EP A/AA/CTAB/P A/81-21
               The Determination of a Range
                   of Concern for Mobile
                    Source Emissions of
                       Sulfuric Acid
                            by



                      Craig A.  Harvey

                            and


                      Robert J. Garbe


                       August, 1981


                          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.
 Control Technology  Assessment  and  Characterization  Branch
           Emission Control Technology Division
       Office of Mobile  Source  Air  Pollution  Control
            Office of Air, Noise and Radiation
           U.S. Environmental Protection Agency
                    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  establish  a  range  of  concern for  sulfuric  acid  (H«SO,)
emissions, from mobile sources.  In light of  the action  called for in section
202(a)(4) of the Clean Air Act (CAA) and due to a  concern within industry as
to what emission levels will be used as the  basis  for  the evaluation of cur-
rent  and  future  technologies,  a  methodology  was developed  in  order  to
bracket  a  range of concern for  various unregulated pollutants.  This  paper
coordinates the  efforts  from two EPA  contracts in order  to use this  meth-
odology  specifically   for   an  evaluation  of  sulfuric  acid.   Mathematical
models  were previously  designed for  various  exposure  scenarios  (such  as
enclosed spaces, expressways, and street canyons)  and were used to  calculate
the ambient air  concentrations resulting from various mobile source sulfuric
acid emission  factors (grams/mile).   In  conjunction with this,  a  sulfuric
acid  health  effects  literature   search   was   conducted   to  aid   in  the
determination of the  final  range of concern.  This search provides  adequate
evidence to support the chosen limits of the range.

The results of  this analysis  provides a range  of  concern for  sulfuric acid
emissions from  motor  vehicles of from 22-350 mg/mile to  1540-23077  mg/mile
depending on the type  of scenario  chosen to  represent public exposure.  The
available  emission factor  data  indicate   that the  current  vehicle  fleet
emission factor  for  sulfuric acid  is 12 mg/mile, which  is  well below  the
lowest  of  the ranges  of concern for  sulfuric  acid.   The  specific  emisson
control  design  / vehicle categories  that  have  emission  factors most  often
appearing within the ranges of concern are  Heavy Duty Trucks and Light Duty
Diesel vehicles with trap-oxidizers  (100 mg/mile).

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                                   -3-
I.    Introduction

It was discovered  in  late 1972 that catalyst  equipped  vehicles operating on
unleaded   fuel  had   substantially   higher   particulate  emissions   than
non-catalyst  vehicles  operating  on  unleaded fuel(l)*.   Analysis  of  the
particulate samples taken from catalyst  cars showed mostly hydrated sulfuric
acid  to   be  present(2).   Analysis  of  particulate  samples  collected  from
non-catalyst vehicles have also shown sulfate but at much lower levels(l,2,).

The  results  of  four  subsequent  studies of motor  vehicle sulfate  emission^
were compiled  by EPA  for  the  report to Congress called for in  the  Clean Air
Act Section 403G as amended August  1977.   Some of  the major conclusions from
this were:

    1)   Oxidation  catalyst-equipped passenger  vehicles   emit  significantly
more   sulfate    (sulfuric   acid)   than   either   production   or   prototype
gasoline-fueled passenger vehicles without catalysts.

    2)   Laboratory-maintained  production  vehicles  exhibit  higher  sulfate
emissions  than  do consumer-owned  production  vehicles.    Deterioration  or
alteration of  the  emission control  system(s) of  consumer-owned/maintained
vehicles  increases  regulated  gaseous emissions (i.e.,  HC,  CO,  and NOx)  and
decreases sulfate emissions from these vehicles.

    3)   Diesel  trucks  exhibit  the  highest  measured   vehicular   sulfate
emission rate,  50 mg/mile.

Health effects research on sulfuric  acid has  been conducted including  in
vitro,  in  vivo,  and  human  epidemiology  studies.   Since  sulfuric   acid
contained in an  aerosol  is  particulate matter, its  toxicity depends  to some
extent on  its  deposition and retention  in  the respiratory tract.  The  acid
is considerably more potent than sulfur dioxide in  exerting physiological
*Numbers in parentheses designate references listed at end of report.

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                                   -4-
effects; for example, one  study showed that sulfuric acid more  than tripled
the increase in pulmonary flow resistance caused by an equimolar amount of
so2.


