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Toxicological information

Acute Toxicity: inhalation

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Administrative data

Endpoint:
acute toxicity: inhalation
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2012
Report Date:
2012

Materials and methods

Test guideline
Qualifier:
according to
Guideline:
OECD Guideline 436 (Acute Inhalation Toxicity: Acute Toxic Class Method)
Deviations:
no
Remarks:
Conducted according to guideline in effect at time of study conduct
GLP compliance:
no
Test type:
acute toxic class method

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
- Purity: 22.82% solids in water

Test animals

Species:
rat
Strain:
other: Crl:CD(SD)
Sex:
male/female
Details on test animals and environmental conditions:
TEST ANIMALS
- Age at study initiation: Approximately 9 weeks
- Weight at study initiation: 318 - 341 grams (males), 220-247 (females)
- Fasting period before study: No
- Housing: Except during exposure, animals were housed individually in solid bottom caging with bedding and nestlets as enrichment.
- Diet (e.g. ad libitum): Ad libitum, except during exposure
- Water (e.g. ad libitum): Ad libitum, except during exposure
- Acclimation period: 6 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 20-26ºC
- Humidity (%): 30-70%
- Air changes (per hr): Not reported
- Photoperiod (hrs dark / hrs light): Approximate 12-hour light/dark cycle. During quarantine, electrical disruption to the test facility occurred for about 10 minutes in one afternoon causing an interruption in the light cycle. This excursion was of insufficient duration to have adversely affected the validity of the study.

Administration / exposure

Route of administration:
inhalation: aerosol
Type of inhalation exposure:
nose only
Vehicle:
other: unchanged (no vehicle)
Details on inhalation exposure:
GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Exposure apparatus: The exposure chamber was constructed of glass (cylindrical). A polycarbonate baffle at the chamber inlet promoted uniform chamber distribution of the test atmosphere.
- Exposure chamber volume: 34L
- Method of holding animals in test chamber: During exposure, animals were individually restrained in perforated stainless steel cylinders with conical nose pieces. The restrainers were inserted into a polymethylmethacrylate faceplate attached to the exposure chamber so that the nose of each animal extended into the exposure chamber. The day before the exposure, animals were placed in restrainers once for approximately 15 minutes to acclimate the animals to the restrainers.
- Source and rate of air: Chamber airflow was 14 L/min which provided 25 air changes per hour
- Method of conditioning air: Chamber oxygen concentration was 21%.
- System of generating particulates/aerosols: Chamber atmospheres were generated by aerosolisation of the test substance in air with a nebulizer. For the first (lower concentration) the test substance was metered into the nebulizer with a syringe infusion pump. For the second exposure, the design concentration was considerably higher; therefore, the infusion pump was replaced with a drive pump equipped with a piston. High-pressure air, metered into the nebulizer by a mass flow controller, carried the resulting atmosphere into the exposure chamber. Chamber concentrations of the test substance were controlled by varying the test substance feed rate to the nebulizer.
- Method of particle size determination: Two samples to determine aerosol size distribution (mass median aerodynamic diameter, geometric standard deviation, and percent aerosol less than 1, 3, and 10 μm diameter) was taken during each exposure with a cyclone preseparator/cascade impactor and air sampler.
- Treatment of exhaust air: Test atmospheres were exhausted through a dry-ice cold trap followed by a charcoal/HEPA filter cartridge prior to discharge into the fume hood.
- Temperature, humidity, pressure in air chamber: Chamber temperature was 21-22°C. The relative humidity of the lower exposure ranged from 52 to 55% while that of the higher exposure ranged from 88 to 93%. Relative humidity in the exposure chamber during the higher exposure was outside the targeted parameters due to the test substance containing 77% water. The chamber environmental conditions were considered adequate for the conduct of the study, and the relative humidity values that were above the targeted maximum of 70% do not adversely affect the results or interpretation of this study. Air pressure was not reported.

