MEMORANDUM

DATE: March 9, 2011 

SUBJECT: HAP Content in Vapor Phase of Gasoline 

 Residual Risk and Technology Review for the Marine Tank Vessel Loading 

Operations Source Category 

 EPA Contract No.: EP-D-07-061; EPA Project No.: 005 

 RTI Project No.: 0212783.005 

FROM: Karen Schaffner and Jeff Coburn, RTI International 

TO: Stephen Shedd and Brenda Shine, EPA 

 The purpose of this memorandum is to review the hazardous air pollutant (HAP) content 

in the vapor phase of gasoline for use in estimating emissions for the residual risk and 

technology review for the Marine Tank Vessel Loading Operations (MTVLO) source category 

for the October 2010 Risk and Technology Review (RTR) proposal (75 FR 65068; October 21, 

2010). 

I. Background 

Section 112 of the Clean Air Act (CAA) establishes a two-stage regulatory process to 

address emissions HAP from stationary sources. In the first stage, section 112(d) (2) requires the 

Environmental Protection Agency (EPA) to develop technology-based standards, referred to as 

maximum achievable control technology (MACT) standards, for categories of industrial sources. 

In the second stage of the regulatory process, EPA is required under section 112(f)(2) to assess 

the health and environmental risks that remain after sources come into compliance with the 

MACT standards. 

As part of this second stage in the regulatory process, EPA identified additional controls 

for certain MTVLO. Specifically, we proposed to require existing major sources1 with MTVLO 

emissions less than 10/25 tons per year (tpy) HAP and existing major source offshore MTVLO 

to use submerged filling for liquids with a vapor pressure exceeding 1.5 psia (20°C) and to use 

vapor recovery controls if the MTVLO loads 1 million bbl/yr or more of motor gasoline.

 

1

 As defined in 40 CFR 63.2, “Major source” means any stationary source or group of stationary sources located 

within a contiguous area and under common control that emits or has the potential to emit considering controls, in 

the aggregate, 10 tons per year or more of any hazardous air pollutant or 25 tons per year or more of any 

combination of hazardous air pollutants, unless the Administrator establishes a lesser quantity, or in the case of 

radionuclides, different criteria from those specified in this sentence. 
II. Issues with HAP Content in Gasoline 

A key factor affecting the cost-effectiveness of the vapor recovery system is the HAP 

content of the gasoline vapor. When developing the impacts for the proposed MTVLO 

standards, we used a vapor-phase HAP content of 7.3 percent for gasoline (Hester, 2006). In 

their comment letter dated December 6, 2010 on the RTR proposal for MTVLO, API noted that 

the HAP content in the vapor phase of gasoline is 3 percent HAP. API used a fixed total vapor 

pressure for gasoline based on old gasoline composition data, but set the MTBE concentration to 

0 percent because use of MTBE as a gasoline additive has been phased out in the U.S. They also 

noted the 3 percent HAP content in the gasoline vapor was likely biased high because the 

benzene concentration in the liquid phase (based on the old concentration data) was 1.8 percent 

and it should be approximately 0.5 to 0.6 percent [by volume] due to new EPA Fuel 

Specifications (effective in January 2011 with phase-in through 2015).2 The API analysis does 

not account for how the total vapor pressure of the gasoline or how the relative concentrations of 

other HAP would be affected by these changes in gasoline composition. 

III. HAP Content Data for Gasoline 

To address this issue, EPA has reviewed the HAP content information for gasoline from 

several data sources, including TANKS data, EPA EPCRA Section 313 information, a recent 

memorandum developed for the Gasoline Distribution Area Source NESHAP rule, and API 

PERF data. The HAP content of gasoline has fluctuated over time based on petroleum industry 

changes, including selection of gasoline additives and regulations regarding gasoline content. In 

Table 1, the gasoline contents from multiple data sources are provided and the progression of 

changes over time is shown. 

 

Both benzene content and MTBE content in liquid gasoline have dropped significantly 

over the past several years and are expected to continue to decline. The quantity of benzene in 

gasoline for calendar years 2000 to 2005 has been in the range of 0.59 to 0.66 percent by volume 

for reformulated gasoline and in the range of 1.07 to 1.21 percent by volume and varies across 

types of gasoline (EPA website). For 2005, the average benzene content in reformulated 

gasoline was 0.67 percent by volume and the average benzene content in conventional gasoline 

was 1.16 percent by volume (EPA, 2008). In a 2007 data collection effort, the benzene 

concentration in liquid gasoline ranged from 0.25 to 1.3 percent by volume for reformulated 

gasoline and 0.1 to 3.6 percent by volume for conventional gasoline (EPA, 2009a). The average 

benzene content in gasoline will continue to decrease from 2011 through 2015 to approximately 

0.62 percent by volume, achieved through credit banking and trading, and the maximum average 

benzene content in gasoline, phased in from 2012 through 2016, will be 1.3 percent by volume, 

which cannot be met with banking credits (the MSAT rule defining these percentages was 

finalized in February 2007).2

 Refinery facilities are required to submit annual gasoline benzene 

 

2

 The Mobile Source Air Toxics Phase 2 rule (MSAT2) rule includes controls on the benzene content in gasoline, 

The average benzene content of a refiners total gasoline pool must be 0.62 percent by volume, with averaging, 

banking, and trading allowed. The average benzene content must be met on January 2, 2011 for most refiners and 

on January 1, 2015 for small refiners. The actual, maximum average benzene content must be 1.3 percent by 

volume, that cannot be met with credits. The maximum average benzene content specification must be met on July 

1, 2012 for most refiners and by July 1, 2016 for small refiners. The MSAT2 rule was finalized on February 26, 

2007 (72 FR 8428). 

2 
pre-compliance reports to show their annual average benzene concentrations, and the latest 

available information is for reporting year 2009. In 2009, the annual average benzene 

concentrations, across all gasoline products, is 1.02 percent by volume (EPA, 2009b).3

 In our 

analysis, we used a typical benzene content in reformulated gasoline of 0.8 percent by weight 

and of 1.4 percent by weight for conventional gasoline.4 

Use of MTBE in gasoline has declined over the past several years as concerns regarding 

MTBE in ground water have grown. While the majority of domestic gasoline no longer contains 

MTBE, gasoline produced for use in other countries may use MTBE, and these MTBEcontaining gasolines may be loaded to marine tank vessels. Because both reformulated and 

conventional gasolines are used in the U.S., we looked at both conventional and reformulated 

gasolines in the analysis. 