In  the  interest  of  establishing  a range  of  concern  for  levels of  H9SO,
in motor vehicle  exhausts, Midwest Research  Institute  (MRI) was  contracted
by  EPA  to  compile  information  on the health  effects  of  sulfuric acid  at
different concentrations^).   The results  of  that work  form the  basis  for
the range of concern determined later in this report.


II.   Background


When the Clean Air Act was  amended in August  1977,  the additions 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:
    "(4)(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  sub-
    section  if  such  device,   system,  or 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  sub-
    paragraph (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 un-
    regulated pollutants;  (ii) available methods for reducing or  eliminating
    any risk  to public  health, 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).

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                                    -5-
    (b)  The Administrator may  conduct such tests and may  require the manu-
    facturer  (or  any such person)  to  conduct  such  tests  and  provide  such
    information as is necessary to  carry out subparagraph  (A)  of  this para-
    graph.   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 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  were  contained  in  the  Code  of  Federal

Regulations,  Title  40,   section 86.078-5b.   This  subsection  is  stated  as

follows:

    "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.

         (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)(l) 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  Adminis-
trator), which will  ascertain  that the technology  for which certification  is

requested  complies with  the  standards set forth in  section 86.078-5(b).   This

statement is made in section 86.078-23(d).


The  EPA  issued  an  Advisory Circular  (AC)  (4)   in  June  1978,  to  aid the
                                                                      a/
manufacturers  in  complying  with  section  202  (a)(4).   Manufacturers    were

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                                   -6-
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. Another  Advisory Circular  (5)  was  issued
in November of that year continuing these procedures for 1980  and  later  model
years.

III.   Methodology Overview

Along  with the  previously  mentioned  activities,  EPA,  with  the  input  from
several interested  parties, has  developed a methodology which  is one possible
approach to implementing  section  202  (a)(4)  of the CAA.  This  approach is  ex-
plained 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" (6).  Only a brief summary of this method  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  ef-
fort.   SwRI developed or modified  mathematical models for  predicting ambient
air  concentrations of  mobile  source  pollutants  for  a  variety  of  exposure
situations  including  enclosed  spaces,  street  canyons,  and  expressways.   Once
vehicle emission  factors for various vehicle  categories  have  been  determined
for  a  particular   pollutant,  these  models  can  then  be  used  to  calculate
corresponding  ambient   air  values  for  both  severe  and   typical   exposure
situations  for  each  scenario.   A  plot  of  ambient  air  concentrations  vs.
emission  factors can then  be designed  for  use  in further  steps  of   this
methodology.

Health effects literature searches have been and are being conducted  by MRI in
an attempt  to  aid  EPA in the  determination of  a  range of concern for various
selected pollutants.  With adequate information, the limits  for this  range  can
be chosen.  The  upper level of the range will be  that  value above  which  the
studies show that the pollutant causes so great a hazard to  human health as to
require formal  rulemaking action.  The lower  value  of the  range will be  the
lowest level at which there is evidence of  adverse  physiological effects.   The
region between these limits will  be termed  the  "ambient air  range of  concern",

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                                    -7-
indicating  scattered data points  providing evidence  of  adverse physiological
effects  caused by exposure  to various concentrations  of  sulfuric  acid. Using
the  ambient  air  vs  emission  factor  plot  developed  earlier,  any technology
emitting  a   concentration  of  a  pollutant  (when  converted  to   ambient  air
concentrations) falling  within the range of concern will  be subject to closer
scrutiny.  Technologies  with emission levels falling below the lowest level of
the  range  will  constitute   "no  problem",  implying  a  low  level of  effort
monitoring.   Technologies with  emission  levels  which fall  above   the highest
value  of the  range will  be considered "dangerous" with respect to human health
and, therefore, this  will  imply a  necessity  for  regulation.

For  the  purpose of this  report,  this  particular methodology  has been used to
develop  a  range  of  concern  specifically  for  motor vehicle  emissions  of
sulfuric acid.

IV.    General Information

Sulfuric  acid  (H2SO,)  is  a  colorless,  odorless,  extremely  corrosive,  oily
liquid,  sometimes called  oil  of  vitriol.  Concentrated  sulfuric  acid has  a
very  strong affinity for  water.  It is  sometimes  used as a  drying  agent  and
can  be used  to dehydrate  (chemically remove water  from)  many compounds, e.g.,
carbohydrates.    It   reacts   with  the   sugar   sucrose,   C,?H,,,,0,,,   removing
eleven molecules  of water,  H^O, from each  molecule  of sucrose and  leaving  a
brittle  spongy black mass  of  carbon  and  diluted sulfuric  acid.  The  acid
reacts similarly with  skin,  cellulose,  and  other plant  and animal  matter.
When   the  concentrated  acid  mixes  with  water,  large amounts  of  heat  are
released.

