Control of Hazardous Air Pollutants
From Mobile Sources

Early CreditTechnology Requirement
Revision
    The U.S. Environmental Protection Agency (EPA) is revising
    the February 26, 2007 mobile source air toxics rule (MSAT2)
requirement regarding the benzene control technologies that qualify
a refiner to generate early benzene credits. This action adds another
specific benzene control technology, benzene alkylation, to the four
operational or technological changes that the 2007 rule currently allows.
This action also allows refiners to request EPA approval of other
benzene-reducing operational changes or technologies for the purpose
of generating early credits.
Background
This action started as a direct final rulemaking (DFRM)[73 FR 13132, March 12,
2008], We received adverse comment on the DFRM, so it was withdrawn. A parallel
Notice of Proposed Rulemaking (NPRM) accompanied the DFRM in case adverse
comment was received. This action finalizes the NPRM,

Commenters were primarily concerned that the rule would not result in reduced
benzene vehicle emissions, and would increase vehicle aromatics emissions. This
action shows that while fuel aromatics and fuel benzene levels both affect vehicle
benzene emissions, fuel benzene has more than a 20-fold impact on benzene
United States
Environmental Protection
Agency
                              Office of Transportation and Air Quality
                                               EPA420-F-08-030
                                                 October 2008

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emissions from vehicles than other fuel components, including fuel aromatics levels. Alkylation
or any other benzene reduction technology reduces benzene vehicle exhaust emissions more
than 95 %. There is less than a 1 % difference among benzene reduction technologies in their effectiveness
at reducing benzene vehicle emissions. Also, converting the small amount of benzene in gasoline
(1 vol%) to aromatics would increase the fuel aromatics levels minimally (compared to total
fuel aromatics of 20-40 vol%), and thus would have a correspondingly minimal effect on vehicle
aromatics emissions,

Commenters also opposed the proposed petition process that would allow other future refinery
operational changes to be approved after review by EPA. The petition process is appropriate
because a refiner must show that the change would reduce fuel benzene levels. The petition
process has the added value of being more timely than a rulemaking, which is important because
of the time constraints surrounding the application for generating early credits and the early
credit generation period itself,

For More Information
For more information, please contact:

          Christine Brunner
          U.S. Environmental Protection Agency
          2000 Traverwood
          Ann Arbor, MI48105

          telephone: (734) 214-4287
          fax: (734) 214-4051
          email: brunner.christine@epa.gov

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