But-2-yne-1,4-diol

Endpoint summary

Description of key information

subacute NOAEL (rat oral) = 1 mg/kg bw/day

subacute NOAEC (rat inhalation, systemic) = 25 mg/m3

subacute NOAEC (rat inhalation, local) = 0.5 mg/m3 (irritation of nose, larynx, trachea)

Key value for chemical safety assessment

Repeated dose toxicity: via oral route - systemic effects

Endpoint conclusion

Dose descriptor:

NOAEL

1 mg/kg bw/day

Study duration:

subacute

Species:

rat

Repeated dose toxicity: inhalation - systemic effects

Link to relevant study records

Reference

Endpoint:

repeated dose toxicity: inhalation

Remarks:

other: subacute/neurotoxicity

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 412 (Subacute Inhalation Toxicity: 28-Day Study)

Qualifier:

according to guideline

Guideline:

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

Deviations:

yes

Remarks:

28-days instead of 90

GLP compliance:

yes

Limit test:

no

Species:

rat

Strain:

Wistar

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Dr. K. Thomae GmbH, Biberach, FRG
- Housing: type MD III of Becker & Co., Castrop-Rauxel, FRG
- Diet (e.g. ad libitum):ad libitum
- Water (e.g. ad libitum):ad libitum

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 20-24
- Humidity (%): 30-70
- Photoperiod (hrs dark / hrs light): 12

Route of administration:

inhalation

Type of inhalation exposure:

nose/head only

Vehicle:

air

Remarks on MMAD:

MMAD / GSD: 0.81 - 0.99 um/ 2.0-2.2

Details on inhalation exposure:

GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Method of holding animals in test chamber: rats were restrained in glass exposure tubes with their snouts projected into the inhalation chamber.
- Temperature, humidity, pressure in air chamber: measured continuously by an automated measuring system.
- Method of particle size determination: metal collecting discs and backup particle filter were eluted individually with bidistilled water into graduated flsks, filled up to the calibration mark and analyzed.

TEST ATMOSPHERE
- Brief description of analytical method used: gas chromatograph
- Samples taken from breathing zone: yes

Analytical verification of doses or concentrations:

yes

Duration of treatment / exposure:

28 days

Frequency of treatment:

6 hours per working day

Remarks:

Doses / Concentrations:
0.5; 5; 25 mg/m3
Basis:

No. of animals per sex per dose:

8 male / 8 female

Control animals:

yes

Details on study design:

Post-exposure period: 2 days

Positive control:

no

Observations and examinations performed and frequency:

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: on exposure days before, during and after exposure. During preflow period and on post exposure day clinical findings were recorded once each working day

BODY WEIGHT: Yes
- Time schedule for examinations:at the beginning of the preflow, on the first exposure day and then once a week.

OPHTHALMOSCOPIC EXAMINATION: Yes
- Time schedule for examinations:prior to and at the end of the exposure period
- Dose groups that were examined:

HAEMATOLOGY: Yes
- Time schedule for collection of blood: at the end of the exposure period
- Anaesthetic used for blood collection: No
- Animals fasted: Yes
- How many animals: 5 animals per sex
- Parameters checked in table 1 were examined.

CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: at the end of the exposure period
- Animals fasted: Yes / No / No data
- How many animals: 5 animals/sex
- Parameters checked in table 2 were examined.

URINALYSIS: Yes / No / No data
- Time schedule for collection of urine:
- Metabolism cages used for collection of urine: Yes / No / No data
- Animals fasted: Yes / No / No data
- Parameters checked in table 3 were examined.

NEUROBEHAVIOURAL EXAMINATION: Yes
- Time schedule for examinations:
- Dose groups that were examined: 3 animals per sex and test group
- Battery of functions tested: functional observational batteries and motor activity measurements

Sacrifice and pathology:

GROSS PATHOLOGY: Yes
HISTOPATHOLOGY: Yes (see table 4)

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):

not specified

Food efficiency:

not specified

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

not specified

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):

focal squamous metaplasia of larynx, focal inflammation of trachea,

Histopathological findings: neoplastic:

no effects observed

Dose descriptor:

NOAEC

Remarks:

for systemic toxicity

Effect level:

25 mg/m³ air

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: no systemic affects at the high dose

Dose descriptor:

NOAEC

Remarks:

for local toxicity

Effect level:

0.5 mg/m³ air

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: respiratory tract irritation

Critical effects observed:

not specified

The following test substance related findings were observed in the high concentration groups (25 mg/m3):

Satellite group(10exposures):

-focal squamous metaplasia and inflammation inlevel I of the larynx

Main group (20 exposures):

-focal squamous metaplasia and inflammation in level I of the larynx

-focal inflammation at the tracheal bifurcation

In the mid concentration (5 mg/m3) satellite group focal squamous metaplasia in level I of the larynx was present. In the main group focal inflammation inlevel I of the larynx was seen additionally.

 There is some indication of increase in inflammation incidence over prolongation of exposure time, but all histopathological changes were graded minimal to slight without increase of severity.