IV. Assumptions Regarding Balance Compounds in Gasoline 

As the composition of HAP in gasoline changes, the vapor pressure and composition of 

the gasoline vapors also changes. Additionally, the relative concentrations of the gasoline 

components are dependent on each other. For example, prior to blending with MTBE, the 

gasoline blending stream would have higher hexane, benzene, toluene or xylene concentrations 

than the blended product. If MTBE is not added, then that impacts the concentration of all other 

components. We did not have a complete analysis of gasoline, including non-HAP volatile 

organic compounds (VOCs), by which to perform the analysis. API PERF data (API, 2002) 

appeared to provide the most recent and complete HAP composition for reformulated and 

conventional gasolines; Potter and Simmons (1998) presented fairly complete overall analysis of 

gasoline composition, but the data are slightly older than the PERF data. Each of these datasets 

was affected by the presence of MTBE. Consequently, several assumptions were required in 

order to estimate the HAP content of gasoline vapor based on the available liquid-phase 

composition data. 

A key factor that affects the HAP content in the vapor phase is the quantity of butane in 

the gasoline. Due to its high volatility, small changes in butane concentration can have 

significant affects on the the overall partial pressure of the system. Potter and Simmons (1998) 

provided a value of 4.7 percent n-butane in gasoline, while API PERF provided a value of 3.23 

percent n-butane on average for gasoline. Calculations are provided below for an n-butane 

content of 4.7 percent; however, we also provide information on calculations using a value of 

3.23 percent. 

 

3

 The annual average benzene concentration is not expected to drop to 0.62 percent by volume or lower until 2013. 

4

 The latest year for which we have specific data for both RFG and CG is for 2005. In 2005, benzene content in 

reformulated gasoline is 0.67 percent by volume and is 1.16 percent by volume for conventional gasoline. Using 

these values, the benzene content on a weighted average basis for all gasoline (one-third reformulated and two thirds 

conventional; see discussion later in memorandum), would be approximately 1.0, which is consistent with the 

average benzene content for all gasoline of 1.02 percent by volume reported in 2009. The density of benzene is 

greater than the average density of gasoline liquid; therefore, the benzene concentration in gasoline expressed in 

weight percent is greater than the benzene concentration when expressed in volume percent. For reformulated 

gasoline, using a benzene content of 0.67 percent by volume is approximately equal to 0.80 percent by weight 

benzene, and for conventional gasoline, a benzene content of 1.16 percent by volume is approximately equal to 1.4 

percent by weight benzene. 

3 
A second factor that affects the HAP content in the vapor phase is the assumption of 

what, if any, additive is used to replace MTBE. Calculations are provided below assuming that 

no other additive is used to replace MTBE, and we also provide calculations assuming ethanol is 

used as an additive to replace MTBE. 

 

Finally, the analysis also required assumptions regarding the balance of VOC compounds 

in gasoline. That is, if the available compositional analysis data accounted for 65 percent of the 

gasoline liquid weight, what makes up the remaining 35 percent of the liquid gasoline mass? 

Compounds that are included in the balance compounds are identified in Table 2. Because 

gasoline composition includes a range of chemicals, we identified a surrogate for the range of 

compounds in the C6, C7, C8, and C9 categories. The composition of C6, C7, C8, and C9 were 

based on information from Potter and Simmons (1998); the percentage of compounds in each 

carbon number category was summed and a surrogate compound was selected to represent the 

compounds in that carbon number category. For the remaining balance of other VOC 

compounds, heptane was selected to represent these compounds. The surrogates and percentages 

identified for C6, C7, C8, and C9 carbon number categories and other VOC are shown in Table 

2. 

V. HAP Content Calculations for Gasoline 

Review and Analysis for API provided data. We reviewed the data provided by API. 

API provided information showing that the sum of HAP in the vapor would be 2.56 weight 

percent, and we recreated the analysis, including the assumptions discussed earlier regarding the 

balance of VOC compounds. Table 3 provides the API data on HAP content in the liquid phase 

of gasoline and estimates of HAP content in the vapor phase based on calculations. In our 

estimate at 60°F, we determined that the HAP content in the vapor would be 3.88 weight percent, 

which is somewhat similar although higher than their value. The difference is attributable to the 

fact that we adjusted the total vapor pressure of gasoline caused by the removal of MTBE, 

whereas API assumed that the total vapor pressure remained constant. We also conducted 

analysis based on vapor pressure at 25°C (77°F). At 77°F, we estimated the HAP content in the 

vapor phase to be 4.36 percent by weight. 

Analysis for API PERF data and Assuming No MTBE content. We also estimated the 

vapor compositions of gasoline based on the API PERF data, based on an assumption that MTBE 

would be replaced with heptane, (our surrogate VOC). Using a temperature of 77°F (25°C), 

EPA estimates that the sum of HAP in the vapor is 4.96 weight percent for conventional gasoline 

and 3.36 weight percent for reformulated gasoline when the Potter and Simmons (1998) value 

for n-butane of 4.7 percent in the gasoline liquid is used. If the API PERF value of 3.23 percent 

n-butane in the gasoline liquid is used(API, 2002), we estimate that the sum of HAP in the vapor 

is 5.79 weight percent for conventional gasoline and 3.92 weight percent for reformulated 

gasoline. The results for HAP content in the vapor phase are provided in Table 4. 

Analysis for API PERF data and Assuming Ethanol Added. Finally, we estimated the 

vapor compositions of gasoline based on MTBE being replaced with 10 weight percent ethanol. 

The heptane concentration (our surrogate VOC) was adjusted so that the total liquid weight 

4 
fraction totaled 100 percent. There was no difference in the HAP content in the vapor phase 

estimates for gasoline with ethanol added versus our surrogate VOC (heptane) because ethanol 

and heptane have similar vapor pressures. Thus, provided that gasoline additives used to replace 

MTBE do not contain significant HAP content, these additives are not expected to significantly 

alter the HAP content of the gasoline vapor; the gasoline additive that most strongly affects the 

HAP content of the gasoline vapor is butane. 

VI. Conclusions Regarding HAP Content in the Vapor 

Because both reformulated and conventional gasolines are used in the U.S., a good 

estimate of the HAP in the vapor would be somewhere between these estimated values. The 

HAP content in the vapor phase ranges from 5.0 to 5.8 percent by weight for conventional 

gasoline and ranges from 3.4 to 3.9 percent by weight for reformulated gasoline, depending on 

the n-butane content in the gasoline. 

