EPA/AA/TSS/83-6
Technical Report
Determination of a Range
of Concern for Mobile
Source Emissions of Methanol
by
Craig A. Harvey
July, 1983
NOTICE
Technical reports do not necessarily represent final EPA
decisions or positions. They are intended to present
technical analyses of issues using data which are currently
available. The purpose in the release of such reports is to
facilitate the exchange of technical information and to
inform the public of technical developments which may form
the basis for a final EPA decision, position or regulatory
action.
U. S. Environmental Protection Agency
Office of Air, Noise and Radiation
Office of Mobile Sources
Emission Control Technology Division
Technical Support Staff
2565 Plymouth Road
Ann Arbor, Michigan 48105
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Summary
This paper describes an effort by the Emission Control
Technology Division of the EPA to suggest a range of concern*
for methanol (CH^OH) emissions from mobile sources. In
light of the action called for in section 202(a) (4) of the
Clean Air Act (CAA) (1)** and due to a concern within
industry as to what emission levels will be used as the basis
for the evaluation of current and future technologies, a
methodology was developed in order to bracket a range of
concern for various unregulated pollutants (2). This paper
uses the results from two EPA contracts to apply this
methodology specifically for an evaluation of methanol.
Mathematical models previously designed for various exposure
scenarios (such as enclosed spaces, expressways, and street
canyons) were used to calculate the ambient air
concentrations resulting from a range of potential mobile
source methanol emissions. It was assumed that methanol
*Range of concern is defined as a range of ambient
concentrations (or corresponding vehicle emissions) of a
given pollutant, the upper limit of which is the value above
which the studies show that the pollutant causes so great a
health risk as to strongly suggest it be avoided; the lower
value of the range will be the lowest level at which there is
some suggestion of adverse physiological effects.
**Numbers in parentheses denote references listed at end of
report.
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fueled vehicles would have to meet the same HC, CO, and NOx
emission standards as gasoline fueled vehicles currently
meet. In order to get a worst case estimate it was also
assumed that the entire vehicle fleet would be methanol
fueled with up to 25% having severe malfunctions.
In conjunction with this work, a health effects literature
search for methanol was conducted by Midwest Research
Institute under contract to EPA to aid in the determination
of the suggested range of concern (3) . The health effects
associated with exposure to methanol ranged from weakness,
shallow breathing and rapid pulse, to headaches, nausea,
vertigo, vision defects, convulsions, and death, depending on
exposure and individual susceptibility.
The results of the Midwest analysis suggest a range of
concern for ambient methanol concentrations of from 4.5 mg/m
to 260 mg/m .* This corresponds to motor vehicle emission
levels of from 1.58-91 g/mile to 107.1-6190.5 g/mile
depending on the type of scenario chosen to represent public
exposure. If the entire vehicle fleet were to run on
methanol fuel, the estimated fleet emission factors are below
the ranges of concern for all expressway and street canyon
scenarios, as well as the typical tunnel scenario. In the
*1 mg/nH = 0.764 ppm.
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severe roadway tunnel scenario, if 25% of the vehicles are
assumed to be malfunctioning severely (e.g., non-functional
catalyst), the resulting methanol concentration could be
somewhat higher than the lower limit of the range of concern.
Parking garages are also estimated to remain below the range
of concern, but personal garages could have methanol
concentrations within the range of concern for brief periods
of time due to vehicle warm-up exhaust emissions or hot soak
evaporative emissions. Exposure resulting from potential
self service methanol refueling (50 mg/m ) is expected to
be within the range but not above it.
It must be mentioned that the range of concern for methanol
suggested in this report is based on its "toxicological
properties and not its photochemical reactivity nor any
possible carcinogenic effects. The consideration of the
photochemical reactivity and oxidant formation due to
methanol is an important one but beyond the scope of this
report. Furthermore, potential combined effects of exposure
to other pollutants along with methanol have not been
considered here.
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I. Introduction
Changing technology (including different vehicle powerplants,
fuels, and emission control systems) can significantly change
the emissions from automobiles. This report deals with
methanol emissions because of the possible use of methanol as
an automotive fuel. The Clean Air Act requires EPA to
evaluate the health risks of new vehicle technologies.
Methanol in vehicle exhaust results from incomplete
combustion of methanol fuel in the engine, in the exhaust
system, or in the catalytic converter. Other sources of
methanol from vehicles are evaporative methanol emissions and
refueling emissions.
Due to its toxic properties and the potential increased use
of methanol as an automotive fuel, tests have been conducted
to characterize methanol emissions as a function of driving
cycle, engine type, and emission control system. These test
results along with health effects test data determine whether
methanol emissions from mobile sources could be of concern
with respect to health and welfare.
To establish a range of concern for exposure to methanol via
inhalation, Midwest Research Institute (MRI) compiled
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information on its health effects in different exposure
situations (3) . That work forms the basis for the vehicle
emissions range of concern suggested in this report.
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II. General Information on Methanol
Methanol is a colorless flammable liquid with a lower heating
value (heat content) half that of gasoline and a vapor
pressure (volatility) about one third to one half that of
gasoline. It burns in air with a transparent blue flame
producing mostly H20 and C02.
Methanol is used in industry as a solvent, a denaturant for
ethanol, a dehydrator for natural gas, and as a raw material
in the production of formaldehyde, methacrylates,
methylamines, methyl halides, ethylene glycol, and plastics.