Sulfuric acid is  one of  the  most  important industrial chemicals.  More of it
'is made  each year than  is made of any other manufactured  chemical;  nearly 30
million  tons  of it  were  produced in the United  States  in  1970.   It has widely
varied uses  and plays some part in  the production of  nearly all manufactured
goods.  The  major use  of sulfuric  acid  is in  the production  of  fertilizers
e.g.,  superphosphate of  lime and  ammonium  sulfate.   It is widely  used  in  the
manufacture   of  chemicals,  e.g,  in  making  hydrochloric   acid,  nitric  acid,
sulfate  salts,   synthetic detergents,   dyes  and  pigments,  explosives,   and
drugs.  It  is used  in  petroleum refining to wash  impurities out  of  gasoline

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                                    -8-
and  other refinery  products.   Sulfuric acid  is used  in  processing  metals,
e.g., in  pickling (cleaning)  iron  and steel before  plating them with  tin or
zinc.  Rayon is made with  sulfuric  acid.  It serves  as  the electrolyte in the
lead-acid storage battery  commonly  used in motor vehicles  (acid  for this use,
containing  about  33%  H-SO,   and with  specific  gravity  about  1.25 is  often
called battery acid).

There are two major  processes  (lead  chamber  and contact) for  production of
sulfuric  acid,  and  it is available commerically in a number  of  grades  and
concentrations.  The lead  chamber  process,  the older of the two  processes, is
used  to  produce  much  of  the acid  used to make fertilizers;  it  produces  a
relatively  dilute  acid  (62%-78%   H2SO,).   The  contact   process  produces  a
purer, more concentrated acid  but  requires  purer raw materials and  the  use of
expensive  catalysts.   In  both  processes  sulfur  dioxide  is  oxidized  and
dissolved in water(7).

Sulfuric  acid  from motor  vehicles  occurs  via  two   basic  processes,  both  of
which begin with  some of  the sulfur in the fuel oxidizing to sulfur  dioxide
(SO ) during  combustion.  After this,  in  vehicles equipped  with  oxidation
catalysts,  some  of  the  S02  is further oxidized by the  catalyst  to  sulfur
trioxide  (SO,) which  can then combine with water to form  sulfuric  acid.   The
other route by which sulfuric  acid  is  formed is  the  photochemical oxidation of
exhaust sulfur oxides to sulfuric acid and sulfate by natural  processes  in  the
atmosphere(8).

Typical ambient  public  exposure to  sulfuric  acid  is  due to  inhalation  of
suspended  sulfuric  acid  particles   from   a   variety  of  sources  such   as
fossil-fueled  industrial  facilities.   It  can  come   from  stationary sources,
electric  power  plants or  motor vehicles.   Overall  automotive  sulfuric acid
emissions are generally  low  (2%) in comparison  to  stationary sources,  but  it
is possible that  high  localized concentrations could occur  under  certain high
volume traffic conditions.

When  sulfuric acid  in  the  form  of  a suspended  aerosol  is  inhaled, it acts  as
an  irritant  to  the respiratory tract.  At  lower  exposures  (less  than  1.0
    o
mg/m  ;  and  smaller  particle  sizes  (less   than 2  urn)  the  effects  include
slight respiratory irritation and significant changes in mucociliary

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                                    -9-
clearance.   With   larger  particles   or   higher  exposures   the   irritation
increases,  making  deep   breathing  difficult  for  some and  increasing  light
sensitivity(3,9).

V.    Emission Factors
Emission factors  for  sulfuric acid were  collected  from a number  of  available
sources and are listed  in  Table I.  These emission factors  have  been compiled
at this time only for the  Congested  Freeway  Driving Schedule.   This particular
driving schedule  is most applicable to the  expressway  exposure situation,  but
may still have utility  for the street canyon situation.   The  emission factors
for the enclosed space conditions, which would best be  derived from an idle or
slow speed schedule, will  be  the  subject of further work  to identify concrete
emission factors for these situations.

