EPA/AA/CTAB/PA/82-7
                          Technical Report
                      Determination of a Range
                        of  Concern  for Mobile
                         Source Emissions  of
                          Hydrogen Sulfide
                                 by

                           Craig A. Harvey
                            January,  1982
                               NOTICE

Technical Reports  do not  necessarily  represent final  EPA decisions  or
positions.  They  are intended  to  present technical  analysis 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 Source  Air Pollution Control
                Emission Control Technology Division
      Control Technology Assessment  and Characterization Branch
                         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  hydrogen  sulfide  (l^S)
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  pol-
lutants^).  This paper coordinates  the efforts  from  two  EPA contracts  in
order  to  use  this  methodology  specifically  for  an evaluation  of hydrogen
sulfide.  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  hydrogen  sulfide  emission  factors  (grams/mile).   In conjunc-
tion with this,  a  hydrogen sulfide  health effects  literature  search  was
conducted by Midwest  Research  Institute under  contract to EPA to aid  in the
determination of the  final range of concern(3).   Some  of  the  typical  health
effects noted  were eye and  respiratory tract irritation, dizziness,  nausea
and  headaches  of  various  degrees  depending  on  exposure.    This  search
provides adequate evidence to support the chosen limits of the range.

The results of this analysis provide a range  of  concern for  ambient hydrogen
sulfide  concentrations  of 0.03  mg/m^  to  14.0 mg/m^.   This  corresponds  to
motor  vehicle  emission levels  of  from 10.5-4,900 mg/mile  to  958.5-447,300
mg/mile on  the  road  and  0.04-204 mg/min  to 3.8-1,770 mg/min for garages,
depending  on  the  type  of  scenario  chosen  to represent  public  exposure.
Under  non-malfunction conditons or  when  the  malfunction does  not cause  a
rich mixture,  high  catalyst  temperature and low exhaust  space velocity,  the
resulting I^S  emissions are  negligible (below the range  of concern for  any
scenario).

The  current  estimated  vehicle  fleet emission factor for hydrogen sulfide,
0.34 mg/mile,  is  well  below  the  lowest  moving   vehicle  scenario  range  of
concern  of  10.5 mg/mile.   For  moving vehicles   the  controlling  (lowest)
ranges  are  those of  the  roadway  tunnel  scenarios.  For  this  to  result  in
ambient  I^S concentrations  within  the range  of  concern,  it would  require
most of  the vehicles to  be  malfunctioning  in  a  way that would cause  high
H2S emissions (over 10.5 mg/mi).

Under  certain  malfunction  conditions,  idling catalyst-equipped vehicles  can
emit H2S at  approximately  1.0  mg/minute.   In  personal  or parking  garage
scenarios this would result  in I^S  concentrations within the range of  con-
cern for  severe  situations.   For  this to  present a  possible  problem in  a
parking garage scenario, a large percentage  (50%)  of the cars would have  to
be  malfunctioning   in  this  manner.    However,  for  a  severe  case  personal
garage  scenario, it  would  only  take  the  one vehicle malfunctioning in  this
manner  to  cause  a chronic repetitive  exposure  of   the  driver  to  a level  of
HoS  within  the  range  of  concern.    Therefore,  closer  scrutiny  of  idle  H2S
emissions is recommended to  determine  if production vehicle/catalyst  systems
could  yield  l^S levels as  high as  those  reported here  (which  were  from
experimental catalysts).
* Numbers in parentheses denote references listed at end of report.

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I.  Introduction

Emissions from gasoline engine vehicles have been characterized by  industry,
government  and private  researchers for  many  years.   While  federal  motor
vehicle regulations have been in effect since 1968 for HC, CO and NOx,  there
are a number  of  unregulated pollutants which are being characterized to  see
if they could represent  an unreasonable risk  to public health and  welfare.
One reason  these other pollutants need to  be studied is that it is  possible
for a new emission control  system to increase an unregulated pollutant  while
decreasing  the regulated ones.  For  instance, catalyst equipped vehicles  can
emit significantly more sulfuric acid than non-catalyst  vehicles  (4).

Hydrogen sulfide is an unregulated pollutant emission that has been  found in
various concentrations in  some  automotive  emission  tests (4,5,6,7).  Due  to
its toxic  properties  and its disagreeable  rotten-egg  odor,  tests have been
conducted  to  characterize  H2&  emissions  as a  function of  driving cycle,
emission control system, and sulfur content of  fuel.   The  results  of  these
tests  along  with  health effects  test data,  as summarized  later  in this
report, are  used  to  determine  the conditions  under which  automotive  t^S
emissions could be of concern with respect to health and welfare.

Barnes and  Summers of General Motors reported in 1975 that three  conditions
favored  the  formation  of  H2S  by  Pt/Pd  oxidation  catalysts:    (1)  rich
air/fuel  ratio  (i.e.,  a   reducing  condition);    (2)  low  exhaust   space
velocity;    and (3) high catalyst temperature.  These conditions rarely  occur
simultaneously  with  properly   tuned  vehicles.   However,  malfunctioning
vehicles  or vehicles with maladjusted carburetors  that run rich   may meet
these  conditions  and  emit H2&  and  COS.   It  should  be  noted  that  the
reducing  conditions   that   favor  sulfide  formation  do  not favor  sulfate
formation.

In the  interest of establishing  a  range  of concern  for  levels  of H2S  in
motor   vehicle  exhausts,   Midwest   Research   Institute   (MRI)   compiled
information  on  the  health effects   of  hydrogen  sulfide  at   different
concentrations^).   The results  of that work form the basis for the  range of
concern determined later in this report.

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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
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.

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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 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",
indicating scattered  data  points providing  evidence  of  adverse  physiological
effects  caused by  exposure to  various  concentrations  of  hydrogen  sulfide.
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
hydrogen sulfide.

