Bis(pentane-2,4-dionato-O,O')magnesium

Repeated dose toxicity: inhalation

Administrative data

Endpoint:

sub-chronic toxicity: inhalation

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Cross-reference

Reason / purpose for cross-reference:

read-across: supporting information

Data source

Reference

Reference 1

Reference Type:

publication

Title:

2,4- Pentanedione: 9-Day and 14-Week Vapor Inhalation Studies in Fischer-344 Rats.

Author:

Dodd DE, Garman RH, Pritts IM, Troup CM, Snellings WM, Ballantyne B

Year:

1986

Bibliographic source:

Fundamental and Applied Toxicology 7: 329-339

Reference 2

Reference Type:

publication

Title:

2,4-Pentanedione. CAS N°: 123-54-6

Author:

OECD Organisation for Economic Co-operation and Development

Year:

2001

Bibliographic source:

SIDS Initial Assessment Report for SIAM 13 (Paris, France, in June) United Nations Environment Programme (UNEP) Publications, Nairobi, Kenya. 82 p. URL https://hpvchemicals.oecd.org/ui/handler.axd?id=AF8877C9-8DFB-45E0-8188-492EBA68CDAE

Materials and methods

Test guideline

Qualifier:

equivalent or similar to guideline

Guideline:

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

GLP compliance:

not specified

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

Pentane-2,4-dione

EC Number:

204-634-0

EC Name:

Pentane-2,4-dione

Cas Number:

123-54-6

Molecular formula:

C5H8O2

IUPAC Name:

pentane-2,4-dione

Test material form:

liquid

Test animals

Species:

rat

Strain:

Fischer 344

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River Breeding Laboratories, Inc. (Kingston, NY, USA).
- Age at study initiation: 34 days
- Housing: 2 animals per cage
- Diet : ad libitum
- Water : ad libitum
- Acclimation period: 18 days

DETAILS OF FOOD AND WATER QUALITY:

ENVIRONMENTAL CONDITIONS
- Temperature : 65-80 °F
- Humidity (%): 13-84%
- Air changes (per hr): approx. 14
- Photoperiod (hrs dark / hrs light): 12/12

Administration / exposure

Route of administration:

inhalation: vapour

Type of inhalation exposure:

whole body

Vehicle:

air

Remarks on MMAD:

MMAD and GSD not availablee

Details on inhalation exposure:

Liquid 2,4-pentanedione was assayed from a piston pump in a heated glass evaporator. The temperature in the evaporator was kept at the lowest level sufficient to vaporize the liquid. The resulting vapor was transported into the chamber by a countercurrent stream of air which entered the bottom of the evaporator.

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

The 2,4-pentanedione concentrations in the test chambers were analyzed approximately 2 times per hour (every 33 minutes during the 6 hours of daily exposure) during the 68 days of gas chromatographic testing. Concentration averages were 650 (± 19.3), 307 (± 10.3) and 101 (± 3.5) ppm for target concentrations.

Duration of treatment / exposure:

14 weeks

Frequency of treatment:

Treatment during 6 hours a day, 5 days a week.

Doses / concentrations

Doses / concentrations 1

Dose / conc.:

0 ppm (nominal)

Doses / concentrations 2

Dose / conc.:

100 ppm (nominal)

Remarks:

Corresponding to 417 mg/m3 of vapours of 2,4-pentanedione

Doses / concentrations 3

Dose / conc.:

300 ppm (nominal)

Remarks:

Corresponding to 1217 mg/m3 of vapours of 2,4-pentanedione

Doses / concentrations 4

Dose / conc.:

600 ppm (nominal)

Remarks:

Corresponding to 2711 mg/m3 of vapours of 2,4-pentanedione

No. of animals per sex per dose:

20 males and 20 females

Control animals:

yes, concurrent vehicle

Details on study design:

20 male and 20 female rats per group, half sacrificed at the end of the exposure period and the remainder after a 4-week recovery period for determining the reversibility of observable effects, exposed to nominal concentrations of 0 , 100, 300 and 650 ppm of test substance, respectively. Ten male rats were added to control and high dose groups for glutaraldehyde infusion and subsequent ultrastructural examination of sciatic nerves.