No substance related clinical (including neurofunc-tion), clinico-pathological or pathological findingsoccurred in the low concentration group(0.5mg/m3).

Conclusions:

The high concentration of Butindiol aerosol (25 mg/m3) caused no systemic toxicity but local irritant effects in the upper respiratory tract(larynx, trachea). Taking into account the results of the preceding 5-day study and the satellite groups of this study, there is no evidence for the accumulation of systemic toxicity over time up to concentrations of 25 mg/m3. The effects found in larynx and trachea are unspecific responses due to the local irritation caused by the deposition of Butindiol aerosol in the aerodynamic traps presented by larynx and tracheal bifurcation. The NOAEC for systemic toxicity under the conditions of this study is 25 mg/m3. The NOAEC for local toxicity in the upper respiratory tract is 0.5 mg/m3.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

NOAEC

25 mg/m³

Study duration:

subacute

Species:

rat

Repeated dose toxicity: inhalation - local effects

Link to relevant study records

Reference

Endpoint:

repeated dose toxicity: inhalation

Remarks:

other: subacute/neurotoxicity

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 412 (Subacute Inhalation Toxicity: 28-Day Study)

Qualifier:

according to guideline

Guideline:

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

Deviations:

yes

Remarks:

28-days instead of 90

GLP compliance:

yes

Limit test:

no

Species:

rat

Strain:

Wistar

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Dr. K. Thomae GmbH, Biberach, FRG
- Housing: type MD III of Becker & Co., Castrop-Rauxel, FRG
- Diet (e.g. ad libitum):ad libitum
- Water (e.g. ad libitum):ad libitum

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 20-24
- Humidity (%): 30-70
- Photoperiod (hrs dark / hrs light): 12

Route of administration:

inhalation

Type of inhalation exposure:

nose/head only

Vehicle:

air

Remarks on MMAD:

MMAD / GSD: 0.81 - 0.99 um/ 2.0-2.2

Details on inhalation exposure:

GENERATION OF TEST ATMOSPHERE / CHAMBER DESCRIPTION
- Method of holding animals in test chamber: rats were restrained in glass exposure tubes with their snouts projected into the inhalation chamber.
- Temperature, humidity, pressure in air chamber: measured continuously by an automated measuring system.
- Method of particle size determination: metal collecting discs and backup particle filter were eluted individually with bidistilled water into graduated flsks, filled up to the calibration mark and analyzed.

TEST ATMOSPHERE
- Brief description of analytical method used: gas chromatograph
- Samples taken from breathing zone: yes

Analytical verification of doses or concentrations:

yes

Duration of treatment / exposure:

28 days

Frequency of treatment:

6 hours per working day

Remarks:

Doses / Concentrations:
0.5; 5; 25 mg/m3
Basis:

No. of animals per sex per dose:

8 male / 8 female

Control animals:

yes

Details on study design:

Post-exposure period: 2 days

Positive control:

no

Observations and examinations performed and frequency:

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: on exposure days before, during and after exposure. During preflow period and on post exposure day clinical findings were recorded once each working day

BODY WEIGHT: Yes
- Time schedule for examinations:at the beginning of the preflow, on the first exposure day and then once a week.

OPHTHALMOSCOPIC EXAMINATION: Yes
- Time schedule for examinations:prior to and at the end of the exposure period
- Dose groups that were examined:

HAEMATOLOGY: Yes
- Time schedule for collection of blood: at the end of the exposure period
- Anaesthetic used for blood collection: No
- Animals fasted: Yes
- How many animals: 5 animals per sex
- Parameters checked in table 1 were examined.

CLINICAL CHEMISTRY: Yes
- Time schedule for collection of blood: at the end of the exposure period
- Animals fasted: Yes / No / No data
- How many animals: 5 animals/sex
- Parameters checked in table 2 were examined.

URINALYSIS: Yes / No / No data
- Time schedule for collection of urine:
- Metabolism cages used for collection of urine: Yes / No / No data
- Animals fasted: Yes / No / No data
- Parameters checked in table 3 were examined.

NEUROBEHAVIOURAL EXAMINATION: Yes
- Time schedule for examinations:
- Dose groups that were examined: 3 animals per sex and test group
- Battery of functions tested: functional observational batteries and motor activity measurements

Sacrifice and pathology:

GROSS PATHOLOGY: Yes
HISTOPATHOLOGY: Yes (see table 4)

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):

not specified

Food efficiency:

not specified

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

not specified

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):

focal squamous metaplasia of larynx, focal inflammation of trachea,

Histopathological findings: neoplastic:

no effects observed

Dose descriptor:

NOAEC

Remarks:

for systemic toxicity

Effect level:

25 mg/m³ air

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: no systemic affects at the high dose

Dose descriptor:

NOAEC

Remarks:

for local toxicity

Effect level:

0.5 mg/m³ air

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: respiratory tract irritation

Critical effects observed:

not specified

The following test substance related findings were observed in the high concentration groups (25 mg/m3):

Satellite group(10exposures):

-focal squamous metaplasia and inflammation inlevel I of the larynx

Main group (20 exposures):

-focal squamous metaplasia and inflammation in level I of the larynx

-focal inflammation at the tracheal bifurcation

In the mid concentration (5 mg/m3) satellite group focal squamous metaplasia in level I of the larynx was present. In the main group focal inflammation inlevel I of the larynx was seen additionally.