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IV.   General Information

Hydrogen sulfide  (t^S)  Is  a colorless gas having an odor  of rotten eggs.   It
can result in  severe  toxic effects if inhaled  at concentrations greater  than
about   200  ppm   (280  mg/m^),   and   various  lesser   effects   at   lower
concentrations as detailed in the health effects section.

The  gas  must   be handled carefully  because  of  (1)  its   toxic   properties
(particularly dangerous  because it may  temporarily  desensitize the olfactory
nerves  thus  making it  impossible  to  sense  its presence),  and (2)  its  ex-
plosive  tendencies  (low ignition  temperature of 260 °C and  wide flammability
range from 4.3 to 44% by volume in air).

Fluorine,  chlorine, bromine and iodine react chemically with  H2S  to form  the
corresponding halogen acid.  Metal sulfides of varying solubilities  are  formed
when H2&  is  passed into solutions  of  the heavy  metals,  such  as Ag,  Pb,  Cu,
and Mn.   This  reaction  is responsible for  the tarnishing  of Ag and  is  the
basis  for  the  separation  of  these metals  in  classical  wet  qualitative
analytical methods.   Hydrogen  sulfide  also reacts  with  many  organic  com-
pounds .

The gas results from the decomposition of metal  sulfides and albuminous  matter
and is found in the areas  of mineral  springs, sewers,  and in  some mines  where
it  is  referred  to as  "stink  damp."   ^S  also is a by-product  of  several
industrial processes,   including  synthetic  rubber,  viscose  rayon,  petroleum
refining,  dyeing,  and  leather-treating  operations.   In  the  laboratory,  H2S
usually is prepared by  treating a sulfide with an acid,  such as iron pyrites
and HC1,  or by  heating thioacetamide  CH3C(S)NH2>   Three processes are  used
industrially to produce H2S in large quantities:

(1) treating a sulfide with an acid,
    2NaHS + H2S04 -» 2H2S
(2) reacting sulfur with an alkali,
    4S + 2NaOH + 2H20 -
(3) directly reacting sulfur with hydrogen,
    S + H2 -» H2S.
Large  quantities  of  by-product  ^S  usually  are  converted  into  elemental
sulfur or ^804.
Industrial  uses  for  ^S  incude  (1)  the  preparation  of  sulfides,  such as
sodium sulfide  and sodium hydrosulfide,  (2)  the  production of  sulfur-bearing
organic compounds,  such as thiophenes, mercaptans, and  organic sulfides,  (3)
the removal of  Cu,  Cd,  and Ti  from spent  catalysts  where  the gas acts to  form
a precipitate,  (4)  the  formulation of  extreme-pressure lubricants, and (5)  the
preparation of rare-earth phosphors used in color  TV tubes(8) .

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                                    -9-

In an automotive system, hydrogen sulfide is formed by  the  reduction of  fuel
sulfur as it  passes  through the exhaust system.  Three-way  catalyst systems
oxidize the hydrocarbons and carbon monoxide to carbon  dioxide and water,  as
do conventional  oxidation  catalysts;  however,  at the  same time they  reduce
NOx  to  nitrogen.   This  reduction  process  provides   a  pathway  for   the
formation of other reduced  exhaust species such as ammonia,  cyanide, organic
amines, hydrogen sulfide and organic  sulfides  that  would not be expected  in
significant quantities from conventional oxidation catalysts(9).

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V.  Emission Factors

H2S  exhaust  emissions have  been measured for  a variety  of vehicle  types.
The  EPA  recommended  procedure  for this measurement  is  described in an  EPA
report  entitled,  "Analytical   Procedures   for   Characterizing   Unregulated
Pollutant Emissions from Motor Vehicles"  (10).   This  basic  procedure  is what
was  used  to  obtain  all  the H2&  emission  factors  in  this report.   Small
amounts  of  H2S  have  been  measured  in  the  exhaust   of  gasoline-fueled
vehicles: equipped with  either  oxidation or three-way catalysts under  normal
operating  conditions,  at  levels between 0.0  and 1.5 mg/mile.   Under mal-
function conditions,  however,  these  emission rates  can increase  consider-
ably.  A reported  emission rate  for a malfunctioning vehicle operating with
a 3-way catalyst was  as high as 8.2 mg/km or  13.2  mg/mile, for  the  sulfate
emission test (SET)* driving schedule (11).

Tests were  run  by EPA-ORD in  order to  evaluate the  impact of  low  ambient
temperatures  on 3-way  catalyst-equipped  car  emissions (12).  These  studies
showed  that  H2S  emissions  for   the  most   part  were  not  significantly
affected by  subambient  temperature operation.   Of the four  vehicles  tested,
only one (Chevrolet Caprice) showed significant  change  due to  the low test
temperature, and this was  mainly due  to the  cold-start portion of  the  test.
For  this  first  portion  of the  test,  the H2S  emissions at the  lower  test
temperature  (60°F) were about 20 mg/mile  as  compared to  0.02 mg/mile at  the
higher (normal) test  temperature (81°F).   For the complete  FTP,  the  maximum
observed H2S emission  rate was  4.21  mg/mile,  which was  at 60 °F for  the
vehicle mentioned above .
Average l^S  emission factors for various  vehicle types were collected  from
several  available  spurces.   The  values  obtained  are  listed  in  Table  I.
These  emission  factors  were  compiled  for  the  SET  driving  schedule,  un-
modified  mode (i.e.  properly tuned),  as well  as  for various  malfunction
modes  (when  such data were  available).   Since the  available  data for  some
technologies  list  both an unmodified  and  a  malfunction emission value,  the
final, average emission  factor was weighted  such that the  value  is 75%  of
the  unmodified  emission  rate  plus   25%  of  the  malfunction  rate.    This
calculation  was   based on  the  assumption that  25%  of  the  vehicle  fleet
operates  in  the  malfunction mode   (i.e.,  rich  idle,  misfire,  high  oil
consumption, etc.) at any given  time  (18).  Further  work may identify a  more
accurate percentage.
*Also  known  as the  Congested  Freeway Driving  Schedule (CFDS),  which is  a
driving cycle  with  a 35 mph average  speed  designed  to represent driving  on
congested freeways.