Examinations

Observations and examinations performed and frequency:

Toxicity monitoring: The following parameters have been determined:
- clinical signs of toxicity (daily)
- ophthalmoscopy of the eye (before and after exposure)
- neurobehavioral screening (monthly before, during and after exposure)
- body weight (weekly during the study and before sacrifice)
- food and water consumption for 14 h in the metabolic cages during the last week of exposure (urine analysis)
- weight of the organs (liver, kidneys, lungs, brain, heart, thymus and testicles)
- urine chemistry (n = 10 per group)
- Serum chemistry and hematology of blood samples taken at the end of the exposure or during the period
recovery of 4 weeks
- macroscopic pathology at the end of exposure in all groups
- histopathology in the high-dose group and the control group and the brains of animals in the mid-dose group

Sacrifice and pathology:

- Rats sacrificed by exsanguination via brachial blood vessels following methoxyflurane anesthesia.
Five additional male rats from the high-concentration and control groups were sacrificed and perfused with glutaraldehyde solution for removal of the sciatic nerve for transmission electron microscopy. Sciatic nerves were also examined by electron microscopy in five control males and high-dose males, although these rats were not perfused with glutaraldehyde solution prior to removal of the sciatic nerve.
Macroscopic necropsies were performed and selected tissues were fixed in 10% buffered neutral formalin.
- The histological evaluation was performed on tissues selected from the animals exposed to the highest exposure level (males), the intermediate exposure level (females) and the control groups.
- The analyzed tissues are: epididymides, spleen, lungs, nasal turbinates, thymus, trachea, bladder, adrenal glands, brain (5 sections), parathyroid, heart, kidneys, larynx, testicles, thyroid, pituitary, muscle-gastronemius, liver, sciatic nerve and sternal bone

Other examinations:

A modified Irwin test (Irwin, 1968) was performed before the first exposure and monthly thereafter. This examination was also performed on the recovery animals just before their sacrifice. The following measures were performed: tremors, convulsions, tail elevation, impaired gait, paresis, salivation, tearing, diarrhea, piloerection, hypothermia, stereotyphia, surface recovery, in-flight recovery reflex, yarn seizure, tonicity body, limb rotation, pupillary response (pre-exposure only), pupil size, skin color, respiration, locomotor acuity, corneal response, tail pinch, toe pinch, surprise auditory response.

Results and discussion

Results of examinations

Clinical signs:

effects observed, treatment-related

Mortality:

mortality observed, treatment-related

Body weight and weight changes:

effects observed, treatment-related

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:

effects observed, treatment-related

Urinalysis findings:

effects observed, treatment-related

Behaviour (functional findings):

effects observed, treatment-related

Immunological findings:

effects observed, treatment-related

Organ weight findings including organ / body weight ratios:

effects observed, treatment-related

Gross pathological findings:

effects observed, treatment-related

Neuropathological findings:

no effects observed

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Histopathological findings: neoplastic:

effects observed, treatment-related

Other effects:

not examined

Details on results:

In the group of animals exposed to 650 ppm, all females and 10 males out of 30 died between the 2nd and 6th week. Rats in this dose group had severe clinical abnormalities (eg, lacrimation, ataxia, hypoactivity, hypothermia). Survivors in the 650 ppm animal group had decreased body weight, reduced organ weight, and minor changes in hematology (reduction in hematocrit and red blood cells, increased corpuscular hemoglobin mean and volume), serum and urinary chemistry. Noteworthy lesions in animals that died after exposure to 650 ppm are: acute degeneration in deep cerebellar nuclei, vestibular and striated cores, and acute lymphoid degeneration in the thymus. Many survivors (7 out of 15 in the non-combined recovery and recovery group) in this group had the following symptoms:
-gliosis and malacia in the same brain regions, but no peripheral neuropathy
- minimal squamous metaplasia in the nasal mucosa
- lymphocytosis.
Most of the alterations observed in male rats in the group of animals exposed to 650 ppm surviving 14 weeks of exposure decreased in frequency and / or severity after the 4-week recovery period.

No substance-related mortality was observed in the animal groups exposed to 300, 100 and 0 ppm. In addition, there was no evidence of clinical signs or histological lesions in these rats. However, females in the 300 ppm animal group had a slight decrease in body weight gain, and in both sexes minor changes in hematology, serum chemistry, and urine were observed. . In addition, these changes appeared completely reversible after a recovery period of 4 weeks. $

In the group of animals exposed to 100 ppm, no difference compared to controls appeared detectable. In all surviving males, mean testis weights and testicular weights expressed as a% of organ weight determined at necropsy at the end of the study were not different from controls in the treatment groups. The same observation was made for animals in the recovery group. No histopathological changes were noted in the testes and epididymis in any dose group of surviving males examined immediately after the end of the study and after a recovery period of 4 weeks, respectively. One control animal out of 10 from the recovery group was diagnosed with epididymitis. In high-dose group animals that died during exposure, atrophy of the seminal vesicles was observed in four males and degeneration of seminiferous tubules in two animals. In females, the cervix and ovaries were examined histopathologically. No pathological findings were observed after macroscopic and microscopic examination of the uterus, cervix and ovaries in all treatment groups immediately after the end of the study. In females in the recovery group, ovarian cysts ("cystic ovarian cyst") were found in 2 out of 10 animals in the control group, but none in the animal groups exposed to the substance. One in 10 control animals and the intermediate dose group experienced changes in uterine size ("luminal ectasia") while 1 in 10 animals in the intermediate dose group had changes in the size of the uterus ("luminal ectasia"). cervix ("luminal ectasia").

