1,3- AND 1,4-CYCLOHEXANDICARBOXYALDEHYDE

Repeated dose toxicity: inhalation

Administrative data

Endpoint:

sub-chronic toxicity: inhalation

Type of information:

experimental study

Adequacy of study:

key study

Study period:

3 July 2013-6 March 2014

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: The study was not conducted according to guidelines but was conducted according to GLPs and the report contains sufficient data for interpretation of study results.

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2014

Report date:

2014

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

OECD Guideline 413 (Subchronic Inhalation Toxicity: 90-Day Study)

Test guideline 2

Qualifier:

according to guideline

Guideline:

EPA OPPTS 870.3465 (90-Day Inhalation Toxicity)

Test guideline 3

Qualifier:

according to guideline

Guideline:

other: EEC, Part B.29

Principles of method if other than guideline:

This study was also designed to evaluate the potential for local (portal-of-entry) and systemic toxicity from inhalation of 1,3- and 1,4-cyclohexanedicarboxaldehyde.

GLP compliance:

yes (incl. QA statement)

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

-

EC Number:

482-020-3

EC Name:

-

Molecular formula:

C8H12O2

IUPAC Name:

cyclohexane-1,3-dicarbaldehyde; cyclohexane-1,4-dicarbaldehyde

Test material form:

other: vapour

Details on test material:

-Name of test material (as cited in study report): 1,3 and 1,4-Cyclohexanecarboxaldehyde
- Composition of test material, percentage of components: A mixture of 1,3-Cyclohexanedicarboxaldehyde and
1,4-Cyclohexanedicarboxaldehyde
- Lot/batch No.: Lot# 201200123-WFE 2-3Mr
-The purity of the test material was determined to be 98.24 ± 0.44% area by gas chromatography (corrected for water) with identification by
proton and carbon-13 nuclear magnetic resonance and gas chromatography mass spectrometry

Test animals

Species:

rat

Strain:

Fischer 344/DuCrj

Sex:

male/female

Administration / exposure

Route of administration:

inhalation: vapour

Type of inhalation exposure:

nose only

Vehicle:

air

Remarks on MMAD:

MMAD / GSD: see "Details on inhalation exposure"

Analytical verification of doses or concentrations:

yes

Duration of treatment / exposure:

6 hours/day

Frequency of treatment:

six hours/day, five consecutive days/week for 13 weeks.

No. of animals per sex per dose:

Male and female (each): 10 animals at 0 mg/m3
Male and female (each): 10 animals at 0.3 mg/m3
Male and female (each): 10animals at 2.67 mg/m3
Male and female (each): 10animals at 24.0 mg/m3

Results and discussion

Results of examinations

Clinical signs:

no effects observed

Mortality:

no mortality observed

Body weight and weight changes:

no effects observed

Food consumption and compound intake (if feeding study):

no effects observed

Food efficiency:

no effects observed

Water consumption and compound intake (if drinking water study):

no effects observed

Ophthalmological findings:

no effects observed

Haematological findings:

no effects observed

Clinical biochemistry findings:

no effects observed

Urinalysis findings:

no effects observed

Behaviour (functional findings):

no effects observed

Organ weight findings including organ / body weight ratios:

no effects observed

Gross pathological findings:

no effects observed

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Description (incidence and severity):

local signs of irritation in the respiratory tract

Histopathological findings: neoplastic:

no effects observed

Effect levels

1

Dose descriptor:

NOAEC

Remarks:

Systemic

Effect level:

> 24 mg/m³ air

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: overall effects clinical signs; mortality; body weight; food consumption; food efficiency; water consumption and compound intake; haematology; clinical chemistry; urinalysis; gross pathology; organ weights; histopathology; other.

2

Dose descriptor:

NOAEC

Remarks:

local

Effect level:

ca. 2.67 mg/m³ air

Based on:

test mat.

Sex:

male

Basis for effect level:

other: Based upon the localized, point of contact histopathological effects in the anterior nasal passage.

3

Dose descriptor:

NOEC

Remarks:

Local

Effect level:

ca. 2.67 mg/m³ air

Based on:

test mat.

Sex:

female

Basis for effect level:

other: Based upon the localized, point of contact histopathological effects in the anterior nasal passage.