TEST ATMOSPHERE
- Brief description of analytical method used: Since the test substance contains volatile component(s), the total airborne (wet aerosol) concentration was measured gravimetrically and the solids component of the test atmosphere was measured using a desiccation and gravimetric technique. The atmospheric concentration of the test substance in the test chamber was determined by gravimetric analysis approximately once per hour. Known volumes of chamber atmosphere were drawn from the sampling port through a 25 mm filter cassette containing a pre-weighed glass fibre (Type A/E) filter. The filters were weighed on a microbalance. The filter weights were automatically transferred to an automated data system, which calculated the chamber concentrations based on the difference between pre- and post-sampling filter weights divided by the volume of chamber atmosphere sampled. Gravimetric sample start- and stop-times for each sample were controlled and recorded by an automated data system. The post-sampling filter weight was used to determine the total aerosol concentration (wet aerosol) in the exposure chamber. Because the test substance contained water, the gravimetric filters were placed in a desiccator overnight and weighed again the following day to determine the chamber concentration of the solids component in the exposure atmosphere.
- Samples taken from breathing zone: yes
- Aerosol size: See Table 1
Analytical verification of test atmosphere concentrations:
no
Duration of exposure:
4 h
Concentrations:
97 ± 11 mg/m³ (total atmospheric concentration) (97 ± 11 mg/m³ solids)
1200 ± 73 mg/m³ (total atmospheric concentration) (700 ± 44 mg/m³ solids)
No. of animals per sex per dose:
3/sex/dose level
Control animals:
no
Details on study design:
- Duration of observation period following administration: 14 days
- Frequency of observations: Animals were observed for mortality and response to alerting stimuli during the exposure and observed for mortality and clinical signs of toxicity immediately after they were removed from the restrainers following exposure. During a 14-day recovery period, all rats were observed each day for mortality, and were weighed and observed for clinical signs of toxicity.
- Frequency of weighing: Rats were weighed on days 0, 1, 2, 3, 7, and 14 relative to study start.
- Necropsy of survivors performed: Gross pathological examination was performed on animals shortly after they were found dead. At the end of the recovery period, all surviving rats were sacrificed by isoflurane anaesthesia followed by exsanguination and subjected to gross examination.

Results and discussion

Effect levelsopen allclose all
Sex:
male/female
Dose descriptor:
other: approximate lethal concentration (ALC)
Effect level:
1 200 other: mg/m³
Based on:
other: total airborne (wet aerosol) concentration
Exp. duration:
4 h
Sex:
male/female
Dose descriptor:
other: approximate lethal concentration (ALC)
Effect level:
700 other: mg/m³
Based on:
other: solids
Exp. duration:
4 h
Mortality:
All animals survived the lower exposure and the subsequent 14-day recovery period. No animals died during the higher exposure, however, 1 (of 3) males died 1 day following exposure and 2 (of 3) females were found dead within 2 days following the exposure.
Clinical signs:
No clinical signs were observed after the 97 mg/m3 exposure or the 14-day recovery period.
All animals had red discharge from nose during clinical observation after animals were removed from the 1200 mg/m3 exposure chamber; these clinical findings are common in nose-only exposures and are not considered to be test substance-related. One female had red discharge from nose and lost 10% body weight on day 1 (and was subsequently found dead on day 2), while the other surviving female had laboured breathing from the day of exposure (day 0) until day 4, red discharge from nose during day 0-1, red stain(s) on facial skin/fur during day 3-5, fast breathing during day 8-10, and was hunched over during day 5-10.
Body weight:
On the first 2 days after the 97 mg/m3 exposure, 2 males and 2 females lost <3% body weight. All males and females gained weight from day 2 and 3, respectively, to the end of the recovery period. On the day following the 1200 mg/m3 exposure, 1 surviving male lost <3% body weight while the other surviving male lost a total of 14% body weight on the first 2 days after exposure. For females, 1 animal lost 10% body weight on day 1 (and was subsequently found dead on day 2). The other surviving female lost weight on each day from day 0 to 10 with a total body weight loss of 33% and then gained weight.
Gross pathology:
There were no gross findings for all animals in the 97 mg/m3 exposure group at the scheduled necropsy.
Gross discoloration of the lungs was present in all female rats and 1 male rat in the 1200 mg/m3 exposure group. All animals with lung discoloration were found dead except for 1 female rat which had dark and tan mottling of the lungs. Also, stain(s) on nose skin and trachea fluid were present in the found dead animals.