Effect levels

1

Key result

Dose descriptor:

NOAEC

Effect level:

ca. 417 mg/m³ air

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: general effect

Remarks on result:

other:

Remarks:

NOAEC of 100ppm is equivalent to 417 mg / m3 or 144.1 mg / kg body weight / day assuming a respiratory volume per minute of 0.24 L / min (14.4 L / hr) and a mean weight of rats of 250g / rat. (see below in table)

2

Dose descriptor:

LOAEC

Effect level:

ca. 2 711 mg/m³ air

Based on:

test mat.

Sex:

male/female

Basis for effect level:

food consumption and compound intake

gross pathology

haematology

histopathology: non-neoplastic

urinalysis

Remarks on result:

other:

Remarks:

LOAEC of 650 ppm equivalent to 2711 mg / m3 or 936.7 mg / kg body weight / day considering a respiratory volume per minute of 0.24 L / min (14.4 L / h) and a mean weight of rats of 250g / rat. (see below in table)

3

Key result

Dose descriptor:

NOAEL

Effect level:

ca. 144.1 mg/kg bw/day (actual dose received)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

other: general effects

4

Dose descriptor:

LOAEL

Effect level:

ca. 936.7 mg/kg bw/day (actual dose received)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

gross pathology

histopathology: non-neoplastic

urinalysis

Target system / organ toxicity

Key result

Critical effects observed:

yes

Lowest effective dose / conc.:

936.7 mg/kg bw/day (actual dose received)

System:

other: urinary, hematopoietic, central nervous system

Organ:

blood

brain

thymus

Treatment related:

yes

Dose response relationship:

yes

Relevant for humans:

not specified

Applicant's summary and conclusion

Executive summary:

Four groups each comprising 20 male and female Fischer 344 rats were exposed for six hours daily, five days per week, for 14 weeks to 2,4-pentanedione vapors at concentrations of 0 (control), 100, 300 or 650. ppm corresponding to 0, 417, 1277 and 2711 mg / m3. Half of the animals were kept for a further 4 weeks to determine the reversibility of the observed toxic effects.

The most remarkable observations of this study are brain and thymus lesions in animals that died by inhalation after exposure to 650 ppm 2,4-pentanedione. Because these degenerative lesions were not observed in male rats exposed to 650 ppm for 14 weeks, deaths were attributed to their development. However, half of the survivors in the 650 ppm group had gliosis or malacia in the vestibular nuclei of the brain and striated bodies. These lesions of the central nervous system were accompanied by neurobehavioral abnormalities.

Each rat exposed to 2,4-pentanedione exhibiting abnormality during the modified Irwin screening test was subsequently found to have brain damage. In general, the opposite of this statement was true; the exceptions being two males exposed to 650 ppm who had normal responses during the Irwin test but in the presence of cerebral malacia.

In addition, several females exposed to 650 ppm exhibited acute degeneration of nuclei and vestibular stromal bodies, but died before the Irwin test could be conducted. Since the results of electron microscopy tests in sciatic nerve preparations were negative, the neurotoxic effects of 2,4-pentanedione appear to be central and non-peripheral.

An explanation of the difference in mortality between sexes (30% versus 100% for males and females, respectively, of the 650 ppm exposure group) is not known. The difference between the sexes may be related to brain thiamin, folic acid and / or pyridoxine concentrations since a proposed mechanism of 2,4-pentanedione toxicity is the inactivation of B vitamins or their coenzymes.

The concentration-response profile for repeated exposures to 2,4-pentanedione is very pronounced. A concentration of 300 ppm, about half the concentration that appears lethal for the majority of exposed rats, did not cause clinical abnormalities or histological tissue lesions.

In fact, only minor changes in body weight and clinical pathology were observed in rats exposed to 300 pppm 2,4-pentanedione and these alterations appeared reversible after a 4-week recovery period. Mild squamous metaplasia in the nasal mucosa was observed in rats exposed to 650 ppm 2,4-pentanedione. Perhaps the inflammation in the nasal mucosa is a transient response to 2,4-pentanedione concentrations of 200 ppm and above. Rats exposed to 100 ppm 2,4-pentanedione for 14 weeks showed no signs of irritation or toxicity. In conclusion, the results of this study indicate an unobservable level of effect in rats of 100 ppm (equivalent to 417 mg / m3) of 2,4-pentanedione vapor.