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                                    PREFACE


    Health and  Environmental  Effects  Documents (HEEDs) are prepared  for  the
Office of Solid  Waste  and  Emergency Response  (OSWER).  This document  series
1s Intended to support listings under  the Resource  Conservation  and  Recovery
Act (RCRA) as  well  as to  provide  health-related  limits and goals for  emer-
gency and  remedial  actions under  the Comprehensive  Environmental Response,
Compensation   and Liability  Act  (CERCLA).    Both   published  literature  and
Information obtained  for  Agency Program Office files  are evaluated  as  they
pertain to potential human health,  aquatic  life and environmental  effects -of
hazardous waste  constituents.   The  literature searched for In this  document
and  the  dates  searched  are  Included 1n  "Appendix: Literature  Searched."
Literature search material  1s  current up to  8 months previous  to the  final
draft date  listed  on  the front  cover.   Final draft  document  dates  (front
cover) reflect the date the document Is sent to the  Program Officer (OSWER).

    Several quantitative  estimates are  presented  provided sufficient  data
are available.   For systemic toxicants,  these  Include  Reference  doses  (RfDs)
for  chronic   and subchronlc  exposures  for  both   the  Inhalation and  oral
exposures.  The  subchronlc or  partial  lifetime  RfD  1s  an estimate of  an
exposure  level   that  would not  be expected  to cause  adverse  effects  when
exposure  occurs  during a  limited  time  Interval  I.e.,  for an Interval  that
does  not  constitute a  significant portion  of the  Hfespan.   This  type  of
exposure  estimate  has  not been  extensively used,  or  rigorously  defined  as
previous risk assessment efforts have  focused  primarily on lifetime  exposure
scenarios.   Animal  data   used  for  subchronlc estimates  generally   reflect^
exposure  durations  of 30-90  days.   The  general  methodology  for estimating..
subchronlc RfDs  1s  the same as  traditionally  employed  for  chronic estimates,
except that subchronlc data are utilized when available.

    In the case  of  suspected  carcinogens, RfDs are not estimated.  Instead,
a  carcinogenic  potency   factor,  or   q-|*   (U.S.  EPA,  1980),   Is provided.
These potency  estimates  are  derived  for  both oral   and Inhalation exposures
where possible.  In addition, unit  risk  estimates for  air  and  drinking water
are presented based on Inhalation and oral data, respectively.

    Reportable quantities  (RQs)  based on both  chronic  toxldty  and  cardno-
genlclty are derived.  The RQ-is  used  to determine  the quantity of a hazard-
ous substance  for  which  notification  Is  required  1n the  event  of a release
as  specified  under  the  Comprehensive Environmental  Response,  Compensation
and Liability  Act  (CERCLA).   These two  RQs  (chronic toxldty  and  cardno-
genlclty) represent two  of six scores developed  (the  remaining  four reflect
IgnltabUHy,  reactivity,  aquatic  toxldty,  and  acute mammalian toxldty).
Chemical-specific RQs reflect the  lowest  of  these  six primary  criteria.  The
methodology for  chronic  toxldty  and  cancer  based RQs are defined  In U.S.
EPA, 1984 and 1986c, respectively.
                                      111

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                              TABLE  OF  CONTENTS
1.  INTRODUCTION	     1

    1.1.   STRUCTURE AND CAS NUMBER	     1
    1.2.   PHYSICAL AND CHEMICAL PROPERTIES 	     1
    1.3.   PRODUCTION DATA	     2
    1.4.   USE DATA	     3
    1.5.   SUMMARY	     3

2.  ENVIRONMENTAL FATE AND TRANSPORT	     5

    2.1.   AIR	     6
    2.2.   WATER	     8
    2.3.   SOIL '.	     8
    2.4.   SUMMARY	    10

3.  EXPOSURE	    12

    3.1.   WATER	    16
    3.2.   FOOD	    16
    3.3.   INHALATION	    12
    3.4.   DERMAL	    16
    3.5.   SUMMARY	    16

4.  ENVIRONMENTAL TOXICOLOGY	    19

    4.1.   AQUATIC TOXICOLOGY 	    19
    4.2.   TERRESTRIAL TOXICOLOGY 	    19

           4.2.1.   Effects on Fauna	    19
           4.2.2.   Effects on Flora	    19

    4.3.   FIELD STUDIES	    20
    4.4.   AQUATIC RISK ASSESSMENT	    20
    4.5.   SUMMARY	,	    20

5.  PHARMACOKINETCS	    22

    5.1.   ABSORPTION	    22
    5.2.   DISTRIBUTION	    23
    5.3.   METABOLISM	    24
    5.4.   EXCRETION	    27
    5.5.   SUMMARY	    28

6.  EFFECTS	    30

    6.1.   SYSTEMIC TOXICITY. .	    30

           6.1.1.   Inhalation Exposure 	    30
           6.1.2.   Oral Exposure	    52
           6.1.3.   Other Relevant Information	    54

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                           TABLE  OF  CONTENTS (cent.)

                                                                        Page
     6.2.   CARCINOGENICITY	;	   58

            6.2.1.   Inhalation	 .   58
            6.2.2.   Oral	   58
            6.2.3.   Other Relevant Information	   60

     6.3.   GENOTOXICITY	   60
     6.4.   DEVELOPMENTAL TOXICITY 	   63
     6.5.   OTHER REPRODUCTIVE EFFECTS 	   65
     6.6.   SUMMARY	   66

 7.  EXISTING GUIDELINES AND STANDARDS	   70

     7.1.   HUMAN	   70
     7.2.   AQUATIC	   70

 8.  RISK ASSESSMENT	   71

     8.1.   CARCINOGENICITY	   71

            8.1.1.   Inhalation	   71
            8.1.2.   Oral	   71
            8.1.3.   Other Routes	   71
            8.1.4.   Weight of Evidence	   71
            8.1.5.   Quantitative Risk Estimates 	   72

     8.2.   SYSTEMIC TOXICITY	   72

            8.2.1.   Inhalation Exposure 	   72
            8.2.2.   Oral Exposure	   76

 9.  REPORTABLE QUANTITIES 	   78

     9.1.   BASED ON SYSTEMIC TOXICITY 	   78
     9.2.   BASED ON CARCINOGENICITY	   83

10.  REFERENCES	   86

APPENDIX A: LITERATURE SEARCHED	113
APPENDIX B: SUMMARY TABLE FOR NITROGEN DIOXIDE 	  116
APPENDIX C: DOSE/DURATION RESPONSE GRAPH(S) FOR EXPOSURE TO
            NITROGEN DIOXIDE 	  117

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                               LIST OF TABLES

No.                               Title                                Page

2-1     Reaction Rate Constants, Pollutant Concentrations and
        Reaction Half-Lives of Expected Removal Processes for N02
        1n a Typical Atmosphere ...................     9

3-1     Mean Nitrogen Dioxide Concentrations In Selected U.S.
        CH1es In 1972 and 1986 ...................    13

3-2     Mean N02 Concentrations In Indoor, Outdoor and Personal
        Air for Homes In Matertown, MA. .  ..............    17

6-1     Susceptibility In the Animal Infectlvlty Model In Mice
     •   Exposed to Nitrogen Dioxide .................    33

6-2     Effects of Exposure to Nitrogen Dioxide on Mechanisms that
        Provide Resistance to Infection ...............    35

6-3     Development of Emphysema 1n Animals Exposed to Nitrogen
        Dioxide ...........................    38

6-4     Development and Regression of Lung Lesions In Rats Exposed
        to Nitrogen Dioxide .....................    41

6-5     Other Effects of Exposure to Nitrogen Dioxide ........    43

6-6     Chronic Inhalation Exposure of Animals to Nitrogen Dioxide. .    46

6-7     LCso Values for Nitrogen Dioxide ...............    57
6-8     Incidence of Pulmonary Adenomas In Strain A/J Mice Exposed
        to Nitrogen Dioxide .....................   59

6-9     Genotoxldty of Nitrogen Dioxide ...............   61

9-1     Inhalation Toxlclty of Nitrogen Dioxide  ...........   79

9-2     Composite Scores for Inhalation Exposure to Nitrogen
        Dioxide ...........................   84

9-3     Minimum Effective Dose (MED) and Reportable Quantity (RQ) .  .   85
                                     vl

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                             LIST  OF  ABBREVIATIONS

AAP                     Army ammunition plants
CAS                     Chemical Abstract Service
CS                      Composite score
FET                     First edge time
FEV-  ,.                 3/4-Second forced expiration volume
FEV,                    Forced expiration volume In/second
FVC                     Forced vital  capacity
GVH                     Graft vs.  host
HEC                     Human equivalent concentration
MED                     Minimum effective dose
NSA                     NUrosatlng agent
PCV                     Packed-cell volume
PHA                     Phytohemagglutlnln
ppb                     Parts per billion
ppm                     Parts per million
RfD                     Reference dose
RGOR                    Regional gas  dose ratio
RNA                     Rlbonuclelc acid
RQ                      Reportable quantity
RV.                     Dose-rating value
RV                      Effect-rating alue
SN                      Serum neutralizing
SRBC                    Sheep red blood cells
STEL                    Short-term exposed level
TL                      Median tolerance limit
  m
TLV                     Threshold limit value
TNT                     Trinitrotoluene
TOC                     Total organic carbon
TPTT                    20% transport time
TWA                     Time-weighted average
v/v                     Volume per volume

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                               1.  INTRODUCTION
1.1.   STRUCTURE AND CAS NUMBER
    The  chemical  nitrogen  dioxide  1s  also  called nitrogen  oxide,  nitrogen
peroxide   and   nitrogen  tetraoxlde  (U.S.  EPA,   1988a).    The  structure,
molecular  formula,  molecular  weight and  CAS  Registry  number  for  nitrogen
dioxide are as follows:
                             N
* — »
N\
eo o
Molecular formula:  NO-
Molecular weight:  46.01
CAS Registry number:  10102-44-0
1.2.   PHYSICAL AND CHEMICAL PROPERTIES
    Nitrogen dioxide  1s  a reddish brown gas at  temperatures  >21.1°C.   Below*
                                                                             f
21.1°C,  H  1s  a brown  liquid,  which becomes a  colorless  solid  below  -11°C.
The  commercial  form  sold  as  a  pressurized  brown  liquid  called  nitrogen
tetroxlde  1s  actually  a  temperature-dependent  equilibrium  mixture of  NO-
and  the colorless  N?04  (Wlndholz,  1983;  Hawley,  1981).  Nitrogen  dioxide
lhas  a  very  pungent  odor  and Is extremely corrosive  (NAS,  1977a).   It  Is
soluble  In  concentrated  nitric  add and  sulfurlc  acids, but decomposes  In
water  (Wlndholz,  1983).   A  few  physical  properties of  this  compound  are
given below (Wlndholz, 1983, unless otherwise stated):
       Melting point:
       Boiling point:
       Density (liquid) at 20°C:
       Density (gas) at 21.3°C:
       Vapor pressure at 25°C:
    -9.3°C
    21.15°C
    1.448 g/cm»
    3.3 g/l
    800 mm Hg (U.S.  EPA. 1985a)
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    Nitrogen  dioxide  may  react  with  water  to  generate  nitric  add  and
nitrous acid according to the following reaction (NAS, 1977a):
                          2 N02 + H20 = OHN02 f OHNO
It  reacts  with  nitric  oxide  (NO) and  water  according  to  the  following
reaction  (NAS, 1977a):
                            N02 * NO * H20 = 20HNO
Nitrogen dioxide also reacts with  alkalies  to  form nitrates  and nitrites  and
Is  corrosive  to  metals  (Wlndholz,  1983;  Cotton  and  Wilkinson,  1980).    A
fairly  strong  oxidizing  agent  In aqueous  solution, 1t  1s  used  1n  organic
chemistry as a selective oxidizing agent (Cotton  and Wilkinson,  1980).   The"
photolysis  of  NO-  1n  sunlight  Is  believed  to be  largely responsible  for
the generation of ozone In sunlit, polluted atmospheres  (NAS, 1977a).
1.3.   PRODUCTION DATA
    Phillips Pacific  Chem.  Co.  and C.F.  Industries  Inc.,  at seven different
U.S.  locations,  produced  between  460  and  1850 million  pounds of  nitrogen
dioxide  1n  1977  (U.S.  EPA,  1977).   A  third  company,  Chevron  U.S.A.  Inc.,
produced <1  million pounds of  the chemical at one  location during  the  same
year.  The  N0_  produced  by  these companies  was  used  on  site and  was  not
available  to  the  commercial  market.   The  Directory  of  Chemical  Producers
(SRI, 1988)  lists Cedar  Chem. Corp.  1n Vlcksburg,  MS,  as the sole commercial
manufacturer  of   this  chemical.   However,   ACS (1987)  lists  the  following
companies as commercial sources of NO.:
0166d                               -2-                              04/10/89

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              A1r Products and Chem., Inc.        Hometown,  PA
              Hatheson Gas Products               Secaucus,  NJ
              Union Carbide Corp.                 Danbury,  CT
              Vertac Chem. Corp.                  Memphis,  TN

The chemical  1s  produced  commercially by the oxidation of  NO with  air.   The
MO may be obtained  at  an  Intermediate stage  during  the  manufacture  of  nitric
add by the oxidation of ammonia (Hawley, 1981;  Wlndholz,  1983).
11.4.   USE DATA
    Nitrogen dioxide  1s an  Intermediate 1n nitric and  sulfuMc acid produc-
tion.  It Is also  used  In the nitration of organic  compounds and  explosives,
1n  the manufacture of  oxidized  cellulose  compounds,  as   an  oxldlzer  for
rocket fuels and  for  bleaching flour, and as a  polymerization  Inhibitor  for
acrylates (Hawley,  1981; Wlndholz, 1983).
                                                                             «
1.5.   SUMMARY                                                               .'
    Nitrogen dioxide  Is a reddish  brown  gas  at  temperatures >21.1°C, a brown
liquid below  this  temperature  and  a colorless  solid  below -11°C  (Hawley,
1981;  Wlndholz,  1983).   It  has  a  pungent  odor  and Is  very   corrosive.
Nitrogen  dioxide  may  react  In  water,  producing nitric   and nitrous  acids
(NAS, 1977a).   It  l,s  a  fairly strong oxidizing  agent  In aqueous solution and
1s  used   In organic  chemistry  as a selective  oxidizing  agent  (Cotton  and
Wilkinson,  1980).   Nitrogen  oxide  1s produced  by  the  oxidation  of NO with
air.  Although  large quantities  of   this  chemical  may  be  used captlvely In
the United  States,  only  five companies  produce  1t commercially  (ACS, 1987;
SRI, 1988;  U.S.  EPA,  1977).  The  current  U.S.  production  and Import volumes
for  N0?   are  not  available.    Nitrogen  dioxide  1s  an  Intermediate  in  the
manufacture of  nitric and  sulfurlc  add.   It Is also  used for nitration of
0166d                               -3-                              04/10/89

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organic compounds,  for  the manufacture  of explosives and  certain  cellulose
compounds, as an oxldlzer for  rocket  fuels  and  for  bleaching flour, and as a
polymerization Inhibitor for acrylates (Hawley,  1981; Wlndholz, 1983).
0166d        rr                      -4-                               04/10/89

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                     2.  ENVIRONMENTAL FATE AND TRANSPORT
    Man-made  sources  account   for  only  a  small   portion  of  total  global
nitrogen-oxide  emissions.   Estimated global  emission  of  NO  (mixture  of  NO
and   NO-)   Is  4.8xl010   kg/year   from  man-made  sources,  compared   with
estimated  NO and  N_0  emissions of  45xl010  kg/year  and  54xl010  kg/year,
respectively, from  natural biologic  processes.   The  NO  (but  not N?0)  thus
formed  enters  the  photolytlc  cycle and  eventually  1s  converted  to  NO-.
Uncontrolled  combustion,  such as 1n  forest  fires, contributes an  estimated
0.2xlO»-l.IxlO10  kg  of  NO-  annually  to  nitrogen oxide  emission  1n  the
United States (NAS, 1977a).
    Although  anthropogenic  sources  of  NO   may  be   small   compared  with
natural  sources,  the  former  can  be significant   1n  localized  urban  atmo-
spheres.   The  Important man-made  sources of  NO   are  mobile (for  example,.
motor  vehicles, aircraft and  other  modes  of  transportation),  stationary [for
example, power  plants,  residential  and commercial  buildings  (primarily from
heating  and   cooking),   Industrial  combustion,   solid   waste   disposal],
Industrial   process  losses and  agricultural  burning.    Estimated  1970  NO
emissions   from  anthropogenic   sources   In  the  United  States   totalled
206.2x10"  kg,  of  which  mobile  and  stationary  sources  constituted  51.5  and
44.1%,  respectively  (NAS,  1977a).   Estimated  emissions  of  N0x  In  the
United  States  totaled   210x10'  kg  1n  1977,   203x10*   kg   In  1980  and
193x10"  kg  In  1986  (Bocola  and  Clrlllo,   1987;  U.S.   EPA,  1988b).   This
decrease Is due  to better pollution control measures  for both mobile  and
some  stationary sources  (U.S.  EPA,  1988b).   AAP  can also emit  N0x  In  the
atmosphere.   The   estimated  emission  of  NO   from  one  AAP  was  10.7x10*
kg/year.   Assuming  that  10 AAPs In  the  United States  (Ryon et al.,  1984)
0166d                               -5-                              07/26/89

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emit  the  same amount  of NOX,  107xl06  kg/year may  be emitted  from  all  the
munition plants  In  the United States.  Thus,  emissions  from this source are
Insignificant  compared  with  the  total  NO   emissions  from  other  anthropo-
genic sources.
2.1.   AIR
    Nitrogen  dioxide  gas absorbs  light  over  a  wide range  (290-430  nm)  and
dissociates  Into  a  ground state oxygen atom  (the  trlplet-P  oxygen  atom)  and
an NO molecule according to the following equation (NAS,  1977a):
                 N0
                     2 * sunlight  (290-430  nm)  =0  (3P)  *  NO
The  trlplet-P  oxygen  formed In air collides with  oxygen  molecules  and forms
ozone according to the following reaction (NAS, 1977a):
                                                                             ^

                           0 (3P) f 02 «• M = 03 * M

M  represents   oxygen,  nitrogen  or  some  other third  molecule  that  absorbs
excess  vlbratlonal  energy, thus  stabilizing  the  ozone  produced  In  this
reaction.   In  polluted  atmospheres,   the  0-  reacts  with  NO  to  regenerate
                                            O
NO
2 according to the following reaction (NAS, 1977a):
                                   NO = N02
Alternatively,  03  may  react  with  NO-  to  produce  a  transient  species
nitrogen trloxlde according to the following equation (NAS, 1977a):
                              03 * N02 = N03 * 02
0166d                               -6-                              07/26/89

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Nitrogen dioxide can also react with 0 (3P)  to produce NO,,:

                          N02 * 0 (3P) * M = NO- * M

The  NO-  formed  by  both  processes  may  react  with  NO,,  forming  N,0C by
       
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Which of  these  reactions  will  be  Important  In the destruction of atmospheric
NO^  may  depend  on  the  rate  constants  and  the  concentrations  of  these
species   1n  the-  atmosphere.   The  reaction  rate  constants,  the  typical
concentrations  of  the species  In  the atmosphere  and  the  reaction half-lives
are  given In Table  2-1,  which demonstrates  that  the reactions of N0?  with
H02  and  N03 will  be  Important   1n  Us  destruction  from  the  atmosphere.
Both  of  these reactions may proceed  with a half-life of <1  hour.   Irradia-
tion  of  a synthetic automobile exhaust containing a  nitrogen  oxides  mixture
showed  that  the   NO- concentration  decayed with  a  half-life  of  <1  hour
after  an  Initial  Increase  1n   concentration  (Splcer  and  Miller,   1976).
Despite  this  short half-life,  equilibrium  concentrations of  NO- 1n  air  may
be  transported  far   from  Us  sources  as  a  result  of  Us  formation as  a
product of other NO   reactions (Perm et al., 1984).
    The  direct  oxidation  reaction  of  SO-  and  NO-  In   rain  and  cloud-
waters  under low  light  conditions could  result  In the  formation   of  the
stable    Intermediate   compound   hydroxylamlne   dlsulfonate,   OHN(S03H)_.
Other  potential  products  of  this  reaction  may  be  hydroxylamlne,  sulfamlc
acid  and  ammonia   (Edwards  et  al., 1984);  however,  this reaction  would  not
remove significant amounts of N0? from the atmosphere.
2.2.   HATER
    Nitrogen  dioxide  Is  not  expected to  be found  In  water   because  of  Us
high  volatility and  Us ability  to react with water  to  generate nitric and
nitrous acid.
2.3.   SOIL
    Both  air-dry  and  moist  soils  showed  substantial  capacity  for  N0?
sorptlon  from air.  Moisture Increased the  sorptlon  ability  of soils.  Soil
properties  that  Increased  the  sorptlon  of  NO-  Included Increases  1n acld-
tUratable  basicity,  CaCO- equivalency,  organic  carbon  content  and   surface
0166d       "                       -8-                              04/10/89

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                                   TABLE  2-1

               Reaction  Rate  Constants,  Pollutant  Concentrations
             and  Reaction  Half-Lives  of  Expected Removal  Processes
                        for NO-2 1n a  Typical  Atmosphere
Reaction
N02 + 0 + M -» N03 * M
N02 <• 03 -» NOs + 02
N02 * N03 f M -» N205 + M
N02 + OH + M -» OHN02
N02 * H02 -» H02N02
3Ak1moto and Takagl, 1986
bGraedel, 1978
cAtk1nson, 1985
dGrosjean, 1985
Rate Constant
Molecule"1
cm3 sec"1
1.5xlO"iaa
3.7xlO~17d
1.2xlO"12a
l.lxlO"lia.d
1.4xlO~12a




Pollutant
Concentration,
Molecules cm"3
2.5xlO*b
7.2xlO»c
2.4xlOBC
5xlOsC
6.5xlO«b




Estimated
Half-Life
214 days ,
7 hours
40 minutes
1.5 days
13 minutes




0166d
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area.   Sorptlon was  followed  by abiotic  reaction  of NCL  with  moisture and
CaCCL  In  the  soil.   The  products  of  these  reactions   Included  nitrate,
nitrite,  ammonia,  N.O  and N.   (Bremner,  1981).   In  acid  soils,  NO.  is
rapidly  converted  to nitric acid;  In  highly buffered calcerous  soils,  some
nitrite  Is  formed  and  readily converted  to  nitrate by  soil  microorganisms
(NAS, 1977a).
2.4.   SUMMARY
    Man-made  sources  account  for only  a  small  amount  of  total  global  NCL
emissions;  however, anthropogenic  sources  can  be  significant  In  localized
urban  atmospheres.   The   Important   man-made   sources   of  NO    are  motor
vehicle,  electric   utility,  Industrial  combustion and residential  emissions
(NAS,  1977a).   A  decreasing   trend   In  atmospheric  NO-   levels  has  been
observed  for  1977-1986.   In  1986, the estimated  total  emission of  NO  In
                                                                         x    -
the  United  States  was  193x10"  kg compared  with 210x10"  kg  In  1977  (U.S.-
EPA, 1988b).
    In  the  atmosphere,  NO- absorbs sunlight and partially decomposes  Into
tMplet-P oxygen  and NO.   The trlplet-P oxygen  then  reacts with 0.  In the
air,  forming   0.,.    The   photolysis   of  NO.  1s  believed  to   be  largely
responsible for  the generation  of  (L  1n polluted  atmospheres  (NAS,  1977a).
Besides  photochemical  decomposition,  NO-  can  be destroyed by  Its  reaction
with free  radicals such  as 0  (3P),  OH, HO. and N03,  and stable compounds
such  as  0,  and   H.O  In  air.    The   reaction  of   N0?  with  HO,,  and  NO^
may be  the  most  Important of  these  reactions  and  the  half-life  of  N02 1n
the atmosphere  may be <1  hour  (see Table  2-1).  The major products  of NOX
reactions  In  the  atmosphere  are ozone,  peroxyacetyl   nitrate,  nitrate and
nitrite (Splcer and Miller, 1976).
0166d                                -10-                             07/26/89

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    NUrogen dioxide  Is  not expected  to  be  found In  water  because  of Us
high volatility and Us reactivity with water  to  produce  nitric and nitrous
add.
    Both dry  and  moist soils  showed  substantial  capacity  for  sorptlon of
N0?  from  air.    The   sorptlon  capacities  Increased  with   add-tHratable
basicity,  CaCO-  equivalency,  organic  carbon  content  and  surface  area of
soils.    After  sorptlon, NO. reacted  with soil components,  forming nitrate,
nitrite, ammonia,  N20  and N_ (Bremner,  1981).
0166d                               -11-                             04/10/89

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                                 3.  EXPOSURE
3.1.   AIR
    Extensive  data  on  the  ambient atmospheric  levels  of N0?  In  the United
States  were  collected  by   the  National  A1r  Sampling  Network  (NASN)  and
Continuous  Air  Monitoring  Project  (CAMP)  of  the  U.S.  EPA,  and  by  the
California  Air Resources Board  Network (ARBN)  as  reported by NAS  (1977a).
More  recent and  detailed  monitoring data on  U.S. ambient air levels  In urban
areas  are  available  from   U.S.  EPA  (1988b).   Outdoor NOp  concentrations
vary  considerably  from site  to  site.   Areas with  the  primary  anthropogenic
sources  of N02  emissions  (e.g.,  higher  vehicular traffic) and  stationary
sources  (e.g.,  electrical utilities,  Industrial  combustion,  residential  and
commercial heating) normally  show higher NO- levels.
    The  mean  concentrations  of  NO-  In six  remote locations  In  the United
States  and  western  Europe   from   1974-1982  were  <0.19-2.3 yg/m3,  with  a*.
mean  of  0.7  yg/m3   (Altshuller,  1986).   The  continental  United  States
background  concentration  of  NO.  measured   at   Pike's   Peak,  CO,  and  the
Appalachian area  of North Carolina  during the  1960s  Indicated a  concentra-
tion  range  of  7.7-8.6  yg/m3,   compared  with   a   lower  value  1n  Panama.
This  suggests  that background concentrations  are  lower  1n  less  Industrial-
ized  areas  (NAS, 1977a).   The mean  concentrations of  NOp  In  selected U.S.
cities 1n  1972 and 1986  are given In Table 3-1, which suggests  that cities
with  expected  higher  traffic densities (e.g.,  Los  Angeles,  Chicago, Balti-
more, Denver and Philadelphia) will .show the highest mean concentrations for
N02.   Annual   NOp  levels averaged over  111  Metropolitan  Statistical  Areas
Increased during 1977-1979 and decreased thereafter through 1986,  except for
a slight Increase  1n  1984 (Figure  3-1).  Between 1977 and 1986, the national
composite  average  NOp  level decreased  by  14%.   This downward   trend  Is
0166d                               -12-                             07/26/89

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                                  TABLE 3-1

               Mean Nitrogen Dioxide  Concentrations  In Selected
                    United  States  Cities  1n  1972 and  1986a
                 Location
     Mean Concentration, yg/m3

         1972b      1986e
Phoenlx-Tuscon, AZ
Los Angeles, CA
San Francisco, CA
Denver, CO
Atlanta, GA
Chicago. IL
Indianapolis, IN
Louisville, KY
Baltimore, MD
Boston, HA
Detroit-Port Huron, MI
M1nneapol1s-St. Paul, MN
St. Louis, HO
Newark, NJ
Buffalo, NY
Cincinnati, OH
Cleveland, OH
Philadelphia, PA
Providence, RI
Chattanooga, TN
Dallas-Fort Worth, TX
Houston-Galveston, TX
Milwaukee, WI
Washington, DC
69-80c
118-182
84-85
42-110
62-80
117-121
56-61
68-87 .
64-96
74
60-80
31-47
58-79
108d
32-49
61-73
53-57
83-84
45
38-53
47-76
64-66
76
64-88
NA
115
47
88
58
77
38
60
68
62
NA
66
66
60
47
55
51
68
47
NA
30
53
51
66
aSource:   Data  from  U.S.  EPA's  A1r  Quality  Control  Regions  as  obtained
 from NAS, 1977a

bTo  convert  units  given  In   ppb   to  yg/m3,  a  multiplication  factor   of
 1.88 has been used.

cWhere  two  values are  given,  the values  are from two different  analytical
 methods (e.g.,  Arsenlte and Chemllumlnescent).

dTh1s  value  Is  from  U.S.  EPA's  National  AerometMc  Data  Bank  (NADB)  as
 obtained from NAS, 1977a.

eThese  are   the   highest  annual  arlthmetrlc  means  among   the  stations
 monitored 1n a  particular area as obtained from U.S.  EPA, 1988b.