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The  emission  factors  obtained  for  the  malfunction  mode  are  especially
important  to  this  effort   due   to  the  fact  that  H2S  emissions  tend  to
increase  under malfunction  conditions.   Maximum  emission  rates  have  been
listed below for three vehicle categories.

         Maximum Reported H2S Emission Rates under Malfunction Modes
         (Highest Values Reported  From Any Source on Any Single Test)

         Vehicle Category                               mg/mile
         non-catalyst                                   SET  0
                                                        FTP   .08

         oxidation catalyst                             SET  6.9
                                                        FTP  1.1

         3-way catalyst                                 SET 13.2
                                                        FTP  9.0

The  reported emission  factor for  the  3-way  catalyst  vehicles under  mal-
function conditions is higher than those of the other  two  categories,  and it
is also much higher than any of the vehicle categories listed in Table I.

The driving cycles considered in this  report were  the  Federal Test  Procedure
(FTP),  the  Sulfate  Emission  Test  (SET),  and  idle  testing.   The  results
available for the Highway  Fuel Economy Test were similar  to  SET values,  but
were usually slightly lower.

It may be more appropriate  to choose driving cycles  which  would specifically
simulate  those  scenarios  under  investigation   (enclosed   spaces,   street
canyons, etc.).   At  present, however,  data do  not  exist to  permit  use  of
this  approach for H2S.   It  is not known at this  point what percent  of
error is introduced by using emission factors  from the standard test cycles.
Available  t^S  idle emissions  data  were used  to estimate  I^S exposures  in
parking garage situations, and  will be discussed later in  this report.   One
study  by  GM  (5)  investigated  idle  sulfide  emissions  as  a  function  of
oxidation  catalyst  temperature and  air/fuel  ratio.   It was  found that  the
mixture had  to be  richer  than the correct setting, and catalyst  temperature
needed  to  be  above  570°C  to  result  in  any  detectable   H2S  formation
(greater than 0.05 ppm).  Obtaining  this condition required cruising  the car
at 96  km/hr  for  seven minutes  (during which no  detectable H2S was emitted)
and then decelerating to idle for the  sample collection.   This would  be  more
representative of  a situation  like a freeway off  ramp rather  than  a  cold
start in a garage.

Using  the  average  H2S  emission  factor data  presented in Table  I,  it  is
possible  to  calculate  a  fleet average  emission factor.   The  information
necessary  to make  these calculations is listed in Table  II.   A  fraction  of
the vehicle  miles  traveled (VMT) is listed for  each  vehicle class.  These
data were  derived  from information presented  in  the  Pedco  Report of  1978
(19), and  the EPA  report,  "Mobile Source Emission Factors: For Low Altitude

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                                    -12-

Areas  Only"  (20).  Each  vehicle class  VMT fraction  is multiplied  by  the
corresponding emission factor  for  that class,  giving a  fraction  quantity of
pollutant emitted from a  particular vehicle category in comparison to  other
vehicle categories  in the fleet.   The EF X VMT  fractions  for each  vehicle
class  are  totaled and then averaged  to obtain a  total  fleet average.   For
hydrogen sulfide  emissions, this value is 0.34 mg/mile.  This average  takes
into  account  only  those  vehicle classes  listed  in  Table  II.   Of  course,
should any of these categories change, so would the total fleet average.

It  is difficult  to predict exactly  what  percentage  of vehicle  categories
will  make up  the entire  fleet at any  one  time.   The most severe  case,  with
respect to any  pollutant emission, would  be that case  in  which  the entire
vehicle fleet was comprised of all  of  the  highest  emitting  technologies.   In
order  to  account for differing  proportions  of  the  highest  I^S emitting
technologies, Table III  was devised.  The  emission  factor  values  presented
here  reflect hypothetical situations in which 25,  50, 75, and  100 percent of
the  vehicle  fleet is comprised  of the  highest  emitting technologies.   The
compiled emission factors listed in Table III will become an  important  tool
in  comparing  vehicle  emissions to  the range(s)  of  concern.  In  subsequent
steps,  these  values  will be  used to calculate  ambient  concentrations  of
H2& for various fleet mixes of emission control technologies.

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                                    -13-

VI. Hydrogen Sulfide Health Effects

A literature review on  the health effects of hydrogen  sulfide  was performed
as an  input to  the  determination of  a  range of  concern for  mobile  source
emissions of this  compound(3,21  ).  A summary  of  this literature  search  is
included as an Appendix to this report.

As indicated in  the methodology, in order  to  focus the  health effects  liter-
ature review, a  preliminary  range  of  ambient levels was  selected  to bracket
the region  of  uncertainty with  respect  to hydrogen sulfide  health effects.
This  range  was  determined  to  be 0.15  mg/m^  -  14.0  mg/m^ for  l^S.   The
lower  end  of  this range  was  selected  to approximate the  lowest  level  at
which adverse physiological  effects could  be  detected.  The  preponderance  of
the evidence  has  shown  little  or no  health effects at  levels of  hydrogen
sulfide  below  this,  although upon investigation a few instances  of adverse
reactions were found  with chronic exposures as  low as  0.05 mg/nH  in  adults
and 0.03 mg/nH in babies.

The upper  level of  the  preliminary  range was  chosen to  be  the  threshold
limit  value (TLV) recommended  by the  ACGIH as 14 mg/m^  (9).  Above  this
level  several  studies  had  shown  an  adverse reaction in  healthy  subjects
which could be harmful under repeated exposure.

The specific health effects  that were  found  included  irritations of the eyes
and respiratory  tract,  dizziness, nausea  and headaches  of various degrees
depending on the exposure  level  and duration.   Chronic  exposures resulted  in
more adverse effects  than acute  exposures  for a given  exposure level.   More
details  of  the  relationship between  health  effects and  exposures are  in-
cluded in Section VIII,  "Determination of the Range of Concern."