Based on “refinery and blender net production” of finished motor gasoline in 2009, 

approximately two-thirds of gasoline is conventional gasoline and approximately one-third of 

gasoline is reformulated gasoline (EIA, 2009). Based on “refinery net production” of finished 

motor gasoline in 2009, conventional gasoline accounts for 97 percent and reformulated gasoline 

accounts for 3 percent; however, considering the production of unfinished gasoline blending 

stocks, reformulated gasoline and reformulated gasoline blending stocks account for 31 percent 

of the total gasoline and unfinished gasoline blending stocks produced at refineries in the U.S. 

(EIA, 2009). Table 5 highlights the HAP content in the vapor phase for each case and provides a 

weighted average HAP content based on 67 percent conventional gasoline and 33 percent 

reformulated gasoline production in the U.S., although use of the higher value for conventional 

gasoline would result in slightly higher HAP contents. 

 Based on our analysis, and considering the uncertainty and variability in the composition 

of gasoline, a reasonable average value for HAP content in the vapor of gasoline (at 77°F) is 5 

percent by weight. 

5 
VII.References 

Murphy, P., Radian Corporation, to J. Durham, EPA. Memorandum on liquid HAP 

concentrations of various petroleum products. August 10, 1993. 

TANKS, Storage Tank Emissions Calculation Software, Version 4.09d. Emission Factor and 

Inventory Group, October 3, 2005. 

RTI International. Draft Emission Estimation Protocol for Petroleum Refineries. For 

EPA/OAQPS. December 2009. 

Hester, C., MACTEC, to S. Shedd, EPA/OAQPS/SPPD. Memorandum on Review of Data on 

HAP Content in Gasoline. May 18, 2006. 

U.S. EPA. Conventional Gasoline Parameters by Reporting Year (1997 – 2005). 

http://www.epa.gov/otaq/regs/fuels/rfg/properf/cg-params.htm 

U.S. EPA. Reformulated Gasoline Parameters by Reporting Year. 

http://www.epa.gov/otaq/regs/fuels/rfg/properf/rfg-params.htm 

U.S. EPA. Composition and Behavior of Fuel Ethanol. EPA Publication No. EPA/600/R-037. 

April 2009. 

RTI International. Emission Estimation Protocol for Petroleum Refineries, Version 2.0, ICR 

Response Version. For OAQPS/EPA. February 2011. 

API PERF study. API Petroleum Environmental Research Forum (PERF) refinery process 

stream speciation study (API, 2002). 7 companies took samples on 665 streams. 

Fuel Trends Report: Gasoline 1995-2005. U.S. Environmental Protection Agency. 

OTAQ/CISD. EPA Publication No. EPA420-R-08-002. January 2008. 

Summary and Analysis of the 2009 Gasoline Benzene Pre-Compliance Reports. U.S. 

Environmental Protection Agency. OTAQ/CISD. EPA Publication No. EPA-420-R-09-017. 

November 2009. 

Section 313 of the Emergency Planning and Community Right-to-Know Act, Toxic Chemical 

Release Inventory, Petroleum Terminals and Bulk Storage Facilities. EPA Publication No. EPA 

745-B-00-002. February 2000. See Table 3-4: Estimated Concentration Values of EPCRA 

Section 313 Constituents in Crude Oil and Petroleum Products (Weight Percent). 

Potter, T.L. and K.E. Simmons, Total Petroleum Hydrocarbon Criteria Working Group Series. 

Composition of Petroleum Mixtures, Volume 2. May 1998. 

6 
7 

Energy Information Administration. Petroleum Supply Annual 2009, Volume 1. See Table 16, 

Refinery and Blender Net Production of Finished Petroleum Products by PAD and Refining 

Districts, 2009. 

Todd, M., API, to Air and Radiation Docket. Docket ID No. EPA-HQ-OAR-2010-0600, Letter 

with Comments on EPA’s Proposed Rule – Residual Risk and Technology Review (RTR) for 

National Emission Standards for Marine Tank Vessel Loading Operations. Docket item no. 

EPA-HQ-OAR-2010-0600-0359. Dated December 6, 2010. 
Table 1. Data on Gasoline HAP Content

TANKS: Gasoline [T]

TANKS: Gasoline (Oxygenated with MTBE) [T]

TANKS: Gasoline (Reformulated with MTBE) [T]

TANKS: Gasoline (Oxygenated with ethanol) [T]

Liquid, wt. % Liquid, wt. % Liquid, wt. % Liquid, wt. % 

106-99-0 1,3-Butadiene540-84-1 octane)

71-43-2 Benzene 1.8 1.8 1.8 1.8 92-52-4 Biphenyl

1319-77-3 Cresols

98-82-8 Cumene

100-41-4 Ethylbenzene 1.4 1.4 1.4 1.4 110-54-3 Hexane 1 0 1 0 1 0 1 0 

CAS Number HAP Component

110-54-3 Hexane 1.0 1.0 1.0 1.0 

1634-04-4 Methyl tertiary-butyl ether 12 8.8 

91-20-3 Naphthalene 

108-95-2 Phenol 100-42-5 Styrene108-88-3 Toluene 7.0 7.0 7.0 7.0 

01330-20-7 Xylene 7.0 7.0 7.0 7.0 

Sum HAP content 18.20 30.20 27.00 18.20 

Notes:[R]: Radian Corporation report prepared for J. Durham, EPA , regarding liquid HAP concentrations of various petrol

1993.[M]: Memoradum from C. Hester, MACTEC, to S. Shedd, EPA/OAQPS/SPPD. Review of Data on HAP Content in 

[T]: Current version of EPA's emission estimation program TANKS 4.0[E]: EPCRA table, Economic Analysis of the Final Rule to Add Certain Industry Groups to EPCRA Section 313, App

Crude Oil and Petroleum Products." February 2000.
Table 1. Data on Gasoline HAP Content

106-99-0 1,3-Butadiene540-84-1 octane)

71-43-2 Benzene92-52-4 Biphenyl

1319-77-3 Cresols

98-82-8 Cumene

100-41-4 Ethylbenzene110-54-3 Hexane

CAS Number HAP Component

Normal Gasoline from 

Gasoline Distribution 

NESHAP BID

Oxygenated Gasoline from 

Gasoline Distribution NESHAP 

BID

1994 1994

Vapor, wt % Vapor, wt % Liquid, wt % Vapor, wt %

0.0037

0.8 0.7 4.72 0.9 0.9 1.61 

0.01 

0.789 0

0.01 0.01 0.849 0

0.1 0.1 1.605 

1 6 1 6 7 138 

2009 Draft 

Gasoline from Draft PetroRef Protoco

Document [R]