Methanol is a well-known poison, discussed today in most
standard reference works on toxic chemicals, "in the past,
methanol's toxicity was debated, and, as late as 1936, doubts
existed as to the toxicity of pure methanol. The toxicity of
wood alcohol was attributed to its impurities by some
authorities (4). A 1904 report by Wood and Buller documented
the earliest recorded cases of methanol poisoning; it stated
that 275 cases of blindness or death attributable to wood
alcohol were reported between 1856 (when the first scientific
report of toxicity was made) and 1904 (5). Nevertheless,
methanol was a frequent component of liniments, toilet
articles, perfumes, and some patent medicines well into this
century.
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Even today, exposure to small amounts of methanol occurs from
a wide variety of sources. For instance, cigarettes have
been found to contain 100 - 200 ug methanoI/cigarette (6) ,
and certain vegetables such as Brussels sprouts, celery,
onions, parsnips, potatoes, and rutabaga have been reported
to contain "large" or "very large" levels (unquantified) of
methanol after boiling for 30 minutes (7). Occupational
exposures to methanol are certainly possible in those
industrial uses mentioned above, but the data available on
this are very limited.
Alcoholic beverages which contain ethanol and which may be
contaminated with methanol may also contribute to an
individual's exposure to methanol and accumulation of
methanol in the blood. Levels of 3.9 to 105.5'mg methanol/
liter have been reported in commercial alcoholic beverages
(8,9,10).
Alcoholics with high blood ethanol levels (100 mg/100 ml)
tend to accumulate methanol in their blood at levels up to
2.7 mg/100 ml after an eleven day intoxication (9). Some of
the methanol accumulated by alcoholics is believed to be
derived from endogenous (originating within the body) sources
and accumulated due to ethanol's disruption of methanol
oxidation and elimination. That some methanol is
endogenously produced is supported by studies finding
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raethanol levels of 0.06 to 0.49 mg/m and 0.40 to 4.52
rag/m (0.3 to 3.4 ppm) in normal human breath(11,12) .
Another study of 54 healthy nonsmoking adults found only 3.6%
of 387 breath samples to contain methanol; the mean
concentration when found was 0.549 mg/m (13).
In the section of this report concerning ambient
concentrations, potential exposures from motor vehicles are
given which can be compared to the exposures mentioned above.
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III. Legislative Background
The Clean Air Act amendments of August 1977 included sections
202 (a) (4) and 206 (a) (3) which deal with mobile source
emissions of hazardous pollutants from vehicles manufactured
after 1978. These sections are as stated below:
202 (a) (4)
11 (A) Effective with respect to vehicles and engines
manufactured after model year 1978, no emission control
device, system or element of design shall be used in a
new motor vehicle or new motor vehicle engine for
purposes of complying with standards prescribed under
this subsection if such device, system, 6"r element of
design will cause or contribute to an unreasonable risk
to public health, welfare, or safety in its operation or
function.
(B) In determining whether an unreasonable risk exists
under subparagraph (A), the Administrator shall consider,
among other factors, (i) whether and to what extent the
use of any device, system, or element of design causes,
increases, reduces, or eliminates emissions of any
unregulated pollutants; (ii) available methods for
reducing or eliminating any risk to public health,
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welfare, or safety which may be associated with the use
of such devices, systems, or elements of design which may
be used to conform to standards prescribed under this
subsection without causing or contributing to such
unreasonable risk. The Administrator shall include in
the consideration required by this paragraph all relevant
information developed pursuant to section 214."
206 (a)(3)
" (3) (A) A certificate of conformity may be issued under
this section only if the Administrator determines that
the manufacturer (or in the case of a vehicle or engine
for import, any person) has established to the
satisfaction of the Administrator that "any emission
control device system, or element of design installed on,
or incorporated in, such vehicle or engine conforms to
applicable requirements of section 202(a)(4).
(B) The Administrator may conduct such tests and may
require the manufacturer (or any such person) to conduct
such tests and provide such information as is necessary
to carry out subparagraph (A) of this paragraph. Such
requirements shall include a requirement for prompt
reporting of the emission of any unregulated pollutant
from a system, device or element of design if such
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pollutant was not emitted, or was emitted in
significantly lesser amounts, from the vehicle or engine
without the use of the system, device, or element of
design."
Prior to these amendments, EPA's guidance to the
manufacturers regarding hazardous unregulated pollutants was
contained in the Code of Federal Regulations, Title 40,
section 86.078-5b. This subsection is stated as follows:
(1) "Any system installed on or incorporated in a new
motor vehicle (or new motor vehicle engine) to
enable such vehicle (or engine) to conform to
standards imposed by this subpart:
(i) Shall not in its operation or function
cause the emissions into the ambient air of any
noxious or toxic substance that would not be
emitted in the operation of such vehicle (or
engine) without such system, except as
... •• >»•*»
specifically permitted by regulation; and
(ii) Shall not in its operation, function, or
malfunction result in any unsafe condition
endangering the motor vehicle, its occupants,
or persons, or property in close proximity to
the vehicle.
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(2) Every manufacturer of new motor vehicles (or new
motor vehicle engines) subject to any of the
standards imposed by this subpart shall, prior to
taking any of the action specified in section 203
(a) (1) of the Act, test or cause to be tested motor
vehicles (or motor vehicle engines) in accordance
with good engineering practice to ascertain that
such test vehicles (or test engines) will meet the
requirements of this section for the useful life of
the vehicle (or engine)."
Before certification can be granted for new motor vehicles,
manufacturers are required to submit a statement, as well as
data (if requested by the Administrator) , which will
ascertain that the technology for which certification is
requested complies with the standards set forth in section
86.078-5b. This statement is made in section 86.078-23(d).
The EPA issued an Advisory Circular (AC 76) in June 1978, to
aid the manufacturers in complying with section 202 (a) (4) .
Manufacturers were asked to continue providing statements
showing that their technologies did comply with the vehicle
emission standards and also will not contribute to an
unreasonable risk to public health and safety.