NA = Not available
0166d
-13-
04/10/89

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        0.07

        O.M
        0.05
        0.04<
        O.M
        0.02
        0.01
            CONCENTTUnOK
        0.00
                «77«78«79880*81B62tt83«84198SBa6
                                  FIGURE  3-1
        Boxplot Comparisons of Trends In Annual Mean Nitrogen Dioxide
                    Concentrations at  111  Sites,  1977-1986
                           Source:  U.S.  EPA,  1988b
0166d
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attributable  to  decreases In  vehicular  and some  Industrial  emissions  (U.S.
EPA,  1988b).   However,  national ambient NO.  levels  did not  change  signifi-
cantly  between  1985 and  1986  (U.S.  EPA,  1988b).   In  1986, only  one  Metro-
politan Statistical Area  1n  the  United  States,  Los Angeles,  CA,  with a  popu-
lation of 7.5 million, exceeded  the  National  Ambient Air  Quality Standard  of
0.053 ppm (100 pg/m3) for N02 (see Table 3-1)  (U.S. EPA, 1988b).
    The  mean  NO-  concentrations  at  19   U.S.  nonurban  locations  during
1974-1977    were    1.9-24.4    ng/m3,   with    a    mean   of    12.8   vg/m3
(Altshuller,  1986).   Similarly,  13 other   nonurban   samples  collected  In
1978-1981   showed   mean   NO-  concentrations   of  2.8-12.6   yg/m3,  with   a
mean  value  of all  sites of  6.8  jig/m3  (Altshuller,  1986).  This  Indicates
the  decreasing  trend  In  NO-  concentrations  In U.S.  nonurban  areas In  the
late 1970s and early 1980s.
                                                                             •«
    Besides  showing site-dependent  variability,   the  concentrations of  NO--
In air  also  show diurnal and seasonal patterns.  The  atmospheric levels  of
N0~  In  urban  areas generally  show  morning  and  evening maxima  consistent
with  Increase 1n   traffic  patterns.   The seasonal pattern of  atmospheric
NO-  levels  follows  that   of  heating  fuel  usage.  In areas where  gas or fuel
oils are  used for  heating January-March,  the atmospheric NO-  levels  show a
corresponding  maximum.   The  levels  of  atmospheric   NO-  show  a  minimum
during June-August,  when  heating  fuels are  rarely used.  However,  1n  areas
such as  Los Angeles,  CA, the minimum  may occur   1n April-June  and  slightly
higher  concentrations  may  be  observed  during summer  months,   because more
Intense  solar radiation  causes  a  higher rate  of  NO-  production from  NO
(NAS, 1977a; Perm et al., 1984).
    In  a  study of  homes  1n Tokyo,  Japan,  the  following trends  In   Indoor
NO-  levels  were  observed  (Yanaglsawa et  al.,  1984).   The  concentration  of


0166d                                -15-                             07/26/89

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NO-  was  highest  1n  the kitchen,  followed by  the  living room;  the  bedroom
had  the  lowest  level.   The  NO-  level  1n  Indoor  air  from  any area  of  the
residence,  however,  was always  higher  than  that  of  outdoor  air.   Similar
results  were  reported by  Noy et al.  (1984)  for  Indoor  and outdoor  air  of
several  dtles  In  the  Netherlands.    The  mean   levels  of  NO-  found  1n
outdoor  air and  1n different areas 1n Watertown,  MA  residences  are  shown  In
Table  3-2.   It was  concluded that both  Indoor  and personal NO.  levels  are
closely  related to the  type  of  cooking fuel used at these homes.  Homes that
use  electricity  for  heating and  cooking  showed  much lower  levels   of  NO-
than  homes  that  use gas.  Also,  these authors  found  no  noticeable  correla-
tion  between  N0_  levels  1n  outdoor and  Indoor air,  signifying  the  differ-
ence  of  NO-  sources.   Other  Investigators have  concluded  that  Indoor  NO-
levels  are higher  In  homes  that  use kerosene  space heaters   (Traynor  and
Nltschke, 1984; Porter, 1984).                                               =
    A  National Occupational  Exposure  Survey conducted  by   NIOSH  estimated
that  18,737 workers are potentially exposed to this chemical  (NIOSH,  1988a).
3.2.   WATER
    Because of  Its reactivity and  Instability  1n water, NO- has  never been
reported 1n water.
3.3.   FOODS
    No report of NO- detection 1n food was  located  In  the literature.
3.4.   SUMMARY
    The  ambient  air  level  for  NO-   varies  from  one location  to  another.
The  mean concentrations  of  NO-  In  six  remote  locations  during 1974-1982
were  <0.19-2.3  wg/m',  with  a  mean  of  0.7  vg/m3  (Altshuller.   1986).
0166d                               -16-                             04/10/89

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                                  TABLE  3-2

              Mean N02 Concentrations (ug/m3)  In Indoor,  Outdoor
                 and Personal A1r for Homes 1n Watertown,  MA*
Location
Personal
Bedroom
Living room
Kitchen
Outdoor
Mean Concentration
Gas
46-49
45-46
52-60
74-86
37-46
for Cooking Fuel
Electric
22-26
14-19 "'
16-19
18-24
37-46
'Source:  Clausing et al., 1984
0166d
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The  continental  United  States   background  concentration  of  NO-  measured
during   the   1960s  was   7.7-8.6  jig/m3   (MAS,   1977a).    The  mean   NO-
concentrations at  13  U.S.  nonurban locations during  1978-1981  were  2.8-12.6
yg/m3,   with   a   mean   value  of   6.8  yg/m3   (Altshuller,    1986).    The
outdoor  air  levels for  N0> are much  higher  In  U.S.  metropolitan  areas.   In
1986,  the  concentrations   of N02  1n  24  U.S.  cities  were  30-115  vg/m3
(U.S.  EPA,  1988b).   From 1977 to  1986,  annual  N02 levels averaged  over  111
metropolitan  areas Increased  from 1977  to  1979  and  decreased  thereafter
through '1986, except  for  a  slight Increase In  1984.  Between  1977 and  1986,
the  national  composite  average NCL  level  decreased  by 14%.    This  downward
trend  Is  attributable   to  a decrease  In  vehicular  and  some  Industrial
emissions.  In 1986, only Los Angeles,  CA, exceeded the National Ambient  Air
Quality  Standard  of   100  ng/m3  for  N02   (U.S.   EPA,   1988b).    The  N02
concentrations  In  Indoor  air  In  homes  that  use  gas  or oil for  heating  and'
gas  for  cooking  can  be  higher than those of outdoor  air  (Yanaglsawa et al.,
1984;  Noy  et al.,  1984; Clausing  et  al.,  1984).   The  levels can  be  even
higher 1n homes  that use kerosene  space heaters (Traynor  and  NHschke,  1984;
Porter,  1984).   Because of  Us   Instability,  N02  has  not been  detected  1n
water or food.
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                         4.  ENVIRONMENTAL TOXICOLOGY
4.1.   AQUATIC TOXICOLOGY
    Pertinent data  regarding the  toxic  effects  of  acute and chronic exposure
of  aquatic  fauna  and flora to nitrogen  dioxide,  or  on  the  potential  for
nitrogen  dioxide  to  bloaccumulate  or  bloconcentrate  1n  aquatic  fauna  and
flora were not located In the available literature cited In Appendix A.
4.2.   TERRESTRIAL TOXICOLOGY
4.2.1.   Effects  on  Fauna.   FuJ1mak1 et  al.  (1984) exposed  11-  to 13-week-
old  Japanese  quails  from  two  distinct strains  (species  not  specified)  to
gaseous  nitrogen dioxide  to  determine mean  survival  times  and  effects  on
antibody  levels.  Representatives  of  a  "low responder"  group and a  "high
responder"  group  exhibited  mean   survival  times  of  7.8 and 16.1  hours,
respectively, for  exposure to  20  ppm nitrogen dioxide.   Antibody response to_
                                                                             ^
sheep  red  blood  cells  In  high responder  quails  exposed  to  20 ppm nitrogen-.
dioxide  for  4 hours  was  significantly enhanced,  while the  response  In  low
responder quails was only slightly enhanced.
4.2.2.   Effects  on  Flora.    Nash   (1976)  exposed  4  lichens  (Anap-tych1a
neoleuco-melaena.   Parmella   praeslgnls.   Lecanora   chrysoleuca   and   Usnea
caver-nosa) to gaseous  nitrogen dioxide  In a  fumigation chamber  for 6 hours
to assess  the effects on  levels  of chlorophyll a  and  b.'  Total chlorophyll
was   significantly   reduced   In  P.  praeslgnls.   L.   chrysoleuca.  and  U.
caver-nosa  upon   exposure  to  >4  ppm  nitrogen dioxide.   Total chlorophylls
were  reduced  In  A. neoleuco-melaena exposed  to 8  ppm nitrogen dioxide for  6
hours, but this  reduction was not statistically significant.
    Wodzlnskl  and  Alexander   (1980) assessed  the  effects  of  exposure  to
gaseous  nitrogen dioxide on photosynthetlc  activity 1n  the  blue-green alga
Anabaena  flos-aouae  and  the  green  algae  Chlamydomonas   relnhardtn  and


0166d                                -19-                             07/26/89

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Anklstrodesmus  falcatus  In  soil  suspensions.   Algae were exposed to nitrogen
dioxide  In  40  i  all-glass  fumigation chambers.  Compressed  nitrogen dioxide
was  diluted  with activated  charcoal  filtered, humidified air  and delivered
to  the  chamber at  40 i/hour.   Photosynthetlc  activity of  A.  flos-aouae 1n
a  suspension of  Oalton  silt  loam was  nearly eliminated within  3  days by
exposure  to  5.0 ppm  nitrogen  oxide but practically  unaffected  In a suspen-
sion of  Lima  loam after  6  days.   Photosynthetlc activity of  A. fIPS-aquae In
a  suspension of Lima  loam  was eliminated after  6  days by  exposure  to 15.0
ppm  nitrogen  oxide.   No  effects  on photosynthesis were observed In either C.
reln-hardtll  or A.  falcatus  following exposure  to 15 ppm  nitrogen dioxide
for  3  days.  The authors concluded that blue-green  and green  algae probably
would not be affected directly by nitrogen dioxide  In polluted air.
4.3.   FIELD STUDIES
                                                                             **
    Pertinent  data  regarding  the  effects  of  nitrogen  dioxide on  flora  and..
fauna  In the  field  were not  located In  the  available literature  cited In
Appendix A.
4.4.   AQUATIC  RISK ASSESSMENT
    The  lack of pertinent  data  regarding  the effects of aquatic  fauna  and
flora  exposure  to  nitrogen  dioxide  prevented  the  development  of aquatic
criteria  by  the  method  of  U.S.   EPA/OWRS  (1986)   for both  freshwater  and
marine systems.
4.5.   SUMMARY
    Fujlmakl et al.  (1984)  reported  that  representatives  of a low  responder
group and a  high responder  group  of  Japanese  quail  exhibited mean  survival
times of  7.8 and 16.1 hours,  respectively, for  exposure  to 20 ppm  nitrogen
dioxide.   Antibody  response   to  sheep  red blood  cells  In  high  responder
0166d                                -20-                              07/26/89

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quails  exposed  to  20 ppm  nitrogen  dioxide  for  4  hours was  significantly
enhanced,  while  the  response  1n  low  responder  quails  was  only  slightly
enhanced.
    Three  species of  lichens  exposed to >4 ppm  nitrogen dioxide  for  6 hours
experienced  significant  reductions  In  the  levels  of  chlorophyll a and  b
(Nash,  1976).   A  nonsignificant reduction In total  chlorophyll was  observed
In a  fourth  species of lichen  exposed to  8 ppm nitrogen dioxide for  6 hours.
Wodzlnskl  and  Alexander  (1980)  reported  that   photosynthetlc  activity  of
several  species of  blue-green and  green  algae  In soil  was  Inhibited  1n one
species of algae  after exposure  to  5 ppm  nitrogen dioxide for 3 days  but was
not affected In  other species of algae  exposed  to  15  ppm  nitrogen  dioxide
for 3 days.   Effects  of nitrogen dioxide  on  photosynthetlc activity  1n algae
also appeared to be a function of soil type.
0166d                               -21-                             07/26/89

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                             5.  PHARHACOKINETICS
5.1.   ABSORPTION
    The  absorption  of  nitrogen  dioxide  In  humans  following  Inhalation
exposure was  measured  by von Nledlng et  al.  (1970).   Ten healthy volunteers
were  briefly  exposed  to  0.55-13.5  mg/m3  (0.29-7.2  ppm)  nitrogen  dioxide
(exposure  length and purity  not  reported).  Nitrogen  dioxide was measured In
Inhaled and  exhaled air.   Net  retention  was  81-87% during normal respiration
and 9OX with maximal ventilation.
    The absorption  of  nitrogen  dioxide  In animals following  Inhalation  was
studied by Goldstein et  al.  (1977).  The  study  used  two anesthetlsed female
rhesus  monkeys  and  nitrogen   dioxide   labeled  with   tracer  quantities  of
13N-n1trogen   dioxide.   At  various   times   during  the  9-m1nute  exposure
period, the  amounts of radioactivity  and nitrogen  dioxide In the Inhaled and_
                                                                             «
exhaled air  were measured.  At  0.56-1.71 mg/m3  (0.30-0.91  ppm),  54-63X of.
Inspired nitrogen dioxide  was  retained  1n the animals,  compared with 31-50X
of  radioactivity  retained  In the respiratory  tract.   These  differences  were
attributed  to partial  transfer  of  the  13N  from  the  chemically  detectable
nitrogen  dioxide  to   chemically undetectable  H13NO_  or  13NO.  Curves  of
pulmonary  radioactivity  showed  that  labeled  nitrogen dioxide  was  absorbed
uniformly  over the 9-m1nute exposure period,  Indicating that  steady state
had not been  reached.  Radioactivity  In  the  pulmonary region at the termina-
tion of exposure  remained  practically undlmlnlshed for  >12  minutes.   In the
same experiment,  the arterial  blood  levels  of  radioactivity  were measured.
The levels In the  lungs directly  correlated  with the  concentration  In the
arterial blood of the animals.   This  Implied that nitrogen  dioxide  or Its
chemical derivatives were absorbed from  the lungs  Into  the blood.
0166d                                -22-                             07/26/89

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    Dalhamn and  SJoholm (1963)  studied the retention of  nitrogen  dioxide In
the  upper  respiratory  tracts  of  12  rabbits.   Anesthetized  rabbits  were
prepared  for  exposure  by retrograde Insertion  of  a  cannula  Into  the cranial
portion of  the  transected cervical  trachea at  the site  of transectlon.   The
jaws  were secured  closed and the  head  was  placed  In  a  chamber  containing
nitrogen  dioxide.   The  rabbits  were  allowed  to  breathe  uncontamlnated  air
through the  distal  portion of  the  trachea.  Each rabbit  was exposed  to  one
concentration of nitrogen dioxide.   Test  concentrations  ranged  from  24-412
g/l.   Chamber  air   was  drawn  through  the  upper  respiratory  tract  at  1
«,/m1nute  for  15, 30 or  45  minutes.  By measuring  the difference  1n concen-
trations  of  nitrogen  dioxide  In  the chamber air  and air drawn  through  the
upper  respiratory  tract,  the  Investigators  estimated  retention  values  of
19-78%.   There  appeared to be considerable Individual variation,  but  reten-
                                                                             •.
                                                                             ^
tlon appeared to be Independent of both exposure duration and concentration. ..
    Vaughan  et   al.   (1969)  performed  a  similar experiment  using  surgically
prepared  beagle and  mongrel  dogs.   A  mixture of  Irradiated  auto  exhaust
containing added sulfur  dioxide and sulfurlc  acid  mist  was drawn  through the
upper  airway  at  3   l/m1nute  for  10-120  minutes.   Removal   of  nitrogen
dioxide from  the mixture of gases by the upper  airway was  reported at 90%.
5.2.   DISTRIBUTION
    Goldstein et al.  (1977)  exposed  two  rhesus  monkeys  by  Inhalation to
0.56-1.71   mg/m3  (0.3-0.91  ppm)  nitrogen  dioxide  labeled with  tracer quan-
tities  of l3N-n1trogen  dioxide.    Following  <9 minutes  of  exposure,  radio-
activity  distribution  within  the  upper abdomen and  thorax was  measured  with
a Nuclear  Data  Selektronlc  Anger  camera.   A  diagram of  the thorax and upper
abdomen Indicated  that  radioactivity was  widely  and  uniformly  distributed
throughout the body.   Within  the  lung field,  the authors  reported a slightly


0166d                                -23-                             07/31/89

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greater  concentration  of radioactivity  In  the  upper lobe compared  with  the
lower  lobe.   They  hypothesized  that  greater  perfuslon of  the  lower  lobe
resulted  1n  more efficient uptake  of  radioactivity by  the  bloodstream from
the lower lobe.
5.3.   METABOLISM
    Inhaled  nitrogen  dioxide  reportedly reacts with  water  In  the  liquid  or
vapor  states 1n  the  respiratory tract  to  form  nitrite  and nitrate  In  the
following reaction (Goldstein et al., 1977;  Oda et al.,  1981):
                         2N02 +  H20  -> NO"  *  N0~  *  2H*.
Goldstein  et al.  (1977)  reported  that  HN02  1n  water  1n  the  vapor  state
rapidly decomposed as follows:
                            2HNO_ -» NO f NO. * H.O.
Oda  et  al.  (1981)  exposed  mice  (unreported  strain)  to  40  ppm  (75  mg/m3)
nitrogen dioxide  In air  for  <2  hours  and measured the nitrite and nitrate In
the  blood  at 0,  5,  10,  20,  30,  60  and 120 minutes after  exposure  (3 mice/
group).   Both nitrite and  nitrate Increased  after the onset of exposure; the
concentration of  nitrate was -10 times higher than  that  of  nitrite.   Equi-
librium  1n  the  blood was  reached In  10  minutes  for nitrite  and 30 minutes
for  nitrate.   When  the  mice were  removed  to fresh air,  nitrite decreased
with a half-life  of  several  minutes while nitrate  declined with a half-life
of -1 hour.
    Bompart  et   al.   (1982)   determined  that   Inhaled   nitrogen   dioxide  1s
rapidly oxidized  to  nitrate  In  the  rabbit and guinea  pig.   Ten guinea pigs


0166d                               -24-                             04/10/89

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and  six  rabbits  were  exposed  to  20  or  30 cmVm3  nitrogen  dioxide  (20  or
30  ppm),   respectively,  for  6  hours.   The  concentrations of  nitrate  and
nitrite were -determined  In lung tissue,  lung  lavage fluid and plasma  at  0,
24, 48 and 72  hours  after  exposure.   Nitrite was  not located  In  any of these
sites In guinea pigs at  any  sample  time.   In  rabbits,  nitrite  was  located  1n
lung lavage fluid  and  plasma only at  0 hours  after  exposure.  Significantly
greater concentrations  than  those  found   In  controls  were measured 1n  all
three  sites  at 0  hours after  exposure.    The  Investigators  concluded  that
nitrogen'  dioxide   was  rapidly  oxidized  to nitrate,  which  was  eliminated
within 24  hours.   The rabbits  appeared  to metabolize nitrogen dioxide more
rapidly  than   did  the guinea  pigs.   Nitrite  and  nitrate are  subsequently
absorbed Into  the  blood.   In the blood, the nitrite can  cause the oxidation
of hemoglobin  to methemoglobln (Kosaka et  al.,  1979).
    Postlethwalt  and  Mustafa  (1981)  found   that.  In   Isolated  rat  lungs^
perfused with  erythrocyte-free medium, nitrite and  not nitrate  was  produced
after exposure to  5  ppm nitrogen dioxide.  When  the perfusate contained 10%
erythrocytes,   however,  nitrate  was  the  primary   product.    The  results
Indicated  that nitrogen  dioxide In  the  lung was converted predominantly  to
nitrite, but after Us absorption  Into the blood, was  oxidized to nitrate by
Interaction with  hemoglobin.   Therefore,   the  primary  reaction  of  nitrogen
dioxide 1n the lungs was not  the  Interaction  with  water  but  the Interaction
with  readily  oxldlzable  pulmonary   tissue  components  such  as  proteins,
Uplds, glutathlone  or  amines, which yields  only nitrite.  The  nitrite was
then absorbed  Into the  blood and oxidized  by  oxyhemoglobln to form nitrate,
which was  recovered  as urinary nitrate {Kosaka et al.,  1979).   Consequently,
the formation  of nitrate or  nitrite 1n the lungs will  be detected as nitrate
1n the urine.


0166d                                -25-                             04/10/89

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    Saul and  Archer  (1983) exposed  six  groups of  three  male Sprague-Oawley
rats  to  1.2-8.8 ppm  (2.3-16.6 mg/m3) nitrogen  dioxide continuously  for  24
hours and  determined  the amount of nitrate  excreted  1n  the urine on the day
of  exposure  and the preceding  and  following 3 days.   A  linear  relationship
between  urinary   nitrate  and  exposure  concentration   was   found.    This
Indicated  that  the  rate-limiting  step   1n  nitrogen  dioxide absorption  Is
first order with respect  to urinary  concentration.   This  fact,  combined with
evidence that  the  reaction rate  of  nitrogen dioxide with  water  1s  too slow
to  account for  the results, Implies  that  the reaction of  water  with nitrogen
dioxide In the  lungs  1s  not the primary  pathway for nitrogen dioxide absorp-
tion.  These  observations support  the  authors' hypothesis  that  Interaction
of  nitrogen  dioxide  with oxldlzable pulmonary tissue  1s  the primary pathway
for  nitrogen  dioxide  absorption.    The   Investigators  estimated   that  9.6
ymol  of  n1tr1te/ppm  nitrogen  dioxide was  formed  In the  respiratory  tract..
for a 24-hour exposure.
    Atmospheric  nitrogen  may  react  with   amines   to   form   carcinogenic
N-nHroso  compounds   In  the  lungs  (Saul  and  Archer  1983;  Hlrvlsh et  al.,
1983).  Alternatively,  nitrogen dioxide may  Interact with oxldlzable  tissue
components   to  form  nitrite,   which  1s  a  precursor  of N-nltroso   compounds
(Saul and  Archer  1983).  Kosaka et  al.  (1987) detected nltrosodlmethylamlne
(NONA) In  the blood of  a rabbit simultaneously exposed  to nitrogen dioxide
by  Inhalation  and  to amlnopyrldlne by Intravenous  Injection.   The amount of
NDMA  In the  blood  Immediately  decreased  when nitrogen dioxide administration
ceased.
    Exposure to nitrogen  dioxide  results  In  the ]t\ vivo formation of an NSA,
which  reacts  with  amines  to  produce  nltrosamlnes  (Hlrvlsh  et  al., 1983).
0166d                               -26-                             07/26/89

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M1rv1sh  et  al.  (1983)  exposed  seven  Swiss  mice  to  50  ppm   (94  mg/m3)
nitrogen  dioxide  In an  Inhalation chamber  for  4 hours.   The  Investigators
found  88% of the NSA  In  the skin  or  hair.   Experiments with  mice In which
exposure  was limited  to  the body  but  not  the  head Indicated that  the  NSA
recovered  from  the  skin and  hair  probably  resulted  from dermal  rather  than
Inhalation  exposure.   Mlrvlsh et al.  (1986) determined  that the  NSA  1n  the
skin of nitrogen dioxide exposed Swiss mice was cholesteryl  nitrite.
    As  stated above,  nitrogen-dioxide  reacts with water  to  form  nitrite  and
nitrate  (Oda  et  al.,  1981).   Ingestlon  of  water containing   nitrite  or
nitrate  results  In  the  conversion of nitrate  to nitrite  by  the Intestinal
mlcroflora,  absorption  of  nitrite  Into the  blood, and  formation  of methemo-
globlnemla  from the oxidation  of  hemoglobin  by  nitrite.  Hethemogloblnemla
potentially  Impairs the supply  of  oxygen  to  the tissues  (Shuval and Gruener,.
1974).    Calabrese   (1978)   reported   four  reasons   why  Infants  are  more-.
susceptible  to  the  effects  of  methemoglob1nem1a  from  Ingesting  nitrate In
drinking water:  1) their  gastric  pH  Is  higher than  that of adults, and this
promotes growth of  the  mlcroflora  that  reduce nitrate to nitrite; 2)  Infants
are  born  with  hemoglobin  F,  which  Is   more  susceptible  to  oxidation  by
nitrite than  Is adult  hemoglobin;  3)  Infants have a  lower enzymatic capacity
to reduce  methemoglobln to hemoglobin; and  4)  Infants  take In  more fluid on
a volume/body weight basis than adults.
!>.4.   EXCRETION
    The  level  of urinary  nitrate  after   Inhalation  of  nitrogen  dioxide by
Sprague-Dawley  rats  for 24  hours  was  determined  by Saul and Archer  (1983).
Six rats/group  were exposed  to  concentrations of 1.2,  3.4,  4.1,  5.6 or 8.8
ppm  (2.3-16.6  mg/ma)   for  24  hours  (see Section  5.3.).   The  recovery of
nitrate  during  3 posttreatment days  was  8. 4±1.1 ymol  nltrate/ppm nitrogen
0166d                               -27-                             07/26/89