While this example is concerned with sulfuric acid only,  the  emission factors
reported here generally  are measurements  of  aqueous  soluble  sulfates.   In most
cases,  the  predominant  soluble sulfate  species  in mobile  source exhaust  is
sulfuric acid (10).  However, other  sulfates such as ammonium  sulfate  could be
present.  For  the purposes   of  this report,  it is  assumed  that the  mobile
source emission factors represent 100 percent sulfuric  acid.

These emission  factors  can  be combined  to calculate  fleet average  emission
factors for the vehicle  fleet by  using available information  on vehicle  miles
traveled  (VMT)  for  the different  vehicle  classes.   For simplicity  in  this
example the VMT fractions will  be derived  from information in  the  Pedco  report
(11)  for  calendar  year 1980 and  Mobile Source Emission  Factors:  For  Low
Altitude Areas  Only  (12).   In future  assessments, other  references may  be
used  to perform these  calculations.   Table II  provides  a  breakdown of  the
vehicle class VMT's and the fleet  average emission  factor  for  sulfuric acid.

Obviously this particular  set of  calculations does not  represent  any  specific
fleet emission factor.   Depending on the make up of the vehicle  fleet at  any
point in  place  or time  that is  of  interest,  the  fleet emission  factor  will
differ.  The  most severe  case  could be  considered to  be the scenario  where
high  sulfuric acid   emitting  technology  is  the  predominant  member  of  the
vehicle fleet.  To address this possibility,  and  the possible presence

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                                    -10-
                                    TABLE I
                        Sulfuric Acid Emission Factors*
        Vehicle Category
Light Duty Diesel Vehicles
   w catalyst
   w trap Oxidizers
Light Duty Diesel Trucks
Heavy Duty Diesel Trucks
Light Duty Gasoline Vehicles
    Non Catalyst; no air pump
    Non Catalyst; air pump
    Oxidation Catalyst; no air pump
    Oxidation Catalyst; air-pump
    3-way Catalyst
    3-way Plus Oxidation Catalyst; air pump
Light Duty Truck
    Non Catalyst
    Catalyst, no air pump
Heavy Duty Gasoline Vehicles
Sulfuric Acid (mg/mile)**
           Avg

             9
           100
           100
            16
           100

            0.2
            1.0
           10
           20
            4
           30

            1.0
           20
            4
         Based   on   congested  Freeway   Driving
         Schedule  and  0.030  wt  %  Sulfur  for
         gasoline and 0.2  wt % for  Diesel  fuel.
         These emission  factors may change  with
         other   fuel   sulfur   levels   or   test
         cycles.
    **   Reference 9, 10, 14, 15, 16,  17.

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                                   -11-
                                   TABLE II

                Fleet  Average  Emission  Factors -  Sulfuric Acid*
Vehicle Class
Light Duty Diesel Automobiles
Light Duty Diesel Trucks
Heavy Duty Diesel Trucks
Light Duty Gasoline Vehicles
Non Cat.; no air pump
Non Cat . ; air pump
Ox. Cat.; no air pump
Ox. Cat.; air pump
3-way Cat.; no air pump
3-way Plus Ox. Cat.; air pump
Light Duty Gasoline Trucks
Non Catalyst
Catalyst
Fraction
VMT
0.015
0.002
0.027

0.147
0.098
0.289
0.261
0.012
0.008
0.096
0.010
Emission Factor
(mg/mile)
9.0
16.0
100.0

0.2
1.0
10.0
20.0
4.0
30.0
1.0
20.0
EFxVMT
Fraction
0.135
0.032
2.700

0.029
0.098
2.890
5.220
0.048
0.240
0.096
0.200
Heavy Duty Gasoline Trucks
0.035
4.0
0.140
         Total Fleet Average Sulfuric Acid
                 11.8 mg/mile
*These  calculations  were based  on available information  from the  reference
listed  above  (12,  13)  and  in  Table  1.   Buses, which  may  be  a  significant
source  of  sulfuric acid emissions under  certain conditions,  are not .included
in these fleet averages.

