211B Research Group
woman pumping gas

TIER 2 REPORTS

Under the Alternative Tier 2 rule, toxicological studies are required that assess various health endpoints as a result of exposures to the evaporative emissions from baseline gasoline or oxygenated gasoline. The Alternative Tier 2 Rule also included development of pharmacokinetic data on the pure oxygenates and a multi-city exposure study to characterize high-end exposures from vehicle exhaust and evaporative emissions.

The toxicology studies required under the final Alternative Tier 2 Rule are based on rodent inhalation exposures to the evaporative emissions from baseline gasoline or oxygenated gasoline (see Table below for chemical composition). The health endpoints included assessments for subchronic toxicity, neurotoxicity, genotoxicity, immunotoxicity, developmental toxicity, reproductive toxicity, and chronic toxicity/carcinogenicity (by endpoint and by fuel type in the below tables).

In addition, the Alternative Tier 2 Rule also included development of pharmacokinetic data on the pure oxygenates and a multi-city exposure study to characterize high-end exposures from vehicle exhaust and evaporative emissions.

The Research Group submitted data on tertiary-amyl methyl ether (TAME), methyl tertiary-butyl ether (MTBE), and ethanol (EtOH). The Environmental Protection Agency (EPA) found this data to be sufficient to meet the requirements of the Alternative Tier 2 Rule. Studies on ethyl tertiary-butyl ether (ETBE), ), di-isopropyl ether (DIPE), and tertiary-butyl alcohol (TBA) were still required.

A screening study of high-end exposures to people was conducted in Houston, Chicago, and Atlanta (winter and summer) to examine the impact of reformulated gasoline (with either MTBE or EtOH) on various micro-environment exposures to people. The micro-environments evaluated were:

  1. In-Car on Congested Freeway
  2. In-Car in Urban Canyon
  3. In-Car while Refueling
  4. In-Car at Underground Garage
  5. In-Car at Toll Plaza
  6. In-Car in Roadway Tunnel
  7. Out-of-Car while Refueling
  8. Out-of-Car on City Sidewalk
  9. Out-of-Car at Sidewalk/Bus Stop
  10. Out-of-Car at Surface Parking Lot
  11. Out-of-Car at Underground Garage
  12. Out-of-Car at Outdoor Toll Plaza
  13. In-Car Trailing High-Emitting Vehicles

Composition of Test Articles

Compounds1 Baseline Gasoline Gasoline w/EtOH Gasoline w/TBA Gasoline w/MTBE Gasoline w/ETBE Gasoline w/TAME Gasoline w/DIPE
EtOH   13.3          
TBA     16.5        
MTBE       21.3      
ETBE         16.3    
TAME           11.9  
DIPE             17.8
Isobutane 3.6 2.2 3 2.2 2 1.9 2
n-Butane 15.2 11.6 9.9 11.1 10.6 10.4 11.5
Isopentane 35.1 34 25.2 31 32.5 33.6 32.2
n-Pentane 13.2 10.2 11.6 9.1 9.8 10.3 9.6
t-2-Pentene 2.5 2.1 2.1 2 2.1 2.3 2.1
2-Methyl-2-butene 3.8 3.1 3.2 2.9 3.2 3.4 3.1
2,3-Dimethylbutane 1.6 2.2 1.6 0.9 1.4 1.5 1.3
2-Methylpentane 6.3 5.1 6.1 4.5 5.1 5.6 4.5
3-Methylpentane 3.6 2.9 3.8 2.6 2.9 3.2 2.7
n-Hexane 3 2.4 3.4 2.1 2.4 2.6 1.8
Methylcyclopentane 1.5 1.2 1.6 1.1 1.3 1.4 1
2,4-Dimethylpentane 1 1 1 0.9 1 1.2 1
Benzene 2.1 1.6 2 1.5 1.8 2 1.8
2-Methylhexane 1.1 1.1 1.3 1 1.1 1.2 1.1
2,3-Dimethylpentane 1.1 1.1 1.3 1 1.1 1.3 1.1
3-Methylhexane 1.3 1.2 1.5 1.1 1.3 1.5 1.3
Isooctane 1.3 1.3 1.5 1.2 1.4 1.5 1.4
Toluene 3 2.4 3.4 2.5 2.7 3.2 2.6
1 Values reported as area percent

Data from Henley, M., Letinsky, D.J., Carr, J., Caro, M.L., Daughtrey, W.C., and White, R.D., 2014.  Health Assessment of Gasoline and Fuel Oxygenate Vapors: Generation and Characterization of Test Materials.    Reg Toxicol Pharmacol, in press.  Available online 20 May 2014.  http://dx.doi.org/10.1016/j.yrtph.2014.05.012 

Alternative Tier 2 Testing Reports by Endpoint

ENDPOINT

ENDPOINT Baseline Gasoline Gasoline w/MTBE Gasoline w/EtOH Gasoline w/TAME Gasoline w/ETBE Gasoline w/DIPE Gasoline w/TBA
90-Day Subchronic with Neurotoxicity (Histopathology/Motor Activity)
Glial Fibulary Acidic Protein
Immunotoxicity
Micronucleus
Sister-Chromatid Exchange
Developmental Toxicity MR M1M2R R R R R R
Reproductive Toxicity
Chronic Toxicity/Carcinogenicity
Pharmacokinetic Data
In Progress
High-End Exposure Screening Study
Required
Not Required
M
Study Conducted with Mice
R
Study Conducted with Rats

Alternative Tier 2 Testing Reports by Fuel Type

FIELD TYPE

Fuel Type 13-Week Repeat-Dose Study including Immunotoxicity, Neurotoxcity, and Genotoxicity Satellite Studies in Rats Developmental Toxicity in Rats Developmental Toxicity in Mice Reproductive Toxicity in Rats Chronic/Cancer Study in Rats Pharmacokinetic (PK) Studies High-End Exposure Screening Study
Baseline Gasoline
Gasoline w/MTBE
Gasoline w/EtOH
Gasoline w/TAME
Gasoline w/ETBE
Gasoline w/DIPE
Gasoline w/TBA
Required
Not Required
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