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d1ox1de/24-hour  exposure  (slope ^95X  confidence  limits).   The Investigators
estimated  that  -20X  of  this  represented  Ingestlon  during  grooming  of
reaction products  of  nitrogen dioxide with components  of  the hair and skin,
and  that  -80%  (6.7  pmol/ppm  nitrogen  dioxide/24  hours)  resulted  from
absorption  of  reaction   products  of  nitrogen  dioxide  1n  the  respiratory
tract.   Urinary  excretion  of  nitrate  was  rapid;  the  majority  of  the
excretion  occurred  within 24  hours  after  treatment.  The  total  Increase  In
urinary  nitrate was  linearly related  to  the administered  concentration  of
nitrogen dioxide.
    To  quantify  the conversion of nitrite  In the  blood  to urinary nitrate,
Saul and Archer  (1983)  Intravenously  Injected rats 'with  single  15, 30 or  45
umol  (0.69,   1.38   or  2.07  mg)  doses  of  nitrite  In  saline and  measured
nitrate excreted In the urine on  the day of treatment and on the 3 pretreat-
                                                                             «
                                                                             ••
ment and  posttreatment  days.  The pattern  of nitrate  excretion  was  similar..
to  that  In rats exposed  to  nitrogen dioxide by  Inhalation.   A  linear rela-
tionship existed between  the nitrite dose and urinary  excretion  of nitrate.
From  the  slope  of  this   line,  the  Investigators   estimated  that 0.1  ytnol
nHrate/yimol   of  Injected   nitrite  was  formed.  By  assuming equal efficiency
or  absorption  of   nitrogen   dioxide  from  ambient air  and  conversion  of
nitrogen dioxide to  urinary  nitrate  by rats  and  humans, and  by applying
reference  respiratory  rates  for  both  species,   Saul  and  Archer   (1983)
estimated  that  humans exposed to ambient  air  containing 0.1  ppm nitrogen
dioxide  (typical  concentration In an urban  setting)  would  form -3.6 mg of
nitrite 1n the respiratory tract each  day.
5.5.   SUMMARY
    Nitrogen  dioxide appears  to be rapidly  and efficiently absorbed from the
respiratory  tracts  of  humans  (von  N1ed1ng  et   al.,  1970)  and  monkeys


0166d                                -28-                             07/26/89

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(Goldstein et al.,  1977).   Investigators  hypothesized  that  retained nitrogen
dioxide  reacted  with  water  In  the  respiratory  tract  to  form nitrite  and
nitrate, which were  subsequently absorbed  Into  the  bloodstream (Goldstein et
al.. 1977;  Oda  et al.,  1981).   In the bloodstream, nitrite  In  the presence
of oxyhemoglobln was  rapidly  oxidized to nitrate (Kosaka et  al.,  1979).   In
the  process,  however,  oxyhemoglobln  was  oxidized  to methemoglobln,  which
Impaired delivery of oxygen to the  tissues  (Shuval  and Gruener,  1974).   More
recent  perfuslon  (PostlethwaH  and Mustafa,  1981)  and  Inhalation  (Saul  and
Archer,  1983) experiments,  however, Indicated that the  primary  reaction  was
the  formation of  nitrite from the  Interaction of nitrogen  dioxide with lung
tissue,  and that  nitrate was  formed  1n the  bloodstream from the Interaction
of nitrite with hemoglobin.   The nitrate  thus  formed  was rapidly excreted In
the  urine  (Saul  and  Archer,  1983).   Alternatively,  nitrogen  dioxide  or
nitrite  can react with amines In the  lungs  to  form potentially carcinogenic*
nltrosamlnes (M1rv1sh et al.,  1983; Saul and Archer, 1983).
0166d                                -29-                              04/10/89

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                                  6.   EFFECTS
6.1.   SYSTEMIC TOXICITY
6.1.1.   Inhalation  Exposure.   U.S.  EPA   (1982)  thoroughly  reviewed  the
voluminous  literature  available  through  1978  on  the effects  of  Inhalation
exposure to  nitrogen  dioxide In humans and  animals.   It  1s  beyond the scope
of  this  document  to  duplicate  this  effort.   However,  the  U.S.  EPA  (1982)
analysis has  been reviewed  to  Identify  the critical  effects  for  Inhalation
exposure.   This  review was  limited  to  the  highest quality  studies  from the
older  literature and  from  the  more  recent literature  that   clarifies  the
pathogenesls and  Identifies thresholds for nitrogen dioxide-Induced effects.
    6.1.1.1.   SUBCHRONIC —Many  of  the  above  studies  evaluated  nitrogen
dioxide  In   the  animal   Infectlvlty model.   In  which   susceptibility  to
pneumonia,  which was  due  to airborne  Infections  (Streptococcus  pyogenes.
                                                                             f
                                                                             4
Klebslella  pneumonlae.  Dlplococcus pneumonlae.  Influenza  A2/Ta1wan  virus or
A/PR/8  Influenza  virus)  was  measured  In  hamsters, mice or  squirrel monkeys
exposed  to  the  test  agent.   Mice  were  the  most  sensitive species,  and
sensitivity  was  greatest  when S^  pyogenes  was  the challenge organism.  In a
series of  studies,  mice were exposed to nitrogen  dioxide concentrations of
1-14  ppm (1.880-26.320 mg/m3)  for single  exposures  of 0.5-7  hours  so that
the product  of concentration  (ppm)  and  time (hours)  approximated 7  (Coffin
et al.,  1977;  Gardner  et  al., 1977a).  Following exposure to  the  test agent,
the mice were  exposed  to  S_._ pyoqenes. and mortality was compared  between the
groups.   Infections  were  more   severe   and mortality  greater when  higher
concentrations were given  for shorter periods  than when lower  concentrations
were  given  for  longer periods.   The Investigators  concluded that suscept-
ibility  to Infection depends  more  on concentration  than duration of  exposure.
0166d                                -30-                              07/26/89

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    In  a  more  extensive  study,  Gardner  et  al.  (1977b)  exposed  mice  to
concentrations  of  0.5-28  ppm  continuously  for  35  minutes   to  12  months
(Figure  6-1).   The Infective agent  was  S.  pyoqenes;  K.  pneumonlae  was  used
at  0.5  ppm.   For  each  exposure,  mortality  was  linearly  related  to  exposure
duration.   However,  for  exposure  regimens yielding  Identical products  of
time  and concentration, mortality  Increased at  higher  concentrations.   This
study confirmed  that Increased  susceptibility  to pneumonia depends more  on
concentration than on duration,  particularly at lower concentrations.
    To  determine  the   Impact  of mode  of  exposure,  Gardner  et  al.  (1979)
exposed  mice  continuously or  Intermittently  (7  hours/day,  7  days/week)  to
"1.5 ppm for  -3  weeks  or to  3.5  ppm for -2  weeks.   The  Infective  agent  In
these  studies  was  S.  pyogenes.   At  the   higher  concentration,  mortality
Increased with continuous exposure.   When the  data were adjusted  for concen- .
                                                                              i
                                                                              •
tratlon  x  duration, however, there was  little  difference between  continuous .-
and Intermittent  exposure.   At  the  lower concentration,  the differential  In
mortality  between  continuous  and  Intermittent  exposure  disappeared  by  14
days.
    Several  studies  (Table   6-1)   suggested  that  the  NOAEL   for   Increased
susceptibility In  the animal  1nfect1v1ty model  was between 0.05 ppm (Gardner
et  al.,  1981) and  0.5  ppm  (Ehrllch  and Henry,  1968; Blair  et  al!,  1969).
Other  effects  observed  In these studies  Included  exacerbation of  prollfera-
tlve  lesions  Induced by exposure  to Influenza  virus  (Motomlya et al., 1973),
pneumonltls and   the  development of  lesions  suggestive of  early   emphysema
(Blair et al.,  1969).   The super1mpos1t1on of  two 1-hour peaks of  0.8 ppm  5
days/week  on   a  background   exposure  of  0.2   ppm  Increased  mortality  to
Infective  challenge and  to   Impaired lung  function,   and  may have Induced
subtle hlstopathologlc changes In the lungs (Miller et al.,  1987).


0166d                                -31-                             07/26/89

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      I   III   I
I   I   I  I     II
I         I
                    I   I    I  I     II     I     II
                                          I    I  I     111
                                     TIME
                                 FIGURE 6-1

    Regression  Lines of Percent Mortality of Mice vs.  Length  of Continuous
    Exposure to Various N02 Concentrations  Prior  to Challenge with Bacteria

                       Source:  Gardner et al.,  1977D
0166d
               -32-
                                                                   04/10/89

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                                                                               TABLE 61

                                           Susceptibility In the Animal  Infectlwlty Model  In Nice  Exposed  to Nitrogen Dioxide
            Strain       No.  of
                      An\ma Is/Sex
               Exposure Protocol
                        Exposure
                      Concentration
                          (PP«)
         Response
               nts
   Reference
            Swiss      >30/F/group
            NR        NR





            Cf-l       280/F/group
            NR
NR
            CO-1       18-21/F/
                      group
               continuous for          O.S
               <12 aonths
               6 or 18 hours/day       O.S
               for <12 Months

               continuous for          O.OS
               14 days

               continuous for          0.3-O.S
               6 aonths
               continuous for          O.S. 1.0
               3 Months                or 1.5
6. 18 or 24 hours/      O.S
day for 3. 6. 9 or
12 Months
               23 hours/day for        0.2
               
-------
    Exposure  to nitrogen  dioxide  affected  specific  mechanisms  that  afford
resistance  to  Infections  (Table 6-2).   Giordano and Morrow  (1972)  reported
reverslbly  decreased  rates  of  mucodllary  clearance  1n rats  continuously
exposed  to  6  ppm  for 6  weeks.   Aranyl et  al.  (1976)  observed  morphologic
changes  In  alveolar macrophages harvested  by  lavage from mice continuously
exposed  to  2  ppm for 21  weeks.  These  changes did  not  occur  with continuous
exposure  to  0.5 ppm.  Mice  exposed  Intermittently  to  10 ppm showed  altered
humoral  response to  SRBC,  altered  host response  to  Immunocompetent  donor
lymphocytes, and reduced  survival  1n  a tumor  rejection test  (Holt  et  al.,
1979).   Altered  SN  antibody  response  was  reported  In  mice  continuously
exposed  to  2  ppm and vaccinated with Influenza  virus (Ehrllch  et al.,  1975)
and  1n monkeys  continuously  exposed  to 1  ppm and challenged  with  virulent
Influenza virus  (Fenters et al.,  1973).   Continuous  exposure  to  0.3 or  0.8
ppm  enhanced  expression  of  endogenous  retrovlrus  genes  In  both  high  (AKR)"-
and low  (Swiss  Webster)  expressor  strains of mice  (Roy-Burman et  al., 1982).
A concentration-related  suppression of  primary Jki  vitro antibody  response to
SRBC was  reported 1n  mice  continuously  exposed  to  0.4 or 1.6 ppm for  4  weeks
(Fuj1mak1 et al., 1982).
    Exposure to  nitrogen dioxide also affected  the morphology,  function  and
biochemistry of  the  lungs.   U.S.  EPA  (1982)  described the  pathogenesls of
emphysema,  the critical   lung  effect associated  with  long-term  exposure to
nitrogen dioxide.   Initially,  there was accumulation  of alveolar macrophages
and destruction  of  Type  I  pneumocytes and  dilated epithelial cells followed
by hypertrophy  of  the lung  epithelium  and   differentiation of  Type II  cells
Into Type I  cells.
    The  development  of these  lesions  In the respiratory tract has recently
been more thoroughly  characterized  1n  hamsters  exposed to  relatively  high


0166d                               -34-                             04/10/89

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                                                                                I ABIE 62

                                       iffects of Exposure  to MUragen Dloslda on Mechanisms that Provide Resistance to Infection
or>
o>
Spec les/
Strain
Rat/Long-
ivans
House/NR

House/
BAlB/c
No. of Exposure
Animals/Sex Protocol
16/f /group continuous for
6 weeks
MR continuous for
<33 weeks
continuous for
<24 weeks
20/f/group 2 hours/day.
S days/week
for <30 weeks
Exposure
Concentration Response
(PP*>
6 Decrease In mucoclllary clear-
ance (ftf and 1P11); edema and
vascular congestion In alveolar
region
2 Alveolar manophages had loss
of surface projections, bleb
or fenestrace formation,
degeneration
0.5 Alveolar Mcrophages unchanged
10 Interstitial pneumonia; trans-
lent leukocytes Is; altered
humoral response to SRBC.
Comments
Individual variation were
large; effect was fully
reversible In 7 days
Alveolar manophages harvested
by lavage

Also congestion of alveolar
septal capillaries, enlarge-
ment of peripheral air spaces.
Reference
Giordano and
Narrow. 197?
Aranyl
et al.. 1976

Holt et al..
1979
 CO
 in
            House/
            Swiss
>14/H/group
continuous for
<40 weeks
depressed spleen cell PHA
response; altered GVH response;
reduced survival In tumor
rejection test

transient depression of SN
tlters and seroconversion
rates; Increase In serum Igm.
                                                                                    Increased concentration of
                                                                                    goblet  cells
Similar response In mice
exposed to O.S ppm subjected
to 1-hour peaks at 2 ppm S
days/week.  Nice vaccinated
with A?/latwan Influenza virus
after 12 weeks.
Ehrllch
et al.. 1975
 GO
 vD
House/AKR
House/
Swiss -
Webster
House/
BAlBc

-60-70/f/
group
-60-70 H/
group
6/H/group

8 hours/day. 0.3»0.05
5 days/week
for <20 weeks
8 hours/day. 0.8»0.05
5 days/week
for <20 weeks
continuous for 0.4 or 1.6
4 weeks

Enhanced expression of endo-
genous retrovlrus genes In
spleens of both strains of
mice
Same as above
Dose-related suppression of
primary response and stimula-
tion of secondary response to
SRBC; no effect on 1 and B
lymphocyte activities
Retrovlrus expression evaluated
In lung, kidney, thymus and
spleen. AKR Is naturally high
retrovlrus expressor.
Same as above
In vitro antibody response
studied

Roy-Burman
et al.. 1982
Roy-Burman
et al.. 1982
FuJImakt
et al.. 1982


-------
                                                                         1ABIE 6-2 (cont.)
Species/
Strain
Monkey/
squirrel
No. of
Animals/Sex
4/N/group
Exposure
Protocol
continuous for
493 days
Exposure
Concentration
(PP»)
1.0
Response
Increased SN antibody response
to challenge with Influenza
Comments
Monkeys were challenged on
exposure days 0. 41. 83. 146.
Reference
renters
et a).. 1973
                                                                         A/PR/8/34  virus.   No effect  on
                                                                         HI  antibody response;  evidence
                                                                         of  mild emphysema  only In
                                                                         •onkeys exposed to M(>2 and
                                                                         virus.   No effect  on hemalo-
                                                                         crlt. hemoglobin,  chemical
                                                                         biochemistry
?66 and 493.  There was marked
Individual variation In response
and no statistical analysts was
performed
          NR * Not reported
CD
vD
                                                                                        tl

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concentrations  (30  ppm)  for <12 months  (Klelnerman et al.,  1985a,b;  Gordon
et al.. 1986)  (Table  6-3).   Initial  exposure  (first 3-4 days) caused diffuse
Injury  to  the lung tissue,  Involving  the vascular bed and  resulting  In  the
production  of edema,  and  focal  damage  to  the epithelium of the  terminal
airways and adjacent  alveoli  followed  by  marked  epithelial  proliferation.
The edema  tended  to clear with continued exposure.  The  presence  of damaged
epithelial  cells  resulted  In  an  Inflammatory  response  with  an  Influx  of
neutrophlls  and  macrophages.  The  Inflammatory  cells   secreted elastase,  an
enzyme  that  attacked  elastln In  the parenchyma  of  the  lung with  the release
of a unique  amlno acid,  desmoslne;  this  amlno  acid was  excreted In the urine
and monitored.  The Influx  of  Inflammatory cells was  limited to the first 30
days   of   exposure.   Defensive   mechanisms   (proteases   that   Inactivated
elastase)  limited the  progression of these lesions to  the first few weeks of
exposure.   Therefore,  continued  exposure did  not  lead  to  progesslon  of  the-:
Intensity or severity of the lesions.
    In  hamsters,   the  morphology  of   the   epithelium   of   the  terminal
bronchioles  changed following death  and loss  of  some of  the cells  of  the
original  population  (Klelnerman  et  al.,  1985a).  These  changes  Included
Increased  cell  turnover,  Increased  cell  size and  volume,  alterations  In  the
morphology  of  the Clara cells and  the  dilated epithelial  cells, decreased
proportion  of  secretory  cells, the development  and aggregation Into nodules
of cells  of mixed  morphology  (1ndeterm1nant  cells)  and  the  development of
Intracellular  cilia  and   Intraeplthellal  cysts.   Ultrastructural  studies
revealed  reduced  numbers,  disruption  and fragmentation  of  the  tight junc-
tlonal  fibrils between epithelial  cells  1n  the  terminal bronchlolar regions,
and,  to a  lesser  degree,   1n  the alveoli,  that  may  have  compromised  the
barrier  function  of  the epithelium  (Gordon  et  al.,   1986).   These lesions


0166d                               -37-                .             04/10/89

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                                                                              1ABLE 6-3

                                                    Development  of  Emphysema  In Animals Exposed  to Nitrogen Dioxide
Species/
Strain
Hamster/NR
No. of
Animals/Sex
6 9/sex MR
Exposure
Protocol
22 hours/day
for <365 days
Exposure
Concentration
2
Response
Injury to terminal bronchioles
and alveoli leading to trans-
ient destruction of nature of
eptthelliM (see text)
• Contents
Norphometrtc. biochemical and
hlstopathologlc Investigation
of pathogenesls of emphysema
Reference
Klelnerun
et al.. )985a
           Hamster/NR    4-6/sex MR
i
to
00
I
            Hamster/
            Syrian
            Rat/SPF
            Mlstar
            Hamster/
            Syrian
20/M/group
78/H
7-9/M/group
            Rat/SPF-
            Ulstar
3/H/sacrl-
flce group
               22 hours/day
               for 
-------
                                                                           1ABIE 6-3 (cont.)
Exposure
Species/ No. of Exposure Concentration Response
Strain AntMls/Sex Protocol (ppm)
Rat/F344 SO/sex/group 7 hours/day. 1 or S
5 days/week.
for <15 weeks
Transient biochemical altera-
tions (elevated LOH. GSM R.
AlKP) In both groups; lesions
Halted to 5 ppm groups In-
cluded subpleural macrophage
accumulations and focal hyper-
inflation
Cements Reference
Groups of 10 rats/sex/group Gregory
killed at 0.4. 1.7. 2.1. 6 or et al.. 1983
IS weeks, findings suggested
•axtMM damage at 1.7-2.7 weeks
followed by maximum repair at
6 weeks
CO
\£
I
Rat/JCL:      36/M/group     continuous for    0.4. 1.2. 4    concentration-related Increase
Wtstar                       <16 weeks                        In llpld peroxldatlon (evidence
                                                              of oxldatlve stress).  Response
                                                              was generally duration-dependent
                                                              after 4-8 weeks.  Activity of
                                                              protection Initially Increased
                                                              then decreased

Mouse/        60 N/group     6 hours/day.      0.34           Increased number of Type II
Swiss-                       5 days/week                      pneumocytes (number of cells/
Webster                      for 6 weeks                      field and total area of
                                                              alveolus)


House/        45/H/group     6 hours/day.      0.3*0.05       Increased number of Type II
Swiss-                       5 days/week                      pneumocytes (p<0.025).  Con-
Webster                      for 6 weeks                      slderable reversion toward
                             starting at                      control values In a 10-week
                             birth                            recovery period

Rat/JCL-SD    3 or 7/f/      continuous for    0.1. O.S.      consistently statistically
              group          1 month           3.0, 10.0      significant concentration
                                                              related Increase In arithmetic
                                                              mean air-blood barrier thickness
                                                              at 3.0 and 10.0 ppm; magnitude
                                                              of response least In 12-month-
                                                              old rats
                                                                                                           llpld peroxldatlon and actlv-    Ichlnose and
                                                                                                           Itles of protective enzymes      Sagal.  1982
                                                                                                           measured at several Intervals
                                                                                                           during exposure
Quantification by Image analy-   Sherwln and
sis.  In absence of hlstopatho-  Rlchters. 1982
logical or functional Impair-
ment, these changes are not
considered adverse

Test groups also exposed -1      Sherwln
week jn vitro                    et al.. 1985
                                                                                                           Electron microscopic morpho-     Kyono and
                                                                                                           metric evaluation of rats at     Kawal.  198?
                                                                                                           1. 3. 12 and 21 months of age
            MR « Not reported

-------
persisted  throughout  the  exposure  period  and  were  Incompletely  reversed
after  9  months of  a recovery  period  without exposure to  nitrogen  dioxide.
Despite  the  persistence of the  epithelial  lesions,  there was  IHtle  effect
on  several  mechanical   Indicators  of  pulmonary  function  (total  pulmonary
resistance,  upstream  airways  resistance  and  static  compliance).    These
Indicators were measured throughout  the exposure period  (Klelnerman et  al.,
19855).
    As Indicated  above,  the threshold  for  significant morphological altera-
tion may be  considerably  lower  than  that  for  measurable  effects  on pulmonary
function.   The development  and regression  of  lung  lesions  over  a  28-day
exposure and  56-day recovery period were  recently studied 1n  rats  continu-
ously  exposed  to  10.6  ppm by  Rombout  et al.  (1986)  (Tables 6-3 and  6-4).
These  data  Indicate  that  lesions   In  rats  generally  resemble  those  In
hamsters.                                                                    *
    In  subchronlcally  exposed   hamsters,  the  threshold  for  mechanical  or
hlstopathologlc  evidence  of  emphysema  appeared to  be  <2  ppm,  although
morphometrlc alterations  were reported  at  that concentration  (Lafuma et al.,
1987).   In  subchronlcally exposed  rats  the  threshold   for  hlstopathologlc
evidence of emphysema appeared  to  be  <2.7  ppm (Rombout et al.. 1986;  Gregory
et  al.,   1983).  'Morphometrlc  (Kyono  and  Kawal,   1982)  and  biochemical
Investigations suggested  that alterations  occurred at  lower  levels,  but that
exposed  rats  were  able to  cope by applying defense  and  repair  mechanisms
(Gregory et al.,  1983;  Ichlnose and.Sagal,  1982).  Increased numbers of Type
II cells,  estimated by  quantitative Image analysis,  were reported 1n mice
Intermittently exposed  to  0.3  ppm (Sherwln  and Rlchters, 1982;  Sherwln  et
al.,   1985).   The  Investigators stated  that   the  Increase  1n Type  II  cells
suggested  that  Type I  cells  had  been  Injured.   The effects  appear  to have


0166d                               -40-                             04/10/89

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                                  TABLE 6-4

              Development and Regression of Lung Lesions  In  Rats
                        Exposed to Nitrogen D1ox1dea«b
DuMnq Exposure0
Chanqe (days)
0 1 2 4 8 16 28
During Recovery0
(days)
29 30 32 36 44 56
Loss of d!1a

Hypertrophy of
bronchlolar
epithelium

Hyperplasla of
bronchlolar
epithelium

Necrosis of
type I cells

Increase of
type II cells

Increase of
alveolar
macrophages

Focal dilatation
of alveoli

Thickened
centMlobular
septa
                tt
t   tt  tt  tt  tt
    t   tt  tt  tt
f   f
                          f <•   +•    f
                              ff   f
                              t   f
aSource: Rombout et al., 1986

^Exposure was continuous at 10.6 ppm

c-,  Absent;  i,  focal;  *, present  In moderate degree;  t*,  present  1n  high
 degree
0166d
       -41-
04/10/89

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been  largely,  but not  totally,  reversible after  a 10-week  recovery  period
(Sherwln  et  a!., 1985)  and  the  toxlcologlcal  significance  of  Increased
numbers  of  Type  II  cells  without  other hlstopathologlcal  or  functional
evidence of damage Is unknown.
    Most  of  the  recent   studies   with   nitrogen   dioxide  Investigated  the
occurrence  of   emphysema-like   lesions   In   the  lungs.    However,   several
studies, particularly  the earlier  ones,   reported  other effects  (Table  6-5).
An  early  study reported mortality  In  rats and  monkeys continuously  exposed
to  11.3  ppm and  In  guinea  pigs  and rabbits  at  4.9 ppm,  but cause  of  death
was  not  determined,  group  sizes not  reported  and statistical analysis  not
performed  (Steadman  et al.,  1966).   The Investigators  remarked  that  their
findings  contradicted  earlier   studies   that  did  not report  mortality  at
comparable  exposure  levels.  They  considered  that these  discrepancies  may
                                                                             f
have  been  due  to experimental differences Including degree of  animal  crowd-.
Ing,  purity of  the  test  material,  differences  In analytical  procedure  and
sex,  strain or  age differences  In  sensitivity.  There  were no  effects on rate
of  body weight  gain  or  hematology  (RBC,  WBC,  PCV).  Bronchitis  and pneumonia
were  reported  In guinea pigs at 11.3  ppm.  Freeman et al.  (1969) attributed
mortality to respiratory  failure In 4/56 rats exposed continuously to 15 ppm
for <20  weeks.   Mortality  data  were not  reported  for controls;  statistical
analysis was  not possible  and  the  occurrence of  respiratory  Infections  not
mentioned.   In  contrast to these studies, Glasgow et  al.   (1987)  reported no
mortality  1n  rats continuously  exposed  to   30  ppm for <20  weeks,  although
rate  of  body  weight  gain  decreased.  The mortality  reported  by  Steadman et
al. (1966)  and  Freeman  et al. (1969)  was considered  unrelated to treatment.
Reversible  depression  of   body  weight  gain  was  observed  In  rats  exposed
continuously at  15 ppm for <20  weeks  followed  by a recovery period (Freeman


0166d                                -42-                             07/26/89

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                                                                                TARIE 6-5

                                                              Other Effects of Exposure to Nitrogen Dioxide
o
—i
•—
ro

\
CD
Species/Strain
• i
Rat/Long-Evans or
Sprague-Oawley
Guinea plg/NR
Rabbit/New Zealand
Monkey/squirrel
Oog/beagle
Number/Sex
15/sex NR
15/sex NR
3/sex NR
3/sex NR
3/sex NR
Exposure
Protocol
8 hours/day.
5 days/week for
30 exposures
Exposure
Concentration
(Ppm)
35.6
Response
Mortality In all species except
dogs; all monkeys died on first
day. Signs included dyspnea.
lethargy, vascular congestion
and focal hemorrhage (agonal
changes)
Comments
No effects on hematology or
body weight gains of survivors
Reference
Steadman
et al.. 1966
     Rat/Long-Evans  or
     Sprague-Dawley         NR
     Guinea  plg/NR         NR
     Rabbit/New Zealand     NR
     Monkey/squirrel       NR
     Oog/beagle            NR
Rat/Sprague-Dawley    120/M
Rat/NR
                            56/sex NR
      House/Swiss-Webster    300/N adults
                            134/H neo-
                            nates
                                        continuous for
                                        90 days
continuous for
<20 weeks
continuous for
<20 weeks
                                        8 hours/day.
                                        5 days/week for
                                        6 weeks
                    0.48
                    0.53
                    4.89
                   11.32
                   11.48
                                                                 30
                                                           15»2
                                                                0.35*0.05
Rats and monkeys:  mortality at
11.32 ppm; guinea pigs and
rabbits: mortality at 4.89 ppm;
no mortality In dogs
No morbidity or effect on
behavior; reduced rate of body
weight gain, altered lung
morphometries, morphology,
biochemistry

Death of 4/56 attributed to
respiratory failure; reduced
body weight, elevated lung
weights; duration-related
Increase In Intensity and
severity of lung lesions

Elevated relative spleen
weights (p<0.05) and size of
splenic lymphold nodules and
nonlymphold areas;  reduced
splenic hematopolesls In adults
and newborns
No effects on hematology. body    Steadman
weight gain or gross pathology    et al.. 1966
except for bronchitis and pneu-
monia In guinea pigs at >4.89
ppm.  Group sizes not reported;.
no statistical analysis

Pathogenesls of lung effects      Glasgow
appeared to parallel that of      et al., 1987
hamsters reported by Klelnerman
et al. (1985a.b)
Effects on body weight were       freeman
fully reversible; effects on      et al.. 1969
lungs were largely but not
totally reversible; mortality
data not provided for controls
                                                                      Investigation limited to          KuraUls
                                                                      effects on body weight and        et al.. 1981
                                                                      spleen.  Effects not consid-
                                                                      ered adverse.