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                                   -12-
                                   Table III
                   Sulfuric Acid Emission Factors - Compiled

Fleet Category                                          mg/mile@

Fleet Average (FA)                                         12
FA + 25% 3W +OC*                                           17
FA + 50% 3W-OC                                             22
FA  + 75% 3W+OC                                            26
100% 3W-OC                                                 30

FA + 25% D+C**                                             34
FA + 50% IM-C                                               56
FA + 75% EHC                                               75
100% Diesel Cat.                                          100

FA + 25% D+To***                          .                 34
FA + 50% D+To                                              56
FA + 75% IH-To                                              75
100% D+To                                                 100
@   Normalized to the Congested Freeway Driving Schedule
*   Light Duty Gasoline Vehicle - Three way + Oxidation Catalyst with air pump
**  Light Duty Diesel Vehicle - Catalyst equipped
*** Light Duty Diesel Vehicle - Trap-oxidizer equipped

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                                    -13-
of future  technology,  the fleet  average emission  factor  can be modified  to
reflect  different  proportions  of these  higher  emitting  technologies.   As  a
worst case, a vehicle  fleet  consisting  of 100 percent of  the  highest emitting
technology could be calculated.

Table  I   also   presents  emission   factors  for  vehicle/emission   control
categories which  are  expected to be  the highest  emitters of  sulfuric  acid
under a  variety of  conditions.   Obviously,   it  is these  technologies,  on  an
individual basis, that might  be expected to  constitute the most likely  source
of an unreasonable  risk to  public  health.   Since  most  of these  technologies
are not yet in  common  use  except  on  an experimental basis, the potential  risk
can  be   considered   to  be  a  future concern.   To  establish  bounds  on  the
potential  risk  from sulfuric acid that  these technologies present,  they  will
be considered in a  number, of  hypothetical calculations to comprise 25,  50,  75
and 100 percent of the total vehicle  miles traveled.

By using the  fleet  average emission factors  in  Table  II and  the  hypothetical
calculations listed  above,  a list of  emission factors  can  be  calculated  to
use in subsequent steps.  This list is presented in Table III.

VI.   Sulfuric Acid Health Effects
A literature review on the health effects of sulfuric acid was performed as an
input to  the  determination of a range of  concern  for mobile source  emissions
of this compound.   This  literature  search is included as  Appendix II to  this
report.

As  indicated  in  the methodology,  in  order  to  focus  the health effects
literature review, a  preliminary range of  ambient  levels has been selected to
bracket  the  region  of   uncertainty  with  respect  to  sulfuric  acid  health
                                                          3              3
effects.   This  range has been determined  to  be  10 ug/m   - 1000  ug/m  for
sulfuric acid.  The  lower end of this range has  been selected to approximate
the lowest level at  which adverse  physiological  effects  can be detected.  The
preponderance of the  evidence has shown  little or  no health effects at levels
of  sulfuric  acid  below  this,  although  there   are some   indications   that

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                                    -14-
sensitive  subgroups  of asthmatics may  show some  reaction  to these  levels of
sulfuric acid.  To as great an extent as  possible, this lower level also takes
into  account   the   interactions  of  various  pollutants   such   as   S00  and
H2S04.

The upper  level of the  range  is  chosen  to be the  TLV  recommended  by  NIOSH and
                        2
the ACGIH  as 1000 mg/m  (9).   Above  this level  several  studies have  shown
an adverse  reaction  in healthy  subjects  which  may be  harmful under repeated
exposures.

VII.  Sulfuric Acid Ambient Air Concentrations

By  using  modeling   techniques   in   conjunction  with  sulfuric  acid  emission
factors,  ambient  concentrations  can be  determined  that  should  bracket  the
range of possible sulfuric acid emission concentrations from mobile sources.

The  range  of  exposures   of  the  general  public to  motor  vehicle  exhaust
emissions  can  be  estimated  by considering  a   limited  number  of  specific
scenarios.   The  scenarios   selected   are  all   expected   to  be  dominantly
influenced  by mobile  source  emissions.   Personal garages,  parking  garages,
roadway  tunnels,  street canyons, and urban expressways have been  selected to
bracket  the range of  sulfuric  acid concentrations from mobile   sources  that
influence  short term health effects  in the exposed population.  Each scenario
is developed as both severe and  average exposure  situations  calculated by  the
use of existing ambient air modeling techniques.   No  attempt has  been made to
determine  the  cumulative effects   of  these   situations  on  general  public
health.   Appendix I contains a detailed  explanation  of   the  rationale  for
choosing  the  specific   situations and  parameters  which  lead to the  numerical
results  presented  here.   Figure  one  depicts  graphically  the   ambient  air
concentrations  vs motor  vehicle  emission  factors for  the  eleven  specific
situations discussed below.

Two personal garage  situations are presented, one  (average  or typical) using a
30  second  vehicle warmup time  and  the  other   (severe)  using a  five minute
vehicle warmup time. These two situations are intended to  simulate summer  and
winter conditions, respectively.