110-54-3 Hexane

1634-04-4 Methyl tertiary-butyl ether

91-20-3 Naphthalene

108-95-2 Phenol100-42-5 Styrene108-88-3 Toluene

01330-20-7 Xylene

Sum HAP content

1.6 1.6 7.138 

0 11.9 3.54 

0.05 0.05 0.444 

0.0551 

3.528 

1.3 1.1 7.21 0.5 0.4 7.17 

5.26 16.76 38.67 
Table 1. Data on Gasoline HAP Content

106-99-0 1,3-Butadiene540-84-1 octane)

71-43-2 Benzene92-52-4 Biphenyl

1319-77-3 Cresols

98-82-8 Cumene

100-41-4 Ethylbenzene110-54-3 Hexane

CAS Number HAP Component

MACTEC Summary of Data MACTEC Summary of Data

MACTEC Summary of 

Data

2005 OTAQ Data Current Data [2006] Future (2015)

Vapor, wt % Vapor, wt % Vapor, wt %

0.83 0.75 0.750.74 0.27 0.170.01 0.012 0.0120.14 0.053 0.053

110-54-3 Hexane 1 6 1 8 1 8

1634-04-4 Methyl tertiary-butyl ether

91-20-3 Naphthalene

108-95-2 Phenol100-42-5 Styrene108-88-3 Toluene

01330-20-7 Xylene

Sum HAP content

1.6 1.8 1.82.4 2.4 0.0

0.046 0.00027 0.00027

1.3 1.4 1.4

0.53 0.56 0.567.60 7.25 4.75
Table 1. Data on Gasoline HAP Content

106-99-0 1,3-Butadiene540-84-1 octane)

71-43-2 Benzene92-52-4 Biphenyl

1319-77-3 Cresols

98-82-8 Cumene

100-41-4 Ethylbenzene110-54-3 Hexane

CAS Number HAP Component Liquid, wt % Vapor, wt% Liquid, wt % Vapor, wt % Liquid, wt % 

0.0009 0.010333014

2.94 0.7914 1.10 API PERF 0.2974 

1.4 0.6074 0.8

EPA Fuel

Trends Rpt 0.3657 

0 API PERF 0

0 0

0.219 0.005475 0.19 API PERF 0.004781 

1.490 0.07729 1.26 API PERF 0.06578 

2 22 1 834 1 36 API PERF 1 131 

2010 Final 2010 Final Dec

API Comment L

Crude Oil and P

TA

Conventional Gasoline from PetroRef 

Protocol Document [P]

Reformulated Gasoline from PetroRef Protocol 

Document [P]

110-54-3 Hexane

1634-04-4 Methyl tertiary-butyl ether

91-20-3 Naphthalene

108-95-2 Phenol100-42-5 Styrene108-88-3 Toluene

01330-20-7 Xylene

Sum HAP content

2.22 1.834 1.36 API PERF 1.131 

0 API PERF 

0.415 0.0005961 0.21 API PERF 0.0003036 

0 API PERF 0

0.0767 0.002758 API PERF 0

7.75 1.2023 7.0 API PERF 1.093 

6.56 0.3133 7.31 API PERF 0.3514 

23.07 4.84 19.23 3.31 2
Table 2. Balance VOC Compounds in Gasoline

Liquid, wt %

n-Butane 4.7

isobutane 1.7

Pentane 3.9

Isopentane 7.9

2-Methylpentane (surrogate for C6 cpds) 10.08

2-Methylhexane (surrogate for C7 cpds) 7.21

2,3,4-Trimethylpentane (surrogate for C8 cpds) 3.21

1,2,4-Trimethylbenzene (surrogate for C9 cpds) 7.29

Other VOC (assume Heptane is the surrogate for Other VOC) X

Balance VOC compounds

HAP Component
Table 3. Review of HAP Content Data provided by Commenter

Liquid, wt % Vapor, wt % (at 15C) Vapor, wt % (at 15C) Vapor, wt % (at 25C)

106-99-0 1,3-Butadiene

540-84-1 2,2,4-Trimethylpentane (iso-octane) 4.0 0.64 0.97 1.08

71-43-2 Benzene 1.8 0.57 0.85 0.94

92-52-4 Biphenyl

1319-77-3 Cresols

98-82-8 Cumene 0.5 0.01 0.01 0.01

100-41-4 Ethylbenzene 1.4 0.04 0.06 0.07

110-54-3 Hexane 1.0 0.51 0.78 0.83

1634-04-4 Methyl tertiary-butyl ether 0.0 0.0 0.00

91-20-3 Naphthalene 0.0 0.0 0.00

108-95-2 Phenol

100-42-5 Styrene 0.00

108-88-3 Toluene 7.0 0.62 0.94 1.09

01330-20-7 Xylene 7.0 0.17 0.27 0.34

Sum HAP content 22.70 2.56 3.88 4.36

26635-64-3 iso-octane

00098-82-8 Isopropyl benzene

00110-82-7 Cyclohexane

00064-17-5 Ethanol

Assume balance compounds/composition as follows:

CAS Number HAP Component

API Comment Letter, Att 2 (cites EPCRA Crude Oil 

and Petroleum Products, and TANKS) [T] [E]

December 2010

Estimated values

Assume balance compounds/composition as follows:

n-Butane 4.7 49.61 46.93

isobutane 1.7 6.49 6.41

Pentane 3.9 11.35 11.37

Isopentane 7.9 7.82 8.22

2-Methylpentane (surrogate for C6 cpds) 10.1 11.17 11.70

2-Methylhexane (surrogate for C7 cpds) 7.2 2.34 2.60

2,3,4-Trimethylpentane (surrogate for C8 cpds) 3.2 0.41 0.48

1,2,4-Trimethylbenzene (surrogate for C9 cpds) 7.3 0.06 0.08

Other VOC (assume Heptane is the surrogate for 

Other VOC)

31.31 6.88 7.84

100.00 100.00 100.00
Table 4. HAP Content Calculations based on API PERF Data.

n-Butane at 4.7 percent n-Butane at 3.23 percent

Liquid, wt % Vapor, wt% Liquid, wt % Vapor, wt % Liquid, wt % Vapor, wt% Liquid, wt % Vapor, wt %

106-99-0 1,3-Butadiene 0.0009 0.01033 0.0009 0.01205

540-84-1 2,2,4-Trimethylpentane (isooctane)2.94 0.7909 1.10 API PERF 0.2974 2.94 0.9225 1.10 API PERF 0.3472

