(VCCEP) Tier 1 Pilot Submission for BENZENE - Tera

e similar to those in other U.S. studies, despite the various gasoline benzene contents.
Egeghy, et al. (2000) also found that exposure levels decreased with increasing refueling time.
This counter-intuitive result was believed to have occurred due to inclusion of non-refueling
activities (e.g., cleaning the windshield, paying for gas) in the recorded ‘refueling’ time period.
API (1993) and Vainiotalo, (1999) used more tightly defined refueling periods that excluded
such ancillary activities.
Four studies were selected as having the best representative data for this exposure assessment
and are summarized in Table 7.32. These key studies focus on the exposure of a self-service
customer while refueling; occupational exposure concentrations were excluded. Data collected
before 1990 were not considered to be representative of current gasoline formulations. The
gasoline content of benzene in each of the key studies is similar. The presence or absence of
VRS controls at the pump was also documented in the studies.
Table 7.32: Summary of Key Refueling Studies
Study
Smith, 1999
Benzene VCCEP Submission
March 2006
Date/location data
collected
Toronto, Canada
Completion by
March 21, 1999
Vainiotalo, 1999 August 1996,
Helsinki, Finland
API, 1993 October -
November 1990
Cincinnati, OH,
Phoenix, AZ and
Los Angeles, CA
Backer, et al.,
1997
January - March,
1995
Fairbanks, AK
Controls at the
Pump
Varied
No Stage II VRS,
had splash
collars
Only LA had
Stage II VRSs
and extensively
used pump safety
latches
132
Type of Gasoline a
Regular, mid-grade, premium
Unleaded 95-, 98-, and 99-RON RFG
Three grades of gasoline were evaluated:
regular unleaded, mid-grade unleaded, super
(premium) unleaded. Regular leaded gasoline
was also measured for 4 samples at one
Phoenix station and 2 samples at the other
Phoenix station.
No stage II VRS Regular gas and E10 gas
Based on decreases in benzene content in gasoline and improvements in vehicle emission
controls since the time of these studies, it is likely that the air concentrations reported in these
studies overestimate current day exposures. Therefore a refueling normalization factor (NF)
was derived to account for these changes.
The refueling NF was derived similar to that for the indoor air. EPA’s MOBILE6.2 model was
used to estimate the change in benzene emission rates given the historical and current
conditions of fleet and fuel properties. In doing so, the year-specific fuel and fleet properties for
each of the studies listed on Table 7.32 (excluding the Finland study) and that for 2003 were
used to model refueling emission rates. The change in the emission rate was then used to
estimate the emission factor change attributable to benzene content decreases and emission
factor changes attributable to fleet improvements. A detailed discussion of the refueling NF
derivation is presented in Appendix B.