 There is some indication of increase in inflammation incidence over prolongation of exposure time, but all histopathological changes were graded minimal to slight without increase of severity.

No substance related clinical (including neurofunc-tion), clinico-pathological or pathological findingsoccurred in the low concentration group(0.5mg/m3).

Conclusions:

The high concentration of Butindiol aerosol (25 mg/m3) caused no systemic toxicity but local irritant effects in the upper respiratory tract(larynx, trachea). Taking into account the results of the preceding 5-day study and the satellite groups of this study, there is no evidence for the accumulation of systemic toxicity over time up to concentrations of 25 mg/m3. The effects found in larynx and trachea are unspecific responses due to the local irritation caused by the deposition of Butindiol aerosol in the aerodynamic traps presented by larynx and tracheal bifurcation. The NOAEC for systemic toxicity under the conditions of this study is 25 mg/m3. The NOAEC for local toxicity in the upper respiratory tract is 0.5 mg/m3.

Endpoint conclusion

Endpoint conclusion:

adverse effect observed

Dose descriptor:

NOAEC

0.5 mg/m³

Study duration:

subacute

Species:

rat

Additional information

1,4 -Butynediol (B3D) was given to male and female Wistar Imp:DAK rats by oral gavage for 28 consecutive days in daily doses of 1, 10, or 50 mg/kg/day (Jedrychowski et al, 1992). After 28 days all animals were necropsied, blood samples were obtained and selected organs were weighed and prepared for histological examination. Treatment-related effects in the high-dose group consisted of: fatality in both sexes; decreased body weight gain in males; increase of absolute and/or relative weights of liver and kidneys in both sexes; depressed red blood cell count, haematocrit value and haemoglobin concentration in female rats; elevated reticulocyte count and leukocyte count in both sexes; increased total serum protein content in females; elevated glucose concentration in males and higher activity of sorbital dehydrogenase in both sexes; histopathological evidence of hepatotoxicity and nephrotoxicity in decedents; and hepatic and splenic changes in survivors. Minor hepatic, splenic, and erythrocyte changes were also found in some females given the middle dose. The dose of 1 mg/kg/day was considered to the NOAEL, and 10 mg/kg/day the LOAEL.

Sixteen male and sixteen female Wistar rats per test group were head-nose exposed to liquid aerosols of an aqueous solution of B3D for 6 hours per working day (BG Chemie, 1998). The target concentrations of treatment groups were 0.5, 5 and 25 mg/m3. A concurrent control group was exposed to clean air. Half of the animals (satellite groups) were examined after 10 exposures (15 study days), the other half (main groups) were examined after 20 exposures (30 study days). The high concentration (25 mg/m3) caused no systemic toxicity but local irritant effects in the upper respiratory tract (larynx, trachea). Taking into account the results of the preceding 5-day study (BG Chemie, 1997) and the satellite groups of this study, there is no evidence for the accumulation of systemic toxicity over time up to concentrations of 25 mg/m3. The effects found in larynx and trachea are considered unspecific responses due to the local irritation caused by the deposition of B3D aerosol in the aerodynamic traps presented by larynx and tracheal bifurcation. The NOAEC for systemic toxicity under the conditions of this study is 25 mg/m3. The NOAEC for local toxicity in the upper respiratory tract is 0.5 mg/m3.

Repeated dose toxicity: via oral route - systemic effects (target organ) cardiovascular / hematological: spleen; digestive: liver; urogenital: kidneys

Justification for classification or non-classification

1,4-Butynediol (B3D) is classified as Xn; R48/22 (Harmful, danger of serious damage to health by prolonged exposure if swallowed) under Annex I of EU Directive 67/548/EEC, and as Specific Target Organ Toxicity - Repeated Exposure (STOT-RE), Category 2 under Annex VI of Regulation (EC) 1272/2008. On the basis of the serious effects observed at 50 mg/kg/day, with minimal effects at 10 mg/kg-bw, following administration of B3D to male and female Wistar Imp:DAK rats by oral gavage for 28 consecutive (Jedrychowski et al, 1992), the Xn; R48/22 classification is warranted. Data are insufficient to enable a reliable classification for repeated dose toxicity by the inhalation and dermal routes, except that the effects observed in the upper respiratory tract (larynx, trachea) of male and female Wistar rats exposed to liquid aerosols by inhalation (head-nose only) at concentrations of 5 and 25 mg/m3 for 6 hours per working day (BG Chemie, 1998) are regarded as adaptive responses to a respiratory irritant and are, therefore, not classified as repeated dose toxicity. The corrosive / irritating nature of B3D should be sufficient to prevent long-term repeated exposures capable of causing systemic toxicity.