71-43-2 Benzene 1.4 0.7263 0.8 EPA Fuel 

Trends Rpt

0.4178 1.4 0.8472 0.8 EPA Fuel 

Trends Rpt

0.4879

92-52-4 Biphenyl API PERF API PERF

1319-77-3 Cresols

98-82-8 Cumene 0.219 0.005472 0.19 API PERF 0.004779 0.219 0.006383 0.19 API PERF 0.005581

100-41-4 Ethylbenzene 1.490 0.07724 1.26 API PERF 0.06576 1.490 0.09010 1.26 API PERF 0.07679

110-54-3 Hexane 2.22 1.833 1.36 API PERF 1.130 2.22 2.138 1.36 API PERF 1.320

1634-04-4 Methyl tertiary-butyl ether API PERF API PERF

91-20-3 Naphthalene 0.415 0.0005958 0.21 API PERF 0.0003035 0.415 0.0006949 0.21 API PERF 0.0003544

108-95-2 Phenol API PERF API PERF

100-42-5 Styrene 0.0767 0.002757 API PERF 0.0767 0.003215 API PERF

108-88-3 Toluene 7.75 1.202 7.0 API PERF 1.093 7.75 1.402 7.0 API PERF 1.276

01330-20-7 Xylene 6.56 0.3131 7.31 API PERF 0.3513 6.56 0.3653 7.31 API PERF 0.4102

Sum HAP content 23.07 4.96 19.23 3.36 23.07 5.79 19.23 3.92

26635-64-3 iso-octane

00098-82-8 Isopropyl benzene

00110 82 7 Cyclohexane

2010 Final

Reformulated Gasoline from PetroRef Protocol 

Document [P]

CAS Number HAP Component

Conventional Gasoline from 

PetroRef Protocol Document [P]

Reformulated Gasoline from PetroRef Protocol 

Document [P]

Conventional Gasoline from PetroRef

Protocol Document [P]

2010 Final 2010 Final 2010 Final

00110-82-7 Cyclohexane

00064-17-5 Ethanol

Assume balance compounds/composition as follows:

n-Butane 4.7 46.68 4.7 46.99 3.23 37.41 3.23 37.70

isobutane 1.7 6.37 1.7 6.42 1.7 7.43 1.7 7.49

Pentane 3.9 11.31 3.9 11.39 3.9 13.19 3.9 13.29

Isopentane 7.9 8.18 7.9 8.23 7.9 9.53 7.9 9.61

2-Methylpentane (surrogate for 

C6 cpds)

10.08 11.64 10.08 11.72 10.08 13.57 10.08 13.68

2-Methylhexane (surrogate for 

C7 cpds)

7.21 2.59 7.21 2.61 7.21 3.02 7.21 3.04

2,3,4-Trimethylpentane 

(surrogate for C8 cpds)

3.21 0.473 3.21 0.476 3.21 0.55 3.21 0.56

1,2,4-Trimethylbenzene 

(surrogate for C9 cpds)

7.29 0.0808 7.29 0.0813 7.29 0.09 7.29 0.09

Other VOC (assume Heptane is 

the surrogate for Other VOC)

30.94 7.71 34.78 8.73 32.41 9.42 36.25 10.62

76.93 95.04 80.77 96.64 76.93 94.21 80.77 96.08

100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0
Table 5. HAP Content Calculations based on API PERF Data.

n-Butane at 4.7 percent n-Butane at 3.23 percent

Conventional Gasoline 

from PetroRef Protocol 

Document [P]

Reformulated Gasoline 

from PetroRef Protocol 

Document [P] Weighted average

Conventional Gasoline 

from PetroRef Protocol 

Document [P]

Reformulated G

from PetroRef 

Document 

2010 Final 2010 Final 2010 Final 2010 Fin

Vapor, wt% Vapor, wt % Vapor, wt % Vapor, wt% Vapor, wt 

106-99-0 1,3-Butadiene 0.01033 0.006887 0.01205 540-84-1

2,2,4-Trimethylpentane (isooctane) 0.7912 0.2975 0.626634 0.9225 

71-43-2 Benzene 0.7266 0.4180 0.623749 0.8472 92-52-4 Biphenyl

1319-77-3 Cresols

98-82-8 Cumene 0.005474 0.004781 0.005243 0.006383 

100-41-4 Ethylbenzene 0.07727 0.06578 0.073442 0.09010 

CAS Number HAP Component

110-54-3 Hexane 1.833 1.131 1.599092 2.138 

1634-04-4 Methyl tertiary-butyl ether

91-20-3 Naphthalene 0.0005960 0.0003036 0.000499 0.0006949 0

108-95-2 Phenol100-42-5 Styrene 0.002758 0.001838 0.003215 108-88-3 Toluene 1.202 1.093 1.165704 1.402 

01330-20-7 Xylene 0.3133 0.3514 0.325985 0.3653 

Sum HAP content 4.96 3.36 4.43 5.79 
Appendix A 

TANKS, Storage Tank Emissions Calculation Software, Version 4.09d. Emission Factor and 

Inventory Group, October 3, 2005. 
Sum HAP 27

TANKS v4.09d Data on Gasoline HAP Content

HAP (and other compounds) Liquid wt %

Gasoline Benzene 1.8

Ethylbenzene 1.4

Hexane (‐n) 1.0

Toluene 7.0

Xylene (‐m) 7.0

Sum HAP 0.182

Gasoline (Oxygenated with MTBE) Benzene 1.8

Ethylbenzene 1.4

Hexane (‐n) 1.0

MTBE 12

Toluene 7.0

Xylene (‐m) 7.0

Sum HAP 0.302

TANKS also specifies the following compounds:

iso‐octane 4.0

Isopropyl benzene 0.5

Cyclohexane 0.24

Gasoline (Reformulated with MTBE) Benzene 1.8

Ethylbenzene 1.4

Hexane (‐n) 1.0

MTBE 8.8

Toluene 7.0

Xylene (‐m) 7.0

Sum HAP 0.27

TANKS also specifies the following compounds:

iso‐octane 4.0

Isopropyl benzene 0.5

Cyclohexane 0.24

Gasoline (Oxygenated with ethanol) Benzene 1.8

Ethylbenzene 1.4

Hexane (‐n) 1.0

MTBE 8.8

Toluene 7.0

Xylene (‐m) 7.0

Sum HAP 0.27

TANKS also specifies the following compounds:

iso‐octane 4.0

Isopropyl benzene 0.5

Cyclohexane 0.24

Ethanol 5.6
Appendix B

Section 313 of the Emergency Planning and Community Right-to-Know Act, Toxic Chemical 