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                                    -14-

VII.  Hydrogen Sulfide Ambient Air Concentrations
The I^S emission  factor information provided in Table  I through III  can  be
used  in conjunction  wth  the  modeling  techniques  developed  by  Southwest
Research  Institute (SwRI)  (see  Reference  2),  in  order  to  calculate  the
ambient air  concentrations  produced by varying  levels  of H^S vehicle emis-
sions  for  different  exposure  situations.   Future  work  may identify  other
scenarios which would also be  appropriate for the  assessment  of human  ex-
posure  to  exhaust pollutants,  but,   for  this  task,  only  five  exposure
scenarios  were investigated:   personal  garages,  parking  garages,  roadway
tunnels, street canyons,  and urban expressways.  A typical and  severe  case
situation was  developed  for  each  of  these scenarios.   Each situation  has
been considered separately, and,  therefore,  no cumulative effects have  been
determined  at  this point.   Reference  (2)  discusses   the  reasoning  behind
using  these  specific  scenarios as  well as the information  used  in  the  de-
termination of the modeling techniques.

Table  IV  presents  ambient  air  concentrations  of  hydrogen sulfide,  as  a
function  of vehicle  emission  rates,  for  eleven ambient  situations.   The
vehicle emission  rates  correspond to  those emission factors which  were  cal-
culated for the  various combinations  of fleet  categories  found  in  Table
III.   This  information  will later  be used to develop  a plot which  graphi-
cally  represents  the  relationship between the  emission factors  for  various
scenarios and ambient  air concentrations.

Each scenario  is  intended to  represent a specific  type of situation,.   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,  and
are intended to correspond to summer and winter conditions,  respectively.

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  parking level and ramp  level.   The  severe  case
represents an  underground garage wherein  the  exposed  population is  assumed
to be  at  parking  level  five  (lowest  level).  It is also assumed that  this
exposure  occurs  20  minutes   after a  major  event  in  which  the  parking
structure  is  essentially  full.   The   initial  concentration   of   H2S   is
assumed to be low ( 0.001 mg/m^).
In order  to more closely  assess public exposure  to I^S  in  a garage  situ-
ation, idle  emissions  data were averaged from  a  limited number of  sources.
Although  there  was  deviation depending on  catalyst  composition and type  of
malfunction,  the available  idle  data  indicate   that  vehicles  with  3-way
catalysts, operating in  the  malfunction mode can  emit  t^S at  rates  ranging
as high as 0.5 - 1.2 mg/rain.  For calculation purposes a rate  of  1.0  mg/min.
will be assumed.

In a worst case situation, where 100% of the vehicle fleet consists of  auto-
mobiles with 3-way catalysts,  operating in  the  malfunction  mode,  the  H2S
ambient air  concentrations for  each  of the  garage  situations would be  as
listed below.   This,  of  course, might  be  a reasonable  case  for  a personal
garage situation in which a person starts his vehicle, equipped with  a  3-way
catalyst presently operating in the malfunction mode,  in an enclosed garage.

-------
                                    -15-

                    H?S  Ambient  Air  Concentrations,

                   Emission         Personal Garage     Parking Garage
Fleet Make Up      Factor           Typical  Severe     Typical  Severe

100% 3W            1 mg/min.        0.008    0.067      0.009    0.056
Since these values  more  accurately reflect the  I^S  vehicle emissions  in  an
actual garage situation,  they  should  be used  in the identification  of  those
scenarios which may be of most concern  to public health, with  respect to ex-
posure  to H2S.   Due to  limited  data, idle  emission  values can  only  be
evaluated for  vehicles  with 3-way catalysts  (operating  in the  malfunction
mode).   In  the  future,  when more  idle  data have  been  collected, it may  be
possible  to evaluate  other  categories which would contribute  to  the vehicle
fleet make up.

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.   The 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 within  the  canyon.  The typical condition is calculated  for a
two lane  street canyon  with a  traffic  load of 800  vehicles  per hour  and a
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
the exposed population is located inside the vehicles.

Three different cases were  considered  in order  to cover the  possible  range
of exposures in an  expressway situation.  The off  road case estimates an ex-
posure involving  a  close  proximity to  the  highway (i.e.,  living or working
close to  a  heavily-traveled freeway).   This  case is calculated  on a  short
term  basis  for a  distance of  50  meters downwind of  the  roadway.   The
typical, on road exposure is based on a four  lane expressway with a traffic
load  of  1400  vehicles  per  hour  and   a  westerly  wind  (perpendicular   to
roadway)  of 1.0 meter/second.   In  this situation, the exposed  population  is
located  inside  the  vehicle.  The  severe  case represents a  heavily-traveled
(3600 vehicles/hour), ten lane freeway  with a 1.0  meter/second westerly wind
(perpendicular  to roadway),  and  an in-vehicle location of  the  exposed  popu-
lation.

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                                    -16-

VIII. Determination of the Range of Concern

The range of  concern  for hydrogen sulfide emissions from  automobiles  is de-
termined using  the  outputs from the previous three  areas,  emission factors,
health  effects  and exposure  estimation (the emission  factors and  exposure
estimates have  already  been  combined  in Table  IV) .  Using  the  preliminary
range  (0.15  mg/m3 -  14  mg/m3) 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  an epidemiological  study  (22)  which shows that
a chronic  exposure  concentration as low as 0.05 mg/m3  caused a  50%  higher
morbidity rate  as well  as  headaches,  weakness,  nausea, and  vision problems
in a group of apartment house residents.