Target system / organ toxicity

Critical effects observed:

not specified

Any other information on results incl. tables

There were no exposure-related effects on body weights/body weight gains, feed consumption, clinical observations, functional tests,hematology, prothrombin time, clinical chemistry, urinalysis, or organ weights. Based on BAL analyses, male and female rats exposed to1,3- and 1,4-cyclohexanedicarboxaldehyde vaporsat concentrations up to and including 24.0 mg/m³showed no evidence of exposure-related cellular injury or inflammation. Compared to control rats, no increase in total BAL cell numbers and no evidence of acute neutrophilic inflammation were detected in any test material-exposed group. No treatment-related alterations were noted in BAL protein or LDH levels.

There were no treatment-related gross pathologic observations.

There was no histopathological evidence of treatment-related systemic toxicity in males or females exposed to the highest exposure concentration of 24.0 mg/m³. Males exposed to 2.67 or 24.0 mg/m³and females exposed to 24.0 mg/m³had treatment-related histopathological changes that were confined to the anterior nasal cavity consistent withlocalized, point of contact irritant effects resulting from repeated inhalation of 1,3- and 1,4-cyclohexanedicarboxaldehyde vapors. The effects observed in the males at the 2.67 mg/m3 were very slight and represented an adaptive change (increase in mucouse secretion) rather than an adverse effect. Nasal airways of males exposed to 0.30 mg/m³and females exposed to 0.30 or 2.67 mg/m³had no treatment-related changes. There were no treatment-related histopathological changes in the posterior nasal airways, larynx, trachea or lungs in males or females in any of the exposure groups.

A limited assessment of the effects of repeated inhalation exposure to 1,3- and 1,4-cyclohexanedicarboxaldehyde on pulmonary function and non-specific airway reactivity (methacholine-challenge) was also conducted on 4 rats/sex from the control and high exposure groups. The rats were monitored for signs of treatment-related alterations in respiratory parameters after exposure during the 9^thexposure week and following the last day of exposure (at the end of the 13^thweek of exposure). No treatment-related alterations in pulmonary function were observed during post-exposure monitoring. Prior to necropsy, the previously monitored rats were evaluated for exposure-related changes in nonspecific airway responsiveness (measured as a change in Penh) by exposure to increasing concentrations of aerosolized methacholine hydrochloride (MCh) in whole-body barometric plethysmography chambers. Compared to air-exposed control rats of the same sex, malebut not female rats exposed to 24.0 mg/m³had increased airway responsiveness to MCh challenge as evidenced by Penh values that were statistically higher than control rats. The observed increase in airway reactivity in only one sex and the absence of morphologic evidence of pulmonary airway inflammation or remodeling suggests exposure-related irritation, and not allergic sensitization, as the underlying cause of the increased responsiveness to methacholine challenge.

Histopathological lesions were limited to the anterior nasal cavity, consistent with the irritant qualities of 1,3- and 1,4-cyclohexanedicarboxaldehyde. Based on the absence of exposure-related systemic effects, the 13-week no-observed-adverse-effect level (NOAEL) for 1,3- and 1,4-cyclohexanedicarboxaldehyde vapors in male and female F344/DuCrl rats was determined to be greater than the highest concentration tested, 24.0 mg/m³. Based upon the localized, point of contact histopathological effects in the anterior nasal passage, the no-observed-effect level (NOAEL) for male and female F344/DuCrl rats repeatedly exposed to 1,3- and 1,4-cyclohexanedicarboxaldehyde vapors for 13 weeks (65 exposures) was and 2.67 mg/m³.

Applicant's summary and conclusion

Conclusions:

The adminsitration of the test material to male and female rats for 90-days (6h/d) resulted in local, site of contact irritation effects to the upper respiratory tract only. There was no indication of systemci toxicity at any dose level. The methacholine-challenge provided further information for the presence of an irritating effect (rather than an allergic reaction). The NOAEL for local effects is therefore the mid dose group - 2.67 mg/m3, and the NOAEL for systemic toxicity is the top dose of 24 mg/m3.