-------
                                                                     TABU b-S (cont.)
Species/Strain
Rat/JCL: Mlstar
• i
NiMber/Sex
48 N/griMips
Exposure
Protocol.
continuous for
14 weeks
Exposure
Concentration
(PP-)
0.4. 1.?. 4.0
Response
All levels: periodic reduction
of •IcrosoMl P-450 and cyto-
Comeri Is
Investigation Halted to
•IcrosoMl enzyme activities. .
Reference
Takahasht
et al.. 1986
                                                                           chro*e  reductase  In  lung.   .       Exposed rats were periodically
                                                                           periodic reduction of cytochrooe   able to overcome decreased
                                                                           P-4SO and NADPH-cytochroxw P 450. .lilcrosoMl enzyM activities
                                                                           reductase In  liver ulcrosoaes.
                                                                           At  1.2  and 4.0 pp«.  periodic
                                                                           Increase In MlcrosoiMl cytochrone
                                                                           p 450.  cytochroM bs. NADH-cyto-
                                                                           chro*e  P-4SO  reductase and NAOH-
                                                                           cytochrone 65 reductase
MR * Not reported

-------
et  al.,  1969).   Slight  Increases   In  relative  spleen weights  and  slight
changes  In  the. proportions  of  the different  types of  splenic  cells  were
reported 1n mice exposed  Intermittently to  0.35  ppm  (Kura1t1s  et  al.,  1981).
In  the absence  of  hlstopathologlc  evidence of  cellular  or  organ  damage,
however,  these  changes  are   not   considered  adverse.   Low-level   exposure
altered the activities  of mlcrosomal enzymes  1n  the  lungs,  liver  and kidneys
of rats  (Takahashl  et  al.,  1986).   These biochemical  Indicators  of  exposure
are not considered adverse.
    6.1.1.2.   CHRONIC — Chronic Inhalation  studies  with  rats  are summa-
rized  In  Table  6-6.   Concentrations >12  ppm were  associated with  reduced
body weights,  Increased breathing  rate,  dramatically  Increased  lung  volume
resulting In morphologic distortion  of  the  skeletal  confines  of  the  thoracic
cavity, and hlstopathologlc lesions  as  described  1n  Section 6.1.1.1. (Haydon.
                                                                             .•
et al., 1965;  Juhos et  al., 1980).   These  lesions altered the epitheliums of-.
the  terminal   bronchioles  and  adjacent  alveoli, accumulation  of  cellular
debris  and  fibrin,  degeneration  of  cilia  and  reduction of  the  lumenal
diameter of  the terminal bronchioles.   Elevated respiratory  rates  and  mild
hlstopathologlc  changes  equivocally associated  with  exposure  to  nitrogen
dioxide  were   reported  at 0.8  ppm  (Haydon et  al.,  1965,  Freeman et  al.,
1966).   In  the  absence  of   other evidence  of damage   or  Impaired  lung
function, the  elevated  respiratory  rates are not considered adverse.  Ultra-
structural   evaluation  revealed  effects  on  the  epitheliums of  the  terminal
bronchioles  at  2   ppm   (Stephens  et  al.,   1971).    Permanent  morphological
changes were  reported  In  the  lungs of  dogs exposed  Intermittently to  0.64
ppm for  68  months  followed by  a 3-year recovery period  (Hyde et al.,  1980)
(see Table 6-6).
0166d                               -45-                             07/26/89

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                                                                           TABIF 6-6

                                                   Chronic Inhalation Exposure of  Animals to Nitrogen Dioxide
o.
o>
o»
ex
Species/
Strain
Rat/NR
Number/Sex
2-3/H/
groups
Exposure
Protocol
continuous for
<17 Months
Exposure
Concentration
(ppm)
15.?f0.71
Response
Consistently reduced body
weight and Increased absolute
Comments
No mention of survival or non-
respiratory effects
Reference
Juhos et al. .
I960
        Rat/NR
15/sex NR
        Rat/NR
         Rat/NR
9/sex NR
10/sex NR
         Rat/JCL:
         Ulstar
12/N/group
continuous for
<813 days
continuous for
<977 days
continuous for
2 years
continuous for
9. 18 or 27
months
12
                                                     0.8
                                                     4.0*0.4
lung weight and volume.   Hlsto-
pathologtc lesions of emphysema
(see text) In terminal bronch-
ioles; duration-related reduc-
tion In mean diameter of
bronchioles

Decreased body weight. In-
creased lung weight and breath-
Ing rates.  Gross distortion of
thoracic cavity and hlstopatho-
loglc lesions of emphysema
(see text)

Elevated breathing rate, mild
hlstopathologlc lesions equivo-
cally attributed to exposure;
no effects on survival,  body
or organ weights

Loss of cilia, failure of new
cilia to develop; dlsorlenta-
tlon of basal bodies; formation
of Intracytoplasmlc ciliated
vacuoles and crystalloid
Inclusions

Progressive hypertrophy and
hyperplasla of bronchial epi-
theliums, thickened walls,
cellular Infiltration and
Hbrotlc organliltlon; In-
creased ANT.  No lesions of
frank emphysema
Severity of effects on the        Haydbn et al..
lungs correlated with duration    1965
of exposure
                                                  Four  of  nine allowed  to  live a     Haydon et  al..
                                                  natural  llfespan;  small  group     196S;  freeman
                                                  sizes, no  statistical  analysis     et al.. 1966
                                                  Evaluation  limited  to  ultra-       Stephens
                                                  structural  examination of  lung     et  al..  1971
                                                  Morphometrtc. morphological  and    Sagal  et  al..
                                                  biochemical  studies  on  lung.       1984;  Sagal
                                                  No  effect on survival or  body      and Ichlnose.
                                                  weight.  Concentration-related     1987;  Kubota
                                                  but  non-significant  Increase       et  al..  1987
                                                  In  lung weights.  Biochemical
                                                  evidence of  llptd peroxldatlon
                                                  at  all exposure  levels
 co
                                                                                         It

-------
                                                                         TABU 66 (cont.)
Species/ dumber/Sex
Strain
Rat/JCt :
..Wlstar
• i
Dog/NR 6 or I?/
group.
sex MR
Exposure
Protocol
16 hours/day
for 68 wmths
followed by
3-year recovery
period
Exposure
Concentration
v
OB

-------
    A  series  of  experiments  1n rats characterized  the  morphologic, morpho-
metrlc and  biochemical  changes  1n  the lung associated with exposure to 0.04,
0.4  or 4.0  ppm  continuously  for  9, 18  or 27  months  (Sagal et  al.,  1984;
Sagal  and  Ichlnose,  1987;  Kubota  et  al.,  1987).   Concentrations  were contin-
ually  monitored  throughout  the  exposure  period.  Ambient  temperatures  were
maintained  at  24-26°C.   At 4.0 ppm,  progressive  development of hypertrophlc,
hyperplastlc  lesions  Including thickened bronchial  walls,  Infiltration  with
Clara  cells and  flbrotlc  organization was  observed.  Alterations  were  not
detectable  by  light  microscopy  at   0.4  ppm  until   27  months of  exposure.
Morphometrlc  changes   (Increased  arithmetic  mean   thickness  of  air-blood
barrier,  volume density of  Type  I and Type  II  cells 1n  the  alveolar  wall,
and mean  number  of alveolar  cells and volume density/cell)  were detectable
at  all  exposure  levels.    Biochemical  Investigation  Indicated   that  Upld
                                                                             .•
                                                                             f
peroxldatlon  Increased  at  all  exposure  levels  and that ant1ox1dat1ve protec-.
tlve mechanisms  were  depressed  at  0.4 and  4.0 ppm.  Although microscopically
detectable  lesions  were observed  In  the  0.4 ppm  group,  they  did not  appear
until  27  months of exposure.  However, adverse  effects  (thickened air-blood
barrier,  Increased  I1p1d  peroxldatlon,  depressed  ant1ox1dat1ve  protection
mechanisms), which might be  considered  harbingers of the effects  observed at
the  highest  concentration  studied,  were  seen  at  thrat  exposure  level,
considered  the  LOAEL.   Although  the  0.04 ppm  level  was  associated  with
morphometrlc  and  biochemical   changes  (thickened  air-blood  barrier  and
Increased  I1p1d  peroxldatlon).  no  accompanying  hlstologlcal changes  were
observed, resulting 1n  the evaluation of this exposure level as a NOAEL.
    Ep1dem1olog1c  studies   Investigated  the  effects of  humans   living  In   a
heavily polluted  region, and  the  effects  on children and adults of  living 1n
homes  with gas  stoves  (which  exhaust  nitrogen  dioxide).   The  well  known


0166d                               -48-                             03/13/90

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Chattanooga School  Children  Study (Shy et al.,  1970a,b,  1973;  Shy and Love,
1979)  examined  the relationship  between  ambient  nitrogen  dioxide pollution
levels and acute  respiratory  disease   and  pulmonary  function  In children.   A
total  of  987  children  participated  1n  ventllatory  function testing  and
respiratory Illness  surveys.   The children  lived  1n one of  four  geographic
areas:   1) a  high nitrogen dioxide exposure area  close  to  a  plant producing
TNT  and  emitting large quantities  of nitrogen dioxide during  production;
2) an  area  of  suspended participates;  3) a control  area between  the  first
two  areas;  and  4) a second control  area  that  was not between  areas  one  and
two.  The ventllatory  functions of  the  children  were determined by measuring
FEV  75  once  weekly during November  1968  and  March  1969.  The Incidence  of
acute  respiratory   Illness   In   the   children  was   also  studied  November
1968-Aprll  1969  using  a  biweekly  respiratory Illness  survey.  The  average
nitrogen dioxide  concentrations  found 1n  the  various areas were  as follows:"
0.083  ppm  for   the high  nitrogen  dioxide area;   0.055  ppm  for the  high
partlculate area; 0.063 ppm  for  control  area 1;  and 0.043  ppm  for  control
area  2.    Shy  et  al.  (1970a,b)  reported  significantly  lower  ventllatory
performance  In  the high  nitrogen  dioxide  region   (p<0.05)  than that  of
children 1n the  control areas.   Respiratory  Illness  rates of  the children 1n
the high nitrogen dioxide  area were significantly greater- (p=0.005) over the
entire study period than the  Illness rates In  the  two control  areas.
    U.S.  EPA  (1982) criticized this  study for  using  an unreliable  analytical
method  for nitrogen   dioxide and  noted  considerable  overlap  In nitrogen
dioxide  concentrations  between  the different  study  areas.   Furthermore, the
high nitrogen dioxide  area also  had  the  highest concentrations of suspended
nitrates   and  sulfates.   Differences  In   the  concentrations  of  nitrogen
dioxide,   suspended  nitrates,  suspended  sulfates,  total  suspended partlcu-
lates and soiling Index between the four areas were  small.
0166d                               -49-                             07/31/89

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    Harrington and  Krupnlck  (1985)  criticized Shy and  Love  (1979)  for  using
rudimentary   statistical   techniques   1n   analyzing   the   data   from   the
Chattanooga study and  reanalyzed  that data.  They observed  that,  although  a
statistically  significant   difference   existed   between  the  Incidence  of
respiratory  Illness 1n  the  high  nitrogen  dioxide  area  compared  with  the
control  areas,  this difference was  not  monotonlc,  but  exhibited a U-shaped
relationship.   They determined  that more  Illness  was  associated  with  low
pollution  values  (0.053  ppm)  than with   high  (0.204  ppm)  values.   This
U-shaped relationship  was  found  In  several subpopulatlons as well  as  In the
entire  data  set.    The  authors  were   unable  to  explain  this  unexpected
observation.
    U.S. EPA  (1982)  reviewed several other studies of  pulmonary  function  of
adults  from  areas  relatively  high  or  low  In   nitrogen  dioxide  pollution..
                                                                             •I
(Spelzer and  Ferris,  1973a,b; Cohen  et  al.t 1972;  L1nn et  al.,  1976).   The--
results  generally  Indicated  no  clear  correlation  of  Impaired  pulmonary
function  and  levels   of  nitrogen  dioxide.   A   Japanese  study  reported  a
negative correlation between pulmonary  function   and  nitrogen dioxide  levels
In  school  children  believed  to be  unusually sensitive  to  nitrogen dioxide,
but a  greater negative  correlation was observed between  pulmonary function
and ambient  temperature (Kagawa and  Toyama,  1975).   It was  not  possible to
factor  out  the  Impact of  other  pollutants  such as  sulfur  dioxide,  hydro-
carbons, ozone, nitrous oxide and suspended partlculates.
    In a prospective study,  Spelzer  et  al.  (1980) compared lung function and
the Incidence  of respiratory  disease  In children from  households  using gas
stoves  with  children   from   households  using  electric  stoves.    The  study
Involved -8000,  6-  to  10-year-old  children.  Within each  of  the six cohorts
studied, households  with gas  stoves had  nitrogen  dioxide  levels  4-7  times
those of households  with electric  stoves.   Data  on  Incidence of respiratory

0166d                                -50-                             07/31/89

-------
disease  were  obtained  by  questionnaire;  FVC  and  FEV,  were  measured  at
school.   The FEV   obtained  were  adjusted  using  predicted  values based  on
height.   The  effect  of parental smoking, air  conditioning,  social  class  and
type  of  home-heating fuel was  controlled.  Significantly  Increased Incidence
of  serious  respiratory disease before  age  2  (p<0.01) and decreased  FVC  and
FEV.  (p<0.01)  were  associated  with   gas   cooking  compared  with  electric
cooking.
    These   data   were   subsequently   expanded  and  reanalyzed,   with   the
conclusion  that  there  was no  effect  of gas  stove cooking  on  the Incidence of
respiratory  disease  (Ferris et  al.,  1983).   The Investigators  attributed  the
difference  In conclusions  to  differences   In definition of  the  variables
considered.   In  the Spelzer  et al.  (1980)  study, respiratory  Illness  data
were  pooled regardless  of gender,  households were categorized  Into  cooking^
                                                                             *
with  gas  only or  electricity only,  the  smoking variable was  determined  by>
the presence  of  any smoker In  the household, and social  class  was based  on
education level  and  occupation  of  parents.   In the latter  study, respiratory
Illness  data were  separated  by  gender,  cooking  method  was  designated  "no
gas" or  "any  gas,"  only  maternal  smoking  was considered and  social class  was
based on education level alone.
    In' a  more  recent  case-control   study,   Hoek  et al.   (1984)  found  no
relationship  between  Indoor nitrogen dioxide levels and  respiratory symptoms
In  school  children.  Children suffering  from  respiratory  Illness  (bron-
chitis,  asthma,  frequent cough  or colds and allergy)  were Identified  by a
standard  questionnaire  and  compared  with   children  with  no  respiratory
Illness.   A  total   of  231  children  participated In  the  study,  with  128
symptomatic and  103  control  children.   The  weekly  average level of nitrogen
dioxide was  determined  In each  home of  the  study population.  Virtually no
differences were observed In  the  nitrogen dioxide levels  In  the homes of the

0166d                                -51-                             07/31/89

-------
symptomatic  and  the  control  children.   Consequently,  no  relationship  was
seen  between  a history  of  respiratory  symptoms  In the children  and  Indoor
nitrogen dioxide  levels.  The  Investigators  observed  that  the study may have
been  biased  by the high  mobility  of the study population  and  the Inability
to  quantify  historical  exposure to nitrogen dioxide.   The  authors concluded
that  an  association between  Indoor  nitrogen dioxide  levels  and  respiratory
symptoms could not be excluded.
    Fischer  et  al.   (1985)  performed  a  longitudinal  field study  of  the
effects  of home  nitrogen dioxide  levels on  the  pulmonary  function  of  97
nonsmoking women.   A  battery of pulmonary  function tests  were performed  at
three  yearly   Intervals,  and  nitrogen dioxide  levels  were measured  In  the
subjects'  homes  for  1   week/year.   The  estimated  personal  exposure  levels
ranged  from  0.0058-0.066 ppm.   Negative, but not  significant,  associations.
                                                                             • *
between  nitrogen  dioxide level and several  pulmonary function  parameters-.
were observed.
    Robertson  et  al.  (1984)  compared FEV.  and the  Incidence of  respiratory
symptoms  In  560 British coalmlners exposed  to relatively  high  (126 workers)
or  low (434  workers) levels  of oxides   of nitrogen over 8  years.   The mean
concentrations  of nitrogen  dioxide  experienced  by workers  exposed to h'yh
and low  levels of total oxides of nitrogen  were  not reported.   No relation-
ship was found  between  exposure at  this  level  and  lung function or Incidence
of  respiratory   symptoms.    A  relationship  was  found,  however,  between
exposure to coal dust or smoking and decreased FEV..
6.1.2.   Oral Exposure.
    6.1.2.1.    SUBCHRONIC -- Data  were   not  located  regarding  the  toxldty
of  Ingested  nitrogen  dioxide  gas;  however,  nitrogen  dioxide  In  water  1s
converted  to  nitrite  and  nitrate  (U.S.  EPA,   1986a).   U.S.  EPA   (1986a)


0166d                               -52-                             07/26/89

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derived  an  oral  RfD  for  nitrogen  dioxide N  by  analogy to nitrate.   An  RfO
for  nitrate N was  based on  a  NOEL  for  methemogloblnemla 1n  human  infants
exposed  to  low   levels  of  nitrate  In  drinking  water.    This  approach  to
derivation  of  an oral RfO  for  nitrogen  dioxide  Is  appropriate,  because  the
laws of  thermodynamics dictate  that  all  nitrogenous  substances  In  water  tend
to  convert  to  nitrate (NAS,  1977b).   The key study  selected  for  derivation
of  the  oral  RfD  was an ep1dem1olog1cal  study  by  Walton (1951),  who analyzed
data for  214  Infant methemogloblnemla cases reported 1n 17  states  for  which
water n'Urate  N  data were available.  No cases were  associated  with  concen-
trations of nitrate  N  ranging from  0-10  ppm,  and  U.S. EPA  (1986a)  Judged  the
10  ppm  level  a  NOEL  In  this  study.   Five cases  (2.3%) were  associated with
concentrations  of  11-20  ppm,  36  cases  (16.8%)   with  21-50  ppm,  81  cases
(37.8%)  with  51-100  ppm  and 92 cases  (43.1%) with  >100  ppm.  Some  states
(Ohio,  Oklahoma,  Texas)  reported  a  substantial  number   of  water  samples;
exceeding 10 ppm nitrate  N, but no  cases of  Infant  methemogloblnemla.  This
study also  was the  basis for the  verified  RfD for oral exposure  to  nitrite
(U.S. EPA, 1986b).
    6.1.2.2.   CHRONIC — Pertinent data  regarding the  chronic oral  effects
of  nitrogen  dioxide were not  located 1n  the available literature  cited  In
Appendix  A.   Several  chronic  animal  studies  on exposure  to nitrate  were
recently  reviewed  by U.S.  EPA  (1985b).   U.S.  EPA (1985b,  1986a)  concluded
that animals are not appropriate models  for  methemogloblnemla,  the critical
effect  of  exposure to nitrate;  the  human data were  used  to  derive  an  RfD.
It  1s  beyond  the scope  of this  task  to  evaluate  studies of  chronic  oral
exposure of animals to nitrate.
0166d       '                        -53-                             06/07/90

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6.1.3.   Other  Relevant  Information.   The  effects  of  acute  occupational
exposure  of  humans  to  nitrogen   dioxide  have  been  reported  by  several
Investigators  (Lowry  and Schuman,  1956;  Darke and  Warrack,  1958; Jones  et
al.,  1973;  Tse  and  Bockman,  1970; Morrlssey  et al.,  1975;  Muller,  1969;
Fleming  et  al.,  1979).   One  of the  earliest  recognized syndromes has  been
labeled  "silo-filler's  disease"  and results  from acute exposure  to nitrogen
dioxide  that  forms 1n  the  early stages  of  fermentation of freshly  ensiled
corn  (Lowry and Schuman,  1956; Morrlssey  et  al.,  1975).   At  the  time  of
exposure,  there  Is the sensation  of  respiratory Irritation accompanied  by
dyspnea,  cough,  choking and  weakness.   These  symptoms  moderate  over  -3
weeks,  after  which time  a  second  phase  of  Illness occurs characterized  by
chills,  fever,  cough,  and  severe  dyspnea and  cyanosis,  which appear  to  be
responsive  to  large doses of  steroids.  The second  phase  of  Illness has been
                                                                            •
described  pathologically as  bronchloUtls  obllterans, a  proliferation  of-
flbroblasts Into the  lumen  of  the  small airways.   A similar  clinical  picture
has  been reported   In  Indlvuals  exposed  to high  levels of nitrogen  dioxide
resulting  from blasting used  1n underground  mines  (Muller,  1969; Jones  et
al.,  1973), from the  use of nitric  acid In the cleaning of  metals (Darke and
Warrack, 1958;  Fleming  et  al.,  1979)  from  the use of  oxyacetylene  burners
and welders (Jones  et  al.,  1973) and  from fumes released In toxic fires (Tse
and   Bockman,  1970).   None  of   these reports  estimated   actual  exposure
concentrations.
    Grayson  (1956) reported  two other  cases  of silo  filler's  disease  In
which concentrations  of nitrogen dioxide  were estimated at  300-500  ppm. The
Investigator  Indicated that acute  exposure  at concentrations  1n this  range
were  likely to be  fatal.  Acute  exposure  to  150-200 ppm was likely to result
1n  severe  bronchloUtls.   Exposure to 50-100 ppm  was  likely  to  result  1n


0166d                               -54-                             04/10/89

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reversible  bronch1olH1s.   Exposure  to  25-75 ppm  was likely  to result  In
bronchitis or bronchial pneumonia from which recovery 1s apparently complete.
    Numerous  Investigators   have  studied  the  effects of  acute  laboratory
exposure  to nitrogen  dioxide on  the lungs  of  normal  and asthmatic  human
subjects.   The  subjects were exposed to  0.086-8  ppm  for  15  minutes  to  4
hours.   Some  of  the  experimental   protocols  Included  light  to  moderate
exercise.   Clinical  signs  and  several measures of  pulmonary  function were
monitored.   Generally,  no  adverse  lung  effects  were observed  In  healthy
Individuals at concentrations <1.0 ppm nitrogen dioxide (Adams  et  a!.,  1987;
Koenlg et  al.,  1985,  1987;  Avol  et al., 1988; Drechsler-Parks  et  al.,  1987;
Kerr  et  al.,  1979; Stacy et  al.,  1983;  Kagawa 1983;  Hazucha et al.,  1983;
Follnsbee  et  al.,  1978; Hackney et  al.,  1978;  Linn et al.,  1985a;  Klelnman
et  al.,   1983).   Bylln  et   al.  (1985,  1987),  however,  reported  Increased.
                                                                             *
airway resistance at  0.244  ppm and decreased airway resistance  at  0.484  ppm-
In  nonasthmatlc  subjects.    Similar  trends were observed  In asthmatic  sub-
jects, but the magnitude of  the changes were not  statistically significant.
    At 0.1-0.5  ppm,  however, patients with  a history of asthma  experienced
Increased   specific   airway  resistance   and  potentlatlon  of   chemical-,
exercise- or  cold  air-Induced  bronchoconstrlctlon  (Bylln  et  al.,  1985;
Mohsenln 1987; Linn et  al.,  1985b;  Bauer et  al.,  1986; Orehek et al., 1976).
Kerr  et al.  (1979), however,  reported no physiologically  significant changes
In  lung  function In asthmatics  exposed  for  2 hours  at 0.5 ppm;  Hackney et
al. (1985) reported no  effect on specific  airway  resistance or  several  other
Indicators  of  lung function  In mildly  asthmatic   volunteers  exposed  for  1
hour  to   0.3,   1.0  or  3.0  ppm.    Von  Nledlng  and Wagner   (1979)  reported
Increased  specific  airway  resistance In patients with  chronic  bronchitis at
1.5 ppm  but  not  at  lower  concentrations. Effects  were  observed  at higher
concentrations  (-4 ppm)  In  human  subjects  without  respiratory  problems.

