Dinitrogen tetraoxide

Acute Toxicity: inhalation

Administrative data

Endpoint:

acute toxicity: inhalation

Type of information:

experimental study

Adequacy of study:

weight of evidence

Reliability:

3 (not reliable)

Rationale for reliability incl. deficiencies:

significant methodological deficiencies

Cross-reference

Reason / purpose for cross-reference:

reference to same study

Data source

Reference

Reference Type:

publication

Title:

The responses of animals inhaling nitrogen dioxide for single, short-term exposures

Author:

Carson TR, Rosenholtz MS, Wilinski FR and Weeks MH

Year:

1962

Bibliographic source:

Am. Ind. Hyg. Assoc. J. 1962 Nov-dec; 23; 457-62

Materials and methods

Principles of method if other than guideline:

Groups of animals were exposed to various concentrations of the test item for single, short-term exposures.

GLP compliance:

no

Remarks:

Pre-dates GLP

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

Nitrogen dioxide

EC Number:

233-272-6

EC Name:

Nitrogen dioxide

Cas Number:

10102-44-0

IUPAC Name:

nitrous acid

Test material form:

gas

Details on test material:

- Physical appearance: gas
- Purity: not indicated
- Batch No.: not indicated
- Supplier: not indicated

Test animals

Species:

rat

Strain:

not specified

Sex:

male

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Age at study initiation: Young
- Weight at study initiation: 100 to 120 gm

Administration / exposure

Route of administration:

inhalation: gas

Type of inhalation exposure:

whole body

Details on inhalation exposure:

Experimental procedures
Techniques of exposures
-Dispersion: the test item was metered from a cylinder through a 1000 mL expansion flask and a manometer containing silicone oil and then into a 400 L dynamic exposure chamber. The test item cylinder expansion flask, and manometer were maintained at 31 °C in a constant temperature box.
- Collection and analysis of chamber air samples: chamber air samples were pulled by vacuum into calibrated gas sampling bottles. Sampling bottles of volume from 50 to 1000 mL and sampling rates from 50 to 500 mL/min were used; the choice depended on the concentration of the test item being sampled. The gas bottles were then cooled in a dry ice-acetone bath and the absorbing reagent was introduced. The samples were analyzed colorimetrically. A sample was drawn before and another during the 5-min exposure. Two to 3 samples were drawn during the longer exposures. There was very little variation between the several samples taken at various times during the exposures. The concentrations are expressed as ppm of the test item.

Exposure of animals
- High level exposures: young male rats were exposed in groups of 10 to various concentrations of the test item for single 5-, 15-, 30-, and 60-min periods.
- Low level exposures: in order to determine the levels of the test item causing minimal or no toxic effects, young male rats were exposed in groups of 30 for single 5-, 15-, and 60-min periods to progressively lower concentrations approximating 50, 25 and 15 % of each of the LC50¿s.

Analytical verification of test atmosphere concentrations:

yes

Duration of exposure:

>= 5 - <= 60 min

No. of animals per sex per dose:

- High level exposures: 10/sex/dose
- Low level exposures: 30/ sex/dose

Control animals:

yes

Details on study design:

- Duration of observation period following administration: 21 days

Exposed rats at all concentrations and a group of controls were sacrificed in groups of 5 at 4, 24, and 48 h; and 7, 21, and 42 d after exposure. Toxic signs, kidney to body and lung to body weight ratios, and pathologic changes were used in evaluating the effects of each exposure. Kidney to body weight ratios were determined only at concentrations of 50 and 25 % of the LC50¿s.

Rats from the high level exposures were examined for gross pathologic changes. Organs from animals exposed to the test item at concentrations below the LC50 level were examined for both macro- and microscopic changes. These organs included lung, liver, kidney, spleen, heart, eyes, and gastrointestinal tract. Thiopental sodium was used, interperitoneally, to sacrifice the animals. The kidneys and lungs used to determine organ-body weight ratios were removed from rats held under light anesthesia. Control animals for each exposure group were sacrificed under the same conditions. Tissues for microscopic studies were fixed in 10 % Formalin and stained with hematoxylin and eosin.

Results and discussion

Effect levels

Effect levels 1

Sex:

male

Dose descriptor:

LC50

Effect level:

416 ppm

Based on:

test mat.

Exp. duration:

5 min

Effect levels 2

Sex:

male

Dose descriptor:

LC50

Effect level:

201 ppm

Based on:

test mat.

Exp. duration:

15 min

Effect levels 3

Sex:

male

Dose descriptor:

LC50

Effect level:

162 ppm

Based on:

test mat.

Exp. duration:

30 min

Effect levels 4

Sex:

male

Dose descriptor:

LC50

Effect level:

115 ppm

Based on:

test mat.

Exp. duration:

60 min

Mortality:

- High level exposure: the times of death varied from 30 min to 3 d after exposure.
-Low level exposure: no deaths

Clinical signs:

other: -High level exposure: toxic signs included severe respiratory distress, eye irritation as shown by reddened conjunctiva, 10 to 15 % body weight suppression lasting for 2 d and death. Animals surviving 3 d after exposure appeared to have recovered from the

Gross pathology:

- High level exposures: the gross pathology in rats showed many darkened areas about the surface of the lungs, and, in some instances, purulent modules involving entire lungs of some of the surviving rats were seen.

- Low level exposure: the gross pathologic findings in rats exposed to concentrations approximating 50 % of the LC50¿s showed many darkened areas about the surface of the lungs during the first 7 d after exposure. At 21 and 42 d after exposure some rats showed area of consolidation. Microscopic studies in rats showed pulmonary edema during the first 48 h after exposure. Examination for more complex pulmonary parenchymal lesions was complicated by the presence of chronic murine pneumonia. This pneumonitic process became more prevalent and more extensive as the post-exposure time was increased. There was an impression that exposure to the test item at this concentration level increased the likelihood of seeing chronic murine pneumonia. There were no microscopic changes in the eyes. Other organs studied were within the normal ranges.

No gross pathologic lesions were noted in rats exposed to concentrations approximating 25 % of the rat LC50 values. However, some of the rats examined microscopically at 24 and 48 h after exposure manifested pulmonary edema. Chronic murine pneumonia also was present in some rats. No histological changes were seen in the eyes or other organs studied, except in the lungs.

At concentrations approximating 15 % of the LC50¿s no pathological changes different from the controls were seen.

Other findings:

No changes were noted in the hematocrits or blood platelet counts.

Any other information on results incl. tables

LC₅₀values for animals exposed to the test item

Exposure time (min)	LC50(ppm)	19/20 confidence limits (ppm)	Slope	Standard error of the slope
5	416	376- 461	9.5	± 4.2
15	201	191- 212	15.3	± 4.1
30	162	152- 169	20.7	± 5.1
60	115	113- 117	43.3	± 12.8

 

Exposure to low levels of the test item

Exposure time (min)	Concentrations of the test item Approximate percentage of the LC50¿s for rats
	50 % (ppm)	25 % (ppm)	15 % (ppm)
5	190	104	74
15	90	65	33
60	72	28	11

 

Applicant's summary and conclusion

Interpretation of results:

Category 1 based on GHS criteria

Remarks:

Criteria used for interpretation of results: Regulation (EC) 1272/2008

Conclusions:

Rats were exposed for single 5 to 60 minute periods to various concentrations of the test item. Changes in lung to body weight ratios of rats correlated directly with the severity of exposure to the test tiem. Based on the lung to body weight ratio and the pathological changes found in exposed animals, the threshold concentrations of the test item found were 104, 65 and 28 ppm for 5, 15 and 60 min, respectively.