Release Inventory, Petroleum Terminals and Bulk Storage Facilities. EPA Publication No. EPA 

745-B-00-002. February 2000. 
Table 3-4

Estimated Concentration Values of EPCRA Section 313 Constituents 

in Crude Oil and Petroleum Products (Weight Percent)

EPCRA Section

313 Chemical 

De Minimis

Level*

Crude Oil Gasoline

(Various

Grades)

No.2 Fuel

Oil/ Diesel

Fuel

Jet Fuel

(JP-4)

Kerosene Lubricating

Oil

No. 6

Fuel Oil

Aviation

Gasoline

Benzene 0.1 0.446 R 1.608 R 8.0E-04 A 1.0 A 0.004 A N/A 0.001 0.515 R

Biphenyl 1.0 0.060 R 0.010 R 0.100 0.120 R 0.120 R N/A N/A N/A

Bromine 1.0 N/A N/A N/A N/A N/A N/A 3.0E-06 N/A

Chlorine 1.0 N/A N/A N/A N/A N/A N/A 0.0131 D N/A

Cyclohexane 1.0 0.700 0.240 N/A 1.240 N/A N/A N/A N/A

Ethylbenzene 1.0 0.346 R 1.605 R 0.013 A 0.50 A 0.127 A N/A 0.0022 0.432 R

n-Hexane 1.0 2.463 R 1.0 T 1.0 A 1.5 T 0.005 A N/A N/A 0.126 R

MTBEb 1.0 N/A 15.00 N/A N/A N/A N/A N/A N/A

Naphthalene 1.0 0.219 R 0.444 R 0.550 0.468 R 0.733 R N/A 0.10 0.10 R

Phenanthrene 1.0 N/A N/A 0.125 N/A N/A N/A N/A N/A

Phenol 1.0 0.323 0.055 0.064 N/A 0.770 N/A N/A N/A

PACse 0.1 0.0004 N/A N/A N/A N/A N/A 1.13 N/A

Styrene 0.1 N/A N/A@ 0.032 R N/A N/A N/A N/A N/A

Toluene 1.0 0.878 R 7.212 R 0.032 A 3.20 A .13 T N/A 0.006 7.327

1,2,4-Trimethylbenzene 1.0 0.326 2.50‡ 1.0 ‡ N/A N/A N/A N/A N/A

Xylene 1.0 1.420 R 7.170 R 0.290 A 3.20 A 0.31 A N/A 0.013 2.204

Antimony a 0.1 1.0E-05 N/A N/A N/A N/A N/A 1.0E-06 N/A

Arsenic a 0.1/1.0 c 2.0E-05 N/A 8.5 E-06 N/A N/A N/A 3.06E05DN/A

Berylliuma 0.1/1.0 c 2.0E-07 N/A 5.0 E-06 N/A N/A N/A 2.7E06DN/A

Cadmiuma 0.1/1.0 c 4.0E-07 N/A 2.1 E-05 N/A N/A N/A 2.0E06DN/A

Chromiuma 0.1/1.0 d 4.0E-05 N/A 9.5 E-05 N/A N/A N/A 3.1E-05 DN/A

Cobalta 1.0 0.0003 N/A N/A N/A N/A N/A 1.63E04DN/A

Coppera 1.0 4.0E-05 5.6E-04 N/A N/A N/A 3.0E-05 N/A

Lead Compounds 1.0 (organic)

0.1 (inorg.)

N/A N/A N/A N/A N/A N/A 1.41E04D0.14~

(organic)

Manganese a 1.0 N/A N/A 2.1E-05 N/A N/A N/A 3.5E-05 DN/A

Mercury a 1.0 0.0006 N/A 4.0E-05 N/A N/A N/A 9.2E-07 DN/A
EPCRA Section

313 Chemical 

De Minimis

Level*

Crude Oil Gasoline

(Various

Grades)

No.2 Fuel

Oil/ Diesel

Fuel

Jet Fuel

(JP-4)

Kerosene Lubricating

Oil

No. 6

Fuel Oil

Aviation

Gasoline

 

Nickela 0.1 0.0055 N/A 3.38E-04 N/A N/A N/A 2.6E-03 DN/A

Seleniuma 1.0 4.0E-05 N/A N/A N/A N/A N/A 9.5E-06 DN/A

Silvera 1.0 N/A N/A N/A N/A N/A N/A 2.0E-08 N/A

Zinc Compounds 1.0 N/A N/A N/A N/A N/A 1.0 N/A N/A

Unless otherwise noted, Source: Economic Analysis of the Final Rule to Add Certain Industry Groups to EPCRA Section 313, Appendix

B "Composition of Crude Oil and Petroleum Products."

A American Petroleum Institute report prepared for Mr. Jim Durham, EPA (December 23, 1993), regarding revised estimates of heavy

petroleum product liquid constituents that are listed as hazardous air pollutants (HAPs) under section 112 of the Clean Air Act

Amendments (CAAA). 

R Radian Corporation report prepared for Mr. James Durham, EPA (August 10, 1993), regarding liquid HAP concentrations of various

petroleum products.

D Appendix D, Study of Hazardous Air Pollution Emissions from Electric Utility Steam Generating Units--Final Report to Congress,

USEPA, OAQPS (February 1998) 453/R-98-004b.

T

 These values have been revised to be consistent with the current version of EPA’s emission estimation program TANKS 4.0.

* The de minimis concentration values for the metals is for the metal compound.

~

 Lead compounds concentration for Aviation Gasoline 100 (Exxon-MSDS).

‡

 Concentrations updated with comments received from API.

a

 Constituents are most likely metal compounds rather than the elements. Elements are listed in this table because concentration data

are for only the metals occurring in the fuel. Concentrations for metal compounds would be somewhat higher depending on the metal

compound. For threshold determination, if the weight of the compound is not known, facilities may use the weight of the lowest metal

compound likely to be present.