Executive summary:

This study was designed to evaluate the potential for local (portal-of-entry) and systemic toxicity from inhalation of1,3- and 1,4-cyclohexanedicarboxaldehyde. Groups of ten male and ten female F344/DuCrl rats were exposed six hours/day, five consecutive days/week for 13 weeks (a total of 65 exposures) using a flow-past nose-only inhalation exposure system. The rats were exposed to analytically-determined time-weighted average (TWA) concentrations of0,0.30 ± 0.20, 0, or 24.0 ± 5.2(study TWA±standard deviation)mg 1,3- and 1,4-cyclohexanedicarboxaldehyde vapor/m³air (0, 0.05, 0.47, or 4.2 ppm, respectively). In-life observations (including ophthalmology), functional tests, feed consumption, body weights/body weight gains, urinalysis, coagulation, hematology, clinical chemistry and organ weights were evaluated. Bronchoalveolar lavage (BAL) was performed on all exposure groups to assess exposure-related pulmonary inflammation and injury by measuring the types and numbers of inflammatory cells, the total protein concentration and lactate dehydrogenase (LDH) activity in the recovered lavage fluid. At the end of 13 weeks of exposure necropsy was conducted on all animals and a detailed histopathologic examination of the entire respiratory tract was performed by light microscopy to assess treatment-related portal of entry effects. In addition, a detailed histopathologic examination of all other tissues/organs was performed on the control- and high-exposure group rats to identify treatment-related systemic toxicity.

There were no exposure-related effects on body weights/body weight gains, feed consumption, clinical observations, functional tests,hematology, prothrombin time, clinical chemistry, urinalysis, or organ weights. Based on BAL analyses, male and female rats exposed to1,3- and 1,4-cyclohexanedicarboxaldehyde vaporsat concentrations up to and including 24.0 mg/m³showed no evidence of exposure-related cellular injury or inflammation. Compared to control rats, no increase in total BAL cell numbers and no evidence of acute neutrophilic inflammation were detected in any test material-exposed group. No treatment-related alterations were noted in BAL protein or LDH levels.

There were no treatment-related gross pathologic observations.

There was no histopathological evidence of treatment-related systemic toxicity in males or females exposed to the highest exposure concentration of 24.0 mg/m³. Males exposed to 2.67 or 24.0 mg/m³and females exposed to 24.0 mg/m³had treatment-related histopathological changes that were confined to the anterior nasal cavity consistent withlocalized, point of contact irritant effects resulting from repeated inhalation of 1,3- and 1,4-cyclohexanedicarboxaldehyde vapors. The effects observed in the males at the 2.67 mg/m3 were very slight and represented an adaptive change (increase in mucouse secretion) rather than an adverse effect. Nasal airways of males exposed to 0.30 mg/m³and females exposed to 0.30 or 2.67 mg/m³had no treatment-related changes. There were no treatment-related histopathological changes in the posterior nasal airways, larynx, trachea or lungs in males or females in any of the exposure groups.

A limited assessment of the effects of repeated inhalation exposure to 1,3- and 1,4-cyclohexanedicarboxaldehyde on pulmonary function and non-specific airway reactivity (methacholine-challenge) was also conducted on 4 rats/sex from the control and high exposure groups. The rats were monitored for signs of treatment-related alterations in respiratory parameters after exposure during the 9^thexposure week and following the last day of exposure (at the end of the 13^thweek of exposure). No treatment-related alterations in pulmonary function were observed during post-exposure monitoring. Prior to necropsy, the previously monitored rats were evaluated for exposure-related changes in nonspecific airway responsiveness (measured as a change in Penh) by exposure to increasing concentrations of aerosolized methacholine hydrochloride (MCh) in whole-body barometric plethysmography chambers. Compared to air-exposed control rats of the same sex, malebut not female rats exposed to 24.0 mg/m³had increased airway responsiveness to MCh challenge as evidenced by Penh values that were statistically higher than control rats. The observed increase in airway reactivity in only one sex and the absence of morphologic evidence of pulmonary airway inflammation or remodeling suggests exposure-related irritation, and not allergic sensitization, as the underlying cause of the increased responsiveness to methacholine challenge.

Histopathological lesions were limited to the anterior nasal cavity, consistent with the irritant qualities of 1,3- and 1,4-cyclohexanedicarboxaldehyde. Based on the absence of exposure-related systemic effects, the 13-week no-observed-adverse-effect level (NOAEL) for 1,3- and 1,4-cyclohexanedicarboxaldehyde vapors in male and female F344/DuCrl rats was determined to be greater than the highest concentration tested, 24.0 mg/m³. Based upon the localized, point of contact histopathological effects in the anterior nasal passage, the no-observed-effect level (NOAEL) for male and female F344/DuCrl rats repeatedly exposed to 1,3- and 1,4-cyclohexanedicarboxaldehyde vapors for 13 weeks (65 exposures) was and 2.67 mg/m³.