Dibutyl maleate

Repeated dose toxicity: inhalation

Administrative data

Endpoint:

repeated dose toxicity: inhalation, other

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

supporting study

Study period:

Not available

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

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

Justification for type of information:

Based on the expected metabolism of diesters, n-butyl hydrogen maleate was selected as one of the most suitable read across substances for DBM, as it represents one of the metabolic/chemical breakdown products of DBM. For further information, please refer to Sect 13: "Comprenhensive read across rationale for waiving further studies on reprodutive and developmental toxicity".

Data source

Reference

Reference Type:

publication

Title:

A 6-month multispecies inhalation study wuth lameic anhydride

Author:

Short, DR, FJ Johannsen, and CE Ulrich

Year:

1988

Bibliographic source:

Fundamental and Applied Toxicology 10, 517-524

Materials and methods

Test guideline

Qualifier:

equivalent or similar to guideline

Guideline:

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

Deviations:

yes

Remarks:

15 male and 15 female rats, 15 male and 15 female hamsters, and 3 male and 3 female monkeys. All groups were treated 6 hr a day, 5 days a week for a total of 132 to 136 days of treatment during 6 month period

GLP compliance:

not specified

Limit test:

no

Test material

Specific details on test material used for the study:

maleic anhydride was supplied by Monsanto with a purity of 99%

Test animals

Species:

other: rats, hamsters and monkeys

Details on species / strain selection:

CD Rats, Engle hamsters and Rhesus monkeys

Sex:

male/female

Details on test animals or test system and environmental conditions:

- 15 male and 15 female rats, 15 male and 15 female hamsters, and 3 male and 3 female monkeys
- quarentined for at least two weeks
- rats and hamsters had free access to food and water except during treatment
- monkeys were feed daily with PurineMonakey Chow, fresh apples 3 times/week, and water ad libitum except during treatment

Administration / exposure

Route of administration:

inhalation

Type of inhalation exposure:

whole body

Vehicle:

other: stream nitrogen gas

Details on inhalation exposure:

- Four groups at 0, 1, 3, and 10 mg/m3 of MA
- 6hr a day, 5 days per week for a total of 132 to 136 days of treatment during 6 month period
- were exposed in 15 m3 cubical stailess-steel and glass chmabers with pyramidal tops.
- briquettes with MA were heated to generate MA and vapors were transported with a stream of nitrogen gas

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

- monitored three times a day
- collected samples through Tenax columns and by quantifying the retained materail, after thermal desorption into a nitrogen steam, using gas chromatograph equiped with a flame ionizationdetector and a 5 x 1/8 in stailess steel column packed with 1.5% OV-101 on 100-120 Chromosorb GHP.
- Temperature range was 115 to 150C and 205 to 220C, respectively

Duration of treatment / exposure:

- 0, 1, 3, and 10 mg/m3 of MA
- 6hr a day, 5 days per week for a total of 132 to 136 days of treatment during 6 month period

Frequency of treatment:

6hr a day, 5 days per week

Doses / concentrations

Doses / concentrations 1

Dose / conc.:

0 mg/m³ air

Doses / concentrations 2

Dose / conc.:

1 mg/m³ air

Doses / concentrations 3

Dose / conc.:

3 mg/m³ air

Doses / concentrations 4

Dose / conc.:

10 mg/m³ air

No. of animals per sex per dose:

15 male and 15 female rats, 15 male and 15 female hamsters, and 3 male and 3 female monkeys per dose

Control animals:

yes

Details on study design:

- Four groups at 0, 1, 3, and 10 mg/m3 of MA
- 6hr a day, 5 days per week for a total of 132 to 136 days of treatment during 6 month period

Examinations

Observations and examinations performed and frequency:

-daily observations before and after exposure
- body weights weekly
- ophalmoscopic examination monthly
- blood and urine collected: 5 rats or hamters/sex/group from control and high-dose at 3 months; all groups of rodents at 6 months and all monkeys at 0, 3 and 6 months.
- tests included for hematology, clinical chemistry and urinalysis
-Pulmonary function on all monkeys at 0, 3 and 6 months incluidng respiratory rate, tidal volumenm dynamic compliance, and resistance.

Sacrifice and pathology:

-Histopathologic examinations were performed on tissues and organs from all animals in control and high-exposure groups. The tissues examined were esophagus, stomach, liver, pancreas, small intestine, large intestine, kidneys, urinary bladder, pituitary, thymus, adrenals, thyroid, parathyroids, brain, eye with optic nerve, spinal cord, peripheral nerve, gonads, uterus, testes, prostate, seminal vesicle, heart, aorta, skeletal
muscle, submandibular (pharyngeal) lymph tissue, thoracic (mediastinal) lymph node, mesenteric lymph node, spleen, trachea, lung, and any other tissue with grossly observable lesions.
-Also nasal turbinate sections from all species at all dose levels

Statistics:

A statistical analysis of the body weights, hematology, clinical chemistry, and relative organ weights was performed using an analysis of
variance and Dunnett's test (Steel and Torrie, 1960). Histopathology data for nonnasal tissue were analyzed using the x2 test (Rohlf and Sokal, 1981). The level of significance selected was at p < 0.05.