@ Data from EPA report prepared by Radian Co. for this constituent are considered suspect and are not recommended for use, based on

discussion with Jim Durham of EPA on November 30, 1998. 

b

 MTBE may be present to enhance octane in concentrations from 0-15% (industry practice, not sampling results).

c

 The de minimis level for inorganic compounds is 0.1; for organic compounds is 1.0.

d

 The de minimis level for chromium VI compounds is 0.1; for chromium III compounds is 1.0.

e

 The petroleum products may contain one or more of the following chemicals under the polycyclic aromatic compounds (PACs) category:

benz(a)anthracene, benzo (b)fluoranthene, benzo(j)fluoranthene, benzo(k)fluoranthene, benzo(rst)pentaphene, benzo(a)phenanthrene,

benzo(a)pyrene, dibenz(a,h)acridine, dibenz(a,j)acridine, dibenzo(a,h)anthracene, 7H-Dibenzo(c,g)carbazole, dibenzo(a,e)fluoranthene,

dibenzo(a,e)pyrene, dibenzo(a,h)pyrene, dibenzo(a,l)pyrene, 7,12-dimethylbenz(a)anthracene, indeno[1,2,3-cd]pyrene, 5-methylchrysene,

1-nitropyrene. For No. 6 fuel oil, the value given is for benzo(a)anthracene.
Appendix C 

Hester, C., MACTEC, to S. Shedd, EPA/OAQPS/SPPD. Memorandum on Review of Data on 

HAP Content in Gasoline. May 18, 2006. 
TABLE 1. SUMMARY OF HAP DATA, WEIGHT % IN VAPOR

HAP 1994 NESHAP BID 1994 NESHAP BID February 23, 2005 Current Data F

Normal Gasoline Oxygenated Gasoline Memo - OTAQ data Review

Benzene 0.90 0.90 0.74 0.27 

Cumene 0.01 0.01 0.01 0.012 

Ethylbenzene 0.10 0.10 0.14 0.053 

N-hexane 1.60 1.60 1.6 1.8 

MTBE 0.00 11.90 2.4 2.4 

Naphthalene 0.05 0.05 0.046 0.00027 

Toluene 1.30 1.10 1.3 1.4 

Xylene 0.50 0.40 0.53 0.56 

2,2,4-Trimethylpentane 0.80 0.70 0.83 0.75 

Total 5.26 16.76 7.6 7.3 

*Future (2015) assumes:

1) Benzene content reduction in proposed MSAT rule is implemented, and that implementation does not chan

concentrations.

2) MTBE is replaced as an oxygenate because of groundwater contamination issues related to its use.
Appendix D 

RTI International. Draft Emission Estimation Protocol for Petroleum Refineries. For 

EPA/OAQPS. December 2009. 
Appendix A—Avera

Table A-1. Refinery Average Stream Hazardous Air Pollutant Compositions—Default Values 

CAS 

Number HAP Component 

Gasoline Alkylate Crude Oil Reformate Naphtha Avg. Co

Liquid Vapor Liquid Vapor Liquid Vapor Liquid Vapor Liquid Vapor Liquid 

106-99-0 1,3-Butadiene 0.0037 540-84-1 2,2,4-Trimethylpentane 4.72 0.953 35.4 9.4 0.263 0.247 0.799 0.355 8.51 

71-43-2 Benzene 1.61 0.626 0.118 0.061 0.446 0.807 4.61 3.32 1.244 1.06 1.61 92-52-4 Biphenyl 0.01 0 0 0 0.061 0.00002 0.025 0 0 0 0.02 

1319-77-3 Cresols 0.789 0.00065 0 0 0.218 0.0008 0.141 0.0002 0.0191 0.00003 0.23 

98-82-8 Cumene 0.849 0.01565 0.004 0.0001 0.126 0.0108 0.968 0.033 0.91 0.0368 0.57 

100-41-4 Ethylbenzene 1.605 0.0631 0.011 0.0006 0.346 0.0633 3.73 0.272 1.366 0.118 1.41 110-54-3 Hexane 7.138 4.428 3.22 2.63 2.46 7.11 3.9 4.48 7.53 10.27 4.85 

1634-04-4 Methyl tertiary-butyl ether 3.54 3.62 0 0 0 0 0 0 0 0 0.71 

91-20-3 Naphthalene 0.444 0.0006 0.012 0.00002 0.219 0.00125 0.798 0.0018 0.399 0.0011 0.37 

108-95-2 Phenol 0.0551 0.0001 0 0 0.323 0.0031 0.0276 0.0001 0.066 0.0003 0.09 100-42-5 Styrene 3.528 0.0882 0 0 0 0 0.0907 0.0042 0 0 0.72 108-88-3 Toluene 7.21 0.842 0.503 0.077 0.878 0.477 14.54 3.14 5.05 1.295 5.64 

1330-20-7 Xylene 7.17 0.235 0.0212 0.0009 1.42 0.216 13.79 0.8367 5.49 0.395 5.58 

Sum of listed HAP 38.7 10.9 39.3 12.2 6.76 8.94 44.0 12.6 22.9 13.5 30.3 
Appendix E 

RTI International. Emission Estimation Protocol for Petroleum Refineries, Version 2.1, ICR 

Response Version. For OAQPS/EPA. February 2011. 
Version 2.1 

Final ICR Draft Appendix A—Average Stream Compositions 

Table A-1. Refinery Average Stream Hazardous Air Pollutant Compositions—Default Values 

Average Weight Percent of Compound in Process Unit Streama

1,3-Butadiene 

106-99-0 

n-Hexane 

 110-54-3 

2,2,4-Trimethyl 

pentane 

540-84-1 

Benzene 

71-43-2 

Toluene 

108-88-3 

Xylenes (total) 

1330-20-7 

Ethylbenzene 

100-41-4 

Cumene 

98-82-8 

1,2,4-trimethyl 

benzeneb

95-63-6 

Naphthalene 

91-20-3 

Biphenyl 

92-52-4 

Styrene 

100-42-5

Process Units 

Atmospheric Distillation 0.01 4.28 0.05 0.86 1.7 1.97 0.63 0.12 0.63 0.25 0.06 0.001

Vacuum Distillation - 0.007 0.004 0.004 0.043 0.020 0.024 0.001 0.020 0.12 0.09 - 

Coking Unit 0.04 2.49 0.75 0.42 1.30 1.76 0.70 0.12 0.70 0.28 0.001 0.19

Cat Hydrocracker 0.03 1.86 1.04 1.27 2.72 2.67 1.02 0.09 1.33 0.20 0.001 0.19

FCCU 0.01 0.99 0.29 1.03 3.28 4.90 1.07 0.10 1.92 0.72 0.43 0.14

CRU 0.009 2.75 0.25 6.34 17.44 17.61 3.88 0.42 5.93 0.87 0.001 0.11

Hydrodesulfurization - 1.89 0.0001 0.37 1.72 1.94 0.37 0.07 0.40 0.25 0.22 - 

Alkylation 0.22 1.57 25.24 0.03 2.05 0.08 5.0E-5 5.0E-5 5.0E-5 5.0E-5 5.0E-5 0.02