Applicant's summary and conclusion

Interpretation of results:
Category 3 based on GHS criteria
Conclusions:
The study and the conclusions which are drawn from it fulfil the quality criteria (validity, reliability, repeatability).
ALC (male and female rats) = 1200 mg/m³ total atmospheric concentration and 700 mg/m³ dry solids.
Executive summary:

The acute inhalation toxicity of the test substance was evaluated when administered as an aerosol for a single, 4-hour, nose-only exposure to groups of 3 male and 3 female (nulliparous and non-pregnant) Crl:CD(SD) albino rats. The test substance is an off-white liquid containing 22.82% solids in water. The test atmosphere was generated by aerosolisation of the test substance in air with a Spraying Systems nebulizer. Since the test substance contains volatile component(s), the total airborne (wet aerosol) concentration was measured gravimetrically and the test substance solids component of the test atmosphere was measured using a desiccation and gravimetric technique. During the 14-day recovery period, all animals were weighed and observed for mortality and clinical signs of toxicity. A gross pathological examination was performed on all animals shortly after they were found dead or at the scheduled necropsy.

Two exposure concentration levels were used for this study. The test substance was administered first to a group of 3 male and 3 female rats at a total atmospheric concentration of 97±11 mg/m3 test substance (mean±standard deviation) (i.e., 97±11 mg/m3 test substance solids). The aerosol size was determined twice for the atmosphere and the mass median aerodynamic diameter (MMAD) measured 2.1 μm (2.5) and 2.7 μm (2.4) [MMAD (GSD), geometric standard deviation]. All animals survived the 97 mg/m3 exposure and the subsequent 14-day recovery period. No clinical signs were observed during the exposure or the 14-day recovery period. Two males and 2 females lost <3% body weight on the first 2 days after exposure. All males and females gained weight from day 2 and 3, respectively, to the end of the recovery period. There were no gross pathological findings for all animals at the scheduled necropsy.

A second group of 3 male and 3 female rats were exposed to a total atmospheric concentration of 1200±73 mg/m3 test substance (i.e., 700±44 mg/m3 test substance solids). MMAD (GSD) were 2.7 μm (2.3) and 3.3 μm (2.3). No animals died during the 1200 mg/m3 exposure, however, 1 male and 2 females were found dead during the 14-day recovery period. All animals had red discharge from nose during clinical observation after animals were removed from exposure chamber; these clinical findings are common in nose-only exposures and are not considered to be test substance related. On the next day, 1 male was found dead; 1 surviving male lost <3% while the third male lost a total of 14% body weight on the first 2 days after exposure. For females, 1 was found dead on day 1. One survivor had red discharge from nose and lost 10% body weight on day 1, and was found dead on day 2. The other surviving female had laboured breathing from the day of exposure (day 0) until day 4, red discharge from nose during day 0-1, red stain(s) on facial skin/fur during day 3-5, fast breathing during day 8-10, and was hunched over during day 5-10. This female lost weight on each day from day 0 to 10 with a total body weight loss of 33% and then gained weight and had no abnormalities detected during day 11-14. Gross discoloration of the lungs was present in all female rats and 1 male rat in the 1200 mg/m3 exposure group. All animals with lung discoloration were found dead except for 1 female rat which had dark and tan mottling of the lungs. Also, stain(s) on nose skin and trachea fluid were present in the found dead animals.

Under the conditions of this study, the approximate lethal concentration (ALC) for the test substance in male and female rats is 1200 mg/m3 total atmospheric concentration and 700 mg/m3 dry solids.