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Another Advisory Circular (AC 76-1) was issued in November of
1978 continuing these procedures for 1980 and later model
years. At that time, EPA began work to develop and implement
a methodology which would provide a preliminary assessment of
potential mobile source unregulated pollutant hazards in
order to assist the manufacturers in deciding which, if any,
unregulated pollutants are of particular concern.
Up to this time, several preliminary assessments have been
made covering sulfuric acid, hydrogen cyanide and ammonia.
In each of these cases, the preliminary assessment found no
reason for suspecting a public health problem from the
current fleet emissions of these pollutants, and recommended
that further monitoring may be appropriate to be sure that
new vehicle/emission control system configurations did not
result in greatly increased emissions.
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IV. Methodology Overview
Along with the previously mentioned activities, EPA, with the
input from several interested parties, has developed a
methodology for implementing section 202 (a) (4) of the CAA.
This approach is explained in detail in EPA report number
EPA/AA/CTAB/PA/81-2, "An Approach for Determining Levels of
Concern for Unregulated Toxic Compounds from Mobile Sources"
(2) . Only a brief summary of this methodology will be
presented in this report.
Under contract to EPA, Southwest Research Institute (SwRI),
and Midwest Research Institute (MRI), have provided valuable
information for this effort. SwRI developed or modified
mathematical models for predicting ambient concentrations of
mobile source pollutants for exposure situations including
enclosed spaces, street canyons, and expressways. Once
vehicle emissions for various vehicle categories have been
determined for a particular pollutant, these models are used
to calculate ambient concentrations for both severe and
typical exposure situations for each scenario.
Health effects literature searches have been conducted by MRI
to aid EPA in suggesting a range of concern for various
selected pollutants. The upper level of the range is that
value above which the studies show that the pollutant causes
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so great a health risk as to strongly suggest it be avoided.
The lower value of the range will be the lowest level at
which there is some suggestion of adverse physiological
effects. The region between these limits will be termed the
"ambient air range of concern", indicating the bounds of
uncertainty regarding evidence of adverse physiological
effects caused by exposure to various concentrations of the
pollutant. Any technology whose emissions result in ambient
air concentrations within the range of concern should be
subject to closer scrutiny. Technologies with emission
levels above the highest value of the range should be
considered "high risk" with respect to human health.
For the purpose of this report, this particular methodology
has been used to develop a suggested range of concern
specifically for motor vehicle emissions of methanol.
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V. Vehicle Emissions of Methanol
This report considers only vehicles using 100% methanol
fuel. Nationwide methanol emissions from motor vehicles are
currently negligible due to the small number of methanol
fueled vehicles, but the technology does exist to increase
this use of methanol. Therefore, the following discussion
examines the hypothetical scenario in which all vehicles are
methanol fueled, as well as an intermediate scenario having
25% of the fleet methanol fueled.
The data in Table 1 are based on the assumption that methanol
fueled vehicles will have to meet the same emission standards
that gasoline fueled vehicles now meet, in order to be
certified for sale. It is further assumed "that on the
average, in-use vehicles will exactly meet the HC standard,
except those with malfunctions. The hydrocarbon (HC)
standard (e.g. 0.41 g/mi for light duty vehicles on the FTP)
would presumably apply only to the HC portion of any unburned
alcohol in the exhaust or evaporative emissions. Since HC
comprises only 50% of the mass of methanol, the standard to
be met for actual methanol emissions would in effect be
double that for gasoline (e.g. 0.82 g/mi for light duty
vehicles on the FTP).
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In order to better characterize methanol emissions and
exposures under certain potential high concentration
conditions, a few scenarios are considered which differ
considerably from standard FTP conditions. For instance, the
Hot Start FTP column in Table 1 was derived by taking the
ratio of Hot FTP emissions to regular FTP emissions from
actual methanol vehicle tests (23,25), and then multiplying
that ratio by the emission standard for the FTP. This was
also done for the highway (HFET) column. This was done to
provide a more realistic emissions estimate for scenarios
such as tunnels or highways where cold start emissions would
not normally be encountered.
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Table 1
Vehicle Emissions3
100% Methanol-Fueled Fleet
g/mile
Light Duty Heavy Dutyb Weighted Average0
Scenario
(Driving Cycle With 25% With 25% With 25%
Used) Normal Malfunction Normal Malfunction Normal Malfunction
Street
Canyon ^
(FTP)
Roadway Tunnel
(Hot FTP)
Expressway
1.17
0.08
0.02
2.60
1.22
0.19
5.47
4.05
2.88
11.03
8.94
3.81
1.44
0.33
0.20
3.12
1.70
0.41
(HFET)
(7-Mode S.S.)
Personal &
Parking
Garages (Idle)
0.007e 0.24e
0.007e 0.24e
aBased on expected compliance with light-duty FTP hydrocarbon
standard of 0.41 g/mile (0.82 g methanol/mi) and heavy-duty HC
standard of 1.3 g HC/BHP-hr.
bg/KW-hr engine data converted to g/mile assuming 3 miles/gal
methanol, 0.708 kg fuel/kw-hr.
C93.8% light-duty, 6.2% heavy-duty vehicle miles traveled.
dlncludes evap emissions @ 0.35 g/mi for light-duty and 0.54 g/mi
for heavy-duty, based on 1985 evap standards (2.0 LD, 3.0/4.0 HD HC
g/test) .
eg/minute results from one vehicle; 0.007 is with a warmed up engine
and catalyst; 0.24 is with a warmed up engine and no catalyst.
applicable to scenarios studied.
