Environmental Engineering Reference
In-Depth Information
used only for guidance. They are not legally enforceable, and are subject
to revision as new information becomes available. The USEPA's Health
Advisory program is recognized in the 1996 amendments to the Safe
Drinking Water Act, which state in Section 102(b)(1)(F):
The Administrator may publish health advisories (which are not
regulations) or take other appropriate actions for contaminants not
subject to any national primary drinking water regulation.
As its title indicates, this Advisory includes consumer acceptability
advice as “appropriate” under this statutory provision, as well as a health
effects analysis.
In the Clean Air Act of 1990, Congress mandated the use of reformulated
gasoline (RFG) in areas of the country with the worst ozone or smog prob-
lems. RFG must meet certain technical specifications set forth in the Act,
including a specific oxygen content. Ethanol and MtBE are the primary
oxygenates used to meet the oxygen content requirement. MtBE is used in
about 84% of RFG supplies. Currently, 32 areas in 17 states and the District of
Columbia are participating in the RFG program, and RFG accounts for about
30% of gasoline nationwide.
Studies have identified significant air quality and public health benefits
that directly result from the use of fuels oxygenated with MtBE, ethanol, or
other chemicals. Refiners' fuel data submitted to the USEPA for 1995/1996
indicated that the national emissions benefits exceeded those required. The
1996 Air Quality Trends Report showed that toxic air pollutants declined
significantly between 1994 and 1995, and analysis indicated that at least some
of this progress could be attributed to the use of RFG. Beginning in the year
2000, required emission reductions have become substantially greater, at
about 27% for volatile organic compounds, 22% for toxic air pollutants, and
7% for nitrogen oxides.
Note:
When gasoline that has been oxygenated with MtBE comes in
contact with water, large amounts of MtBE dissolve. At 25°C, the water
solubility of MtBE is about 5000 mg/L for a gasoline that is 10% MtBE by
weight. In contrast, for a non-oxygenated gasoline, the total hydrocarbon
solubility in water is typically about 120 mg/L. MtBE sorbs only weakly
to soil and aquifer material; therefore, sorption will not significantly
retard MtBE transport by groundwater. In addition, the compound gen-
erally resists degradation in groundwater (Squillace et al., 1998).
A limited number of instances of significant contamination of drinking
water with MtBE have occurred because of leaks from underground and
aboveground petroleum storage tank systems and pipelines. Due to its small
molecular size and solubility in water, MtBE moves rapidly into groundwater,