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                                               Figure 1
                                  Pollutant Concentrations vs Emission Factors



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1000
950 .
900 .
850 .
800 .
750 .
700 .

650 .

600 .


550 .


500 .

450 .
400 .
350 .
300 .

250 .
200 .
150 .
100 .
50 .
                                                                                                                   ical)
OC. OQEYER/t*
                                        EMISSION  FACTOR 
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                                    -16-
The two parking garage  situations  simulate  average  and  severe conditions,  with
an above ground, naturally ventilated garage  for  the  former  and an underground
garage for the latter.  The average parking garage  case is calculated assuming
an exit time  in which the vehicle spends equal  time  on the parking  level  and
the ramp  level.  The  severe  parking garage  is  calculated  assuming that  the
exposure takes place 20 minutes after a major sporting  event finishes,  wherein
the exposed population is at  parking  level  5.   The  initial concentration  of
                                                         3
sulfuric acid in this garage is assumed to be low (1 mg/m ).

The roadway tunnel  situations  used two different specific tunnels  to estimate
an average and  severe condition.   A new design,  two  lane roadway  tunnel  with
moderate  traffic  flow is  used for average conditions, while  an old  design,
heavily used roadway tunnel is used for severe conditions.

The two street  canyon  situations  are  simulated by examining the  parameters  of
two street canyons.  The most  sensitive parameter in this model appears to  be
the number of traffic lanes in the canyon.  . The  severe  condition  is  calculated
for a six lane  street  canyon with  a 2400  vehicle/hr traffic load and with  the
exposed population  located inside of  the  vehicle.   The  typical condition  is
calculated  for  a  two  lane canyon  with  800  vehicles/hr  of  traffic  and  a
sidewalk location of the exposed population.

The  expressway  situations  require three   specific estimations to  cover  the
range of  possible  concentrations.  One  highway condition tends to estimate  an
exposure involving a close proximity to the highway such as  would be  gotten  by
living  or  working  close  to  a  heavily   travelled  freeway.   This case   is
calculated on a  short term basis for a distance  of  50  meters downwind of  the
roadway.  The other  two expressway situations simulate a  commuter  (located  in
the vehicle) exposure, with the average  case using a four  lane,  medium use
(1400 vehicle/hour) and a westerly wind at  1.0 meters/sec and  the severe case
using a  ten  lane,  heavily travelled  (3600  vehicles/hr)  freeway with  a  1.0
meter/sec westerly wind.

VIII. Determination of the Range of Concern

The  range  of  concern   for   sulfuric  acid   emissions  from   automobiles   is
determined using the  outputs  from the  previous three areas, emission factors,

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                                    -17-
health  effects  and  exposure  estimation (the  emission  factors  and  exposure
estimates have already been combined  in  Table  IV).  Using the preliminary range
         3              3
(10  ug/m  -  1000 ug/m )  as  a  stepping  stone for  this  effort,  along  with
the guidelines explained earlier in the  methodology section of  this report,  an
upper and lower value can be determined for the final  range of concern.

The literature search reveals a human  study which shows  that an acute exposure
                                       o
concentration  as  low  as   66.0  ug/m   caused  significant   differences   in
lung  function parameters in 3  out  of  18 subjects  tested  (Gardner et. al.
1976).   The   evidence  provided   in   the  literature   also  shows   that   no
physiological  effects  were detected  for exposure  concentrations below  66.0
ug/m .   Since, at  this time,  there  is  no  available  information  definitely
concluding that  there  are  adverse physiological  effects  at concentrations  of
                              3
sulfuric acid  below  66.0 ug/m ,  this value will  be  chosen as  the lower  value
in the range of concern.
The  upper  value of  the  range will  remain at 1000  ug/m  as was  set for  the
preliminary range of concern.  This TLV for sulfuric acid  is  the  time-weighted
average  concentration  for  a normal  8-hour workday  or 40-hour  workweek,  to
which nearly  all workers may be repeatedly  exposed,  day  after  day, without
adverse  effects.   The evidence  of  adverse health  effects  above  this  level
would be sufficient to support regulatory  action.

Between  the chosen  limits   of  this  range,  there are  scattered  data  points
providing  evidence  of adverse   physiological  effects  caused by  exposure  to
various  concentrations  of  sulfuric  acid.   Therefore,   this  region  has  been
termed the  "range of concern" for  sulfuric acid concentrations in the ambient
air.