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Light Duty Vehicles - Urban Emissions (FTP)
For the street canyon scenario, the FTP was chosen as the
most representative driving cycle of those available. The
first column of Table 1 shows the expected methanol exhaust
emissions (0.82 g/mi) based on an HC standard of 0.41 g/mile,
multiplied by 2 to account for the oxygen content of
methanol. Recent tests on properly functioning 4-cylinder
vehicles with oxidation and/or 3-way catalysts yielded
methanol emissions less than this value. For instance, Ford
Pintos with different degrees of engine modifications emitted
between 0.3 and 0.6 g/mile (22), and a recent EPA test
program using a methanol-fueled VW Rabbit and Ford Escort
yielded emissions of 0.1-0.5 g/mile (15).
Hot Start "FTP"
For the severe case tunnel scenario, the average speed is 25
mph, so of the data available, the FTP was again chosen as
the most representative driving cycle. However, in a tunnel,
vehicles are assumed to be warmed up already so the hot start
portion of the FTP data were used (Bags 2 and 3) . The data
collected for this show the hot start methanol emissions to
be approximately 10% of the corresponding FTP emissions, not
including the evaporative emissions, since they would not be
a factor in emissions while actually driving. Using this
proportion together with the effective FTP standard of 0.82
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g/mile, the expected methanol exhaust emissions from the hot
start portion of the FTP would be 0.08 g/mile.
Highway Emissions (HFET)
The EPA driving cycle chosen to represent the expressway
scenario is the Highway Fuel Economy Test (HFET) with its
average speed of 48.2 mph. Recent data (23, 25) from
methanol fueled vehicles with 3-way catalysts and oxidation
catalysts (VW, 3-way catalyst prototypes) show the HFET
methanol exhaust emissions to be about 98% lower than the
methanol emissions from the FTP. Applying this percent
reduction to the FTP standard yields expected emissions of
0.02 g/mile for highway driving conditions. As with the hot
start FTP calculations for the tunnel s'cenario, the
expressway scenario does not include evaporative emissions.
Two contributing reasons for this large difference between
FTP and HFET emissions could be differences in engine speed
and differences in the thermal condition of the catalyst.
The FTP includes a cold start with a large fraction of the
overall emissions being emitted in the first part of the test
before the catalyst is warmed up, but in the highway test,
the catalyst is already warmed up. Some supporting evidence
for the engine speed effect is found in two studies (17,25)
using steady state tests. The first of these showed 95%
lower methanol emissions at 3000 rpm than at 1000 rpm and the
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second one showed a 25% - 65% decrease in methanol emissions
at 50 mph relative to 30 mph. The actual engine speed in the
HFET is a function of the vehicle transmission and axle gear
ratios which may vary.
Heavy Duty Engines
As with light duty vehicles, heavy duty engines need to meet
certain EPA criteria. The regulations call for no more than
1.3 g hydrocarbons per BHP-hr beginning with the 1985 model
year. This, again, would probably apply only to the HC
portion of any unburned fuel, so the effective limit for
methanol exhaust emissions would be 2.6 g/BHP-hr.
For comparison, testing of a M.A.N. methanol-fueled heavy
duty engine with an oxidation catalyst yielded methanol
exhaust emissions of 0.4 g/BHP-hr (0.5g/kW-hr) on the 7 mode
test and 0.7 g/BHP-hr (0.9 g/kW-hr) on the transient test
procedure. Another engine, made by Volvo, used injection of
a pilot charge of diesel fuel to ignite the methanol charge.
When tested with an oxidation catalyst, the unburned methanol
emissions were 0.67 - 0.75 g/BHP-hr (0.9 - 1.0 g/kW-hr) .
Without a catalyst these emissions increased to 1.6 - 3.7
g/BHP-hr (2.2 - 4.9 g/KW-hr) on the 7 - mode and transient
tests, respectively.
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To put these power-specific emissions into terms of g/mile,
they can first be converted to g/kg fuel by dividing by the
fuel consumption (kg fuel/kW-hr). Then, using fuel economy
data from other heavy duty diesel tests (29) ranging from 44
- 69 liters/100 km, and adjusting for the different energy
content of methanol vs. diesel fuel, a corresponding range of
methanol emission factors on a per-mile basis can be
calculated. This is how the heavy duty engine emission
estimates shown in Table I were derived.
Evaporative Emissions
Emissions of evaporated fuel from methanol vehicles can
contribute significantly to the overall vehicle methanol
emissions. Therefore these emissions are included, where
appropriate, in the fleet average emissions in Table I.
These numbers include both diurnal heat build and hot soak
evaporative emissions as specified in the Federal Register
test procedure.
As was done with the FTP emissions above, we will assume that
the evaporative gasoline standards would apply to the HC
portion of evaporative emissions from methanol fueled
vehicles. This would result in maximum methanol evaporative
emissions of 4.0 g/test for light duty vehicles and 6.0 or
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8.0 g/test for heavy duty engines and vehicles, depending
upon their Gross Vehicle Weight Rating (GVWR).
These values can be converted into grams/mile for any
scenario that would include evaporative emissions - namely
street canyons. This is done by taking the total evaporative
emissions per day (diurnal plus hot-soak) and then dividing
by the miles driven per day. According to MOBILE2, in urban
areas, the average light duty vehicle makes 3.05 trips/day,
totalling 31.1 miles. Therefore, to estimate the equivalent
g/mile emissions of a car meeting a 4.0 g/test methanol
evaporative standard, it is necessary to know how much of the
4.0 grams is hot soak vs. heat build.
The hot soak test emissions are usually greater "than the heat
build emissions. For example, in-house tests of a
fuel-injected methanol fueled VW Rabbit have shown hot soak
test emissions to be approximately 1.3 times greater than
heat build emissions (25) . In similar tests at the
University of Santa Clara, the ratio was about 3.0 (28). A
couple of carbureted cars (1980 Ford Pintos modified to run
on methanol) have also been tested. For these vehicles the
ratio of hot soak to heat build emissions were greater,
averaging 10.0.