There is also a  study done  in  an occupational  exposure  setting involving the
babies  of  nursing  mothers who worked in  a  viscose  (rayon)  shop.   During
nursing  these  babies  were exposed  to  hydrogen  sulfide  from the  mothers'
clothing at  concentrations ranging from 0.028 -  0.055 mg/m3.   Compared  to
babies  whose mothers  worked  in  other shops  without   H2S  exposure,  these
babies were more  poorly  developed, vomited  more after feeding,  and were more
susceptible to  severe infectious diseases.
Since  the  nature  of  the  exposure  to  automobile  generated  t^S  will  not
likely be  comparable to  the  above  exposure in that  the exposure will  more
likely be  of an acute  or short term chronic  nature (several hours per  day
repeatedly as a maximum) ,  the upper  level  of the range  of concern  should be
set at  14 mg/m3.  This  exposure  level  corresponds  to  the TLV  for  hydrogen
sulfide as  set  by  the ACGIH  for  8  hr.  per  day/40  hr.  per week  exposure to
healthy workers.

Data  concerning  less  severe  exposures  indicate  that  the  minimum  odor
threshold  was  0.005 mg/m  .   The level  not  affecting  eye  sensitivity  to
light  was   0.008  to   0.010   mg/m3,  while  light   sensitivity-related   eye
responses  were  seen at  0.012 -  0.013  mg/m .   Since  0.03  mg/m^  is  the
lowest level  at which  any indications of adverse health effects  were  found,
this is the  recommended lower limit of the range of concern.

Between the  chosen  limits of this range, there are a few data  points,  some
of which  show adverse  effects and  some  that do not.  Therefore,  this  region
has been  termed the "range  of concern"  for hydrogen sulfide  concentrations
in  the  ambient air.   This range can  now  be  used  in  conjunction with  the
emission  factor data   to  graphically  present the conversion  of  hydrogen
sulfide emissions to ambient air concentrations.

Once the  literature  search  was completed and the  appropriate  information was
tabulated  for  hydrogen sulfide,  a   table  was  prepared  compiling  all  the
information  for the animal  and human studies  (3).  These  tables list  the
studies according to the exposure concentration of hydrogen  sulfide.   Using
this  health  effects  information  along with the emission  factor data  pre-
sented  in  Table  IV,  graphs  were  composed representing  the  relationship
between ambient air  concentrations,  emission factors, and the various  types
of public exposure situations (see Figures 2-6).

-------
                                    -17-

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  hydrogen
sulfide can be  estimated  for the different mobile  source  situations.   Table
V  lists  the vehicle emission factors  which correspond to  the  high  (14.0
mg/m^)  and  low  (0.03  mg/m^) portions  of the  range of concern  for hydro-
gen sulfide.  Inspection of this  table  shows  that the scenarios  result in a
wide range of emission  factors  corresponding  to the health effects  range  of
concern of 0.03 mg/nH to 14.0 mg/m^.

-------
                                    -18-
                       Conclusions - Hydrogen Sulfide

1.  The range of concern for ambient hydrogen  sulfide  concentrations  is 0.03
    - 14.0 mg/m^.

2.  This  range  of  concern corresponds  to  motor  vehicle  emission  rates
    ranging from 10.5 - 4,900  mg/mi to  958.5-447,300 mg/mile depending  on
    the scenario of interest.

3   At  higher  concentrations  (above 0.05  mg/m^)  the possible  health  ef-
    fects range  from minor  eye and respiratory  tract irritation  to  dizzi-
    ness, nausea and  headaches  depending  on degree  of  exposure  and  sus-
    ceptibility.

4.  With  respect to the moving vehicle  scenarios  the controlling  (lowest)
    ranges are  those of the roadway tunnel  scenarios. Some  malfunctioning
    catalyst-equipped vehicles  could emit  t^S at  a  level  within, but  not
    above, the range of concern for  severe  or  typical  tunnel scenarios.  For
    this  to  result  in  ambient  l^S concentrations  within the   range  of
    concern,  it would require most of the vehicles  to  be malfunctioning in a
    way that would cause high t^S emissions (over 10.5  mg/mi).

5.  The  current  estimated  vehicle  fleet  emission   factor   for   hydrogen
    sulfide,  0.34 mg/mile,  is well below the  lowest moving  vehicle scenario
    range of concern of mg/mile.

6.  Under certain  malfunction  conditions, idling catalyst-equipped  vehicles
    can  emit  I^S at  approximately 1.0  mg/minute.   In personal or  parking
    garage scenarios this  would   result  in  l^S concentrations  within  the
    range of concern for  severe  situations. For  this  to  present a possible
    problem in  a parking garage  scenario,  a  large  percentage  (50%)  of  the
    cars would have to be malfunctioning in this  manner.

    However,  for a  severe  case  personal garage scenario,  it would  only take
    the  one  vehicle  malfunctioning in  this manner  to  cause  a  chronic
    repetitive  exposure  of the driver  to a  level  of  t^S within  the  range
    of  concern.   Therefore,  closer  scrutiny  of   idle  t^S  emissions  is
    recommended  to  determine if  production  vehicle/catalyst  systems  could
    yield  H2S   levels as  high  as  those  reported here  (which  were  from
    experimental catalysts).

7.  Under non-malfunction conditions or when the malfunction does  not cause
    a  rich  mixture,  high  catalyst   temperature   and low  exhaust   space
    velocity,  the  resulting I^S  emissions  are negligible (below  the  range
    of concern for any scenario).

-------
                                    -19-

                                   Table I

                     Hydrogen Sulfide Emission Factors®


         Vehicle Category                   Hydrogen Sulfide (mg/mi) SET
                                                 Schedule Average

    Light Duty Diesel Vehicles                         0.0*

    Light Duty Diesel Trucks                           0.0*

    Heavy Duty Diesel Trucks                           0.0**

    Light Duty Gasoline Vehicles

         Non Catalyst; no air pump                     0.00
         Non Catalyst; air pump                        0.02
         Oxidation Catalyst; no air pump               0.31
         Oxidation Catalyst; air pump                  0.87
         3-way Catalyst;  no air pump                  1.02
         3-way Plus Oxidation Catalyst; air pump       0.44

    Light Duty Gasoline Truck

         Non Catalyst, air pump                        0.02
         Catalyst, no air pump                         0.31

    Heavy Duty Gasoline Trucks                         0.08***
6References 13,14,15,16,17

*   Below minimum limits of detection. (FTP)

**  Not tested, but assumed insignificant due to light duty data.

***Due to a lack of sufficient data, this value is assumed  to  be the same as
that  given for  non-catalyst,  light  duty  gasoline   vehicles,  adjusted  for
approximate differences in fuel consumption.

