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:
- In-Car on Congested Freeway
- In-Car in Urban Canyon
- In-Car while Refueling
- In-Car at Underground Garage
- In-Car at Toll Plaza
- In-Car in Roadway Tunnel
- Out-of-Car while Refueling
- Out-of-Car on City Sidewalk
- Out-of-Car at Sidewalk/Bus Stop
- Out-of-Car at Surface Parking Lot
- Out-of-Car at Underground Garage
- Out-of-Car at Outdoor Toll Plaza
- In-Car Trailing High-Emitting Vehicles
| 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
|