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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:
Mar 06, 2015 to Aug 12, 2015
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study

Data source

Reference Type:
study report
Report date:

Materials and methods

Test guidelineopen allclose all
according to guideline
OECD Guideline 403 (Acute Inhalation Toxicity)
Version / remarks:
Sep 07, 2009
according to guideline
EPA OPPTS 870.1300 (Acute inhalation toxicity)
Version / remarks:
May 30, 2008
according to guideline
EU Method B.2 (Acute Toxicity (Inhalation))
Version / remarks:
Aug, 1998
GLP compliance:
yes (incl. QA statement)
Test type:
standard acute method
Limit test:

Test material

Constituent 1
Chemical structure
Reference substance name:
EC Number:
EC Name:
Cas Number:
Molecular formula:
Details on test material:
- Name of test material (as cited in study report): formaldehyde
Specific details on test material used for the study:
- Purity: formaldehyde 10.1 g/100 g (Titration)
- Lot/batch No.: CMPKQ0901
- Expiration date of the lot/batch: 09 Apr 2015
- Physical state / appearance: liquid / colorless, clear

- Storage condition of test material: room temperature
- Stability: expiry date: 09 Apr 2015, under storage conditions over the test period was guaranteed by the sponsor, and the sponsor holds this responsibility
- Homogeneity: homogeneous by visual inspection

Test animals

Details on test animals or test system and environmental conditions:
- Source: Harlan Laboratories B.V. Kreuzelweg 53, 5961 NM Horst, Netherlands
- Females nulliparous and non-pregnant: yes
- Age at study initiation: male animals approx. 9 weeks, female animals approx. 11 weeks
- Weight at study initiation: animals of comparable weight (± 20 % of the mean weight). Mean weight males 261.5 g, mean weight females 214.3 g
- Housing: single housing in Type III (polycarbonate cages) (floor area about 800 cm²) with wooden gnawing blocks and play tunnel
- Diet: Kliba laboratory diet, mouse/rat maintenance “GLP”, 10 mm pellets, Provimi Kliba SA, Kaiseraugst, Basel Switzerland, ad libitum
- Water: Tap water ad libitum
- Acclimation period: at least 5 days

- Temperature: 20 - 24°C
- Humidity: 30 - 70 %
- Air changes (per hr): 15
- Photoperiod: 12 hours / 12 hours

Administration / exposure

Route of administration:
inhalation: vapour
Type of inhalation exposure:
whole body
Remark on MMAD/GSD:
not specified
Details on inhalation exposure:
- Test-substance preparation: unchanged
- Equipment: continuous infusion pumps PHD Ultra, Atomization vaporizer (glass) with thermostat
- Generation technique: a vapor was generated, was produced by continuously pumping amounts of the test substance into the thermostated vaporizer and using compressed air, was mixed with streams of conditioned air and passed into the inhalation systems
- Generator temperature: 40°C
- Whole-body inhalation system: IKA 02 (glass-steel construction, volume V 200 L), animals were kept in compartmentalized wire cages (DKIII) and were exposed inside the chamber, homogenous distribution of test substance atmosphere has been verified with model vapors
- Conditioned air: the central air conditioning system provides cold air of about 15°C, cold air passes through an activated charcoal filter, is adjusted to room temperature of 20 to 24°C and passes through a second particle filter, so generated conditioned air was used to generate inhalation atmospheres
- Compressed air: compressed air was produced by an oil-free compressor, air was filtered by an inlet air strainer and introduced into the compressor, after passing through a second ultra-filter, the compressed air (15 bar) was stored in a storage of 1500 or 5000 L, compressed air was conducted to the laboratories via pipes, where the pressure is reduced to 6 bar
- Exhaust air: was filtered and conducted into the exhaust air of the building, exposure system was located inside an exhaust cabin in an air-conditioned laboratory, during exposure, the following scheduled parameters were recorded four times at about 1- hour intervals: supply air flow (compressed air): 1.0 m³/h, plus a dilution air (condition air): 2.0 m³/h (from a central air-conditioning system)
- Exhaust air flow: 2.9 m³/h, flow was adjusted and continuously measured with a flowmeter, lower amount of exhaust air, which was adjusted by means of a separate exhaust air system, achieved a positive pressure inside the exposure system ensuring that the mixture of test substance and air was not diluted with laboratory air in the breathing zones of the animals

- The concentration in the inhalation atmospheres was determined by gas samples (sampled in evacuated gas container)
- The nominal concentration was calculated from the amount of test substance dosed and the supply air flow
- Sampling position: immediately adjacent to the animals' noses at a separate spare port
- Sampling: Gas sample into evacuated gas sampling tubes (glass)
- Mean and standard deviation were calculated for the concentration from the results of the 8 individual measurements
Analytical verification of test atmosphere concentrations:
Duration of exposure:
4 h
Remarks on duration:
plus equilibration time of the inhalation systems (t99 about 18 min)
463 ppm
No. of animals per sex per dose:
Control animals:
Details on study design:
- Duration of observation period following administration: at least 14 days
- Body weight determination: once during the acclimatization period, shortly before exposure (day 0) and at least on days 1, 3 and 7, and before the sacrifice of the animals at the end of the observation period, body weight was measured in animals that died from study day 1 onwards
- Signs: clinical observations were recorded for each animal separately several times during exposure and at least once daily on the pre-exposure day and during the observation period
- Mortality: a check for any dead or moribund animal was made twice each workday and once on Saturdays, Sundays and on public holidays
- Pathology: at the end of the observation period the surviving animals were sacrificed with CO2-inhalation in a chamber with increasing concentration over time, and were subjected to gross-pathological examination as well as the animal which died
For results of the type ”LC50 greater than”, ”LC50 approx.”, or ”LC50 smaller than”, the binomial test was used for statistical evaluation.

Results and discussion

Effect levels
Dose descriptor:
Effect level:
< 463 ppm
Based on:
test mat.
Exp. duration:
4 h
All of the five male and the five female animals died. Lethality was observed on study day 1 or 2.
Clinical signs:
other: gasping, respiration sounds, breathing in stretched position, closed eyelid, red discharge, red encrusted nose, poor general condition, salivation, piloerection, yellow discolored fur
Body weight:
The mean body weights of the animals surviving the exposure period decreased until death.
Gross pathology:
During necropsy all animals showed dilated stomach, which were filled with gaseous content. Four males and four females additionally showed similar findings in the intestine. Moreover, two males showed effusion (clear fluid) in the thoracic cavity.

Applicant's summary and conclusion

Interpretation of results:
Category 2 based on GHS criteria
LC50 (inhalation, rat, 4h) < 463 ppm
Executive summary:

In a reliable GLP-conform study according to OECD TG 403, male and female Wistar rats were exposed to 463 ppm (analytical concentration) of formaldehyde as a vapor to determine the acute inhalation toxicity (single 4-hour exposure, whole body).

At 463 ppm all of five male and five female animals died. Lethality was observed on study day 1 or 2. Clinical signs of toxicity in animals comprised gasping, respiration sounds, breathing in stretched position, closed eyelid, red discharge and red encrusted nose, poor general condition, salivation, piloerection and yellow discolored fur. Findings were observed from hour 1 of exposure until the death of the animals. The mean body weights of the animals´surviving the exposure period decreased until death. During necropsy all animals showed dilated stomach, which were filled with gaseous content. Four males and four females additionally showed similar findings in the intestine. Moreover, two males showed effusion (clear fluid) in the thoracic cavity.

Under the current study condition, the LC50 was < 463 ppm (analytical concentration) in Wistar rats after 4 hour inhalation exposure to a vapor of formaldehyde.