0166d                               -55-                             07/26/89

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These   effects   Included   Increased   airway  resistance,   decreased   blood
pressure,  and   changes   In  blood  biochemistry  (decrease  In  erythrocyte
acetylchollnesterase activity,  elevated peroxldlzed  erythrocyte  llplds,  and
elevated   levels   of  glucose-6-phosphate   dehydrogenase   and   glutathlone)
(Chaney  et  al.,  1981;  Posln  et  al.,  1978;  Mohsenln and Gee, 1987;  Linn  and
Hackney,  1983;   Von  N1ed1ng  et al.,  1979;  Bell  and  Ulmer,   1976).   Minor
biochemical  changes  were  reported  In  the  blood  of  young,  healthy  adults
exposed  to >1 ppm for 2.5 hours {Buckley et al.,  1976).
    Inhalation  LC5Q  values  for   nitrogen   dioxide   In  various  species   of
animals  are  listed  In  Table  6-7.   Animals acutely exposed  to  nitrogen
dioxide  exhibit  effects  on  the Immune system  and morphological effects  on
the  lung.    Nitrogen  dioxide  exposure resulted   In  Increased  mortality  1n
animals  subsequently challenged with K_._ pneumonlae at  the  following concen-
                                                                             • •
                                                                             •to
tratlons:  3.5 ppm for 2  hours  for Swiss  albino  mice, 35 ppm for 2 hours  for.
golden  hamsters, and  40  ppm  for 2  hours  for  squirrel   monkeys  (Ehrllch,
1966).   Similarly,  McGrath and  Oyervldes   (1985)  determined  that  Inhalation
of 5 ppm for  3 days  depressed host resistance to K_._ pneumonlae  In CF-1 mice.
Lefkowltz et al. (1986)  reported  that  certain Immune  parameters In CD-I mice
were altered  by  exposure  to  5  ppm for 24  hours  (decrease  In  the production
of  antibody-forming  cells,  no change  1n  serum  antibody  tlters or  phago-
cytosis),  but  that  exposure  did  not  result  1n  Increased mortality  to  the
Influenza virus strain PR8.
    Morphological changes  In  the  rat  lung  following  acute  exposure to 5-30
ppm  Included alveolar type  II cell  hyperplasla, pulmonary  alveolar  macro-
phage proliferation, and pulmonary Inflammation and  edema  (Plckrell et al.,
1982; Hayashl  et al.,  1987).   Pulmonary  damage from  nitrogen  dioxide expo-
sure In  dogs was observed  at  much  greater  concentrations than  seen  1n rats.


0166d                               -56-                             07/26/89

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                                   TABLE 6-7
                       LC5Q Values for  Nitrogen Dioxide
Species/Strain
Rat/albino



Rabbi t/NR
Guinea p1g/NR
Hamster/NR
Mouse '
LC50
Concentration
(ppm)
420
(362-487)*
174
(154-197)*
168
(153-185)*
88
(79-99)*
315
30
36
1000
Time
15 minutes
30 minutes
60 minutes
240 minutes
15 minutes
1 hour
48 hours
10 minutes
Reference
Gray et al..
Gray et al..
Gray et al.,
Gray et al.,
Sax, 1984
Sax, 1984
Sax, 1984
NIOSH, 1988b

1954
1954
1954
1954




''Confidence limits
()166d
-57-
04/10/89

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PUkrell et al.  (1982)  reported  bronchlolar  and  type  II  cell  degeneration  at
~70 ppm.
6.2.   CARCIHOGENICITY
6.2.1.   Inhalation.  Groups  of  30 female A/J mice  were exposed by  Inhala-
tion  to  1, 5  or 10 ppm  of  99.7X pure nitrogen  dioxide for  6 hours/day,  5
days/week  for  6 months  1n the  strain  A mouse pulmonary tumor assay  (Adklns
et  al.,  1986).  There  were  no  treatment-related  deaths.   A  significant
Increase  (p<0.05)  1n pulmonary  adenoma formation was  found  in  the  10 ppm
group  (Table  6-8),  but  tumors/mouse averaged 0.45+4).60  (meam-SD)  tumors/lung
1n  the highest  concentration  group compared with  0.40^.0.20  tumors/lung  In
the control group.   WHsch!  (1988) concluded that there was  little evidence
that  nitrogen  dioxide  had been  carcinogenic 1n  the  Adklns  et  al.   (1986)
study  for  the  following reasons:   1) the strain  of animals  used  1n  the  study
Is  highly  susceptible  to  lung  tumors;  2) for  a  compound  to  be labeled  a?
carcinogen,  1t  should   produce  >1   tumor/lung   (nitrogen  dioxide   treated
animals produce only 0.45 tumors/mouse);   and 3)  there  should be a positive
correlation between  concentration or  dose  and  tumor  Incidence  (fewer  lung
tumors were reported at  1  and 5 than at 0  ppm).
6.2.2.   Oral.   Data were  not  located  regarding  the cardnogenldty  of  oral
exposure to nitrogen dioxide,  but there are  several studies  of  the cardno-
genldty of nitrite.   In  most of  these studies, animals exposed to  nitrite
served as  controls  1n  experiments designed  to  test  the cardnogenldty  of
simultaneous administration  of  nitrite with a  nltrosatable  ami no  compound.
Generally,  these studies did not  suggest a carcinogenic  effect  from exposure
to nitrite  as  the  only  test substance, but the studies were  Inadequate  to
confirm that nitrite 1s  noncardnogenk In animals.
0166d                               -58-                             06/07/90

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                                  TABLE 6-8

          Incidence of Pulmonary Adenomas  In  Strain  A/J  Mice  Exposed
                             to Nitrogen D1ox1dea
Concentration1*
(ppm)
0
1
5
10
Mice with
Tumors
(X).
30
12
11
130
Average
Tumors/Mouse
0.40±0.02
0.16±0.30
0.13+0. 21
0.45+G.60C
Average Tumors/
Tumor-Bearing
House Lung
1.39+0.10
1.39+0.24
1.17+0.29
1.55+0.00C
                              Quality  of Evidence
Strengths of Study:
Weaknesses of Study:
Overall Adequacy:
Test material of acceptable purity was administered by*:
a relevant route using  adequate  protocol.   Appropriate'
statistical analysis was applied.

There Is an obvious  reporting problem because >100% of
mice at  10 ppm were reported  as bearing  tumors.   The
strain A  mouse  1s  especially sensitive  to  lung  tumors
and  1s  not an appropriate model from which  to  quanti-
tatively estimate carcinogenic  potency for  humans.

The  study  Is  not  adequate to serve as the  basis  of  a
quantitative  risk  assessment,   and,   because  of   the
problems  described  above, only  weakly provides  quali-
tative evidence of carc1nogen1dty."
aSource:  Adklns et al., 1986

bM1ce were exposed 6 hours/day, 5 days/week for 6 months.

cp<0.05
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              -59-
04/10/89

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6.2.3.   Other  Relevant  Information.   Rlchter  and  Kuraltls  (1983)  studied
the  effect  of  Inhalation  exposure to  nitrogen  dioxide on the  frequency  of
blood-borne  cancer  cell  metastasis  to the  lung.   Groups  of  23-51  C57BL/J6
mice were exposed to  0.3,  0.4,  0.5 or 0.8 ppm 7 hours/day, 5  days/week for 8
or 12 weeks.   Separate control  groups were provided filtered  air and ambient
air, respectively.  After  the exposure period,  the  animals were  Infused with
10s  B16 F10R1  melanoma  cells  through the  tall  vein.  After  3 weeks,  the
animals  were sacrificed  and  their lungs  hlstologlcally examined.   The mean
number  of nodules per  lung Increased  significantly  In  animals  exposed to 0.3
or  0.4  ppm  for 12 weeks, compared  with  controls  exposed  to  filtered  air
(p<0.05).  Mice exposed  to 0.5  ppm nitrogen  dioxide for 8  weeks  did not show
any difference  1n the  number  of nodules per  lung,  Indicating  that the effect
was related  to  duration  rather  than magnitude of  exposure.  The  data for the
                                                                             *
animals exposed to 0.8 ppm for  12 weeks was not reported.
    Although  Rlchter  and  Kuraltls  (1983)  could  not  explain the  Increased
metastasis to  the lungs,  they  speculated  that exposure to nitrogen dioxide
may have Interfered with  Immune function,  altered  the  Integrity  of  the endo-
thellal cells,  caused  general  tissue damage  or caused  aggregation  of cancer
cells.  W1tsch1  (1988)  speculated  that exposure  to low  levels  of  nitrogen
dioxide damaged the mlcrovasculature of  the lungs, allowing  the deposition
of  circulating cancer  cells.   WUschl  (1988)  mentioned  that   exposure  to
nitrogen dioxide  after  Intravenous  Injection with  cancer  cells resulted  In
reduced metastasis  to the lungs,  possibly   because of the  cytotoxldty  of
nitrogen dioxide to tumor  cells.
6.3.   6ENOTOXICITY
    The  genotoxldty  of  nitrogen   dioxide  has  been  studied  1n  several
mlcroblal and   mammalian  test  systems (Table  6-9) with  nearly universally


0166d                               -60-                             03/13/90

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                                                                               TABLE 6-9


                                                                   Genoioxiciiy of Sitrogen Dioxide
Assay
Reverse
Mutation
Reverse
Mutation
Reverse
Mutation
Reverse
Mutation
Induction
of gene
expression
Induction
of gene
expression
Reverse
Mutation
ChroMosoMal
aberrations.
sister
chroMtld
exchange
ChroMosoMl
aberrations
Indicator
Organ ISM
SalMonella
typhlMurluM
straln(s) NR
S. typhlMurluM
1A102. TA104
S. typhlMurluM
stralnfs) NR
S. typhlMurluM.
1A100. 1A102.
1A104
S. tvphlMurluM
TAlS3S/pSK1002
Escherlchla coll
K12
E. coll MP2
Chinese haMster
V79-H3 cells
Sprague-Dawley
rats; lung cells
Application
NR
NR
plate
Incorporation
plate Incorpo-
ration (flow-
through expo-
sure systeM)
plate
Incorporation
plate
Incorporation
plate
Incorporation
cell culture
Inhalation
Concentration Activating
or Dose System
11.3-2400 ppm NR
NR NR
NR _•$ 9
0.5-20 ppM _rS-9
for 6-7 hours
SO ppM for 30 S 9
Minutes
90 nl/t NR
for 30 Minutes
60 240 iil/t NR
for 30 Minutes
5. 10. 20. SO or NA
100 ppM for 10
Minutes
8 27 ppM for 3 NA
hours
Response Coonent
» Magnitude of positive re-
sponse appeared to be More
strongly dependent on dura-
tion of exposure than on
concentration.
» Magnitude of response was
dose-related up to an
equivalent of 100 Mg NaNOp/
plate.
NR NOp was bubbled through
» DMSO. which was Incorporated
Into top agar.
f Positive only In TA100
» Cellular B-galadosldase
activity Monitored as Indi-
cator of gene expression
» Cellular B-galadosldase
activity Monitored as Indi-
cator of gene expression
> Positive response was weak
but concentration-related
» Increased Mutations at >10
ppm
t Increased 2.5- to 11.6-fold
at 8-27 PPM
Reference
Rtneharf
et al.. 1973
Kushl et al..
1985
ShtMlzu et al..
1986
Victor In and
Stahlberg. 1988
NakaMura
et al.. 1987
Kosaka et al..
1987
Kosaka et al..
1987
Tsuda. 1981
IsoMura et al..
1984
CD
10

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                                                               TABLE  69 (cont.)
   Assay
                             Indicator
                             Organ ISM
Application
                                                    Concentration
                                                       or Dose
                   Activating
                     System
Response
nt
Reference
Nutation to
ouabaln
Resistance

ChroMsoMl
aberration
                Sprague-Dauley     Inhalation
                rats; lung cells
                C3H alee; leuko-   Inhalation
                cytes
                8 ?7 pp» for  3      NA
                hours
0.1. 1. S or  10    NA
pp* for 6 hours
                                                                                                          Significant Increase  In
                                                                                                          nutation at IS-?/ ppa
                                                                                                          No  Increase In chrowalld or
                                                                                                          chro«o$a»e type aberrations
                                                                           IsoMira et al..
                                                                           1984
                                                                                           Gooch et al..
                                                                                           1977
NR * Not reported; NA - not available
o
>*
CO
                                                                              n

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positive  results.   The mechanism of the genotoxldty  of  nitrogen  dioxide 1s
not  clearly  understood.   Tsuda  et  al.  (1981)  suggested that nitrogen dioxide
might  form free radicals  that  Initiate I1p1d  peroxldatlon,  particularly of
unsaturated  fatty adds and phosphollplds 1n cellular or nuclear membranes.
6.4.   DEVELOPMENTAL TOXICITY
     Lung  maturation  was assessed  1n rats  born and  raised  1n  air  containing
10  or  15  ppm nitrogen dioxide  (Freeman  et  al.,  1974).  Ten rats  (strain not
reported), -14  days  pregnant,  were placed  1n  chambers  with air  containing  0
or  10  ppm.   The progeny were  subsequently  delivered and allowed to remain 1n
the  chamber  for 90 days.  After 62 days,  the  animals  were  weighed and their
skeletal  length was measured,  and at  90  days, the animals  were  sacrificed
and  the  number  of alveoli  In  the lungs was  estimated.  At 62 days  of  age,
the  treated  animals of  both  sexes weighed significantly  less  (p<0.001  for
                                                                             *
males  and p<0.025  for  females)  and  were significantly shorter  (p<0.001  for.
males  and p<0.005  for  females)  than control animals.   There was  no signifi-
cant difference 1n relative alveolar  maturation  after 90  days of age.   The
same Investigators  (Freeman et al., 1974)  then exposed  18 Hilltop rats, 18
days pregnant,  to  0  or  15  ppm nitrogen  dioxide  In an  Inhalation chamber.
The  offspring were born  shortly  after the dams were  placed In  the environ-
mental   chamber.   Exposure to  nitrogen  dioxide  was   maintained   until  the
offspring were  removed for morphological  examination.   At   1,  3,  5,  10, 15,
20,  30,  40,  50, 60  or 75 days  after  birth three  rats from three different
Utters  were removed   for  lung  examination.  A  consistent  delay  In  the
maturation of   the  lungs  was  observed from  the ages  of 3-60 days.   At 75
days,  however,  the deficit  had been  made  up.  This  Is  consistent with the
observation  that,  1n  the  first  experiment,  no  difference  1n  relative
alveolar  maturation  was observed after 90  days.   The   Investigators reported


0166d                               -63-                             03/13/90

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 that  some pregnant  rats  died  before parturition,  litter  size  was  reduced
 compared  with  controls,  and offspring  mortality  remained high  for  15  days.
 However,  It  was not  clear  If  these  observations pertained  to  both  treated
 groups  or  just  those at  15 ppm.   Raw data  were not  provided and statistical
 analysis was not performed.
    Tabacova  et al.  (1985) exposed  groups  of 20  pregnant  Wlstar  rats  to
 nitrogen  dioxide  at 0, 0.05, 0.10, 1  or  10 mg/m3 (0, 0.027,  0.053,  0.53  or
 5.3 ppm.)  for  6  hours/day  throughout  gestation.   Postnatal viability,  growth,
 physical  maturation,  neuromotor development and  biochemical  parameters  were
 studied for <3  months  In  the  progeny.  Dose-dependent neurobehavloral devia-
 tions   Including  retarded  neuromotor  development,   disturbances  1n  motor
 coordination,   Inhibited  activity  and  reactivity  and  retarded  locomotor
 patterns were  reported  In all  exposed groups,  but  the  relevance of the end-.
 points  evaluated  to determine these  effects  Is unknown.   Also,  consistently'-
 statistically   significant  differences  were   not  apparent  at  <10  mg/m3.
 However,  at  10 mg/m3  the  neurobehavloral  tests  showed  significant  differ-
 ences   from  control.   Signs   of  delayed   development  of  the  liver  drug-
 metabolizing  system  were  also  reported   at   1  and  10  mg/m3.   Postnatal
 viability  and  physical development  were  slightly  affected  only  at  the  10
mg/m3 concentration at day 21.
    The teratologlcal effects of  nitrogen  dioxide on pregnant CO-1  mice were
evaluated  by exposing  groups  of -20  animals  continuously to 0,  22  or 45 ppm
nitrogen dioxide on  gestation days 8-18 (Singh, 1984).   The mice were sacri-
ficed  on  gestation  day  18, and  the  fetuses were  examined  for  any  terato-
loglcal effects.  LUter  means  for fetal weight,  number  of live fetuses and
number  of  dead or  resorbed fetuses  were   used  to  determine  the effects  of
nitrogen  dioxide.   Exposure  to 0,  22 or  45  ppm resulted In  the  death  or


0166d                               -64-                              09/25/89

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resorptlon  of  0.50,  1.00  or  1.54  mean  fetuses  per  litter,  respectively
(p<0.05  1n  the  45  ppm  group).   The  Incidence  of fetal  hematomas  signifi-
cantly  Increased (p<0.05)  In both  treatment  groups  (0,  11.1  and  12.6X  in
control, 22 and 45 ppm groups, respectively).
6.5.   OTHER REPRODUCTIVE EFFECTS
    The effect  of nitrogen  dioxide on  rat  testes  was  evaluated  by KMpke and
Sherwln  (1984).   Groups  of six  male  LEW/f ma1 rats  were  exposed to 0  or  1
ppm for  7  hours/day,  5  days/week for  3 weeks.  The animals  were  then  sacri-
ficed  and  their  testes  examined for abnormalities.  Treated animals  showed
no  gross  abnormalities  or  microscopic evidence  of altered  spermatogenesls,
germinal cell atrophy or abnormality of Interstitial cells.
    ShalambeMdze  and  Tseretell  (1971)   studied  the  effects  of  nitrogen
dioxide  on  the estrous  cycle  and  reproductive capacity of  rats.   Groups  of:.
10  sexually mature rats were  exposed  to  0, 0.07 or 1.25 ppm for 12 hours/day •
for 3  months.   At  the  end of  3  months,   4  rats/group were sacrificed  for
pathological examination, and  the rest were allowed to  recover  for 3 months.
At  0.07  ppm,  there  were no effects on the estrous  cycle or  on  the reproduc-
tive organs.   At 1.25  ppm,  however,  marked  but reversible effects on  the
estrous  cycle  were reported.   The mean  estrous  cycle  length  progressively
Increased during  exposure from a control  length of 5.3  days to 6.4 days, 9.0
days and 9.1 days after  1,  2  and 3 months  of exposure,  respectively.  During
the 3 months of  recovery,  the mean  duration of the cycle returned to control
values.  Pathological  examination  of  the  rats  after  3  months  of  exposure
showed circulatory disturbances  such  as  hyperemla,  stasis  and hemorrhages In
the pituitary,  adrenal, thyroid glands,  ovaries  and uterus.   The glandular
epithelium  of  the uterus  was depleted,  and  the ovaries  showed  fewer  func-
tionally active  follicles.  In the  same  study, seven  rats  were exposed to 0,


0166d                                -65-                             09/25/89

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0.07  or  1.25 ppm  for  12 hours/day for  3  months.   Exposed female  rats  were
then mated with  unexposed males.   The  outcome  of  females  exposed to 0.07 ppm
was  not  reported.   In  the  1.25  ppm  group. Utter  size  at  birth  decreased
from  a  mean of  8.0 1n  controls  to 5.1;  offspring  weight  from birth  to  12
days  of  age decreased  by  20-30%.   These  data  were available  only from  a
secondary  source  and  were  not  reported  In  sufficient  detail  to  permit
critical evaluation.
6.6.   SUMMARY
    Subchronlc  Inhalation  exposure of animals to  nitrogen dioxide  has  been
associated with  nonresplratory  tract effects  Including  decreased survival  In
the animal  Infectlvlty  model  {Ehrllch and  Henry,  1968; Blair et al.,  1969;
Coffin  et  al.,  1977;  Gardner  et  al.,  1977a,b,  1981;  U.S.  EPA,  1982)  and
alterations  In  Immune  response  (Fenters  et al.,  1973;  Ehrllch et al.,  1975;
                                                                             ••
Holt  et  al., 1979;  FuJImakl  et al.,  1982;  Roy-Burman  et al.,  1982).   Mice..
appeared to  be  the  most sensitive species  to these effects  (Roy-Burman  et
al.,  1982;  Miller  et  al.,  1987).   These  data  qualitatively  support  the
observation  that human  exposure  to low ambient  levels of nitrogen  dioxide
can  Increase the  likelihood  of  contracting  contagious respiratory  disease
(Shy  et  al.,  1970a,b;   1973;  Shy  and  Love,  1979;  Spelzer  et  al.8  1980).
although this  conclusion was not shared  by  all  Investigators  1r.  the  field
(Ferris et al.. 1983; Hoek et al., 1984; Harrington and Krupnlck. 1985).
    The most  Important  effects  of  nitrogen dioxide  were those  on  the  lungs
and have been studied extensively  In humans and  laboratory animals.  Initial
exposure of  laboratory  animals  led  to diffuse Injury  followed  by  edema and
the Influx of Inflammatory  cells  (Klelnerman  et  al.,  1985a,b; Gordon et al.,
1986; Rombout  et  al.,  1986).  Morphological  changes  followed  1n  the  cell
types of  the epithelium of  the terminal bronchioles and  adjacent  alveoli.


0166d                               -66-                             09/25/89

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Despite  the  persistence  of  epithelial  lesions,  there were  few effects  on
several  measures  of   pulmonary   function.    MorphometMc   and   biochemical
evidence  of  effects on the  lungs  was  reported  at  concentrations at  which
hlstopathologlc  lesions  had not  occurred  (Rombout et  al.,  1986; Kyono  and
Kawal, 1982;  Ichlnose  and Sagal,  1982; Gregory et al., 1983;  Lafuma  et  al.,
1987).   In  a study  1n  which  rats were  exposed  to nitrogen dioxide  for  <27
months,  hlstopathologlc  lesions   appeared  In  the   lungs   with  continuous
exposure to  4.0  ppm  (Sagal  et  al.,  1984;  Sagal  and Ichlnose.  1987;  Kubota et
al..  1987).   At 0.40  ppm,  lesions did  not  appear until  the 27th month  of
exposure.  Some  morphometrlc  and  biochemical  changes,  but  no lesions,  were
reported at 0.04 ppm.
    Several  epldemlologlcal studies  have  Investigated  the  effects  of living
In  a  region  polluted   with   nitrogen   dioxide   (as   well   as   with  other;
                                                                             •
pollutants)  on  pulmonary function and the Incidence of respiratory  disease."-
Extensive studies  with school children  (Shy  et al.,  1970a,b, 1973;  Shy and
Love,  1979;   U.S.  EPA,   1982;  Harrington and Krupnlck,  1985)  and  adults
(Spelzer  and  Ferris,   1973a.b;  Cohen  et al.,  1972;  Linn  et  al.,  1976),
although  qualitatively  suggestive,  failed  to convincingly  demonstrate  an
effect  of  nitrogen  dioxide.    Similarly,  several studies  (Spelzer  et  al.,
1980;  Ferris  et  al..  1983;   Hoek   et  al..   1984)  found  no  Indisputable
relationship between Indoor nitrogen  dioxide  levels  and respiratory symptoms
or pulmonary function  In  school children.  Indoor  levels  of nitrogen dioxide
are  generally  higher  1n  homes that  cook  with gas  than  In  homes  that  cook
with electricity.
    Acute human  exposure to high  levels (300-500  ppm)  1s  likely to be fatal
(Grayson,  1956).  Exposure  to 150-200  ppm  Is  likely to  result  In severe
bronchlolltls, and  exposure to 25-75  ppm  1s  likely to result In reversible


0166d                               -67-                             09/25/89

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bronchitis or  bronchial  pneumonia.   In  controlled  exposures  In laboratories,
few  effects  have  been  noted  In  humans  with  normal  respiratory  tracts  at
concentrations <1.0 ppm  (Adams et  al.,  1987;  Koenlg et  al.,  1985, 1987,  Avol
et  al.,  1988;  Drechsler-Parks  et  al.,  1987;  Klelnman  et  al.,   1983).
Increased   specific   airway  resistance   and  potentlatlon   of   chemical-,
exercise- or cold  air-Induced bronchoconstrlctlon,  however,  were  reported  1n
chronic asthmatics at  concentrations  as low as 0.1  ppm  (Bylln et al.,  1985;
Mohsenl.n, 1987; Bauer et al., 1986).
    Data were  not  located regarding  the  1ngest1on of nitrogen dioxide  gas,
but U.S. EPA (1986a) verified an oral  RfD for nitrogen  dioxide by analogy  to
nitrite.  The  RfD  for  nitrite was  based  on a  NOEL  for  methemogloblnemla  In
Infants  exposed  to  drinking  water   containing   10  ppm  nitrate  N  1n  an
epidemiology study (Walton et al.,  1951).
                                                                            —•
    Inhalation exposure  to nitrogen dioxide yielded equivocal  results  In the'*
strain  A  mouse  lung  tumor  assay  (Adklns et  al.,  1986; Wltschl.  1988)  but
Increased the  frequency of  metastasis  to the  lungs 1n mice  treated  Intra-
venously with  cancer cells  (Rlchter  and  Kuraltls,  1983).   Nitrogen  dioxide
was shown to be  genotoxlc  In  several  m1crob1al  (Rlnehart et  al.,  1973;  Kushl
et  al.,  1985;  Shlmlzu  et  al.,   1986;   Vlctorln  and  Stahlberg,  1988)  and
mammalian  (Tsuda,  1981;  Isomura  et  al.,  1984;  Kosaka  et  al.,   1987)  test
systems.
    Developmental  toxldty  studies suggested  that  exposure  of neonatal  rats
delayed the maturation of lungs, although the levels of exposure were suffi-
ciently high  to  cause mortality of  some  of  the dams and offspring (Freeman
et al.,  1974).  A developmental  study exposed rats to  low concentrations;
reduced postnatal  viability  and retarded  physical  development were reported
1n the  offspring  of rats  exposed to  5.3 ppm  during gestation (Tabacova  et


0166d                               -68-                             09/25/89

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 al.f 1985).  In a  reproductive  study, exposure  of  female  rats  Intermittently
 to  0.125  ppm resulted  1n alterations  In  the estrus cycle  and evidence of
 fetotoxlclty  (ShalambeMdze  and  Tseretell,   1971),  although  the  data were
 Insufficiently reported for critical  evaluation.
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                            7.   EXISTING GUIDELINES
7.1.   HUMAN
    U.S.  EPA.  (1971)   established  a  national  primary  ambient  air  quality
standard  of  100  yg/m3  (0.05   ppm)  as  an  annual  arithmetic  mean for  the
protection  of human  health.   U.S.  EPA (1985c)  continued  this standard  of
0.05 ppm  for  nitrogen dioxide, but added  that  It  1s  designed  to protect the
general  public  against  chronic  health  effects  with  an  adequate  margin  of
safety.   Sensitive subgroups  Including  young  chllden  and asthmatics  were
considered  1n this decision.   ACGIH  (1988)  recommended a  TWA-TLV of 3  ppm (6
mg/m3)  and  a STEL   of  5  ppm  (10  mg/m3)  based  on  several  older  animal
studies  and  a  recommendation  that   the general  population  should  not  be
exposed  for  more than  1  hour  to  concentrations  >3 ppm  (ACGIH,  1986).   The
OSHA  (1985)  celling  limit  for nitrogen dioxide  1s  5 ppm  (9  mg/m3).   NIOSH
(1976) recommended  an occupational celling  value  of  1 ppm to prevent  acute:
pulmonary Irritation  In exposed workers.
    U.S.  EPA  (1986a)  derived and  verified an  RfD  for  oral  exposure  to
nitrogen  dioxide  nitrogen  of  1 mg/kg/day.   The  derivation  of  this RfD  1s
discussed  In  Chapter   8.   U.S. EPA  (1988c)  listed a  final RQ  for nitrogen
dioxide of 10 based on the reactivity of the chemical.
7.2.   AQUATIC
    Guidelines  and   standards   for  the  protection   of  aquatic   life  from
exposure  to  nitrogen  dioxide  were not  located  In the  available   literature
cited 1n Appendix A.
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                             8.  RISK ASSESSMENT