Once  the  literature  search  was  completed  and  the appropriate information was
tabulated  for  sulfuric acid,  a large  table  was  prepared compiling  all  the
information for the animal and human  studies (see Appendix  III).  These  tables
list  the  studies  according  to  the  exposure  concentration  of  sulfuric  acid
(highest  to lowest  concentration).   Using  this  health  effects information
along  with  the emission  factor  data presented  in  Table  IV,   graphs  were

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                                    -18-
                                   TABLE IV

                    Emission Factors Required to Result in

                 Two Different Ambient Sulfuric Acid Levels**
Ambient Situation*                Emission Factor          Emission Factor
                                    mg/mile for             mg/mile for
                                    66 ug/m3                 1000 ug/m3
                                    exposure                 exposure	


Street Canyon - Typical                1540                     23077
Expressway - Typical                    619                      9375
Expressway - Close Proximity            388                      5882
Street Canyon - Severe                  165                      2500
Expressway - Severe                     132                      2000
Personal Garage - Typical**
Parking Garage - Typical**
Roadway Tunnel - Typical                 59                       822
Roadway Tunnel - Severe                  22                       350
Parking Garage - Severe**
Personal Garage - Severe**


*    In order of increasing ug/m3 concentration for 1 g/mile
     (or 1 g/min) emission rate.

**   These situations were not evaluated for sulfuric acid because of an
     inadequate data base for emission factors under idle and low speed
     conditions.

***  If the severe roadway tunnel situation is of primary interest then a
     fleet emission factor of 22 mg/mile over an appropriate driving schedule
     will be enough to put the ambient concentration within the range of
     concern.  However, if expressway operation is of primary interest, then
     emission factors of up to 132 mg/mile would yield ambient concentrations
     below the range of concern even for severe conditions.

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                                   -19-
composed  representing  the  relationship  between ambient  air  concentrations,
emissions factors,  and the  various  types of  public exposure  situations  (see
Figure 2-6).

According to  the methodology described  earlier  in  the  report, the lower  and
upper levels  which  comprise  the health  effects  range of concern are  compared
to  the  mobile  source situations  to  calculate  the  emission  factor  range  of
concern.  The chief element  of  comparability between the health effects  range
and  the ambient  situations  is  exposure  time.   Most   of  the mobile  source
situations  simulate  short  term exposures  (durations  of an  hour  or less  per
day) perhaps  repeated several  times  per week over   an  extended period.   The
average  exposure situations  appear more likely  to be  repeated often, while
the  severe   exposure  conditions  would  likely   only  occur   on   infrequent
occasions.

With the above  information,  the mobile  source  range of  concern for   sulfuric
acid can  be estimated for the  different  mobile  source  situations.  Table  IV
lists the vehicle  emission factors which  correspond to  the high (1000 ug/m )
and  low  (66  ug/m )  portions   of  the  range  of concern  for  sulfuric acid.
Inspection  of this  table  shows  that the scenarios result  in a  variety  of
ambient concentrations corresponding  to  the health effects range of concern of
66 ug/m3 to 1000 ug/m3.

IX.   Conclusions - Sulfuric  Acid
1)  The  range  of  concern  for sulfuric  acid  emissions  from  motor  vehicles
    varies from 22-350 mg/mile to 1540-23077 mg/mile depending on the  scenario
    and situation of interest.

2)  The lowest  level  of this  range (22 mg/mile)  is  based on  an ambient air
                            3
    concentration of 66 ug/m  for a severe roadway tunnel  situation.

3)  No vehicle  emission  factors  from the garage scenarios were considered  in
    calculating  the  range   of  concern.   More  data  is  probably  needed  on
    emissions of  sulfuric  acid from light  duty vehicles under  idle and slow

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                                    -20-
    speed conditions to evaluate  the  effects of the garage   situations  on the
    sulfuric acid range of concern.

4)  The  roadway  tunnel scenario  appears  to be  a controlling  factor in  this
    methodology for the sulfuric  acid case.   There is some doubt whether  this
    scenario  identifies  a  potential  mobile  source  problem or  a  potential
    roadway  tunnel  ventilation   problem.    If   a   potential  problem   were
    identified  resulting  from  roadway  tunnel  exposures  to  mobile  source
    pollutants, then it is  possible that the most appropriate   solution would
    be  to  increase  tunnel  ventilation rather  than  to  reduce  the vehicle
    emissions.