From this rather limited data it appears that a reasonable
rough estimate of the ratio of hot soak (HS) to heat build
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(HB) emissions for methanol fueled vehicles would be 5.O.*
From this, the grams methanol/mile can be calculated, based
on a vehicle just meeting a 2.0 g/test evaporative HC
standard.
(1) HS + HB = 4.0 grams methanol
(2) HS = 5 x HB
HB = 0.67 grams methanol
HS = 3.33 grams methanol
With one heat build/day, 3.05 hot soaks/day, and 31.1
miles/day, this results in 0.35 g methanol/mile.
Of the cars that have been tested so far, "only one has
exceeded these estimates - a carbureted 1980 Ford Pinto
(designed to meet the California 2 g/test HC standard) with a
total of 5.7 g/test. The other test vehicles ( VW Rabbit,
Ford Pinto, and Ford Escort) have ranged from 1.2 - 2.4
g/test by FID measurement uncorrected for methanol response,
*The corresponding ratio for gasoline fueled vehicles, per
MOBILE2, is 0.59. It is not certain why there should be that
much difference between methanol and gasoline, but it could
possibly be related to the much greater heat of vaporization
of methanol necessitating greater temperature for a given
rate of evaporation. The FTP before the hot soak may result
in a higher temperature or rate of vaporization compared to
the heat build.
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which would be about 1.6 - 3.2 g/test if a typical methanol
response factor of 0.75 is assumed.
Heavy Duty Evaporative Emissions
As mentioned above, the heavy duty vehicle evaporative
emission standards beginning in model year 1985 (depending on
GVWR) are 3.0 and 4.0 g EC/test, which corresponds to 6.0/8.0
g methanol/test. Per Mobile 2, the hot soak portion of the
test contributes 37% of the total test emissions for 1984 and
later model years, which methanol fueled vehicles would be.
This fraction is based on gasoline data since no methanol
fueled heavy duty evaporative data are available. Going
through the calculation to determine g/mile, as was done with
light duty vehicles, but using 6.88 trips/d'ay and 36.70
miles/day for heavy duty vehicles yields 0.53 g/mile up to
14,000 GVWR and 0.70 g/mile methanol over 14,000 GVWR.
For purposes of computing an average heavy duty evaporative
emission rate, the above two numbers need to be weighted
according to their respective fractions of urban VMT. Using
data from the MVMA (33) , only 5% of the non-highway urban
truck VMT is from combination trucks. This should serve as a
good approximation of the truck VMT fraction over 14000
GVWR. Therefore, the weighted average heavy duty vehicle
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evaporative methanol emissions are estimated to be 0.54
g/mile.
Malfunction Conditions
A certain percentage of in-use vehicles have been found to
operate in a less-than-optimum condition (34). For instance,
a disconnected air injection system or a catalyst that has
been either removed or poisoned with use of improper fuel
will all increase emissions. The resulting emissions depend
on the type and degree of malfunction, but at this time the
most data are available for a severe malfunction. This would
be the lack of a catalyst as compared to the presence of a
working catalyst, including particularly the case of a
catalyst equipped vehicle tested without a catalyst. Such a
comparison shows the "malfunctioning" (no catalyst) vehicle
methanol emissions to be much greater than catalyst equipped
vehicles (references: no cat. 14 through 21,25; catalyst 15,
18 through 23,26,27,28). Table II gives the ratios used in
computing the malfunction values in Table I. These are based
on test data from one or more vehicles/engines.
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Table II
Ratios of Malfunction (no catalyst)
to Non-Malfunction Exhaust
Methanol Emissions
HFET
FTP Hot FTP (HP 13-mode) Idle
8.0
5.5
58.0
5.8
35.0
2.3
34.3
Not used
Light Duty
Heavy Duty
The potential effect of these malfunctions on ambient air
concentrations of methanol is shown in columns 2 and 4 of
Table III with 25% of the vehicles assumed to be
malfunctioning. The 25% malfunction fraction was arrived at
from FOSD* data indicating that in areas without
Inspection/Maintenance, after 50,000 miles, 26% of the
vehicles had at least one of the three malfunctions described
above.
*FOSD: EPA Office of Mobile Sources Field Operations and
Support Division.
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VI. Methanol Ambient Air Concentrations
The methanol emission factor information provided in Table I
can be used, in conjunction with the modeling techniques
developed by Southwest Research Institute (2,33), to
calculate the ambient air concentrations produced. Future
work may identify other scenarios which would also be
appropriate for the assessment of human exposure to exhaust
pollutants, but, for this task, five exposure scenarios were
investigated: roadway tunnels, street canyons, personal
garages, parking garages and urban expressways. Two case
situations, "typical" and "severe", were developed tor each
of the first four scenarios, and three cases were considered
for the expressway scenario. Each situation has been
considered separately; no cumulative effects have been
determined at this point for these or other exposures to
methanol. Reference (2) discusses the reasoning behind using
these specific scenarios as well as the information used in
the determination of the modeling techniques.
Table III presents ambient air concentrations of methanol
calculated from the vehicle emissions listed in Table I for
seven ambient situations. Evaluations of the garage
situations are based on idle emission data from only one
vehicle and evaporative emissions from five vehicles.
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Two specific tunnel designs were chosen to estimate the two
roadway tunnel cases. A newly designed, two lane roadway
tunnel, with moderate traffic flow, is used for the typical
condition, while an old design, heavily-traveled roadway
tunnel is used for the severe condition (2) . The
calculations for the typical tunnel exposure situation will
be developed to show how the other concentrations were
determined.