    Statements  concerning  available  literature  In  this  document  refer  to
published, quotable sources and  are  In  no way meant to Imply that confiden-
tial business  Information  (CBI), which  this  document could  not  address, are
not  In  existence.   From examination of  the  bibliographies  of the CBI data,
however,  It  was determined that CBI  data that would  alter  the  approach  to
risk assessment or the risk assessment  values  presented herein do not exist.
8.1.   CARCINOGENICITY
8.1.1.   Inhalation.  A  slightly significant  Increase 1n  the  Incidence  of
pulmonary adenomas  following  Intermittent exposure to 10 ppm,  but not to 1
or  5  ppm,  In a strain A mouse  pulmonary tumor assay  (Adklns et al.,  1986).
The  Investigators  stopped  short,  however,  of declaring  nitrogen  dioxide a;
carcinogen  In  this  animal  model.   Wltschl  (1988)  concluded  that  there was •
little evidence that  nitrogen  dioxide  was carcinogenic In the Adklns  et al.
(1986) study,  primarily  because of a  lack  of multiple tumors/lung  averaged
over all mice  1n  the  10-ppm group.  In  another experiment using mice,  Inter-
mittent exposure  to 0.3 ppm enhanced metastasis of  cancerous  B16  F10R1  cells
to the lung (Rlchter and KuraHls,  1983).
8.1.2.   Oral.  No  studies  were located  regarding  the oral  cardnogenldty
of nitrogen dioxide.
8.1.3.   Other  Routes.   Pertinent  data  regarding  the   cardnogenlclty  of
exposure  to  nitrogen  dioxide   by  other  routes   were not   located  1n  the
available literature cited  1n Appendix A.
8.1.4.   Weight of  Evidence.   Data were  not  located  regarding the  cardno-
genlclty of  nitrogen  dioxide  In humans.  The  Inhalation data in  animals  are
equivocal  and  do  not   suggest  direct   carcinogenic  activity.   Using  the


0166d                               -71-                             09/25/89

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guidelines  for  cancer  risk  assessment  adopted  by  the  U.S.  EPA  (1986c),
nitrogen  dioxide may  be  assigned  to  EPA  group  D:  not  classifiable as  to
carclnogenldty  to humans.
8.1.5.   Quantitative  Risk  Estimates.   Lack  of  adequate  data  precludes
derivation of  quantitative estimates of  cancer  risk for  either  Inhalation  or
oral exposure  to nitrogen dioxide.
8.2.   SYSTEMIC  TOXICITY
8.2.1.   Inhalation Exposure.
    8.2.1.1.   LESS   THAN   LIFETIME   EXPOSURE   (SUBCHRONIC)  -- Subchronlc
Inhalation exposure of  animals  to nitrogen dioxide has  been  associated  with
nonresplratory  tract   effects,  Including  decreased survival  1n  the  animal
Infectlvlty model  (Ehrllch and  Henry,  1968; Blair  et  al.,  1969;  Coffin  et
al.. 1977; Gardner et  al., 1977a,b,  1981;  U.S.  EPA, 1982)  and alterations  In;.
Immune response  (Fenters  et  al.,  1973; Ehrllch  et  al.,  1975;  Holt  et  al.,"
1979; FuJImakl et  al.,  1982;  Roy-Burman et al.,  1982).  Mice appeared to  be
the most sensitive species to these  effects (Roy-Burman  et  al.,  1982; Miller
et al., 1987).   Although  these  data  qualitatively support  the observation  of
some epidemiology  studies that  exposure to  low  levels  of  nitrogen  dioxide
Increase the probability  of  contracting contagious  respiratory  disease,  U.S.
EPA  (1985c) did not  consider  these data  suitable to serve  as the basis  of
an  ambient  air  quality  standard.   Therefore,  they  are  not   considered
suitable to serve as the basis for an RfD for subchronlc Inhalation exposure.
    The most Important  effects  of exposure to  nitrogen  dioxide appear to be
on the lung.   Several  subchronlc  animal  studies (Klelnerman et  al., 1985a,b;
Gordon et  al., 1986;  Rombout et  al.,  1986; Lafuma et al.,  1987; Gregory et
al., 1983; Ichlnose and Sagal,  1982; Sherwln and Rlchters,  1982; Sherwln et
al.,  1985;  Kyono  and  Kawal,  1982)   characterized   the  development  of


0166d                               -72-                             09/25/89

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emphysema-like  lesions  associated  with  exposure  to  0.3-30  ppm  nitrogen
dioxide.   Other  effects  Included  reduced  rate  of body weight  gain  (Glasgow
et al.,  1987;  Freeman  et  al.,  1969),  effects  on the spleen (Kura1t1s et al.,
1981) and  subtle  biochemical  effects on the  liver  (Takahashl  et  al.,  1986).
Data  regarding mortality  were  contradictory;   Steadman  et  al.  (1966)  and
Freeman  et al.  (1969)  reported  mortality In  several  species (Including rats)
at 4.89-35.6  ppm, but Glasgow  et  al. (1987) reported  neither  morbidity  nor
mortality  1n  rats exposed continuously to 30 ppm.   Generally,  these studies
were  not  suitable  for  derivation  of  an RfD  because  thresholds  were  not
Identified,  the  exposure protocol  was  Incompletetly reported, the  duration
of exposure  was   Insufficient, or  the endpolnts observed cannot  be  extrapo-
lated  to humans.   Lacking  suitable  data  from  which  to derive  an  RfO  for
subchronlc  Inhalation exposure,  the  chronic  Inhalation RfO  of  0.02  mg/m3^
(Section   8.2.1.2.)   Is   adopted  as   sufficiently  protective  for   chronic'-
exposure.
    8.2.1.2.   CHRONIC EXPOSURE  -- Several  chronic  Inhalation  studies  using
rats  (Juhos  et   al.,  1980;  Haydon  et al.,  1965;  Freeman  et  al.,  1966;
Stephens et  al.,  1971; Sagal  et al..  1984;  Sagal  and  Ichlnose, 1987;  Kubota
et al.,  1987)  and dogs (Hyde et al.,  1980)  examined the  effects  of  nitrogen
dioxide  on  the  lungs.   In the highest  quality  study,  groups  of 12 male rats
were continuously exposed to 4.0,  0.40  or 0.04  ppm for  9, 18 or  27  months
(Sagal  et  al.,   1984;  Sagal  and Ichlnose,  1987;  Kubota  et  al.,  1987).
Exposure concentrations  were  continually monitored  and exposure  temperature
was  closely  regulated  at   24-26°C.    Hypertrophy  and  hyperplasla  of  the
bronchial  epithelium,  thickening   of  the  walls  from the bronchopulmonary
border to  the  alveolar duct,  cellular Infiltration and flbrotlc  organization
were  observed at 4.0  ppm.   At  this  concentration,   the  Intensity  of  the


0166d                               -73-                             09/25/89

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hlstopathologlc   alteration   Increased   progressively   with   duration   of
exposure.   Although  lung  function  tests were  not  performed,   lung  function
may have  been  Impaired.   This conjecture 1s supported by  the  data  of  Haydon
et al.  (1965),  who reported  Increased  breathing  rates 1n  rats  continuously
exposed  to  0.8  ppm   for   <813  days.   The 4.0  ppm  level,  therefore,   Is
considered  a LOAEL  In  this study.   At 0.4  ppm, hlstopathologlc  lesions were
not detectable  until   the  27th month  of exposure.   Subtle biochemical  and
morphometrlc  changes  were   also  observed  at   this  level,   but   are   not
considered  adverse.   Because  the  duration of exposure exceeded  the  expected
llfespan  for  rats,   this  concentration  Is Judged  a  NOAEL.    Only  subtle
biochemical and morphometrlc changes  were observed at  0.04 ppm.
    Several  ep1dem1olog1cal  studies  have Investigated the  effects  of  living
1n a  region heavily  polluted with nitrogen dioxide  (as  well  as with  other.
pollutants)  on  pulmonary function  and the  Incidence of  respiratory  disease. '
Extensive  studies  1n  schoolchildren   (Shy  et   al.,  1970a,b,  1973;  Shy  and
Love,   1979;  U.S.  EPA,  1982;  Harrington  and  Krupnlck,   1985)  and  adults
(Spelzer  and  Ferris,  1973a,b;  Cohen  et  al.,  1972; L1nn et  al.,  1976),
although  qualitatively  suggestive,  failed  to  convincingly  demonstrate  an
effect  of  nitrogen  dioxide.   Similarly,  several studies  (Spelzer et  al.,
1980;   Ferris  et  al.,  1983; Hoek   et   al.,   1984)  found  no  Indisputable
relationship between  Indoor  nitrogen  dioxide levels  and  respiratory symptoms
or pulmonary function  In schoolchildren.
    In  controlled exposures  of  humans  to <1.0  ppm  In  laboratories,  few
effects have been noted  1n  those with  normal  respiratory  tracts  (Adams et
al.,  1987;  Koenlg  et  al.,  1985,  1987,  Avol  et  al.,  1988; Drechsler-Parks et
al.,  1987;  Klelnman et al.,  1983).   Increased  specific airway  resistance  and
potentlatlon  of  chemical-,   exercise- or  cold  air-Induced bronchoconstMc-
tlon,   however,  was reported  1n chronic  asthmatics  at concentrations  as  low

0166d                               -74-                             09/25/89

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as.0.1  ppm  (Bylln  et  al.. 1985; Mohsenln,  1987;  Bauer et  a!.,  1986).   U.S
EPA  (1985c)  concluded,  however,  that  the controlled  human  exposure  data
presented   "mixed  and  confusing  results"  In   both   healthy   and  asthmatic
Individuals.   The epidemiology  studies  were confounded  by the  presence  of
other  pollutants  and  compromised  by  Inappropriate or  Inadequate monitoring
of  exposure levels;  these  studies  should  be considered only  as  qualitative
Indications  that  exposure of humans  to nitrogen dioxide affects the lung.
    The most  appropriate study  for  Inhalation  RfD  derivation 1s the 27-month
study  using rats, 1n which continuous exposure  of  0.4-4.0 ppm resulted  1n a
progression  of  effects on  the lung  (Sagal  et  al.,  1984;  Sagal and Ichlnose,
1987;  Kubota et  al.,  1987).   Although subchronlc  studies  with Intermittent
exposure  Indicated  that  mice  might  be more  sensitive  than rats (Sherwln and
Rlchters,   1982;  Sherwln  et  al.,  1985),  only  studies  using  continuous.
exposure  were considered because continuous exposure  more accurately models-.
human environmental  exposure.   Furthermore,  It  was  not possible to determine
1f  the  effects reported  by Sherwln and  Rlchters  (1982)  and  Sherwln  et al.
(1985) represented an  adverse or adaptive response.
    In derivation of  the RfD,  1t was decided that  the region of the respira-
tory  tract- Involved was  the  alveolar region.   Regional  gas  doses  for  rats
and  human  were  derived  by  multiplying   the  exposure  level   by  respective
reference  values  for  tidal volumes  and  breathing rates and dividing by the
respective  alveolar  surface areas.   An RGOR of  2.069  was  estimated for rats
and  humans.   The experimental  NOAEL of  0.040  ppm  was  multiplied  by the
molecular  weight  (46.01)  and divided  by  the volume In liters  of  1  g-mol  of
gas at standard pressure and  a  temperature  of  25°C (24.45) and expressed as
0.0753 mg/m3.  Multiplying  the concentration  of  0.0753  mg/m3 by  the  RGDR
of  2.069  yields  a  HEC   of  0.156  mg/m3.   Application   of  an  uncertainty


0166d                                -75-                             03/13/90

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factor  of 100,  10 to  reflect  the  uncertainties  In  estimating a  HEC  from
animal  data  and 10 to provide additional  protection  for  unusually sensitive
Individuals  such  as  asthmatics,  results  In  an  RfD  of  0.00156  mg/m3,
rounded   to  0.002 mg/m3,   for   chronic  Inhalation   exposure  to  nitrogen
dioxide.
    Confidence  In  the  key study 1s medium.  The  study was  well  designed and
performed  using  an  accepted  animal  model.   Exposure concentrations  were
continually  monitored  and  exposure  temperature was  well  controlled.   How-
ever,  the  relatively  small  group sizes  and  absence of lung function testing
preclude   awarding a   higher   confidence  level.    Experiments   In  several
species,  as  well  as  experimental  and  ep1dem1olog1cal  data  1n  humans,
Indicate  that   the lung  1s  the  target  organ  for   Inhalation  exposure  to
nitrogen  dioxide.   Confidence  In  the  data  base  Is  medium,  reflecting  the.
                                                                             «
absence   of  a  multi-generation  Inhalation   reproduction  study.   Medium-
confidence In the  RfD follows.
8.2.2.   Oral Exposure.
    8.2.2.1.   LESS  THAN  LIFETIME   EXPOSURE   (SUBCHRONIC)  -- Data  were  not
located  regarding  the  toxlclty  of  Ingested nitrogen  dioxide  gas; however,
nitrogen  dioxide  In water  1s  converted  to nitrite  and nitrate  (U.S.  FPA,
1986a).   U.S EPA  (1986a)  derived  an  oral RfD for  nitrogen dioxide  N  of 1
mg/kg/day  by  analogy  to  nitrate  (Section  8.2.2.2.).   Lacking  suitable
subchronlc  oral  data   for  nitrogen  dioxide,   the RfD of  1  mg/kg/day  for
chronic Ingestlon  of nitrogen dioxide  N Is adopted as  the  RfD for  subchronlc
Ingestlon of nitrogen dioxide N.   Confidence 1n the  study, data base and RfD
are high for reasons discussed In Section  8.2.2.2.
0166d                               -76-                             03/13/90

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    8.2.2.2.  .CHRONIC EXPOSURE — U.S.  EPA  (1986a)  derived and verified an
RfO of  1  mg/kg/day for chronic 1ngest1on  of  nitrate based on the epidemiol-
ogy  study  by Walton  (1951).   In  this  study,   drinking  water  containing
nitrate  N at <10  ppm was  not  associated with  the  development  of  methemo-
globlnemla  1n human  Infants,  considered to be the sensitive  subgroup In the
population.   Increasingly greater  percentages  of  Infants with methemoglobln-
emla were observed when  nitrate N levels  rose from  11  to >100  ppm.   The 10
ppm level  was considered  a  NOEL.   By assuming that  a  10 kg child consumes  1
l  of  drinking water/day, U.S.  EPA (1986a) estimated  that the  10 ppm level
resulted  In  Ingestlon  of  1  mg/kg/day.  Application  of  an uncertainty factor
of  1  to  reflect   that the  NOEL was  for  the  critical  effect  In the  known
sensitive  population  resulted  1n  an  oral RfD  of  1  mg/kg/day.  Data  that
challenge  this  approach  were  not  found,  and  1  mg/kg/day  1s  considered the.
                                                                             ••
RfD for  chronic  Ingestlon  of nitrogen dioxide (or nitrate)  for the  purposes-.
of this document.
    Confidence  1n  the  study  Is  high  because both  a  LOAEL  and NOEL  were
Identified  In the  known  sensitive  human population.   Other  human  studies
reviewed  by U.S.   EPA  (19855)  support  the NOEL  In  the  Walton  (1951) study.
High confidence In the RfO follows.
0166d                               -77-                             03/13/90

-------
                           9.   REPORTABLE  QUANTITIES
9.1.   BASED ON SYSTEMIC TOXICITY
    The  toxldty  of  nitrogen  dioxide  Is  discussed  In  Chapter  6.   Data
regarding  oral  exposure  to  nitrogen dioxide  were not  located.   Subchronlc
Inhalation exposure  of animals  to nitrogen dioxide has  been  associated  with
decreased survival In  the  animal  Infectlvlty model (Ehrllch and  Henry,  1968;
Blair et al., 1969;  Coffin et  al.,  1977;  Gardner  et  al., 1977a,b,  1981;  U.S.
EPA,  1982), alterations  In Immune response  (Renters et  al., 1973;  Ehrllch  et
al.,  1975;  Holt  et  al.,  1979;  FuJImakl  et  al., 1982;  Roy-Burman  et  al.,
1982)  and  reduced  mucoclHary  clearance   (Giordano   and   Morrow,   1972).
Decreased  survival  In  the  animal  Infectlvlty  model   has  no  known  human
counterpart and 1s not considered In scoring for derivation of candidate CSs.
    Host of the  Immune function  studies were  performed  with mice and  monkeys.
                                                                             «
(see  Table 6-2).   Endpolnts  observed that may apply  to  human  health  Include'
the  following:    transient leukocytosls,  altered humoral and  spleen  cell
response  to  SRBC  and  reduced  survival  1n  the  tumor  rejection  test  In  mice
exposed  Intermittently  to  10  ppm  for  <30  weeks  (Holt  et  al.,   1979);
transient depression of SN  tlters  and seroconverslon  rates  In mice  vacci-
nated with  Influenza virus and  exposed  continuously  to 2 ppm for <40 weeks
(Ehrllch  et   al.,  1975);  and  Increased  SN  antibody   response  1n  monkeys
continuously  exposed  to  1 ppm  for  493  days  and  challenged with  virulent
Influenza virus (Renters et al.,  1973).   The  Holt et  al. (1979)  study 1s not
considered further,  however, because  the  mice  were exposed only  for  2 hours/
day.  The monkey  study by Fenters  et al.  (1973)  1s  similarly Inappropriate
since It failed to Identify a  LOAEL.  The  effects  reported 1n  mice by Ehrllch
et al. (1975) are  presented  In Table 9-1.   Reduced  mucodllary  clearance In
rats  exposed  continuously for  6  weeks  (Giordano  and  Morrow,  1972)  also
appears 1n Table 9-1.

0166d                               -78-                             07/31/89

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                                                                                 TABLE 9-1



                                                                  Inhalation Toxlclty of Nitrogen Dioxide
Species/
Strain
House/Swiss
Rat/Long-
Evans
Rat/NR
Rat/JCL:
Wlstar
Rat/JCL:
Wlstar
Rat/JCL:
Wlstar
Nouse/Swtss
Webster
Nouse/Swtss
Webster
Rat/Wlstar
Number/Sex
>14/N
16/F
15/sex NR
12/N
12/N
12/N
45/N
300/N adults
O34/N
neonates
20/F
Average
Body Weight
(kg)
0.03C
0.35C
0.35C
0.35C
0.35C
0.35=
0.03C
0.03C
0.35C
Exposure
2 ppm continuously for
<40 weeks
6 ppm continuously for
6 weeks
12 ppm continuously for
<813 days
4.0 ppm continuously
for <27 months
0.4 ppm continuously
for <27 months
0.04 ppm continuously
for <27 months
0.3 ppm 6 hours/day. 5
days /week for 6 weeks
0.35 ppm 8 hours/day. 5
days/week for 6 weeks
10 mg/m» (5.3 ppm) 6
hours/day throughout
Transformed
Animal Dosage3
(mg/kg/day)
4.9
7.2
14.4
4.8
0.24
0.05
0.13
0.20
1.59
Equivalent
Human Dosage'*
(mg/kg/day)
0.037d
0.12d
2.46
0.82
0.04
0.008
0.00098d
0.0015d
0.272
Response
Depressed SM liters and sero-
con version rates
'Decreased mucoclllary clear-
ance rate
Evidence of severely Impaired
lung function
Progressive hlstopathologlc
lesions In lung
Norphometrlc and biochemical
changes In the lung
Norphometrlc changes In the
lung
Mild lesions In lungs
Changes In weight and hlsto-
pathologlcal appearance of
spleen
Reduced postnatal viability
Reference
Ehrllch
et al.. 1975
Giordano and
Morrow, 1972
Haydon
et al.. 1965
Kubota
et al.. 1987
Sagal et al..
1984; Sagat
and Ichtnose,
1987; Kubota
et al.. 1987
Sagal et al..
1984; Sagal
and Ichlnose,
1987; Kubota
et al.. 1987
Sherwln
et al.. 1985
Kuraltts
et al.. 1981
Tabacova
et al.. 1985
                                                       gestation
CD

-------
                                                                            TABIF  9-1  (cont.)
o
«J
o>
CT>
O.
Species/
Strain Number /Sex
House/CD- 1 -20/F
ii
Average
Body Weight
(kg)
0.03£
Exposure
22 ppm continuously
during days 8-18 of
gestation
Transformed
Animal Dosage8
(mg/kg/day)
54
Equivalent
Human Dosage'' Response Reference
(mg/kg/day)
4.1 Increased Incidence of fetal Singh. 1984
hematomas
CD

O
I
      'Concentration,  expressed  as  mg/m»,  multiplied  by  reference  animal  breathing  rate  (mVday)  (U.S.  EPA,  1986d)  divided  by body  weight  yields  Inhaled

       dosage (mg/kg/day).


      DTransformed animal dosage multiplied by the cube root  of  the ratio of the animal body weight/reference human body weight (70 kg) (U.S. EPA. 1986d)


      'Reference animal body weight (U.S. EPA. 1986d)


      <*An uncertainty factor of 10 was applied to expand fro* subchronlc to chronic exposure.


      NR > Not reported
o
~j
^.
CO

•^
CD                                                                                         II

-------
    .The  most  Important  effects  of  nitrogen  dioxide were  on  the  lungs.
Several  subchronlc  studies using hamsters,  rats  and  mice  characterized  the
progressive  development  of  emphysema-like  lesions  In all species  studied
(see  Table  6-3).   Chronic   studies  using  continuously  exposed  rats  are
summarized  In  Table  6-6.   Decreased body  weight.  Increased  respiratory  rate,
hlstopathologlc  lesions  resembling  emphysema  and  gross  dlstentlon  of  the
thoracic  cavity,  suggesting  severe  Impairment of  pulmonary  function, were
reported  In  rats  exposed  to  12  ppm  (Haydon  et  al.,  1965).   Progressive
hlstopathologlcal  lesions were observed  In the  lungs of  rats  continuously
exposed  to  4.0 ppm  for <27 months  (Sagal et al., 1984; Sagal  and  Ichlnose,
1987;  Kubota  et al.,  1987).   Biochemical and  morphometMc alterations,  but
no  hlstopathologlcal  lesions,  were  reported In rats exposed to  0.04  ppm  for
<27 months.   These  studies,  which represent the  lowest concentrations  asso-
dated with  these  effects,  are presented 1n Table  9-1.   Data  from  Table  6-6.
not presented  In Table  9-1  Include  hlstopathologlcal  lesions  In the lungs of
dogs  In a study available only as an  abstract  (Hyde et al., 1980) and slight
hlstopathologlcal lesions that  appeared only after  27  months  In rats  exposed
continuously  to  0.4 ppm  (Sagal  et  al.,  1984;  Sagal and Ichlnose,  1987;
Kubota et  al., 1987).  The  latter  observation was not Included because It
was reported  only after the rats had been  exposed  for a period greater than
the expected Ufespan for the species.
    Subchronlc  data   summarized  In  Table 6-3  suggest that  mice  were  more
sensitive than rats   to  the  pulmonary  effects  of nitrogen dioxide (Sherwln
and Rkhters,  1982;  Sherwln et al.,  1985).  M1ld lesions  1n  the lungs were
reported  In  mice Intermittently  exposed  to 0.3  ppm for  6 weeks.   During a
10-week postexposure  period,  the  Increased alveolar wall area  and  mean Type
II  cell  population  of  the exposed  group  failed  to  return  to pretreatment
(control) levels.  These data are presented 1n Table 9-1.

0166d                               -81-                             07/31/89

-------
    Other  effects associated  with exposure  to  nitrogen dioxide  are summa-
rized  In Table  6-4.   Early  subchronlc  studies  reported  mortality  In  rats
continuously  exposed   to  11.32  ppm (Steadman  et al.,  1966) or  to  15  ppm
(Freeman  et  al., 1969), although  a more recent  study  reported  no mortality
or  behavioral  abnormalities  1n rats continuously exposed to  30  ppm continu-
ously  for  20  weeks   (Glasgow  et  al.,  1987).   The mortality  reported  by
Steadman  et  al.  (1966) and  Freeman et al.  (1969)  was  not determined to  be
related  to  treatment  and  1s  not  considered  In derivation  of a  CS.   A study
using mice  that reported  mild changes 1n the  spleen (Kuraltls et  al., 1981)
Is  presented 1n Table 9-1.
    Several  epldemlologlcal  studies (see Chapter 6) were  limited  by factors
such as  simultaneous  exposure to  other  chemicals  and  Inadequate quantifica-
tion of  the  levels of  nitrogen dioxide,  and  are unsuitable for derivation of
                                                                             *
a CS.
    The  data suggest  that exposure to nitrogen  dioxide affected development
and  reproduction.  Freeman et  al. (1974)  reported  transient  retardation  of
lung development, maternal and  fetal  mortality  and reduced litter  size  In
rats  exposed  continuously  to  10  or  15 ppm.   It  was  unclear  whether  the
effects other  than those on  the lung  were  associated with  one or both of the
experimental concentrations.   Raw  data were not  provided, and the study was
considered Inadequately reported for critical  evaluation.  The 10  and 15 ppm
effect  levels  are above  the  5.3  ppm concentration at which  developmental
effects were observed  by Tabacova et  al.  (1985),  however;  so consideration
of  the  Tabacova  et  al.  study  for RQ  derivation  should afford  protection
against any  effects attributable  to the  higher air concentrations  of Freeman
et al.  (1974).   Tabacova  et al. (1985)  reported reduced postnatal viability
and  retarded physical  development In the  offspring of rats Intermittently


0166d                               -82-                              07/31/89

-------
exposed  to  10 mg/m3  (5.3 ppm) during  gestation.   Singh (1984)  reported  an
Increased  Incidence  of fetal  hematomas  In mice  exposed continuously to  22
ppm  during  days  8-18  of  gestation.  The  Tabacova et  al.  (1985) and Singh
(1984) studies are presented In Table 9-1.
    Composite  scores  were calculated 1n Table  9-2 for all  entries  In Table
9-1.   These  scores   ranged  from  5.86-36.20,  and  RQ  values  varied   from
100-1000.  The  lower  RQ of  100 was associated  with mild cellular  changes  1n
the  lungs of  mice Intermittently  exposed to 0.3 ppm for 6 weeks  (Sherwln  et
al.,  1985),   with Increased  relative weight  and  cellular  changes  In   the
spleens  of mice  Intermittently exposed  to  0.35 ppm for  6 weeks  (KuraHls  et
al.,  1981),  and with  reduced  postnatal  survival  In rats exposed  to  5.3  ppm
throughout gestation (Tabacova et  al., 1985).
    The  RQ of  100 pounds  based on the highest  CS  (36.2) associated with  mild.
                                                                            *•
cellular  changes   In  the  lungs  of  subchronlcally-exposed  mice  (Sherwln  et  .
al.,  1985)  Is chosen  to  represent  the  chronic toxlclty of nitrogen  dioxide
(Table 9-3).
9.2.   BASED ON CARCINOGENICITY
    Inhalation exposure to  nitrogen  dioxide yielded equivocal  results  In  the
strain A mouse lung  tumor  assay  (Adklns  et  al.,  1986; WUschl,  1988),  but
Increased the  frequency  of  metastasis  to  the  lungs  In mice  treated  Intra-
venously with  cancer  cells  (Rlchter  and KuraHls, 1983).  Nitrogen  dioxide
was shown to  be genotoxlc In  several  mlcroblal  (Rlnehart et al., 1973;  Kushl
et  al.,   1985;  Shlmlzu  et  al..   1986;  Vlctorln  and  Stahlberg,  1988)  and
mammalian  (Tsuda, 1981;  Isomura  et  al.,  1984;  Kosaka et  al.,  1987)  test
systems.   Because of a lack of human data and the Inadequate  nature  of the
animal data,  nitrogen  dioxide  was assigned to  EPA group D:  not classifiable
as to cardnogenlclty  to  humans.   Because  hazard  ranking Is not possible for
EPA group D compounds, an RQ for cardnogenlclty cannot be assigned.
           » .
0166d                               -83-                             07/31/89

-------
                          TABIF 92



Composite Scores for Inhalation Exposure to Nitrogen Dioxide
0»
Q.