5)  This  preliminary example of  sulfuric acid has not  considered a  specific
    margin of safety.   It is possible that the inclusion of the  roadway  tunnel
    scenario as the controlling  factor in the range  of  concern constitutes  a
    margin of safety in view of conclusion 4 above, but no specific factor has
    been calculated.

6)  The  current  vehicle  fleet   emission  factor  for  sulfuric  acid is   12
    mg/mile, which  is  well  below  the  lowest  of the  ranges of  concern  for
    sulfuric acid.

7)  With  respect  to specific vehicle emission control  designs,  and  referring
    to  Table  I,  it  appears  that  the  emission  control  design/  vehicle
    categories  that  have emission factors  most  often  appearing  within   the
    ranges  of  concern  are Heavy  Duty Trucks  and Light Duty Diesel  vehicles
    with trap-oxidizers (100 mg/mile).

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                                    -21-
                                                               FIGURE 2

                                                       PERSONAL PARKING GARAGE
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                              EMISSION FACTOR  (milli3ram8/mile)

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                                   -22-
                                                             FIGURE 3
                                                          PARKING GARAGE
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                             EMISSION FACTOR  (milli3rane/mile)

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                               -23-
                            FIGURE 4
                         ROADVAY TUNNEL
    73.,
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                          EMISSION FACTOR  (milligrame/milo)

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                                 -24-
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                                        FIGURE  5

                                     STREET CANYON
                                                                        typical
                                                                         /u  	»
                            EMISSION FACTOR (milligrame/mile)

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                                   -25-
       758

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                                    -26-
                                  References

(1) "Characterization of  Particulates  and  Other  Non-regulated Emissions  from
    Mobile Sources  and  the  Effects  of Exhaust  Emission Control  Devices on
    these Emissions," James E. Gentel,  Otto J.  Manary,  and Joseph C. Valenta,
    Final Report EPA Contract EHS 70-101 with Dow Chemical Co., March 1973.

(2) "Sulfuric Acid Aerosol Emissions  from Catalyst-Equipped Engines," William
    Pierson,   Robert  H.  Hammerle, and  Joseph  T. Kummer,  SAE  Paper  740287,
    February  1974;  SAE Transactions 83,  1233 (1975).

(3) "Sulfuric Acid Health Effects," Midwest Research  Institute Report  for EPA
    Contract  No. 68-03=2928,  1981.

(4) U.S. EPA  Advisory Circular 76, June, 1978.

(5) U.S. EPA  Advisory Circular 76-1, November, 1978.

(6) "An  Approach  for  Determining Levels   of  Concern  for Unregulated  Toxic
    Compounds   from   Mobile   Sources,"   Robert   J.    Garbe,   U.S.   EPA,
    EPA/AA/CTAB/PA/80-2,  July,  1981.

(7) The New Columbia Encyclopedia, Columbia University  Press,  New York,  1975,
    page 2649.

(8) "Sulfate   Emissions   from  Catalyst-Equipped  Automobiles,"   Charles   R.
    Begeman,  Marvin W. Jackson,  George  J.  Nebel,  G.M.  Research Laboratories,
    SAE Paper 741060,  October,  1974.

(9) "Emission of  Sulfur-Bearing  Compounds   from  Motor  Vehicle  and  Aircraft
    Engines," EPA Report  No.  600/9-78-028.

(10)     "Regulated   and   Unregulated    Emissions     from    Malfunctioning
         Automobiles," SAE Paper  790606.

(11)     "Air Quality Assessment  of Particulate  Emissions from Diesel-Powered
         Vehicles," Pedco Environmental,  Inc., March, 1978.

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                                    -27-
(12)  "Mobile  Source  Emission  Factors:   For  Low  Altitude  Areas  Only,"  EPA
      Report No. 400/9-78-006, March,1978.

(13)  Multimedia Environmental  Goals for  Environmental Assessment  Volume  1,
      EPA Report No. 700/7-77-136a.

(14)  "Emissions  from  Light   and   Heavy  Duty  Engines,"   EPA  Report   No.
      460/3-79-007.

(15)  "Exhaust  Emissions   from  Malfunctioning  Three-Way   Catalyst-Equipped
      Automobiles,"  SAE Paper 800511.

(16)  "Light Duty Diesel Catalysts," EPA Report  No.  460/3-80-002.

(17)  "Automobile Sulfate Emissions -  A  Baseline Study,"  SAE Paper 770166.

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