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Acute Toxicity: inhalation

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acute toxicity: inhalation
Type of information:
experimental study
Adequacy of study:
key study
Study period:
1992-06-12 to 1992-06-26
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: GLP-compliant regulatory study

Data source

Reference Type:
study report
Report Date:

Materials and methods

Test guideline
equivalent or similar to
OECD Guideline 403 (Acute Inhalation Toxicity)
GLP compliance:
self-certified including GLP compliance statement
Test type:
standard acute method
Limit test:

Test material

Details on test material:
- Name of test material (as cited in study report): Trimellitic anhydride
- Physical state: White flake solid
- Lot/batch No.: ATTA 92-09 (TA 1281)
- Stability under test conditions: Stable when stored under the recommended conditions
- Storage condition of test material: Stored in the original container at room temperature (22°C)

Test animals

Details on test animals and environmental conditions:
The animals were male and female Sprague-Dawley (Crl:CDR BR) rats, approximately 6 weeks of age, obtained from Charles River Laboratories Inc (Portage MI). The rats weighed 128-162 g two days after arrival. They were acclimatised for approximately 4 weeks, during which time they were examined to ensure their health and suitability as test subjects. Individuals were identified by ear tags and cage cards. The rats were acclimatised to the nose-only exposure tubes on three successive days during quarantine and prior to randomisation.
Purina Rodent Chow 5001 and reverse osmosis-purified water were available ad libitum. The rats were housed individually in suspended stainless steel cages with deotized animal cage boards underneath. The animal room average temperature and relative humidity were 23°C and 52%, respectively. Fluorescent lighting was provided on a 12 hour light/dark cycle.

Administration / exposure

Route of administration:
inhalation: dust
Type of inhalation exposure:
nose only
other: unchanged (no vehicle)
Details on inhalation exposure:
The test material was ground in a ball mill for at least 2 hours using a 19 litre jar and stainless steel or porcelain balls. The material was placed in a sieve shaker and material passing through a No. 20 screen was collected and used for the exposure. The generation system consisted of an AccuRate dust feeding with a 0.5 inch helix. The ground test substance was delivered at a constant rate from the dust feeder through 3/4 inch stainless steel tubing into a transvector jet. The exposure was conducted in a 160 litre stainless steel nose-only chamber, airflow was maintained at 150 l/min during the exposure and the chamber was operated under slight negative pressure.
Upon determining output rates and particle sizes, a setting of 160 (approximately 7.2 g/min of output) gave the maximum obtainable chamber concentration while maintaining an acceptable particle size distribution; MMAD <5 µm with 90% or more ≤10 µm. Chamber temperature and airflow were monitored continuously and recorded every half-hour during the exposure. Particle size analysis was performed once using an Anderson 1ACFM Cascade Impactor.
Food and water were not available during the exposure period.
Analytical verification of test atmosphere concentrations:
Concentration was measured gravimetrically by drawing a known volume of exposure atmosphere across a pre-weighed open-faced filter and dividing the sample weight gain by the volume of the sample. Four samples were collected during the exposure.
Duration of exposure:
4 h
Remarks on duration:
single exposure period
The time weighted average aerosol concentration was 2.33 mg/L. This dose level was the maximum achievable concentration.
No. of animals per sex per dose:
One group with 5 females and 5 males.
Control animals:
Details on study design:
Rats were randomly selected for testing. Clinical signs were observed frequently after the exposure, then at least once per day for the remainder of the 14 day observation period. Body weights were recorded prior to exposure, one week later and immediately prior to necropsy. All animals that died during the course of the study and all surviving animals were necropsied.
Statistical analysis was not performed.

Results and discussion

Preliminary study:
No preliminary results
Effect levels
Dose descriptor:
Effect level:
> 2.33 mg/L air
Based on:
test mat.
Exp. duration:
4 h
Remarks on result:
other: Nose-only exposure. Two males and one female died at this exposure level
Three animals died during the course of the study. Mortalities were reported in one female and two males in the 2.33 mg/L bw dose group. At 2.33 mg/L there was 20% mortality in females and 40% mortality in males. Deaths occurred near the end of the exposure, approximately 1.5 hour and one day after exposure.
Clinical signs:
Animals showed signs of laboured breathing in four males, rales in five males and two females, redness around the nose/eyes in four males and two females, discoloration around the mouth in two males and one female, discoloration of the paws in three males, clear nasal discharge in one male, wet inguinal fur and lacrimation in one male and two females, lacrimation in one male and one female. All the males and four females had their inguinal fur soiled with urine/faeces.
Body weight:
All surviving animals gained weight during the course of the study.
Gross pathology:
At necropsy, all the surviving rats displayed red foci on their lungs. Two males that died during the course of the study showed dark red coloured lungs. Other findings noted included fluid filled, enlarged or mottled appearance of the lungs.
Other findings:
No other findings reported.

Any other information on results incl. tables

Table 1: Summary of mortality data

Dose levels (mg/L)

Number of deaths/group










>2.33 mg/L

The average exposure temperature was 24.2°C. Chamber relatively humidity could not be monitored.

Applicant's summary and conclusion

Interpretation of results:
not classified
Migrated information Criteria used for interpretation of results: EU
The acute inhalation LC50 is estimated to be > 2.33 mg/L in both sexes.
Executive summary:

Trimellitic anhydride was administered to one group of 5 animals/sex at 2.33 mg/L. Clinical signs and body weights were recorded over a 14 day post exposure period. All animals that died during the course of the study and all surviving animals were necropsied.

Mortalities were reported in one female and two males. Clinical signs reported included laboured breathing, rales, redness around the nose/eyes, discoloration around the mouth and of the paws, clear nasal discharge, wet inguinal fur and lacrimation. All surviving animals gained weight during the course of the study. At termination, all the surviving rats displayed red foci on their lungs. Two males that died during the course of the study showed dark red coloured lungs. Other findings noted included fluid filled, enlarged or mottled appearance lungs.

Under the conditions of this test, the inhalation LC50 of trimellitic anhydride was greater than 2.33 mg/L, the maximum achievable concentration. However, the clinical and gross necropsy observations suggest that a single exposure to this concentration produced severe pulmonary irritation resulting in the death of 3/10 rats. On this basis, trimellitic anhydride does not warrant any classification according to Directive 67/548/EEC and Regulation (EC) No. 1272/2008.