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Repeated dose toxicity: inhalation

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Administrative data

sub-chronic toxicity: inhalation
Type of information:
migrated information: read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: GLP guideline study According to ECHA Practical Guide 6 the maximum score for read across is rel. 2

Data source

Reference Type:

Materials and methods

Test guideline
according to guideline
OECD Guideline 413 (Subchronic Inhalation Toxicity: 90-Day Study)
GLP compliance:

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): Diethanolamine (DEA; CAS 111-42-2)
- Lot/batch No.: no data
- Appearance: white crystalline solid at rt and viscous liquid above 28 °C
- Purity: > 99 %
- Stability: The stability of the substance under the specific storage conditions was ensured for the study duration by covering with N2.

Test animals

Details on test animals or test system and environmental conditions:
Strain: CrlGlxBrIHan:WI
- Source: Charles River, Sulzfeld, Germany
- Age at study initiation: about 7 weeks
- Weight at study initiation (mean): males 225-226 g, females 165-167 g
- Housing: individually in Makrolon wire cages type MD III (Becker & Co, Castrop-Rauxel, Germany)
- Diet and water: ad libitum
- Acclimation period: no data; for adaptation to the exposure conditions the animals were exposed to clean air in the exposure system on 3 to 5 days before start of the exposure period under comparable conditions in each study.

- Temperature (°C): 20-24
- Humidity (%):30-70
- Air changes (per hr): no data
- Photoperiod (hrs dark / hrs light): 12/12

Administration / exposure

Route of administration:
inhalation: aerosol
Type of inhalation exposure:
nose/head only
Remarks on MMAD:
MMAD / GSD: MMAD between 0.6-0.7 µm/GSD in the range of 2-3
Details on inhalation exposure:
For each concentration group, the liquid test substances were supplied to a two component atomizer by means of a continuous infusion pump and were atomized with compressed air. Due to the relatively high freezing point of 28 °C and (Knaak et al., Rev. Environ. Contamin. Toxicol. 149, 1–86, 1997) the syringes, tubes and atomizers of the aerosol generation systems were heated. The test substances were sprayed into cyclone separators and, after dilution with conditioned air, the aerosol was supplied to the cylindrical past-flow head nose exposure systems, constructed from stainless steel (90 L volume). For exposure the rats were transferred to glass exposure tubes and only the animals’ snouts protruded into the inhalation systems. The inhalation concentrations were adjusted by the infusion pump rates. The exposure systems were operated with an air exchange of above 50 times/h and a positive pressure relative to the laboratory air. Air flow rates as well as relative humidity and temperature of the inhalation atmospheres were monitored continuously. The measurements were within the range of the OECD guideline requirements for temperature (20–24 °C) and humidity (30–70 %) or as scheduled for the air flow rates (around 3 m³/h).

The stability of the concentrations during the daily exposure periods was measured with scattered light photometers (RAM, Mie, USA). Particle size analyses were performed, using cascade impactors (Marple 298, Andersen, USA). Mass median aerodynamic diameter (MMAD) and geometric standard deviation (GSD) were calculated from the measured mass distributions. 6-8 measurements per concentration were performed.
Analytical verification of doses or concentrations:
Details on analytical verification of doses or concentrations:
Measurement of DEA concentrations (two samples per concentration and exposure) was carried out by spectrophotometry of absorption samples in distilled water after derivatization with biuret agent.
Duration of treatment / exposure:
13 weeks (in total 65 exposures)
Frequency of treatment:
6 hours/day; 5 days/week
Doses / concentrationsopen allclose all
Doses / Concentrations:
0, 1.5, 3, and 8 mg/m³
other: target concentrations
Doses / Concentrations:
0, 1.6, 3.3, and 8.2 mg/m³
analytical conc.
No. of animals per sex per dose:
10; additional 10 females for recovery (control, mid and high dose)
Control animals:
yes, concurrent vehicle
Details on study design:
- Dose selection rationale: For the concentration range finding study, groups of 10 animals/sex were exposed for 6 h/day over a time period of 2 weeks (10 exposures) to target concentrations of 100, 200, or 400 mg DEA/m³. No substance related findings were obtained at the two lower concentrations. Exposure to 400 mg/m³ resulted in decreased body weight and body weight gain in males and slightly decreased serum cholesterol in both sexes. Additionally, the relative and absolute liver weights were increased in the female animals. No histopathological findings were observed in the resp. tract (nasal cavity, trachea, lungs), however, the examination of the larynx was not included in the range finding study. Based on these results, target concentrations of 1.5, 3, and 8 mg/m³ were chosen for the main study.
- Study design main study: 10 animals/sex and group were exposed to target concentrations of 1.5, 3, and 8 mg/m³ for 6 h/day on 65 days over a time period of 99 days (90-day study). The animals were exposed on all workdays. Control groups with the respective number of animals/sex were exposed to clean air.
- Post-exposure recovery period: In this study also included were recovery groups of 10 additional female animals exposed to 0, 3 or 8 mg/m³, which were observed for a post-exposure period of three months.