From Section V of this report, the average methanol emissions
from light and heavy duty vehicles in a typical tunnel would
be 0.38 g/mile. Per the model developed by Southwest
Research Institute (2) , an average emission factor of 1
g/mile of any pollutant for traffic in a typical roadway
tunnel would result in a concentration of I."l2 mg/m for
that pollutant. Multiplying this by the average emissions of
0.38 g/mile gives an expected methanol concentration of 0.43
mg/m .
The street canyon situations are simulated by examining the
parameters of two street canyons. The typical condition is
calculated for a four lane street canyon with a traffic load
of 800 vehicles per hour and sidewalk location of the exposed
population. The severe condition is based on a six lane
street canyon with a 2400 vehicles per hour traffic load, and
sidewalk location of the exposed population.
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Three different cases were considered in order to cover the
possible range of exposures in an expressway situation. The
typical on road exposure is based on a four lane expressway
with a traffic load of 1400 vehicles per hour and a wind of
1.0 meter/second at 315 degrees to the direction of travel.
In this situation, the exposed population is located inside
the vehicle. The severe case represents an identical
situation except with much more traffic (3675 vehicles/hour),
on a ten lane freeway. The third case necessary to consider
is the "off road" case which is an exposure involving a close
proximity to the highway (i.e., living or working close to
it) . This case is calculated on a short term basis (rush
hour) for a distance of 100 meters downwind of the roadway.
Garages
The typical personal garage situation represents a 30 second
vehicle warm-up time, and the severe situation simulates a
five minute vehicle warm-up time. Both of these cases, of
course, take place within a residential garage with the door
open, and are intended to correspond to summer and winter
conditions, respectively. Evaporative emissions, as well as
idle emissions will be examined.
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Currently, methanol idle emission data are only available
from one vehicle - a VW Rabbit tested with various catalysts
and calibrations. Methanol emissions at idle range from
0.001 to 0.034 g/min.f averaging .007 g/min. However, these
tests are with a warmed up engine and catalyst rather than
cold-starts as would occur in a garage scenario. So, a more
accurate assessment of cold-start idle emissions might come
from using idle tests of this vehicle without a catalyst.
These data range from 0.18 to 0.31 g/min., with an average of
0.24 g/min. In a personal garage under the severe exposure
situation, 0.24 g/min would yield a methanol concentration of
16.08 mg/m3.
Evaporative emissions in a personal garage are potentially a
greater problem than start-up emissions, because the garage
door would more likely be closed, reducing the ventilation
from 615 cfm to 20 cfm. Only the hot soak situation will be
examined, since these emissions are usually greater than the
diurnal heat build emissions of methanol.
To calculate expected methanol concentrations from
evaporative emissions, it will first be assumed that vehicles
will meet the standard of 2.0 g EC/test. As described in
Section V, this would result in one-hour hot soak methanol
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emissions of 3.33 grams due to inclusion of the oxygen mass.
in a typical residential garage of 2189 ft (61.95 m )
the resulting concentration of methanol, neglecting
3
ventilation, would be 54 mg/m . With ventilation taken
into account (20 cfm), the lower bound on the concentration
would be 30 mg/m . This figure corresponds to an initial
concentration of 54 mg/m reduced over a one hour time
period by ventilation at 20 cfm, with no further methanol
evaporated during that hour. Since what actually occurs
(continuous evaporation and continuous ventilation) is
somewhere in between 54 mg/m and 30 mg/m , the
concentration corresponding to 3.3 grams of evaporated
methanol is estimated to be 40 mg/m .
The exposure to this concentration of 40 mg/m would occur
only if a person re-enters the garage within the hour, and
the exposure will also usually be short, lasting from the
time the person enters the garage until either the
ventilation from the opened garage door reduces the methanol
concentration significantly or the person drives out of the
garage. After 10 minutes with the garage door open the
concentration in the garage would drop by 94% (3, Figure 21) .
The typical parking garage case simulates an above the
ground, naturally ventilated garage in which it is assumed
that a vehicle spends an equal amount of time on both the
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parking level and ramp level. The emission factors used in
this scenario are idle emissions, since there are no data
available for any parking garage driving cycle. The severe
case represents an underground garage wherein the exposed
population is assumed to be at the lowest parking level. It
is also assumed that this exposure occurs 20 minutes after a
major event in which the parking structure is emptying from
an essentially full condition. The initial concentration of
methanol is assumed to be low (1 ug/m ) , since the
ventilation system in a parking garage would remove most of
the evaporative emissions as they occur (2).
Concerning evaporative emissions in a parking garage, the
only potentially high concentration situation would be
following the arrival of many vehicles, which th'en proceed to
give off hot soak emissions. This is not expected to be a
problem for two reasons. First, there is plenty of
ventilation (30,000-40,000 cfm per parking level compared to
20 cfm for a closed-door personal garage). Secondly,
immediately after parking, the drivers would leave the garage.
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Table III
Ambient Air Scenarios
Methanol Concentrations
Scenario
Entire Fleet
CH30H
Fueled
Entire Fleet
CH30H
Fueled
25%
Malfunction
25% of Fleet
CH30H
Fueled
25% of Fleet
CH30H
Fueled
25%
Malfunction
Roadway Tunnel
Typical 0.43
Severe 1.09
Expressway
Typical 0.02
Severe 0.10
Close 0.02
Proximity
Street Canyon
Typical 0.06
Severe 0.41
Parking Garage
Typical 0.03
Severe 0.39
Personal Garageb
Typical 0.06
Severe 0.47
Hot Soak 40.00
2.87
7.31
0.05
0.21
0.04
0.13
0.88
0.94
3.63
1.90
16.08
40.00
0.11
0.27
0.01
0.03
0.01
0.02
0.10
0.01
0.10,
0.06
0.47
40.00
0.72
1.83
0.01
0.05
0.01
0.03
0.22
0.23
0.91
1.90
16.08
40.00
aBased on weighted average emission factors from Table I.
