Fuel Scenarios Based on ARB’s “Upper-Bound Model Simulations”

Chemical 1997 MTBE 2003

MTBE 2003

Et2% 2003

Et3.5% 2003

NonOxy Upper 8.6 E-6 7.2 E-6 7.2 E-6 8.6 E-6 7.2 E-6 Acetaldehyde Lower 8.6 E-6 6.7 E-6 7.2 E-6 8.1 E-6 6.7 E-6 Upper 1.1 E-4 6.3 E-5 6.2 E-5 6.4 E-5 5.9 E-5 Benzene Lower 1.0 E-4 5.7 E-5 5.6 E-5 5.8 E-5 5.3 E-5 Upper 1.3 E-4 7.4 E-5 7.0 E-5 7.4 E-5 7.4 E-5 Butadiene Lower 1.3 E-4 7.0 E-5 6.7 E-5 7.0 E-5 6.7 E-5 Upper 3.3 E-5 2.6 E-5 2.4 E-5 2.5 E-5 2.4 E-5 Formaldehyde Lower 3.3 E-5 2.5 E-5 2.4 E-5 2.5 E-5 2.4 E-5 Upper 3.6 E-6 2.2 E-6 0 0 0 MTBE Lower 3.3 E-6 2.0 E-6 0 0 0 Upper 2.9 E-4 1.7 E-4 1.6 E-4 1.7 E-4 1.6 E-4 Cumulative Lifetime Risk Lower 2.7 E-4 1.6 E-4 1.5 E-4 1.6 E-4 1.5 E-4

Upper 290 170 160 170 160 Excess Cancer Cases Per Million Individuals Lower 270 160 150 160 150



### For non-cancer cumulative impacts, the toxicological endpoints of concern, acute eye irritation (Table A-5), acute respiratory irritation (Table A-6), and chronic respiratory irritation (Table A-7), remained the same under the modified model simulations. The only noticeable difference among the fuel scenarios was that for acute eye irritation, the 2003 MTBE and 3.5% ethanol fuels had slightly higher upper range acute HIs relative to the other year 2003 fuels. The secondary pollutant PAN was primarily responsible for the increased disparity, due to the higher upper range estimate of its HQ under these two fuel scenarios. However, the lower range of the cumulative HIs does not show as great a disparity among the fuel scenarios. There is considerable uncertainty involved in the model predictions, including both the range of estimates with this “upper bound model” and the differences between this model and the earlier one. It cannot therefore be definitely concluded that the 3.5% ethanol fuel will result in greater eye irritation relative to the other fuels. Improvement in atmospheric modeling and measurement may eventually resolve this uncertainty.OEHHA REPORT ON ETHANOL IN GASOLINE - 02/15/00

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### Table A-5. Maximum Acute Hazard Quotients (HQ) and Cumulative Acute Hazard Indices (HI) for Eye Irritation for Each of the Five Fuel Scenarios Based onARB’s “Upper-Bound Model Simulations”

Chemical 1997 MTBE 2003

MTBE 2003

Et2% 2003

Et3.5% 2003

NonOxy Upper 0.3 0.2 0.2 0.2 0.2 Acetaldehyde Lower 0.2 0.1 0.2 0.2 0.1 Upper 0.002 0.002 0.004 0.005 0.002 Ethanol Lower 0.001 0.001 0.004 0.005 0.001 Upper 0.5 0.3 0.3 0.3 0.3 Formaldehyde Lower 0.3 0.2 0.2 0.2 0.2 Upper 0.01 0.006 0 0 0 MTBE Lower 0.003 0.002 0 0 0 Upper 5.5 3.5 3.3 3.6 3.2 PAN Lower 2.7 1.7 1.7 1.8 1.6 Nitrogen dioxide Best 1.0 0.8 0.8 0.8 0.8 Ozone Best 2.7 2.1 2.0 2.1 2.0 Upper 10.0 6.9 6.6 7.0 6.5 Cumulative HI Lower 6.9 4.9 4.9 5.1 4.7



### Table A-6. Maximum Acute Hazard Quotients (HQ) and Cumulative Acute Hazard Indices (HI) for Respiratory Irritation For Each of the Five Fuel Scenarios Based on ARB’s “Upper-Bound Model Simulations”

Chemical 1997 MTBE 2003

MTBE 2003

Et2% 2003

Et3.5% 2003

NonOxy Upper 0.3 0.2 0.2 0.2 0.2 Acetaldehyde Lower 0.2 0.1 0.2 0.2 0.1 Upper 0.002 0.002 0.004 0.005 0.002 Ethanol Lower 0.001 0.001 0.004 0.005 0.001 Upper 0.01 0.006 0 0 0 MTBE Lower 0.003 0.002 0 0 0 Nitrogen dioxide Best 1.0 0.8 0.8 0.8 0.8 Ozone Best 2.7 2.1 2.0 2.1 2.0 Upper 4.0 3.1 3.0 3.1 3.0 Cumulative HI Lower 3.9 3.0 3.0 3.1 2.9OEHHA REPORT ON ETHANOL IN GASOLINE - 02/15/00

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### Table A-7. Maximum Chronic Hazard Quotients (HQ) and Cumulative Chronic Hazard Indices (HI) for Respiratory Irritation for Each of the Five Fuel Scenarios Based on ARB’s “Upper-Bound Model Simulations”

Chemical 1997 MTBE 2003

MTBE 2003

Et2% 2003

Et3.5% 2003

NonOxy Upper 0.4 0.3 0.3 0.4 0.3 Acetaldehyde Lower 0.4 0.3 0.3 0.3 0.3
Best 0.0001 0.0001 0.0002 0.0003 0.0001 Ethanol

Upper 2.4 1.9 1.7 1.8 1.7 Formaldehyde Lower 2.4 1.8 1.7 1.8 1.7 Nitrogen dioxide Best 0.8 0.8 0.8 0.8 0.8 PM 10 Best 1.9 1.9 1.9 1.9 1.9

Upper 5.5 4.9 4.7 4.9 4.7 Cumulative HI Lower 5.5 4.8 4.7 4.8 4.7



### In conclusion, the modified model simulation did not change the original finding that the different fuel types are substantially the same with regard to airborne cancer and noncancer health risks. However, given that we have more confidence in the relative risk estimates than the absolute values of the risks, the slight increase in atmospheric PAN concentration resulting with the new model input should be further explored.
While the modified model simulation resulted in lower cancer risks and noncancer health effects under all 2003 fuel scenarios relative to the original model simulation, it should be emphasized that these changes are modest and do not diminish the need for the existing regulatory action on automobiles. With the complexities involved in predicting atmospheric concentrations, it is uncertain whether further refinements of the atmospheric modeling will increase or decrease the overall health risks. Ultimately, the differences for cancer and noncancer health risks are not substantial enough between the 2003 fuel types to recommend one fuel over another based on airborne exposure, nor is there any indication that any of those fuel choices would result in worse health impacts than the current situation.