-------
                                   Table II
               Fleet Average Emission Factors -Hydrogen Sulfide
(Sulfate Emission Test Cycle)
Vehicle Class
Light Duty Diesel Vehicles
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)
0.0
0.0
0.0

0.00
0.02
0.31
0.87
1.02
0.44

0.02
0.31
EF x VMT
Fraction
0
0
0

0.000
0.002
0.090
0.027
0.012
0.004

0.002
0.003
Heavy Duty Gasoline Trucks
0.035
0.08
0.003
Total Fleet Average
                                                                  0.34 mg/mile

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                                      -21-
                                  Table III

                Hydrogen Sulfide Emission Factor - Compiled

Fleet Category                                                mg/mile

Fleet Average (FA)                                            0.34
75% FA + 25% OC*                                              1.2
50% FA + 50% OC                                               2.1
25% FA + 75% OC                                               2.9
100% OC                                                       3.8

75% FA + 25% OC/3W+air*                                       1.7
50% FA + 50% OC/3W+air                                        3.1
25% FA + 75% OC/3W-air                                        4.5
100% 3W                                                       5.9
                 1
                 ' *   I
75% FA + 25% 3W***                                            2.0
50% FA + 50% 3W                                               3.7
25% FA + 75% 3W                                               5.4
100% 3W                                                       7.1
*    Light Duty Gasoline Vehicles, without  air  pump,  with  oxidation catalyst
    under worst-case malfunction conditions.
**    Light  Duty  Gasoline  Vehicles,  with  air  pump, with either  oxidation
    catalyst or three-way catalyst under worst-case malfunction conditions.
***  Light Duty Gasoline Vehicles, without  air  pump,  with  three-way catalyst
    under worst case malfunction conditions.
NOTE; The malfunction emissions  for  this  analysis  are not  the single  one
test  results  reported earlier.   They are  the  average  results  from  several
test programs, the  average  being  taken for those malfunctions  producing  the
highest H2S value.

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                                                                    Table IV


                                                              Ambient Air Scenarios


                                                      Hydrogen Sulflde Concentrations
                                               Enclosed Spaces
Street Canyon
Expressway
Fleet E
Make F
up n
Fleet Average
75% FA**
+25% OC***
50% FA
+50%OC
25% FA
+75% OC
100% OC
75% FA
+25%OC/3w+air@
50% FA
+50% OC 3W*air
+75% OC/3W+air
100% OC/3VH-air
75% FA
+25% 3W1
50% FA
+50% 3W
25% FA
+75% 3W
100% 3W
[mission Personal Garage*
'actor
ig/mlle typical severe
0.34
1.2
2.1
2.9
3.8
1.7
3.1
4.5
5.9
2.0
3.7
5.4
7.1
Parking Garage* Roadway
typical severe typical
.0004
.0013
.0024
.0033
.0043
.0019
.0035
.0051
.0066
.0023
- .0042
.0061
.0080
Tunnel
severe
.0010
.0034
.0060
.0083
.011
.0049
.0089
.013
.017
.057
.011
.015
.020


typical severe
(2)
(2)
.0001
.0001
.0001
.0001
.0001
.0001
.0002
.0001
.0001
.0002
.0002
.0001
.0004 •
.0007
.0010
.0013
.0006
.0010
.0015
.0020
.0007
.0012
.0018
.0024



on road on road
off road typical severe
.0001
.0002
.0004
.0005
.0006
.0003
.0005
.0008
.0010
.0003
.0006
.0009
.0012
(2)
.0001
.0003
.0004
.0005
.0002
.0004
.0005
.0007
.0002
.0005
.0007
.0009
.0002
.0006
.0010
.0025
.0033
.0015
.0027
.0039
.0051
.0017
.0032
.0045
.0062

**  FA = fleet average.
*** OC - Light Duty Gasoline Vehicles - Oxidation Catalyst without air pump, worst case malfunction.
@   OC/3VH-air = Light Duty Gasoline Vehicles - Three-way + Oxidation Catalyst with air pump.
1   3W " Light Duty Gasoline Vehicles - Three-way Catalyst without air pump, worst case malfunction.
2      = Less than 0.00005
                                                                                                                                                  I
                                                                                                                                                  to
                                                                                                                                                  N)
                                                                                                                                                  I

-------
                                    -23-

                                           Table  V
                                      Hydrogen Sulfide

                           Emission Factors Required to Result in
                    Exposure Limits for the Ambient Mr Range of Concern


Ambient Air Scenario*         Emission Factor (mg/mile)  Emission Factor (mg/mile)
                              corresponding to a         corresponding to a
                              0.03 mg/m^ exposure        14.0 mg/m^ exposure
Street Canyon - Typical                958.5                      447,300

Expressway - Typical                   246.0                      114,800

Expressway - Close Proximity           177.0                       81,900

Street Canyon - Severe                  89.7                       41,860

Expressway - Severe                     60.6                       28,280

Roadway Tunnel - Typical                26.7                       12,460

Roadway Tunnel - Severe                 10.5                        4,900

Personal Garage - Typical**              3.8                        1,770

Parking Garage - Typical**               3.4                        1,588

Parking Garage - Severe**                0.5                          252

Personal Garage - Severe**               0.4                          204
*        In order of increasing mg/m^ concentration for 1 g/mile (or Ig/min)
         emission rate (excluding garage situations).

