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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
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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
-------
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
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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
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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).
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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
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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
-17-
04/10/89
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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.
0166d -18- 04/10/89
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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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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
0166d
-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
-------
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
-------
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
-------
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
-------
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
-------
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
-------
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.
0166d -69- 09/25/89
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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.
0166d : -70- 06/07/90
-------
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
-------
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
-------
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
-------
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
-------
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
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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
-------
10. REFERENCES
ACGIH (American Conference of Governmental Industrial Hyglenlsts). 1986.
Documentation of the Threshold Limit Values and Biological Exposure Indices,
5th ed. Cincinnati, OH. p. 435, 436.
ACGIH (American Conference of Governmental Industrial Hyglenlsts). 1988.
Threshold Limit Values and Biological Exposure Indices for 1988-1989.
Cincinnati, OH. p. 28.
ACS (American Chemical Society). 1987. Chemocyclopedla, 1987. ACS,
Washington, DC. p. 222.
4
Adams, W.C., K.A. Brookes and E.S. Schelegle. 1987. Effects of nitrogen
dioxide alone and In combination with ozone on young men and women. J.
Appl. Physlol. 62(4): 1698-1704.
Adklns, 8., Jr., E.W. Van Stee, J.E. Simmons and S.L. Eustls. 1986.
Oncogenlc response of strain A/J mice to Inhaled chemicals. 0. Toxlcol.
Environ. Health. 17(2-3): 311-322.
Aklmoto, H. and H. Takagl. 1986. Formation of methyl nitrite In the
surface reaction of nitrogen dioxide and methanol. 2. Photoenhancement.
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Rlchter, A. and K. Kura1t1s. 1983. Air pollutants and the facilitation of
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Rlnehart, R.R., M.J. Towle, F.J. Ratty and E. Hack. 1973. The mutagenlclty
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Mutat. Res. Sect. Environ. Hutag. Relat. SubJ. 21(4): 232-233.
0166d -103- 07/31/89
-------
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
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Roy-Burman, P., P.K. Pattengale and R.P. Sherwln. 1982. Effect of low
levels of nitrogen dioxide Inhalation on endogenous retrovlrus gene
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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-
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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
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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
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444-456.
0166d -104- 07/31/89
-------
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
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Shalamberldze, O.P. and N.T. Tseretell. 1971. Effect of small concentra-
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Sherwln, R.P. and V. Rlchters. 1982. Hyperplasla of type 2 pneumocytes
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•
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
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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,
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nitrates and nitrites 1n water and food. Eff. Agrlc. Prod. Nitrates Food
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0166d -105- 07/31/89
-------
Shy, C.M. and G.J. Love. 1979. Recent evidence on the human health effects
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Shy, C.M., J.P. Creason, M.E. Pearlman, K.E. McClaln, F.B. Benson and M.M.
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Chattanooga Schoolchildren Studies and the Health Criteria for NO.
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0166d -106- 07/31/89
-------
Spelzer, F.E. and B.G. Ferris, Jr. 1973b. Exposure to automobile exhaust.
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•
Stacy, R.W., E. Seal, Jr., D.E. House, J. Green, L.J. Roger and L. Ragglo.
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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-
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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.
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and slster-chromatld exchanges Induced by gaseous nitrogen dioxide In
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0166d -108- 07/31/89
-------
U.S-. EPA. 1980. Guidelines and Methodology Used 1n the Preparation of
Health Effect Assessment Chapters of the Consent Decree Water Criteria
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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
-------
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.
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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
-------
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
-------
iee
^
«
v. ie -
9i >
£
w
jj
0
V
0. *'
2
&
e
z
f e.i-
X
801 -
a.
• 1 ' 'IT!. T, 1 1— TTTTTT] 1 1 ! 1 1 ,lf| -| 1 T 1 ' 7 T 1 1 T— | , | , |,,. a
F :
: • l • i
F A
A « .
' L
= r I L 1
1 L !
- 1 _, :
— -• — ^
:" n ^_ ~
; «n n :
n
n
n
T n -
Z n :
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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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