Isomerization - 3.22 0.01 0.51 0.64 0.15 - - - - - - 

Polymerization - 0.54 0.73 1.24 1.76 1.18 0.09 - - - - 

Products 

Aromatics Extract - 

Benzene - - - 99.99 0.009 0.002 - - - - - - 

Aromatics Extract - 

Toluene - - - 0.296 95.61 3.49 2.82 - 0.3 - - - 

Aromatics Extract - 

Xylenes - - - - - 77.89 16.08 0.59 - - - - 

Aromatics Extract - 

Heavy Aromatics - - - 5.7 19.36 25.03 3.56 0.965 4.94 0.314 - - 

Commercial Jet Fuel - 1.68 0.0006 0.577 0.965 1.22 0.257 0.106 0.815 0.627 0.409 - 

Conventional Gasoline 0.0009 2.22 2.94 1.4c 7.75 6.56 1.490 0.219 3.002 0.415 - 0.0767

Aviation Gasoline - 2.30 - 1.01 7.69 3.37 1.2 0.103 0.5 0.695 - - 

Reformulated Gasoline - 1.36 1.10 0.8c 7 7.31 1.26 0.19 2.52 0.21 - - 

Diesel Fuel - 0.030 0.007 0.004 0.081 0.241 0.053 0.056 0.349 0.285 0.117 - 

Home Heating Oil - - - - 0.108 0.300 0.095 - 0.429 0.453 0.181 - 

Solvent-refined Lubes - - - - - - - - - - - - 

Crude Oil 

9.81E05 1.341 0.185 0.312 0.542 0.811 0.186 0.108 0.377 0.139 0.030 

 

a

 Based on Petroleum Environmental Research Forum (PERF) refinery process stream speciation study (API, 2002), 

unless otherwise specified. 

b

 1,2,4-Trimethylbenzene is not a HAP, but it is a prevalent VOC in many refinery streams. c

 Average benzene content of conventional and reformulated gasoline based on Fuel Trends Resport: Gasoline 

1995-2005 (U.S. EPA. Report No. EPA420-R-08-002. January 2008), corrected to weight percent using the 

density correction factor of 0.876/0.739 (i.e., 1.16vol%×0.876/0.739 = 1.4wt%; 0.67vol%×0.876/0.739 = 0.8wt%). 
Appendix F 

Todd, M., API, to Air and Radiation Docket. Docket ID No. EPA-HQ-OAR-2010-0600, Letter 

with Comments on EPA’s Proposed Rule – Residual Risk and Technology Review (RTR) for 

National Emission Standards for Marine Tank Vessel Loading Operations. Docket item no. 

EPA-HQ-OAR-2010-0600-0359. Dated December 6, 2010. 
ATTACHMENT 2 – HAP Emissions per Million Gallons of Gasoline Loaded 

The estimated HAP emissions per million barrels per year (M bbl/yr) of gasoline loaded depends upon the 

assumed concentration of volatile organic compound (VOC) vapors in the air/vapor mixture displaced from 

the cargo compartments, and the concentration of HAP constituents in that vapor. 

VOC emission factors. Emission factors for the loading of gasoline at marine terminals are given in Table 

5.2-2 of EPA’s AP-42 document. These values range from 0.7 pounds of VOCs per thousand gallons loaded 

(lbs/103 gal) to 3.9 lbs/103 gal, depending upon the size of the vessel and the prior condition of the cargo 

compartment. The value that would result in the highest emissions estimate, then, would be 3.9 lbs/103 gal. 

HAP content. EPA recommends, in paragraph 7.1.4 of AP-42, the application of Raoult’s Law to determine

the HAP content in the vapor phase of a hydrocarbon mixture from the HAP content in the liquid phase of 

that mixture. Typical HAP concentrations in the liquid phase of normal gasoline may be obtained from 

EPA’s TANKS software program (similar concentrations are given in EPA’s EPCRA Section 313 Industry 

Guidance, Petroleum Terminals and Bulk Storage Facilities, EPA 745-B-00-002, February 2000). The use 

of MTBE in motor gasoline has been phased out in the United States, and thus the concentration of MTBE 

should be given as 0%. Using typical values for the properties of gasoline and a temperature of 60oF, the 

determination of vapor phase concentrations by Raoult’s Law is illustrated in the following table:

RVP Ml A B Pva (psia) Mv

Gasoline 10 92 11.724 5237.273 5.19 66

temp(F) 60 Yi ( Mi / Mvt )

liquid liquid phase liquid temp(C) 15.6 vapor partial vapor HAP/VOC

phase molecular wt. phase pressure pressure phase vapor phase

Wi Mi Xi Antoine's Constants (deg.C) Pi* Pi Yi Zi

Species: {wt percent} {lb/lb-mole} {mole frac.} A B C vapor pressure {psia} {mole frac.} {wt percent}

n-hexane 1.0% 86.18 0.011 6.878 1171.5 224.37 1.9126 0.0204 0.0039 0.51%

benzene 1.8% 78.11 0.021 6.906 1211 220.79 1.1709 0.0248 0.0048 0.57%

iso-octane 4.0% 114.23 0.032 6.812 1257.8 220.74 0.5962 0.0192 0.0037 0.64%

toluene 7.0% 92.14 0.070 7.017 1377.6 222.64 0.3311 0.0231 0.0045 0.62%

ethylbenzene 1.4% 106.17 0.012 6.950 1419.3 212.61 0.1037 0.0013 0.0002 0.04%

xylene (-m) 7.0% 106.17 0.061 7.009 1462.3 215.11 0.0903 0.0055 0.0011 0.17%

cumene 0.5% 120.19 0.004 6.929 1455.8 207.20 0.0479 0.0002 0.0000 0.01%

MTBE 0.0% 88.15 0 6.872 1116.8 224.74 3.2415 0.0000 0.0000 0.00%

naphthalene 0.0% 128.17 0 7.146 1831.6 211.82 0.0024 0.0000 0.0000 0.00%

22.7% = sum of HAP in the liquid sum of HAP in the vapor = 2.56%

This analysis is conservative, in that it uses a benzene concentration of 1.8%, whereas actual benzene 

concentrations in gasoline in the United States has been driven down to the range of 0.5-0.6% by EPA’s 

Fuels Specifications. Nevertheless, the HAP concentration in the vapor phase will be rounded up to 3% for 

purposes of this illustration.