**       Emission factors are  given in rag/minute for garage exposures.

-------
                                                Figure  1
                                    Pollutant Concentrations va Emission Factors
 I
-3-
Cv)
 I



1*
i
4)
1
0
•rf
Jl
o
*»
E
0

0)
o
I.
0
•rf
E
v>
a
M
<
t~
z
UJ
m
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1000 -
950 J
900 .
850 .
800 .
750 .
700 .

650 .
600 .


550 .


500 .
'
450 .

400 .
350 .

300 .

250 .
200 .
150 .
100 .
50 .
                                                                                                               cal)
                                         EMISSION FACTOR 

-------
                                       -25-
                                                                FIGURE2
                                                       PERSONAL PARKING GARAGE
 c
 o
 E
 O
 ••••.

I
 E
 O
 o
 o
UJ
i—»
DQ
                               EMISSION FACTOR  (milliqrajaa/raile)

-------
                                     -26-
                                                             FIGURE 3

                                                          PARKING GARAGE
 c.
 o
 B

 o
•t*'



 o

 o
 O


 O
C33
                              EMISSION FACTOR (milli3ram0/mile)

-------
          -27-
   FIGURE 4
ROADWAY TUNNEL
       W   53
       •—•   •—•
  EMISSION FACTOR (mi

-------
         -28-
              FIGURE  5
          STREET CANYON
S    H3    g
,_4    w—*    
-------
                                       -29-
       953..
       TUB..
 o
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                                    FIGURE e

                                   EXPRESSWAY
              KJ
                  £2
eg   tn    csa    i
£5   O»S    trt    e
w—•   •—«    «—•    w


 EMISSION FACTOR

-------
                                       -30-

                                 References

1)  "Clean  Air  Act  as  Amended  August 1977,"  Public  Law  88-206,  89-272,
    89-675, 90-148, 91-604, 92-157, 93-319, 95-95, 95-190.

2)  "An  Approach for  Determining Levels  of  Concern  for  Unregulated  Toxic
    Compounds  from Mobile Sources,"  R.  Garbe,  EPA Technical  Report  No.
    EPA/AA/CTAB/PA/81-2, July 1981.

3)  "Hydrogen  Sulfide  Health  Effects,"  EPA report  no.  EPA-460/3-81-028,  by
    Midwest  Research   Institute  under contract  no.  68-03-2928,  EPA  Project
    Officer Robert Garbe.

4)  "Emission  of Sulfur Bearing  Compounds from  Motor  Vehicle and  Aircraft
    Engines,"  EPA report no.  EPA-600/9-78-028,  by  J. Kawecki,  Biospherics
    Inc., contract no. 68-02-2926, August 1978.

5)  "Sulfide  Emissions from  Catalyst-Equipped  Cars," S.  Cadle,  P.  Malawa,
    Environmental Science  Department,  General Motors Research Laboratories,
    1977.

6)  "Measurements of  Unregulated Emissions from  General Motors'  Light  Duty
    Vehicles," S. Cadle, G.  Nebel, and  R.  Williams, SAE Paper 790694,  June
    1979.

7)  "Hydrogen  Sulfide Formation Over  Automotive Oxidation  Catalysts,"  G.
    Barnes, J. Summers, SAE Paper 750093, February 1975 .

8)  Van  Nostrand's  Scientific  Encyclopedia,  Fifth  Edition,  D.   Considine,
    Ed., 1976, P. 1315.

9)  "Characterization of Exhaust Emissions from Passenger Cars Equipped  with
    Three-way  Catalyst  Control  Systems,"  L.  Smith,  F.  Black,  SAE  Paper
    800822, June 1980.

10) "Analytical   Procedures   for   Characterizing   Unregulated    Pollutant
    Emissions from Motor Vehicles," EPA report no. 600/2-79-017.

11) Final Report for EPA Contract  no.  68-03-2485 by Exxon Research Corp.  on
    Unregulated  Emissions  from  Malfunctioning  3-way Catalysts  on  a  1977
    Light Duty Gasoline Vehicle.

12) "Impact of Low Ambient  Temperature on 3-way Catalyst Car  Emissions,"  J.
    Braddock, SAE Paper 810280, February 1981.

13) "Regulated  and  Unregulated  Emissions   from  Malfunctioning   Oxidation
    Catalyst  Automobiles," EPA  report  No.   EPA-460/3-81-003,  by  Southwest
    Research Institute, Contact no. 68-03-2499,  January 1980.

14) "Regulated   and   Unregulated  Exhaust  Emissions  from   Malfunctioning
    Three-way    Catalyst   Gasoline    Automobiles,"    EPA    report    no.
    EPA-460/3-80-004,   by   Southwest   Research   Institute,   contract  no.
    68-03-2588, January 1980.

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                                      -31-
15) "Regulated  and  Unregulated  Exhaust  Emissions  from  a  Malfunctioning
    Three-way    Catalyst    Gasoline    Automobile,"    EPA    report    No.
    EPA-460/3-80-005,  by   Charles   Urban,  Southwest  Research   Institute,
    contract no. 68-03-2692, January 1980.

16) "Unregulated  Exhaust Emissions  from  Non-Catalyst Baseline  Cars  Under
    Malfunction  Conditions,"  EPA  report  no.  EPA-460/3-81-020,  by  Charles
    Urban, Southwest Research Institute, contract no. 68-03-2884,  May 1981.

17) Nissan submission for the  EPA 1981  Status Report, Chapter II.  G.,  "Un-
    regulated Emissions."

18) "Inspection  and Maintenance  for 1981  and  Later Model  Year  Passenger
    Cars," SAE Paper 810281, D. Hughes,  February  1981.

19) "Air  Quality Assessment  of  Particulate Emissions  from  Diesel-Powered
    Vehicles,"  PEDCo Environmental,    Inc.,  EPA  Contract  No.  68-02-2515,
    Project Officer, J.  Manning, March 1978.

20) "Mobile Source  Emission Factors:   For   Low  Altitude  Areas Only,"   EPA
    report no. EPA-400/9-78-006, March 1978.