1
CD
1









0
— J
CJ
*v
CD

Species/Strain

House/Swiss

Rat/Long-Evans

Rat/NR

Rat/JCL: Wlstar

Rat/JCL: Wlstar





House/Swiss
Webster
House/Swiss
Webster
Rat/Wlstar

House/CD- 1

•Equivalent human
NR . Not reported



Transformed
Animal Dosage
(•g/kg/day)
4.9

7.2

14.4

4.8

0.05





0.13

0.20

1.59

54

dosage (mg/kg/day)





Human NED* RVd
(mg/day)
25.0 3.38

8.4 4.10

172 2.15

57.4 2.86

0.57 5.86





0.069 7.24

0.11 6.95

19.0 3.58

284 1.82

In Table 9-1 multiplied by





Effect RVe CS RQ

Depressed SN tilers and sero- 3 14.65 1000
conversion rates
Decreased mucoclltary clear- 3 12.29 1000
ance rate
Evidence of severely Impaired 9 19.31 1000
lung function
Progressive hlstopathologlc 6 17.17 1000
lesions In lung
Norphometrlc and biochemical 1 5.86 1000
evidence of exposure




Reversible, mild cellular 5 36.20 100
changes In lung
Relative weight and cellular 5 34.76 100
changes In the spleen
Reduced postnatal viability 10 35.81 100

Increased Incidence of fetal 10 18.2 1000
hematomas
70 kg to express the NEO as mg/day for a 70 kg human



. tf

Reference

Ehrllch
et al.. 1975
Giordano and
Morrow. 1972
Haydon
et al.. 1965
Kubota
et al.. 1987
Sagal et al..
1984; Sagal
and Ichlnose.
1987; Kubota
et al.. 1987

Sherwln
et al.. 1985
Kuraltls
et al.. 1981
Tabacova
et al.. 1985
Singh. 1984







-------
                                  TABLE 9-3
                               Nitrogen Dioxide
           Minimum Effective  Dose  (MED) and Reportable Quantity (RQ)

Route:                  Inhalation
Species/Sex:            mouse/M
Duration:               6 weeks
MED*:                   0.069 mg/day
Effect:                 mild cellular changes In lung
RVd:                    7.24
RVe:                    5
Composite Score:        36.20
RQ:                     1000
Reference:              Sherwln et al., 1985

*Equ1valent human dose
0166d                               -85-                             07/31/89

-------
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0166d                               -87-                             07/31/89

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0166d                               -88-                             07/31/89

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Edwards, L.O.,  F.B. Meserole, R.L.  Leonard  and  T.A. Hall.   1984.   Non-photo-
                                                                             *
chemical  Interactions  of  sulfur  and  nitrogen  compounds In  acid  deposition..
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Ehrllch, R.   1966.   Effect of nitrogen dioxide on  resistance  to  respiratory
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PostlethwaH,  E.M.   and   M.G.  Mustafa.    1981.   Fate  of  Inhaled  nitrogen
dioxide  1n  Isolated  perfused rat  lung.   J. Toxlcol.  Environ.  Health.   7:
861-872.

Rlchter, A. and K.  Kura1t1s.   1983.  Air  pollutants and  the  facilitation  of
cancer metastasis.  Environ. Health Perspect.  52: 165-168.

Rlnehart, R.R., M.J.  Towle, F.J. Ratty and E. Hack.  1973.  The mutagenlclty
of  oxides of  nitrogen  and  methyl  benzenamlne  In Salmonella  typhlmurlum.
Mutat. Res. Sect.  Environ. Hutag. Relat. SubJ.  21(4):  232-233.
0166d                               -103-                            07/31/89

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Robertson, A.,  J.  Dodgson,  P.  Colllngs and  A.  Seaton.  1984.   Exposure  to
oxides  of  nitrogen:   Respiratory   symptoms   and  lung  function  In  British
coalmlners.  Br. 0. Ind. Med.  41(2):  214-219.

Rombout,  P.J.,  J.A.  Dormans, M. Marra  and  G.J.  Van Esch.   1986.   Influence
of exposure regimen on  nitrogen  dioxide-Induced morphological  changes  In  the
rat lung.  Environ. Res.  41(2): 446-480.

Roy-Burman, P.,  P.K.  Pattengale and  R.P.  Sherwln.   1982.   Effect  of  low
levels   of  nitrogen   dioxide   Inhalation  on  endogenous   retrovlrus   gene
expression.  Exp. Mol. Pathol.  36(2):  144-155.

Ryon, M.G., B.C.  Pal, S.S.  Talmage  and R.H.  Ross.  1984.   Database  assess-,
                                                                             *
ment  of  the health  and environmental   effects  of  munition  production  waste-
products.   Final  Report.   ORNL-6018.  (NTIS  DE84-016512).   Oak  Ridge  Natl.
Lab., Oak Ridge, TN.  p. 41, 111, 191-192,  217.

Sagal,  M.  and   T.  Ichlnose.   1987.    L1p1d-perox1dat1on  and  antloxldatlve
protection  mechanism  In  rat  lungs   upon  acute  and  chronic  exposure  to
nitrogen-dioxide.  Environ. Health Perspect.  73:  179-189.

Sagal, M.,  T.  Ichlnose and  K.  Kubota.  1984.   Studies  on  the biochemical
effects  of nitrogen  dioxide.   IV. Relation between  the  change  of  llpld
peroxldatlon and the  antloxldatlve  protective system In rat lungs  upon life
span  exposure  to  low  levels  of  N0_.   Toxlcol.  Appl.  Pharmacol.   73(3):
444-456.
0166d                               -104-                            07/31/89

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Saul,  R.L.  and M.C.  Archer.   1983.   Nitrate formation  1n  rats exposed  to
nitrogen dioxide.   Toxlcol. Appl. Pharmacol.   67(2):  284-291.

Sax, N.I.  1984.  Dangerous  Properties of  Industrial Materials,  6th  ed.   Van
Nostrand Relnhold Company, New York.  p.  2023.

Shalamberldze,  O.P.  and N.T. Tseretell.   1971.   Effect of small concentra-
tions  of  sulfurous  gas  and  nitrogen  dioxide on  the  estral  cycle  and  the
genital  function  of  animals  1n  experiments.   G1g.  Sanlt.   36(8):  13-17.
(Cited In Barlow and Sullivan, 1982)

Sherwln,  R.P.  and  V.  Rlchters.   1982.   Hyperplasla  of  type 2  pneumocytes
following  0.34   ppm  nitrogen  dioxide   exposure:  Quantltatlon  by   Image.
                                                                             •
analysis.  Arch. Environ. Health.  37(5): 306-315.

Sherwln,  R.P.,  V.  Rlchters  and  A.  Rlchters.   1985.    Image analysis  quantl-
tatlon  of type 2  cells and  alveolar  walls:  2.  Influence  of 0.3 parts  per
million  nitrogen  dioxide  exposure on  the developing mouse  lung.   J.  Am.
Toxlcol.  4(1): 27-43.

Shlmlzu.  H.,   Y.  Suzuki  and K.  Hayashl.  1986.   The  bubbling method  for
detecting mutagenlc activity  In gaseous compounds.  Mutat. Res.  164: 280,

Shuval, H.I. and N.  Gruener.  1974.   Effects  on man  and animals of Ingesting
nitrates  and  nitrites  1n  water and  food.   Eff. Agrlc.  Prod.  Nitrates Food
Water  Particular  Ref.  Isot.  Stud.,  Proc. Rep.  Panel  Experts,  Meeting Date
1973.  IAEA: Vienna, Austria,  p. 117-130.

0166d                               -105-                            07/31/89

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Shy, C.M. and G.J. Love.  1979.  Recent  evidence  on  the  human health  effects
of nitrogen  dioxide.   In:  Proceedings of  the  Symposium on Nitrogen  Oxides,
Honolulu, Hawaii, April 4-5,  1979.   (Cited In U.S. EPA.  1982)

Shy, C.M.,  J.P.  Creason,  M.E. Pearlman,  K.E.  McClaln,  F.B.  Benson and  M.M.
Young.    1970a.   The  Chattanooga schoolchildren  study:  Effects of  community
exposure to  nitrogen dioxide.  1. Methods, description of  pollutant exposure
and results  of ventllatory function testing.   J.  Air. Pollut.  Control  Assoc.
20(8):  539-545.

Shy, C.M.,  J.P.  Creason,  M.E. Pearlman,  K.E.  McClaln,  F.B.  Benson and  M.M.
Young.    1970b.   The  Chattanooga schoolchildren  study:  Effects of  community
exposure to  nitrogen dioxide.   II.  Incidence  of acute  respiratory  Illness...
J. A1r  Pollut. Control  Assoc.  20(9):  582-588.

Shy, C., M.  Nlemeyer,  L.  Truppl  and  J.  English.   1973.   Reevaluatlon  of the
Chattanooga   Schoolchildren   Studies   and   the   Health   Criteria  for   NO.
Exposure.   Inhouse technical  report.   Health  Effects   Research  Laboratory,
Environmental  Research   Center,   U.S.   Environmental    Protection   Agency,
Research Triangle Park, NC.   March,  1973.  (Cited In U.S. EPA, 1982)

Singh,  J.  1984.   Teratologlcal  evaluation  of  nitrogen  dioxide.   Proc. Annu.
Tech. Meet.  Inst. Environ. Sc1.  30: 229-231.

Spelzer, F.E. and  B.G.  Ferris, Jr.    1973a.  Exposure to automobile exhaust.
I. Prevalence of  respiratory  symptoms  and disease.  Arch.  Environ.  Health.
313-318.  (Cited 1n U.S. EPA, 1982)

0166d                               -106-                            07/31/89

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Spelzer, F.E. and  B.G.  Ferris,  Jr.   1973b.  Exposure to automobile  exhaust.
II. Pulmonary function measurement.  Arch.  Environ.  Health.   26(6):  319-324.
(Cited In U.S. EPA, 1982)

Spelzer, F.E., B. Ferris, Jr., Y.M. Bishop  and  J.  Spengler.   1980.   Respira-
tory  disease  rates and  pulmonary  function In  children  associated  with NO.
exposure.  Am. Rev. Resplr.  D1s.   121(1):  3-10.

Splcer,  C.U.  and  D.F.  Miller.   1976.   Nitrogen  balance  In  smog  chamber
studies.  J. Air Pollut.  Control  Assoc.   26: 45-50.

SRI   (Stanford  Research  Institute).    1988.    1988  Directory  of   Chemical
Producers.  SR.I  International, Menlo Park, CA.   p. 803.
                                                                             •

Stacy, R.W.,  E.  Seal, Jr., D.E.  House,  J.  Green, L.J.  Roger  and L.  Ragglo.
1983.   A survey of  effects  of gaseous  and aerosol pollutants  on  pulmonary
function of normal males.  Arch.  Environ.  Health.  38(2):  104-115.

Steadman,  B.L.,  R.A. Jones,  D.E.  Rector and  J. Slegel.  1966.  Effects  on
experimental animals  of  long-term continuous  Inhalation  of  nitrogen dioxide.
Toxlcol. Appl. Pharmacol.  9(1):  160-170.

Stephens, R.J.,  G. Freeman, S.C.  Crane  and N.J. Furlosl.   1971.  Ultrastruc-
tural  changes  In  the  terminal   bronchiole of  the  rat  during  continuous,
low-level exposure to nitrogen dioxide.  Exp. Mol. Pathol.   14(1):  1-19.
0166d                               -107-                            07/31/89

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Tabacova, S.,  8.  N1k1forov and  L.  Balabaeva.   1985.   Postnatal  effects of
maternal exposure  to nitrogen  dioxide.   Neurobehav.  Toxlcol.  Teratol.  7:
785-789.

Takahashl,   Y., K.  MochUate  and  T.  M1ura.    1986.   Subacute  effects  of
nitrogen dioxide on membrane constituents of  lung, liver and kidney of  rats.
Environ. Res.  41(1): 184-194.

Traynor, G.W.  and  I.A.  NHschke.   1984.   Field  survey of Indoor air pollu-
tion  In  residences  with suspected  combustion-related  sources.  Presented at
Proc.  Intl.  Conf.   on  Indoor  Air  Quality and Climate,  Swedish Council  for
Building Research,  Stockholm,  Sweden.   NTIS PB85104214.  p.  343-348.
                                                                            «
Tse,  R.L.  and  A.A.  Bockman.   1970.   Nitrogen  dioxide  toxlclty:  Report of
four cases In  firemen.   J.  Am.  Hed.  Assoc.  212:  1341-1344.

Tsuda, H., A.  Kushl, 0. Yoshlda  and F.  Goto.   1981.   Chromosomal  aberrations
and  slster-chromatld  exchanges  Induced  by  gaseous  nitrogen  dioxide  In
cultured Chinese hamster cells.   Mutat. Res.  89(4):  303-309.

U.S.  EPA.    1971.    National   Primary  and  Secondary  Ambient  Air  Quality
Standards.   Federal Register.   36: 8186-8201.

U.S.  EPA.   1977.   TSCAPP   (Toxic  Substances  Control  Act  Plant  Production)
file.  On-line retrieval.  May 13, 1988.
0166d                               -108-                            07/31/89

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U.S-.  EPA.   1980.   Guidelines and  Methodology  Used  1n  the  Preparation  of
Health  Effect  Assessment  Chapters  of  the  Consent  Decree  Water  Criteria
Documents.  Federal Register.  45(231): 79347-79357.

U.S.  EPA.   1982.   Air  Quality Criteria for Oxides of Nitrogen.   Prepared  by
the  Office  of  Health  and Environmental  Assessment,  Environmental  Criteria
and  Assessment  Office,  Research  Triangle  Park,  NC.   EPA-600/8-82-026F.   NTIS
PB83-163337.

U.S.  EPA.   1984.   Methodology and Guidelines  for Ranking Chemicals  Based  on
Chronic Toxldty  Data.   Prepared by the  Office of Health and  Environmental
Assessment, Environmental Criteria and  Assessment  Office, Cincinnati,  OH for
the Office of Emergency and Remedial  Response, Washington,  DC.
                                                                            ••

U.S.  EPA.   1985a.  Physical-chemical  properties  and categorization of  RCRA
wastes  according   to   volatility.   Office   of  A1r  Quality   Planning   and
Standards.  EPA-450/3-85-007.  NTIS PB85-204527.

U.S.  EPA.   1985b.   Drinking  Water  Criteria  Document  for  NHrate/NHrHe.
Office of Drinking Water, Washington, DC.   Final Draft.   NTIS PB 86-117959.

U.S.  EPA.   1985c.   Retention  of  the National Ambient Air Quality Standards
for Nitrogen Dioxide.  Federal Register.  50:  25532-25544.

U.S.  EPA.   1986a.   Integrated Risk  Information  System (IRIS):  Reference  Dose
(RfD)  for  Oral  Exposure  for  Nitrogen  Dioxide.   Online.   (Verification  date
02/26/86.)   Office  of  Health  and  Environmental  Assessment,  Environmental
Criteria and Assessment Office, Cincinnati, OH.

0166d                                -109-                            09/27/89

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U.S.  EPA.   1986b.   Integrated  Risk  Information  System (IRIS):  Reference  Dose
(RfD)  for  Oral  Exposure  for  NHrHe.   Online.   (Verification date 02/26/86.)
Office  of  Health  and  Environmental  Assessment,  Environmental Criteria  and
Assessment Office, Cincinnati,  OH.

U.S.  EPA.   1986c.   Guidelines   for   Carcinogen  Risk  Assessment.   Federal
Register.  51(185): 33992-34003.

U.S.   EPA.    1988a.    SANSS  (Structure   and  Nomenclature   Search  System).
Database.  On-Hne retrieval. Hay 13,  1988.

U.S.  EPA.   1988b.  National A1r  Quality  and Emissions  Trend Report. 1986.
EPA  450/4-88-001.   Office of  A1r  Quality Planning and Standards,  Research..
Triangle Park, NC.

U.S.  EPA.   1988c.   Integrated  Risk  Information  System (IRIS).  Chemical  File
for  Nitrogen  Dioxide.   Online.   Office  of Health  and  Environmental  Assess-
ment, Environmental Criteria and Assessment Office,  Cincinnati, OH.

U.S.  EPA.   1988d.  Interim  Methods for  Development  of  Inhalation Reference
Doses.  October  1988  Draft.   Office of  Health  and  Environmental  Assessment,
Environmental Criteria and  Assessment Office,  Research  Triangle Park,  NC.
EPA/600/8-88/066F.  April.

U.S.  EPA/OWRS  (Office of  Water  Regulations  and  Standards).. 1986.   Guide-
lines  for  Deriving Numerical  National Water Quality for  the Protection  of
Aquatic Organisms and their Uses.  Washington, DC.  GRAI8522.


0166d                               -110-                            09/27/89

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 Vaughan,  R.R., I.E.  Jennelle  and  T.R. Lewis.   1969.   Long-term  exposure to
 low levels  of  air  pollutants.  Arch.  Environ. Health.   19: 45-50.

 V1ctor1n,  K.  and  M.  Stahlberg.    1988.   A method for  studying  the mutagen-
 1c1ty of  some gaseous  compounds  In  Salmonella  typhlmuMum.   Environ.  Mol.
 Mutagen.   11(1): 65-75.
 von  Nledlng,   G.   and   H.M.  Wagner.   1979.   Effects  of  NO.  on  chronic
 bronchHIcs.   Environ.  Health Perspect.  29:  137-142.
 von Nledlng,  G.,  M. Wagner,  H.  Krebeler, U.  Smldt and  K.  Muysers.   1970.
 Absorption of  NO.  In  low concentrations  In  the respiratory  tract  and  Us
 acute  effects  on  lung  function  and  circulation.   Presented at  the  Second.,
                                                                             ••
 International  Clean  Air  Congress at  the Union of  Air  Pollution Prevention
 Assoc.,  Washington,  DC.   Dec.  6-11.   (Cited In  Goldstein et al.,  1980)
 von Nledlng,  G.,  H.M.  Wagner,  H.  Krekeler,  H.  Loellgen,  W. Fries  and A.
 Beuthan.   1979.   Controlled studies of human exposure to single and combined
 action of  nitrogen  dioxide,  ozone and  sulfur  dioxide.   Int.  Arch.  Occup.
'Environ.  Health.   43(3): 195-210.

 Walton,  G.  1951.   Survey of  literature  relating  to  Infant  methemogloblnemla
 due to nitrate-contaminated water.   Am.  J.  Public. Health.   41: 986-996.

 Wlndholz,  H., Ed.   1983.   The  Merck  Index.  An  Encyclopedia of  Chemicals,
 Drugs   and  B1olog1cals,   10th  ed.    Merck  and  Co..  Inc.,  Rahway,   NJ.
 p.  947-948.


 0166d                                -111-                           07/31/89

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W1tsch1, H.   1988.  Ozone,  nitrogen dioxide  and lung  cancer:  A  review  of
some recent Issues and  problems.  Toxicology.  48(1):  1-20.

Wodzlnskl,   R.S.  and M.  Alexander.   1980.   Effects  of  nitrogen dioxide  on
algae.  J.  Environ. Qual.  9(1): 34-36.

Yanaglsawa,  Y.,  H. Matsukl,  F. Osaka,  H.   Kasuga and  H. Nlshlmura.   1984.
Annual  variation   of  personal   exposure  to  nitrogen  dioxide.   Presented  at
Proc.  Intl.  Conf.  on  Indoor Air  Quality and  Climate,  Swedish Council  for
Building Research, Stockholm, Sweden.  NTIS PB85-104214.   p.  33-36.
0166d                                -112-                             07/31/89

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                                  APPENDIX A

                             LITERATURE SEARCHED



    This  HEED  1s  based  on  data   Identified   by   computerized   literature

searches of the following:

              CHEMLINE
              7SCATS
              CASR online (U.S.  EPA  Chemical  Activities  Status  Report)
              TOXLINE
              TOXLIT
              TOXLIT 65
              RTECS
              OHM TADS
              STORET
              SRC Environmental  Fate Data  Bases
              SANSS
              AQUIRE
              TSCAPP
              NTIS
              Federal  Register
              CAS ONLINE (Chemistry  and Aquatic)
              HSOB
              SCISEARCH
              Federal  Research  In Progress


These  searches  were conducted   1n  Hay,  1988,  and  the following  secondary

sources were reviewed:
    ACGIH  (American  Conference of Governmental  Industrial  Hyglenlsts).
    1986.  Documentation  of the  Threshold  Limit Values  and  Biological
    Exposure Indices, 5th ed.  Cincinnati, OH.

    ACGIH  (American  Conference of Governmental  Industrial  Hyglenlsts).
    1987.  TLVs:  Threshold  Limit Values  for  Chemical  Substances  1n the
    Work  Environment  adopted   by   ACGIH  with  Intended  Changes  for
    1987-1988.  Cincinnati,  OH.  114 p.

    Clayton,  G.O.  and  F.E.  Clayton,  Ed.    1981.   Patty's  Industrial
    Hygiene  and  Toxicology,  3rd rev.  ed.,  Vol.  2A.   John  Wiley  and
    Sons, NY.  2878 p.

    Clayton,  G.D.  and  F.E.  Clayton,  Ed.    1981.   Patty's  'industrial
    Hygiene  and  Toxicology,  3rd rev.  ed.,  Vol.  28.   John  Wiley  and
    Sons, NY.  p. 2879-3816.
0166d                               -113-                            07/31/89

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    Clayton,   G.O.  and  F.E.  Clayton,  Ed.   1982.   Patty's  Industrial
    Hygiene and  Toxicology,  3rd  rev.  ed.,  Vol.  2C.    John  Wiley  and
    Sons, NY.   p.  3817-5112.

    Grayson,  M. and  D. Eckroth,  Ed.   1978-1984.  Klrk-Othmer  Encyclo-
    pedia of  Chemical Technology, 3rd ed.  John  Wiley and  Sons,  NY.   23
    Volumes.

    Hamilton,  A. and H.L. Hardy.  1974.   Industrial  Toxicology,  3rd  ed.
    Publishing Sciences Group, Inc.,  Littleton,  MA.   575  p.

    IARC  (International  Agency  for   Research  on Cancer).   IARC  Mono-
    graphs on  the  Evaluation  of  Carcinogenic  Risk  of  Chemicals   to
    Humans.  IARC,  WHO, Lyons, France.

    Jaber, H.M.,  W.R.  Mabey,  A.T.  Lieu,  T.W.   Chou and H.L.  Johnson.
    1984.   Data  acquisition   for  environmental  transport  and  fate
    screening for compounds  of Interest  to  the Office  of  Solid Waste.
    EPA  600/6-84-010.    NTIS  PB84-243906.    SRI  International,   Menlo
    Park, CA.

    NTP  (National Toxicology  Program).   1987.   Toxicology  Research  and
    Testing  Program.   Chemicals  on  Standard  Protocol.    Management
    Status.

    Ouellette,  R.P.  and  J.A.  King.   1977.    Chemical  Week  Pesticide
    Register.   McGraw-Hill Book Co.,  NY.

    Sax,  I.N.   1984.   Dangerous Properties of  Industrial Materials,  6th
    ed.  Van  Nostrand Relnhold Co.,  NY.

    SRI  (Stanford  Research  Institute).   1987.   Directory of  Chemical
    Producers.  Menlo Park,  CA.

    U.S.  EPA.   1986.  Report  on Status  Report  1n  the  Special  Review
    Program,   Registration  Standards  Program  and  the   Data  Call   In
    Programs.    Registration  Standards  and  the  Data  Call  In  Programs.
    Office of Pesticide Programs, Washington, DC.

    USITC  (U.S.  International  Trade  Commission).    1986.   Synthetic
    Organic Chemicals.   U.S.  Production  and  Sales,  1985, USITC  Publ.
    1892, Washington, DC.

    Verschueren, K.   1983.   Handbook of  Environmental   Data  on Organic
    Chemicals, 2nd ed.   Van Nostrand Relnhold Co., NY.

    Wlndholz,  M.. Ed.  1983.   The Merck Index,  10th  ed.   Merck and Co.,
    Inc., Rahway,  NJ.

    Worthing,  C.R.  and S.B.  Walker,  Ed.   1983.  The Pesticide Manual.
    British Crop Protection Council.  695 p.
0166d                               -114-                            07/31/89

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    In addition,  approximately 30  compendia of aquatic  toxldty data were

reviewed, Including the following:


    Battelle's  Columbus  Laboratories.   1971.   Water  Quality  Criteria
    Data  Book.   Volume  3.   Effects   of  Chemicals   on   Aquatic   Life.
    Selected  Data  from the Literature  through  1966.   Prepared for  the
    U.S. EPA under Contract No. 68-01-0007.   Washington,  DC.

    Johnson,  W.W.  and  M.T. Flnley.   1980.   Handbook  of Acute  Toxldty
    of  Chemicals  to   F1sh and  Aquatic  Invertebrates.   Summaries   of
    Toxldty  Tests  Conducted  at  Columbia  National  Fisheries  Research
    Laboratory.   1965-1978.    U.S.  Oept.  Interior,  Fish  and  Wildlife
    Serv. Res. Publ. 137,  Washington,  DC.