Results and discussion

Results of examinations

Clinical signs:

effects observed, non-treatment-related

Mortality:

mortality observed, non-treatment-related

Description (incidence):

-survival > 90% in rats and monkeys
-equal number of deads of hamsters in control and treated group aften after collecting blood samples

Body weight and weight changes:

no effects observed

Description (incidence and severity):

- No statistically significantly differences were observed at the low dose for eitehr sex in rats
- Effects were observed temporaly in rtas at short intervals in the male and female mid-dose and for longer periods of time in the high-dose but at the end BW was reduced only for male rats at the high-dose
- No statistically significant differences were observed in the BW of eitehr hamsters or monkeys

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:

effects observed, non-treatment-related

Description (incidence and severity):

- Changes within the range or normal values or did not exhibit a dose-response relationship in rats, hamsters and monkeys.

Clinical biochemistry findings:

effects observed, non-treatment-related

Description (incidence and severity):

- a few effects not specified but within the range or did not show dos-response relationship

Urinalysis findings:

effects observed, non-treatment-related

Description (incidence and severity):

- Urinalysis values were normal for male rats and significanlty reduced volume with anincreased specifci gravity in female rats. However, these findings were not not dose related.
- Urynalysis values were normal for male and female hamsters and monkeys.

Behaviour (functional findings):

not specified

Immunological findings:

not examined

Organ weight findings including organ / body weight ratios:

no effects observed

Description (incidence and severity):

Organ weighs changes were observed in rats (8 of 9 tissues), hamsters (2 of 9 tissues) and monkeys (1 of 9 tissues).
Rats: mid and high doses: relative pituitaria weight, increased relative adrenal weight, and reduced absolute and relative thyroid weight.
Hamsters and monkeys: no significant organ weights were reported.

Gross pathological findings:

effects observed, non-treatment-related

Description (incidence and severity):

Microscopic examination of tissues showed nasal irritation in all species or inflammatory. However, all changes were judged to be reversible.

Neuropathological findings:

not specified

Histopathological findings: non-neoplastic:

not specified

Histopathological findings: neoplastic:

not specified

Effect levels

Dose descriptor:

other: TLV

Effect level:

1 ca. mg/m³ air (nominal)

Based on:

test mat.

Sex:

male/female

Remarks on result:

not determinable due to absence of adverse toxic effects

Any other information on results incl. tables

Table 1. Body weights of male rats exposed to maleic anhydride via inhalation

Month	0.0 mg/m3	1.1 mg/m3	3.3 mg/m3	9.8 mg/m^3
0	268*	269	267	269
1	385	374	372	371
2	423	416	400	395**
3	467	446	437**	417**
4	480	471	456	430**
5	500	495	480	448**
6	526	524	510	482**

* Mean gram/rat for 15 rats/group

**Significantly different from control

Table 2. Body weights of female rats exposed to maleic anhydride via inhalation

Month	0.0 mg/m3	1.1 mg/m3	3.3 mg/m3	9.8 mg/m^3
0	188	187	187	185
1	252	250	247	251
2	279	275	265	263**
3	300	293	285	276**
4	312	303	293	286**
5	326	318	302**	294**
6	342	332	320	320

* Mean gram/rat for 15 rats/group

**Significantly different from control

Table 3. Relevant observations and organ weights in the rat, hamster and monkeys exposed to maleic anhydride* represented in the number of animals affected (% of total affected). Tissues from 15 rats/sex/group, 15 hamsters / sex/ group and 3 monkey/sex/group were examined.

Histological observations	0.0   Male	9.8 mg/m^3 Male	0.0  ^3 Female	9.8 mg/m^3 Female
Rats
Testes Testicular degeneration  -Moderate	0(0)	1(7)
Kidneys Acute to subacute pyelonephritis – Moderate Acute to subacute pyelitis - Moderate	0(0)       0(0)	1(7)       0(0)	0(0)       0(0)	0(0)       1(7)
Urinary bladder Acute cystitis Slight Moderate Mucosal hyperplasia	0(0) 0(0) 0(0)	1(7) 0(0) 1(7)	0(0) 0(0) 0(0)	0(0) 1(7) 0(0)
Hamsters
Testes Necropsis with abscess formation - Marked	0	1(7)
Kidneys Tubular nephrosis – Slight Microconcretions in the tubules - Slight	3(20)     0	4(27)     0(0)	1(7)     0(0)	1(7)     1(7)
Monkeys
Kidney Tubular nephrosis	0(0)	1(33)	0(0)	0(0)

* Authors presented only those results that “occurred more frequently in treated animals.”

Only those observations with statistically significant relative to control animals were presented in the table.

Applicant's summary and conclusion

Conclusions:

this study was conducted to determined if the current TLV for maleic anhydride of 1 mg/m3 based on irritation could be supported with specific toxicity. although signs of nasal and ocular irritation occurred, systemic toxicity was not relevant in any of the species exposed to concentrations of maleic anhydride equivalent to the TLV.

Executive summary:

Based on the results of the study, it can be concluded that systemic toxicity would occur only a levels near to 10 times higher than the TLV.