21) "Health Effects of Hydrogen  Sulfide, A Literature  Review,"  Conducted as
    part of an evaluation of the health effects  of auto emissions  from mal-
    functioning  3-way oxidative catalysts,  G.  Fairchild,  DVM,   Biomedical
    Research Branch, Clinical Studies Division, U.S. EPA.

22) "Basic Principles for  the  Determination of  Limits of Allowable  Concen-
    trations of  H2S in  Atmospheric Air," R. Loginova, in: Limits  of  Allow-
    able  Concentrations  of  Atmospheric  Pollutants III,  V.  Riazanov,  Ed.,
    1957.

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                                  -32-
           TABLE S-2.  SUMMARY OF HUMAN EXPERIMENTAL EXPOSURE TO H2S
 Level
(mg/m3)
Exposure   Table
Effects
3,499-
8,165
1,420-
4,700
994-
1,988
284-
568

0.20-
0.96

0.08-
0.50

0.27

0.15

0.1
0.031-
0.09

0.012-
0.03
Acute      IV-1    Eye, nose, and mouth irritations, leading
                   to congestion and secretion.  Higher ex-
                   posures also caused dizziness, trembling,
                   numbness, and heart palpitations.  After-
                   wards, swollen and light-sensitive eyes,
                   headache, fatigue, diarrhea, and bladder
                   tenesraus lasting from several hours to a
                   day.

Acute      IV-1    Irritation of eyes, nose, throat, and
                   trachea, leading to tearing, swelling, and
                   catarrh.  Symptoms increased with increas-
                   ing time and concentration.  Sometimes irri-
                   tation and headache continued for several
                   hours after exposure stopped.

Acute      IV-1    Weak irritation of the eyes and throat at
                   the lower levels.  At the highest level,
                   bronchitis, rhinitis, and heavy conjunc-
                   tivitis lasted up to 4 d.

Acute      IV-1    No signs of irritation, as determined by
                   cursory observation and subjective reaction.

Acute      IV-1    All people in the test group detected the
                   odor.

Acute      IV-1    Range of odor thresholds within a group.
Acute      IV-1    Range of odor thresholds within a group.

Acute      IV-1    Threshold of objectionability (not odor).

Acute      IV-1    Most people in the test group detected the
                   odor.

Acute      IV-1  •  Some of the people in the test group de-
                   tected the odor.

Acute      IV-1    Range of odor thresholds within a group.
                                 (continued)

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                                    -33-

                           TABLE S-2.   (concluded)
Level
(mg/m3)
0.012
0.026
0.012-
0.013
(2 studies)
0.010
(2 studies)
0.005-
0.009
Exposure
Acute
Acute
Acute
Acute
Table Effects
IV- 1 Odor was not detected.
IV- 1 Increased light sensitivity- related eye
responses .
IV-1 One study found significantly increased
light sensitivity-related eye responses.
The other study did not.
IV-1 Range of "calculated" odor thresholds
within several groups.
0.008
0.00067
Acute      IV-1    No effect on the ability of the eye to
                   adapt to darkness.

Acute      IV-1    Lowest concentration at which all subjects
                   recognized the odor.

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                                       -34-
   TABLE S-3.  SUMMARY OF OCCUPATIONAL AND EPIDEMIOLOGICAL EXPOSURES TO H2S
 Level
(mg/m3)
Exposure
  time     Table
                        Effects
S 28.4-
> 852
(and low
concns. of
HCN, S02,
CS2, hydro-
carbons)

326.6
40-185
•v 142
 Acute"    V-l
13.7-
36.6
15-35
28.4
(often ex-
ceeded)

7.1-14.2
.(and S02 and
lower ali-
phatic com-
pounds)

7.1-14.2
(and S02)

< 14.2
  20 min   V-l
Acute,
repeated
5-15 y
V-l
           V-l
           V-l
"Acute"    V-l
           V-l
           V-l
V-l
           V-l
        Fatigue, dizziness, unconsciousness with or
        without respiratory failure.  Rapid recovery
        (0.5 h) except for some nervous symptoms
        possibly lasting up to 1.5 mo.
Unconsciousness, cramping, slow and shallow
breathing, and low blood pressure.  Fully
recovered in 6 mo.

Within several hours, many signs of eye,
nose, and throat irriation.  Wide variation
in individual responses.

Within several hours, many signs of eye
irritation.  A wide variation in individual
response, light cases recovering in a few
hours, and severe cases in a week.

Eye irritation of varying severity, lasting
from several hours to days.  Some individuals
had repeated episodes.

Nausea, weakness, and pain in the chest.
Complete recovery within a week, no sequelae.

Fatigue, loss of appetite, irritability,
headache, loss .of memory, itching, and irri-
tation of the eyes and respiratory tract.

Respiratory, gastroenteric, eye, and skin
irritation.
Dermal symptoms suggestive of an allergic-
type response.  Some lung damage.

Weakness, nausea, dizziness, headache,
nervousness, and occasional unconsciousness.
                                 (continued)

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                                       -35-
                           TABLE S-3.   (concluded)
 Level
(mg/m3)
Exposure
  time
Table
Effects
0-9.94
  0.03-
  0.43
0.005-
0.300
0.028-
0.055
3 d        V-l     Occasional slight and irregular changes in
                   serum Fe and transferrin levels and in
                   fractions of urinary sulfates.

29 d    .   V-2     Mild symptoms of nausea, vomiting, headache,
                   shortness of breath, burning eyes, respira-
                   tory tract irritation, gastrointestinal
                   complaints, and disturbed sleep.

Chronic    V-2     Headache, weakness, nausea, vision problems,
                   and higher general morbidity rates in those
                   households with ^ 0.05 rag H2S/m3.

Chronic    V- 1    Babies were poorly developed, underweight,
                   listless, anemic, dyspeptic, and more sus-
                   ceptible to infectious diseases.

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