    McKee,  J.E.  and H.W.  Wolf.  1963.  Water Quality Criteria, 2nd  ed.
    Prepared  for  the  Resources   Agency  of  California,   State   Hater
    Quality Control Board.  Publ.  No.  3-A.

    Plmental, D.   1971.   Ecological Effects  of  Pesticides  on  Non-Target
    Spedes.  Prepared for the U.S.  EPA, Washington,  DC.   PB-269605.

    Schneider, B.A.  1979.  Toxicology  Handbook.   Mammalian and Aquatic
    Data.   Book  1:  Toxicology  Data.   Office  of  Pesticide Programs,  U.S.
    EPA, Washington, DC.  EPA 540/9-79-003.   NTIS PB  80-196876.
0166d                               -115-                            07/31/89

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o



0>
                                                                           APPENDIX B



                                                               Summary Table for Nitrogen Dioxide
Species
Inhalation Exposure
Subchronk rat
Chronic rat
CarclnogenlcUy ID
Oral Exposure
Subchrontc human
Chronic human
CarclnogenlcUy (0
REPORTABLE QUANTITIES
Based on chronic toxlclty:
Based on carclnogenlclty:
Exposure

0.40 ppm (0.753 mg/m») con-
tinuously for 2? months
0.40 ppn (0.753 mg/m») con-
tinuously for 27 months
ID

TO ppm nitrate N In drinking
water (T mg/kg/day)
TO ppm nitrate N In drinking
water (T mg/kg/day)
ID

1000

Effect

NOAEL for emphysema -like
lesions In the lung
NOAEL for emphysema -like
.lesions In the lung
10

NOAEL for methemoglobln-
emla
NOAEL for methemoglobln-
emta
10


NO
RfO or qj* Reference

0.02 mg/m» Kubota et al.. 19B7;
Sagal et al.. 1984;
Sagal and Ichlnose,
1987
0.02 mg/m» Kubota et al.. 1987;
Sagal et al.. 1984;
Sagal and Ichlnose.
1987
NO 10

1 mg/kg/day Ma It on. 1951
1 mg/kg/day Walton. 1951
NO ID

Kuraltls et al.. T981
ID
8
         ID = Insufficient  data;  NO -  not  derived
00

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                                  APPENDIX C
        OOSE/OURATION RESPONSE GRAPHS FOR EXPOSURE TO NITROGEN DIOXIDE
C.I.  DISCUSSION
    Dose/duration-response  graphs   for  Inhalation  exposure   to   nitrogen
dioxide generated by  the method  of  Crockett  et  al.  (1985) using the computer
software by  Durkln  and Meylan  (1988)  under  contract to  ECAO-C1nc1nnat1  are
presented  1n  Figures C-1  through  C-4.  Data  used  to generate  these  graphs
are  presented  In  Section  C.2.   In  the  generation  of   these  figures  all
responses are  classified  as  adverse (FEL, AEL  or LOAEL)  or  nonadverse (NOEL
or  NOAEL)  for  plotting.  The  ordlnate expresses concentration  In  either  of
two ways.   In  Figures C-1  and C-2,  the experimental  concentration  expressed
as  mg/m3  was  multiplied  by  the  time parameters  of  the exposure  protocol
(e.g.,  hours/day  and  days/week) and  Is  presented  as  expanded  experimental..
concentration  [expanded exp  cone   (mg/m3)].    In Figures C-3  and   C-4,  the
expanded experimental  concentration was multiplied  by  the cube root  of  the
ratio  of  the  animal:human body weight to  estimate  an  equivalent  human  or
scaled  concentration  [scaled  cone  (mg/m3)]   (U.S.  EPA,  1980;  Mantel  and
Schnelderman,  1975).
    The boundary  for adverse  effects   (solid  line)  Is drawn  by Identifying
the lowest-adverse-effect  dose or  concentration at  the  shortest duration of
exposure at  which an adverse  effect occurred.  From  this point an Infinite
line  1s  extended  upward  parallel  to  the  dose axis.  The  starting  point 1s
then  connected to  the  lowest-adverse-effect   dose  or  concentration  at  the
next  longer  duration  of  exposure   that  has  an  adverse-effect  dose  or
concentration  equal  to  or  lower  than  the  previous  one.  This process  Is
continued  to  the  lowest-adverse-effect  dose   or  concentration.   From this
point  a  line  1s  extended  to the right parallel to the  duration  axis.  The
region of adverse effects lies above the adverse effects  boundary.

0166d                                -117-                            07/31/89

-------
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9i >
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• 1 ' 'IT!. T, 1 1— TTTTTT] 1 	 1 ! 1 1 ,lf| 	 -| 	 1 T 1 ' 7 T 1 1 	 T— | , | , |,,. 	 a
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: • l • i
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00081 0.0001 0.001 0i0i fl.l ; 2
< I
     i an on
HUMAN EQUIU DURATION (fraction lif*sp«n>

           ENVELOP NTTHOP
    Key:    F . PEL
           A - AEL
           L . LOAEL
           N . NOAEL
           Solid line • Adverse Effects  Boundary
           Dotted line • No Adverse  Effects  Boundary
                                       FIGURE C-l

              Dose/Duration  - Response Graph for Inhalation Exposure to NO?:
                  Envelope Method (Expanded Experimental Concentration)
      0166d
            -118-
                                                                          07/31/89

-------
 ?
 0.
 X
 hi

 A
 hi
 C
        100
         10 T
        0.1 T
       0.01
                                          F


                                          f
           r
                                        n

                                        n
           0.00001
OnKfclation Exposure)
0.0001        0.001         0.01          g;i

     HUMAN EQUIU MIRATION (fFaction  lif*span)

           CENSORED  DATA METHOD
                                                                                 IU.
       Key:   F - FEL
              A . AEL
              L • LOAEL
              N • NOAEL
              Solid line » Adverse Effects Boundary
              Dashed line • No Adverse Effects Boundary
                                       FIGURE C-2

             Dose/Duration - Response Graph for Inhalation Exposure to
               Censored Data Nethod (Expanded Experimental Concentration)
     0166d
                -119-
07/31/89

-------
r
V

A

d
C
      laae
       100 •-
        IB -r
         i -r
       e.i
                                                     l|    I  I  I I 1 I!
                                                                          i  i i i m
                                          r
                                          r
                                          f
                                                                n
                                                                n
                                           I   1  I
          a. eaa0i
(inhalation Exposure)
                        0.0001        0.001         0.01          0.1
                             HUMAN EQUIV MIRATION (fraction 1 if •spin)
                                        ENVELOP METHOD
        1   2
    Key:   F « PEL
           A . AEL
           L . LOAEL
           N • NOAEL
           Solid  line • Adverse Effects Boundary
           Dashed line • No Adverse Effects Boundary
                                      FIGURE C-3

            Dose/Duration - Response Graph for Inhalation Exposure to
                        Envelope Method (Scaled Concentration)
    0166d
                                         -120-
07/31/89

-------
 t
 ft
 w
 e
u
       1000
100 T
         10 r
        0.1
0.00001
(Inflation Exposup«>
                                         r

                                         F
                                         I
                                            l   i i  i r
                                                                          A   •
                                                                n

                                                                n
                 0.0001        0.001         0.01
                      HUMAN EQUIU DURATION 
-------
    Using the envelope  method,  the boundary  for  no adverse  effects  (dashed
line) 1s drawn  by  Identifying  the highest no adverse  effects concentration.
From this point a  line  parallel to  the  duration  axis  1s  extended to the dose
or  concentration  axis.   The  starting  point  Is  then  connected  to the  next
highest  or  equal   no  adverse effect  concentration at a  longer  duration  of
exposure.  When this  process can no  longer  be  continued, a  line  Is  dropped
parallel to  the concentration  axis to  the  duration axis.  The  region  of  no
adverse effects lies  below  the  no adverse effects  boundary.   At either  ends
of  the  graph between the adverse  effects and no  adverse  effects  boundaries
are  regions  of  ambiguity.   The  area  (If  any) resulting  from Intersection  of
the  adverse  effects  and no  adverse effects  boundaries  Is  defined  as  the
region of contradiction.
    Because  of  the enormous number  of  studies  available, data  Included  Irv.
the  graphs  were restricted  to the  better  quality animal studies from the
more  recent  literature  that Investigated  endpolnts  of  relevance to  human
health.  Individual  human  ep1dem1olog1cal studies  and case  reports were not
Included because they were complicated  by exposures to mixtures  of compounds
and/or  concentrations of nitrogen dioxide were  not sufficiently quantified.
Collectively, studies of controlled  human exposure Indicated that no adverse
effects occurred at  1.0 ppm, and  this  point Is plotted.   It appears as the
NOAEL at the far left on the graphs.
    The  cluster of  FELs  In the  upper   left  quadrant  are LC5Q  values   taken
from Table  6-6.  The adverse effects boundary Is  defined by LC5Q values In
rabbits and  guinea pigs  (Sax,  1984),  by a PEL for  reduced neonatal viability
In  rats (Tabacova et al.,  1985)  and  by a LOAEL  for lung  lesions  In rats
exposed  for  15  weeks (Gregory et al.,  1983).   Of particular  Interest  Is the
small  region of contradiction  created  from such  a  large  and  diverse data


0166d                               -122-                            07/31/89

-------
base.  This may reflect  the  fact  that  only selected data were Included.   The

NOAEL from  the  27-month rat  study  that served as  the  basis for  the  RfO is

the  higher  of the  two  located at  1.125  Hfespans.  The  RfO of  0.02 mg/m3

1s located below the scale In the no adverse effects region.

C.2.  DATA USED TO GENERATE DOSE/DURATION-RESPONSE GRAPHS

Chemical Name:    Nitrogen Dioxide
CAS Number:       10102-44-0
Document Title:    Health and Environmental Effects Document on Nitrogen
                  Dioxide
Document Number:   pending
Document Date:    pending
Document Type:    HEED
RECORD #1:

Comment:
Citation:
RECORD #2:

Comment:
Citation:
Species: Mice Dose: 3.760
Sex: Hale Duration Exposure: 40.0 weeks
Effect: LOAEL Duration Observation: 40.0 weeks
Route: Inhalation
Number Exposed: 14
Number Responses: 0
Type of Effect: ENZYM
SHe of Effect: BLOOD
Severity Effect: 1
2 ppm continuous; transient depression of SN tUers and
seroconverslon rates.
Ehrllch et al.. 1975
Species: Rats Dose: 11.300
Sex: Female Duration Exposure: 6.0 weeks
Effect: LOAEL Duration Observation: 6.0 weeks
Route: Inhalation
Number Exposed: 16
Number Responses: 0
Type of Effect: TOXSL
Site of Effect: LUNG
Severity Effect: 5
6 ppm continuous; decreased mucodllary clearance; edema and
vascular congestion 1n alveolar region.
Giordano and Morrow, 1972
0166d
-123-
07/31/89

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RECORD |3:
Comment:


Citation:
Species:
Sex:
Effect:
Route:
Hamsters
NR
AEL
Inhalation
Dose:
Duration Exposure:
Duration Observation:
Number Exposed:     4
Number Responses:   NR
Type of Effect:     DEGEN
Site of Effect:     LUNG
Severity Effect:    6

30 ppm, 22 hours/day for up to 365 days
In terminal bronchioles and alveoli.

Klelnerman et al., 1985a,b
51.700
12.0 months
12.0 months
                               H1stolog1c  lesions
RECORD #4:


Species: Rats
Sex: Male
Effect: AEL



Dose: 19.900
Duration Exposure: 4.0 weeks
Duration Observation: 4.0 weeks
Route: Inhalation





Number Exposed:
Number Responses:
Type of Effect:
Site of Effect:
Severity Effect:
78
NR
HYPRP
LUNG
4





Comment:       10.6 ppm continuous; degenerative and hyperplastlc lesions  In
               lungs.

Citation:      Rombout et al., 1986
RECORD #5:


Species: Rats
Sexr Male
Effect: LOAEL



Dose: 5.100
Duration Exposure: 28.0 days
Duration Observation: 28.0 days
Route: Inhalation





Number Exposed:
Number Responses:
Type of Effect:
Site of Effect:
Severity Effect:
3
NR
HYPRP
LUNG
3





Comment:


Citation:
2.7 ppm continuous; mild degenerative and hyperplastlc
lesions.  Concentrations tested: 0.5, 1.3, 2.7 ppm.

Rombout et al.. 1986
0166d
                     -124-
                                           07/31/89

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RECORD #6:

Comment:
Citation:
RECORD #7:

Species: Rats
Sex: Male
Effect: NOAEL
Route: Inhalation
Number Exposed: 3
Number Responses: NR
Type of Effect: HYPRP
SHe of Effect: LUNG
Severity Effect: NONE
1.3 ppm continuous; no les
Rombout et al., 1986
Species: Rats
Sex: Both
Effect: LOAEL
Route: Inhalation
Number Exposed: 50
Number Responses: NR
Type of Effect: DEGEN
Site of Effect: LUNG
Severity Effect: 4
Dose:
Duration Exposure:
Duration Observation:

1ons (see previous record)

Dose:
Duration Exposure:
Duration Observation:
50
NR
ENZYM
LUNG
1
2.400
28.0 days
28.0 days

•

2.000
15.0 weeks
15.0 weeks

Comment:       5 ppm 7 hours/day, 5 days/week; mild Inflammatory lesions  and
               biochemical evidence of tissue damage due to exposure.
               (Concentrations tested: 1  and 5 ppm).

Citation:      Gregory et al., 1983
RECORD #8:


Species: Rats
Sex: Both
Effect: NOAEL



Dose:
Duration Exposure:
Duration Observation:
0.400
15.0 weeks
15.0 weeks
Route: Inhalation





Number Exposed:
Number Responses:
Type of Effect:
Site of Effect:
Severity Effect:
50
NR
DEGEN
LUNG
NONE
50
NR
ENZYN
LUNG
NONE





Comment:       1 ppm (see previous record); no lesions, but biochemical
               endpolnts showed changes.

Citation:      Gregory et al., 1983
0166d
-125-
07/31/89

-------
RECORD |9:
Comment:


Citation:
Species:
Sex:
Effect:
Route:
Rats
Male
NOAEL
Inhalation
Dose:                  0.750
Duration Exposure:      16.0 weeks
Duration Observation:   16.0 weeks
Number Exposed:      36
Number Responses:    NR
Type of Effect:      ENZYM
SHe of Effect:      LUNG
Severity Effect:     1

0.4 ppm continuous;  biochemical  evidence of  llpld  peroxl
datlon at all concentrations  (0.4,  1.2,  4 ppm).

Ichlnose and Sagal,  1982
RECORD #10: Species: Mice
Sex: Hale
Effect: NOAEL



Dose: 0.100
Duration Exposure: 6.0 weeks
Duration Observation: 6.0 weeks
Route: Inhalation
Number Exposed:
Number Responses:
Type of Effect:
Site of Effect:
Severity Effect:
60
NR
HYPRP
LUNG
NONE

4



Comment:       0.3 ppm 6 hours/day, 5 days/week;  reversible Increase  In  Type
               II pneumocytes, reversible after 10-week recovery  period.

Citation:      Sherwln et al., 1985
RECORD #11: Species: Hamsters
Sex: Male
Effect: NOAEL



Dose: 0.9CC
Duration Exposure: 8.0 weeks
Duration Observation: 8.0 weeks
Route: Inhalation
Number Exposed:
Number Responses:
Type of Effect:
SHe of Effect:
Severity Effect:
7
NR
HYPRP
LUNG
NONE





Comment:


Citation:
2 ppm 8 hours/day, 5 days/week; morphometrlc evidence of
emphysema but no hlstopathologlcal lesions.

Lafuma et al., 1987
0166d
                     -126-
                                           07/31/89

-------
RECORD 112:
Comment:


Citation:
Species:
Sex:
Effect:
Route:
Rats
Male
LOAEL
Inhalation
               Number Exposed:      120
               Number Responses:    NR
               Type of Effect:      WGTDC
               Site of Effect:      BODY
               Severity Effect:     4
Dose:
Duration Exposure:
Duration Observation:
                             120
                             NR
                             DEGEN
                             LUNG
                             6
56.000
20.0 weeks
20.0 weeks
30 ppm continuous;  reduced rate of  body weight  gain; altered
morphology of lungs.

Glasgow et al., 1987
RECORD #13:
Species: Mice
Sex: Male
Effect: NOAEL
Route: Inhalat
Number Exposed:
Number Responses:
Type of Effect:
SHe of Effect:
Severity Effect:
Ion
134
NR
WGTIN
SPLEN
NONE
Dose: 0.160
Duration Exposure: 6.0 weeks
Duration Observation: 6.0 weeks
Comment:       0.35 ppm 8 hours/day, 5 days/week for 6 weeks;  elevated  rel
               spleen wt., cellular changes.

Citation:      Kura1t1s et al.. 1981
RECORD #14:



Species:
Sex: '
Effect:
Route:
Rats
Maje
NOAEL
Inhalation
Dose:
Duration
Duration


Exposure:
Observation:

0.800
14.0 weeks
14.0 weeks

Comment:


Citation:
Number Exposed:     48
Number Responses:   NR
Type of Effect:     ENZYM
SHe of Effect:     LIVER
Severity Effect:    NONE

0.4 ppm continuous; altered activities of liver mlcrosomal
enzymes.  Concentrations tested: 0.4, 1.2, 4.0 ppm.

Takahashl et al., 1986
0166d
                     -127-
                                           07/31/89

-------
RECORD |15:
Comment:


Citation:
Species:
Sex:
Effect:
Route:
Rats
Male
AEL
Inhalation
               Number Exposed:     2
               Number Responses:   NR
               Type of Effect:     DEGEN
               Site of Effect:     LUNG
               Severity Effect:    6
Dose:
Duration Exposure:
Duration Observation:
                             2
                             NR
                             HGTDC
                             BODY
                             4
29.500
17.0 months
17.0 months
15.7 ppm continuous;  reduced body weight,  Increased  lung
weight and volume, emphysema-like lesions.

Juhos et al.,  1980
RECORD #16:


Species: Rats
Sex: NR
Effect: AEL



Dose:
Duration Exposure:
Duration Observation:
23.000
813.0 days
813.0 days
Route: Inhalation





Number Exposed:
- Number Responses:
Type of Effect:
Site of Effect:
Severity Effect:
15
NR
DEGEN
LUNG
6
15
NR
UGTDC
BODY
4





Comment:       12 ppm continuous; Increased lung weight and breathing rate,
               gross distortion of thoracic cavity,  hlsto.  lesions of
               emphysema, decreased body weight.

Citation:      Haydon et al., 1965
RECORD #17:


Species: Rats
Sex: NR
Effect: NOAEL



Dose: . 1.500
Duration Exposure: 977.0 days
Duration Observation: 977.0 days
Route: Inhalation





Number Exposed:
Number Responses:
Type of Effect:
SUe of Effect:
Severity Effect:
9
NR
OTHER
LUNG
NONE





Comment:       0.8 ppm continuous; elevated breathing rate, mild hlsto.
               lesions equivocally attributed to exposure, no effect on
               survival, organ or body weight.

Citation:      Haydon et al., 1965; Freeman et al., 1966
0166d
                     -128-
                                           07/31/89

-------
RECORD
Comment:


Citation:
Species:
Sex:
Effect:
Route:
Rats
Male
LOAEL
Inhalation
               Number Exposed:      12
               Number Responses:    NR
               Type of Effect:      DEGEN
               Site of Effect:      LUNG
               Severity Effect:    6
Dose:                 7.500
Duration Exposure:    27.0 months
Duration Observation:  27.0 months
                             12
                             NR
                             ENZYM
                             LUNG
                             1
4.0 ppm continuous;  progressive hyperplastlc  pre-emphysema-
llke lesions.  Concentrations  tested:   4.0,  0.40  and  0.04  ppm.

Kubota et al., 1987
RECORD #19:








Comment:



Citation:
RECORD #20:








Species: Rats
Sex: Hale
Effect: NOAEL
Route: Inhalation
Number Exposed: 12
Number Responses: NR
Type of Effect: DEGEN
Site of Effect: LUNG
Severity Effect: NONE
Dose:
Duration Exposure
Duration Observat

12
NR
ENZYH
LUNG
NONE
0.750
: 27.0 months
Ion: 27.0 months


.
*•


0.40 ppm continuous, see previous record; lesions appeared
only at 27 months not cons
changes. Additional ref:
Ichlnose, 1987.
Kubota et al., 1987
Species: Rats
Sex: Hale
Effect: NOAEL
Route: Inhalation
Number Exposed: 12
Number Responses: NR
Type of Effect: DEGEN
SUe of Effect: LUNG
Severity Effect: NONE
Idered adverse; mild
Sagal et al., 1984;


Dose:
Duration Exposure
Duration Observat

12
NR
ENZYM
LUNG
NONE
biochemical
Sagal and


0.075
: 27.0 months
Ion: 27.0 months






Comment:       0.04 ppm continuous, see previous records; some slight
               morphometrlc and biochemical changes.  Additional ref:
               Kubota et al., 1987.

Citation:      Sagal et al., 1984; Sagal and Ichlnose, 1987
Cll66d
                     -129-
                                           07/31/89

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RECORD |21
Comment:


Citation:
Species:
Sex:
Effect:
Route:
Humans
Both
NOAEL
Inhalation
Dose:                  0.300
Duration Exposure:      1.0  days
Duration Observation:   1.0  days
Number Exposed:      NR
Number Responses:    NR
Type of Effect:      FUNS
Site of Effect:      LUNG
Severity Effect:     NONE

1 ppm for 4 hours;  a synthesis  of  several  acute human
controlled exposure studies  that  Indicate  a  NOAEL.

Adams et al., 1987;  Koenlg  et  al.,  1985,  1987; Avol  et  al.t
1988; Drechsler-Parks et  al.,  1987;  Kerr  et al.,  1979; Stacy
et al.,  1983;  Kagawa,  1983; Hazucha  et  al., 1983; Follnsbee
et  al.,  1978;  Hackney   et  al.,  1978;  Linn  et  al., 1985a;
Klelnman et al.,  1983
RECORD #22:



Species:
Sex:
Effect:
Route:
Mice
NR
PEL
Inhalation
Dose:
Duration
Duration


Exposure:
Observation:

13.000
1 .0 days
1 .0 days

Comment:

Citation:
Number Exposed:     NR
Number Responses:   NR
Type of Effect:     DEATH
SHe of Effect:     BODY
Severity Effect:    9

1000 ppm 10-mlnute LC50.

NIOSH, 1988
RECORD #23:



Species:
Sex:
Effect:
Route:
Hamsters
NR
PEL
Inhalation
Dose:
Duration
Duration


Exposure:
Observation:

68.000
2.0 days
2.0 days

Comment:

Citation:
Number Exposed:
Number Responses:
Type of Effect:
SHe of Effect:
Severity Effect:

36 ppm, 48-hour LC5Q.

Sax, 1984
                                   NR
                                   NR
                                   DEATH
                                   BODY
                                   9
0166d
                     -130-
                                           07/31/89

-------
RECORD #24:

Comment:
Citation:
RECORD #25:

Comment:
Citation:
RECORD #26:

Comment:
Citation:
Species: Guinea pigs Dose: 2.400
Sex: NR Duration Exposure: 1.0 days
Effect: PEL Duration Observation: 1.0 days
Route: Inhalation
Number Exposed: NR
Number Responses: NR
Type of Effect: DEATH
Site of Effect: BODY
Severity Effect: 9
30 ppm 1-hour LCsg.
Sax, 1984
Species: Rabbits Dose: 6.170
Sex: NR Duration Exposure: 1.0 days
Effect: PEL Duration Observation: 1.0 days
Route: Inhalation
Number Exposed: NR
Number Responses: NR
Type of Effect: DEATH
Site of Effect: BODY *
Severity Effect: 9
315 ppm 15-mlnute LC$Q In rabbits.
Sax, 1984
Species: Rats Dose: 8.230
Sex: NR Duration Exposure: 1.0 days
Effect: PEL Duration Observation: 1.0 days
Route: Inhalation
Number Exposed: NR
Number Responses: NR
Type of Effect: DEATH
Site of Effect: BODY
Severity Effect: 9
420 ppm, 15-mlnute LC5Q 1n rats.
Gray et al., 1954
0166d
-131-
07/31/89

-------
RECORD |27:
Comment:

Citation:
Species:
Sex:
Effect:
Route:
Rats
NR
PEL
Inhalation
Dose:                  6.820
Duration Exposure:      1.0 days
Duration Observation:   1.0 days
Number Exposed:
Number Responses:
Type of Effect:
Site of Effect:
Severity Effect:

174 ppm, 30-m1nute

Gray et al.. 1954
                                   NR
                                   NR
                                   DEATH
                                   BODY
                                   9
RECORD #28:



Species:
Sex:
Effect:
Route:
Rats
NR
PEL
Inhalation
Dose:
Duration
Duration


Exposure:
Observation:

13.200
1 .0 days
1.0 days

Comment:

Citation:
Number Exposed:
Number Responses:
Type of Effect:
Site of Effect:
Severity Effect:

168 ppm, 1-hour

Gray et al., 1954
                                   NR
                                   NR
                                   DEATH
                                   BODY
                                   9
RECORD #29:



Species:
Sex:
Effect:
Route:
Rats
NR
PEL
Inhalation
Dose:
Duration
Duration


Exposure:
Observation:

27.600
1 .0 days
1 .0 days

Comment:

Citation:
Number Exposed:
Number Responses:
Type of Effect:
Site of Effect:
Severity Effect:

88 ppm, 4-hour

Gray et al.. 1954
                                   NR
                                   NR
                                   DEATH
                                   BODY
                                   9
0166d
                     -132-
                                           07/31/89

-------
RECORD 130:
Comment:


Citation:
Species:
Sex:
Effect:
Route:
Rats
Female
PEL
Inhalation
Dose:                  2.490
Duration Exposure:     21.0 days
Duration Observation:   21.0 days
Number Exposed:     20
Number Responses:   NR
Type of Effect:     DEATH
Site of Effect:     FETUS
Severity Effect:    9

5.3 ppm 6 hours/day throughout gestation; reduced postnatal
viability.

Tabacova et al.( 1985
RECORD #31:



Species:
Sex:
Effect:
Route:
Mice
Female
Ml
Inhalation
Dose:
Duration
Duration


Exposure:
Observation:

41.000
11.0 days
11.0 days

Comment:


Citation:
Number Exposed:     20
Number Responses:   NR
Type of Effect:     TERAS
Site of Effect-:     FETUS
Severity Effect:    9

22 ppm continuous during gestation; Increased Incidence of
fetal hematomas.

Singh, 1984
0166d
                     -133-
                                           07/31/89

-------