'•'Since the personal garage scenario considers only one vehicle,
the 25% malfunction and/or methanol-fueled fractions in columns 2,
3, and 4 were not taken.
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Vehicle Refueling Exposures
With the use of methanol as a fuel, another scenario that
needs to be investigated is the exposure encountered by a
vehicle owner filling up his fuel tank at a self service
station. According to 1982 information from EPA's FOSD it
was found that 75% of the refueling is done on a self serve
basis (42) .
The estimate of methanol exposure presented here is a very
rough estimate based on the limited exposure data that was
collected for benzene (43). It was found that a person
refueling a car with gasoline would be exposed to about 0.785
mg/m3 of benzene from gasoline vapor containing 0.8%
benzene. This means a total gasoline vapor exporsure of about
100 mg/m . Since methanol has a vapor pressure
approximately half that of gasoline, a typical refueling
would result in a methanol concentration of about 50
mg/m . The average refueling time for a gasoline fueled
automobile is 1.7 minutes. For methanol, with its lower
energy content, average refueling time would double, to 3.4
minutes on the average.
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VII. Methanol Health Effects
Ingestion Studies
A literature review concerning the health effects of methanol
was performed by Midwest Research Institute (3). In addition
to inhalation data, this review also covered exposures from
ingestion and skin absorption, which could occur with use of
methanol as a vehicle fuel.
Practically all the methanol toxicity data involve its
ingestion with, or as a substitute for, ethanol (ethyl
alcohol). The immediate symptom is an inebriation,
indistinguishable from that from ethanol ingestion. After 12
to 18 hours, the characteristic methanol toxicity appears,
presumably caused by its metabolites, formaldehyde and formic
acid. Symptoms include headache, weakness, leg cramps, and
vertigo; nausea and vomiting sometimes with violent abdominal
pain; back and leg pain; vision defects; rapid, shallow
breathing from metabolic acidosis; and weak, rapid pulse with
hypotension; progressing to apathy and coma, or to
excitement, mania, and convulsions. Death, if it occurs, is
usually from respiratory failure. In nonfatal cases,
convalescence is often protracted and complicated by
debility, blindness, and kidney problems.
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Relatively few experimental studies on methanol toxicity have
been published, and most of them involved very large doses,
mechanistic studies of the retinal toxicity, or both. Most
human reports are case studies, with little exposure data.
Toxicity has occurred from ingestion, inhalation, contact,
and confounded exposure through two or all three routes.
Methanol's toxicity (especially its ocular effects) is
generally believed to be caused by its metabolities, although
its metabolism is not fully understood. In humans and other
primates, methanol is first oxidized to formaldehyde by the
enzyme catalase, but in lower animals this oxidation is
effected by alcohol dehydrogenase. The highly reactive
formaldehyde quickly disappears from the tissue and was
formerly believed to be the cause of toxic effects. More
recently, the further metabolites, formic acid or formate
esters, have been suggested to be the toxic products (38).
Animal Studies
The bioassay data were limited in applicability to human
toxicity, but did demonstrate that in the animal ini vitro
systems studied, methanol is not very toxic and not
mutagenic. In the one in vitro respiratory tissue study, the
exposure to 0.4 to 1.4 mg methanol in aerosol at the rate of
27 ml/sec for 2 seconds inhibited ciliary activity in the
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esophageal tract of the leopard frog. Another study found
low levels of methanol (15 ug) increased release of lung
prostaglandins; higher methanol levels decreased rate of
release (3).
In different animal studies the results varied quite a bit.
Rats exposed to 50 mg/m methanol for 12 hr/day for 8 weeks
developed respiratory tract irritation, liver degeneration,
and cortical neuropathy, but no such effects were found at
1.77 mg/m (39). Similarly, minor toxicity was found in
rats exposed continuously to 5.32 mg/m methanol. Dogs
exposed to about 600 mg/m methanol 18 hr/day for over a
year developed no noticeable adverse effects.
Human Studies
Human experimental studies have not been conducted
specifically to identify methanol health effects by
inhalation, but several studies have determined an odor
threshold for methanol. The highest of these was 7,800
3 3
mg/m , while the lowest was 4.3 mg/m (3).
Experiments have also been conducted measuring eye
sensitivity to light(39). A threshold of 3.3 to 3.7 mg/m
was found for degradation of light sensitivity (dark
adaptation), and 1.8 to 2.4 mg/m had no effect. At a
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concentration of approximately 4.5 rag/m the pattern of
dark adaptation was markedly altered from that of the
controls.
One documented study of occupational exposures to methanol
found that a group of office workers exposed to about 22 to
500 mg/m from spirit duplicating machines experienced
recurrent headaches. Workers who were actually operating the
machines had more severe symptoms (3).
Skin Absorption
Various animal studies have shown methanol exposure via skin
absorption to have effects similar to inhalation (3). Also,
recent work with humans has shown methanol sk'in absorption
and ingestion to result in similar quantities of methanol
being excreted in urine and exhaled air indicating similar
effects on the body.
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VIII. Determination of the Range of Concern and Conclusions
The definition of "range of concern" is that range of
exposure concentrations which may be detrimental to human
health. The lower value of this range would be the lowest
concentration at which there is some suggestion of adverse
physiological effects. The upper value of this range would
be that level above which the studies show that the pollutant
causes so great a health risk as to strongly suggest it be
avoided. The Threshold Limit Value* (TLV) for a given
pollutant is usually appropriate to use as the upper level of
the suggested range of concern.