Observations and examinations performed and frequency:
The animals were observed for evident signs of toxicity or mortality twice on all exposure days and once during preflow and post-exposure examination. The body weight was determined at the beginning of the preflow period, before the first exposure (day 0), and once a week during exposure period.

No blood and urine examinations were conducted.
Sacrifice and pathology:
All animals were necropsied and assessed by gross pathology, and histopathology examination was conducted from all gross lesions. According to the focus on the respiratory tract, histopathological investigations of nasal cavity, larynx and trachea with bifurcation were performed in all test groups. Lungs, and mediastinal lymph nodes of the control and high exposure group were examined in addition. Nasal cavity and larynx of those recovery groups, which could contribute data on the reversibility of effects were also examined.
For clinical examinations (body weight, body weight change, grip strength fore and hind limbs and hot plate test) the data were analyzed statistically using two-sided ANOVA (Cochran, 1957) and Dunnett’s test (1955, 1964). For clinical chemistry and hematology, a one-way analysis of variance was done via the F-test
(ANOVA; Winer, 1971). If the resulting p-value was less than 0.05 a pair-wise comparison of each test group with the control was carried out using the Dunnett’s test (1955, 1964) for the hypothesis of equal means. Statistical analyses of absolute and relative organ weights were performed using non-parametric one-way analysis of variance (Kruskal–Wallis H-test, Miller, 1981; Siegel, 1956). If the resulting p-value was less than 0.05, a pair-wise comparison of each group was done with the Wilcoxon U-test (Nijenhuis and Wilf, 1978; Hettmansperger, 1984) using the hypothesis of equal medians.
The concentration response relation of laryngeal irritation was assessed using a benchmark multistage model posted on the web site of the US EPA (http://www.

Results and discussion

Results of examinations

Details on results:
Text according to publication:

Clinical examination
"From the recovery groups, one female each of the control group and of the high exposure group died during exposure and recovery period, respectively. Both deaths were regarded as incidental. No substance-related clinical signs or effects on body weight and body weight change were observed."

Pathology of the respiratory tract
"There was a significant increase of relative liver weight in high-concentration (8 mg/m³) females." "No significant weight changes were noticed in the recovery group after 3-month post-exposure." At the high concentration, upper respiratory tract irritation was evident. "Male and female animals revealed a focal squamous metaplasia of the laryngeal epithelium (level 1) and submucosal inflammation in a few cases. In 2 males, squamous metaplasia was also observed at level 2 of the larynx. Squamous metaplasia was noted in 3 of 10 males of the intermediate exposure group, which was not accompanied by epithelial inflammatory cell infiltration. In control animals, grade 1 (1 animal of each sex) and 2 (1 male) inflammatory cell infiltration was also observed occasionally. Examination of the URT after the recovery period of three months revealed no histological changes. No other parts of the RT showed substance-induced histomorphological changes at any concentration in this study. No treatment related histopathological changes were observed in the larynx at 1.5 mg/m³."

Effect levels

Dose descriptor:
Effect level:
1.5 mg/m³ air
Basis for effect level:
other: Signs of upper respiratory tract irritation (epithelial changes in larynx) only in males at the next higher concentration (3 mg/m³); cp. MAK documentation for Diethanolamine, 2007.

Target system / organ toxicity

Critical effects observed:
not specified

Any other information on results incl. tables

The substance contains approx. 40 % 2,2'-iminodiethanol (CAS No 111-42-2), therefore data of 2,2'-iminodiethanol are relevant for toxicological assessment and were thus included in the IUCLID.

Applicant's summary and conclusion

Executive summary:

In this 90 -days repeated inhalation study according to OECD TG 413 male and female rats were head-nose exposed to aerosolised 2,2'-iminodiethanol at concentrations of 0 (solely air exposed), 1.5, 3, and 8 mg/m³. Investigations included comprehensive histopathological examinations of the respiratory tract.

DEA showed toxicity to the upper respiratory tract (URT), in form of epithelial changes in the larynx in a concentration-dependent manner. These lesions were reversible within three months after the end of the exposure period and were, in accordance with published scientific evidence (Burger et al., Toxicol. Appl. Pharmacol. 101, 521–542, 1989; ESTP, expert workshop on "larynx squamous metaplasia", final minutes, 2007; ”; Osimitz, Toxicol. Appl. Pharmacol. 225, 229–237, 2007), judged as an adaptive instead of a toxic response. Consequently the transient larynx effects at 3 mg/m³ observed in males only, were regarded as of borderline toxicological significance and assessed to represent the NOAEC by the study authors.

However, according to MAK (MAK documentation for Diethanolamin, 2007; the effects at the concentration of 3 mg/m³ are assessed as substance-related and thus 1.5 mg/m³ is used as NOAEC.