Although it would be more appropriate to consider exposure
concentrations relative to their corresponding exposure times
for each resulting health effect, this degree of detail was
not feasible with the data available. The determination of
the range of concern was based primarily on acute human
experimental studies, since these were thought to most
closely simulate the exposure situations examined in this
report.
*The Threshold Limit Value, set by the American Council of
Governmental Industrial Hygienists, is the recommended
maximum time weighted average concentration to which workers
can be exposed for an 8-hour work day or 40-hour work week.
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The Threshold Limit Value for methanol inhalation exposure is
260 mg/m , which is suggested as the upper limit of the
range of concern. Although a direct comparison of inhalation
vs. ingestion exposure would not be valid due to
uncertainties in absorption and metabolism processes, it is
interesting to note the correlation that seems to exist in
the exposure range around the TLV.
One reference (40) indicates that the lowest ingested dose at
which some toxic effect occurred for humans was 100 mg/kg
body weight. For a 70 kg (154 Ib) person this translates
into 7 grams or 8.75 ml. Another study (4) cited one unusual
case in which ingestion of only 3 teaspoons of 40% methanol
(6 ml methanol) resulted in death, whereas a third study (41)
reported no toxic reaction from ingestion of about 2 ml. For
comparison, an inhalation exposure at the TLV of 260 mg/m
would yield an 8 hr. cumulative exposure of 3.25 ml if it
were all absorbed (3). However, it is probably not valid to
compare absorption and ingestion in this fashion.
Documentation of adverse physiological effects of low level
methanol exposure is poor, making the selection of a lower
limit to the range of concern difficult. The level suggested
as the lower limit is 4.5 mg/m , which was the level at
which the pattern of dark adaptation markedly altered from
that of the unexposed control sample (39). These changes
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-42-
resulted from a 5-minute exposure, but they were reversible
within a couple hours following exposure.
Below this level certain physiological effects have been
found, such as changes in the alpha-rhythm amplitude of the
cerebral cortex reflex activity (1.17 - 1.46 mg/m ). It is
not known whether these alpha-rhythm changes represent
adverse physiological effects or just altered physiological
parameters. Since the limits of the range of concern are
based on evidence of adverse physiological effects, 4.5 mg/m
is considered to be conservative (i.e. on the low side) for
the lower limit of the range of concern.
The next step in making use of this suggested range of
concern is to translate it into terms of automotive emission
factors for each scenario. Table IV shows fleet average
emission factors that would result in the lower and upper
limits of the ambient air range of concern. Since these
numbers are total emission factors, they include the
evaporative emissions (for the street canyon scenario) as
well as the tailpipe emissions.
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-43-
Table IV
Emission Factors (g/mile) Corresponding to the
Lower and Upper Limits of the Methanol Range of Concern
4.5 mg/m3
260 mg/m3
Roadway Tunnel
Street Canyon
Expressway
(typical)
(severe)
(typical)
(severe)
(typical)
(severe)
(off road)
4.01
1.58
107.14
15.96
36.88
9.09
42.86
231.5
91.0
6190.5
922.0
2131.1
525.3
2476.2
Comparing these figures with the emissions listed in Table I,
it appears that the severe tunnel scenario is the only one of
the roadway scenarios having the potential for exposure
within the range of concern. Using the weighted average
emission factors from Table I, the average em-ission factor
for each scenario can be compared to the corresponding lower
limit of the range of concern. This is done in Table V.
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Table V
Range of Concern Compared to Potential Emissions
grams/mile
A
Limits of
Range of Concern
(Severe Case)3
i.e. Fleet Average
Emissions Needed
to be of concern
B
What Fleet Average Column B
Emissions Would Be with 25%
Assuming 100% CH30H of Fleet
Fueled, Catalyst-equipped Malfunctioning
Vehicles'3 Severely13
Roadway
Tunnel
Street
Canyon
Expressway
1.58- 91.0
15.96-922.0
9.09-525.3
0.38
1.44
0.20
2.56
3.12
0.41
aFrom Table IV
DFrom Table I
As shown in Table V, even if it is assumed that all light and
heavy duty vehicles on the road are methanol fueled (with
oxidation or 3-way catalysts) , the emissions could be within,
but not above, the suggested range of concern for the severe
roadway tunnel scenario. The street canyon and expressway
scenarios appear to be below the suggested range of concern.
Garage scenarios were discussed in Section VI. Parking
garage exposures, even with all vehicles using methanol,
would be below the suggested range of concern, based on the
few idle and evaporative tests that have been run. However,
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personal garages are estimated to have as much as 16 mg/m
during a cold start, and as much as 40 mg methanol/m
during periods of hot soaks. Exposure to this concentration
would probably be brief, but within the range of concern.
Therefore, further monitoring of idle and evaporative
emissions from methanol fueled cars may be appropriate, since
exposures in this scenario are likely to occur much sooner
than any of the roadway or parking garage scenarios which
call for a large fraction of the vehicle fleet to be methanol
fueled.
Vehicle refueling exposures, as discussed in Section VI,
could involve concentrations of approximately 50 mg/m for
a few minutes at a time, each time the tank is filled. This
is within, but not above, the range of 'concern, and
therefore, may call for closer examination as to possible
adverse effects and methods of minimizing this type of
exposure. For instance, Stage II refueling loss controls
would be one way of reducing these emissions and resulting
exposures. use of Stage II control may be easier here than
for gasoline-fueled vehicles since both the vehicles and
service station pumps would probably be newly designed.
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14. "Fuels and Emissions -- Update and Outlook, 1974", R.
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