Dioctyl maleate, branched

Repeated dose toxicity: inhalation

Administrative data

Endpoint:

chronic toxicity: inhalation

Type of information:

experimental study

Adequacy of study:

key study

Study period:

1987

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

comparable to guideline study with acceptable restrictions

Justification for type of information:

Study conducted outside the EU over 10 years before the EU cosmetic testing ban came into effect.

Cross-reference

Reason / purpose for cross-reference:

read-across: supporting information

Reference

Endpoint:

chronic toxicity: inhalation

Type of information:

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

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Justification for type of information:

Full read-across information is appended.

1. HYPOTHESIS FOR THE ANALOGUE APPROACH
The source substance and target substances behave in substantially similar ways in water, and are considered to be functionally similar when inside the body. The target substance has a higher molecular weight and lower dermal absorption coefficient, and is therefore considered to be less likely to enter the body through the skin or via oral absorption. The potential for acute dermal toxicity, repeated dose toxicity and toxicity to reproduction is therefore lower in the target substance than the source substance.

2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES)
Both substances are esters, with the carbonyl (C=O) part of each ester separated by 2 carbons. In addition, the two carbons are unsaturated as they share a double bond. In both cases this double bond is present in the cis geometry. The principle difference between the two substances is that the maleic anhydride is a ring structure, with the esters sharing the hydroxy group between them; whereas in the target substance there are two distinct ester components with branching chains (a methyl (odd) and a hexyl (even)).
Both substances can undergo hydrolysis to produce the same carboxylic acid as shown in the appended .pdf (Table 4). However, Maleic anhydride undergoes this process more readily as it is hygroscopic. The carboxylic acid formed is maleic acid, which can undergo hydration upon further reaction with water to produce malic acid.
The principle difference between how the source and target substances undergo hydrolysis is that one mole of maleic anhydride only produces one mole of maleic acid and no other organic species, whereas one mole of the target substance bis(1-methylheptyl) maleate produces one mole of maleic acid and two moles of 2-octanol. The 2-octanol is a branched alcohol, with an odd numbered branch (due to the methyl chain) and an even numbered branch (due to the hexyl chain).

3. ANALOGUE APPROACH JUSTIFICATION
Due to the similarities of the source and target substance with regards to chemical structure, physico-chemical properties, and Lipinski’s rule of 5, the target substance is expected to behave in a substantially similar manner in vivo.
The target substance is therefore predicted to also have a NOAEC of >10 mg/m3 after repeated dosing in the rat. By extension, the target substance is considered not to fulfil the criteria for acute dermal toxicity under the Classification, Labelling, and Packaging (CLP) regulation (1272/2008).

4. DATA MATRIX
See appended read-across justification.

Reason / purpose for cross-reference:

read-across source

Dose descriptor:

NOAEC

Effect level:

10 mg/m³ air (nominal)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

body weight and weight gain

histopathology: non-neoplastic

Critical effects observed:

not specified

Data source

Reference

Reference Type:

publication

Title:

A 6-Month Multispecies Inhalation Study with Maleic Anhydride

Author:

Short, R.D., Johannsen, F.R. & Ulrich, C.E.

Year:

1988

Bibliographic source:

FUNDAMENTAL AND APPLIED TOXICOLOGY, Vol 10, pp. 517-524

Report date:

1987

Materials and methods

Test guideline

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 452 (Chronic Toxicity Studies)

Deviations:

not applicable

Remarks:

The test was conducted prior to the adoption of the testing guideline.

Principles of method if other than guideline:

Hamsters and monkey data is not presented as this does not follow the OECD guideline. Not additional hazard was determined in either the hamster or monkey test.

GLP compliance:

no

Remarks:

Testing conducted prior to GLP adoption.

Test material

Test material information

Constituent 1

Reference substance name:

Maleic anhydride

EC Number:

203-571-6

EC Name:

Maleic anhydride

Cas Number:

108-31-6

Molecular formula:

C4H2O3

IUPAC Name:

furan-2,5-dione

Test material form:

not specified

Specific details on test material used for the study:

Maleic anhydride was supplied by Monsanto Co. as white briquettes with a purity of greater than 99%.

Test animals

Species:

rat

Strain:

Crj: CD(SD)

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River Breeding Laboratories, Portage, MI
- Females nulliparous and non-pregnant: Yes
- Age at study initiation: 6 weeks
- Weight at study initiation: F 185-188 : M 267-269
- Fasting period before study: No
- Diet (e.g. ad libitum): Purina Laboratory Chow (Ralston Purina, St.Louis, MO) - Ad libitum
- Water (e.g. ad libitum): - Ad libitum
- Acclimation period: 2 weeks

DETAILS OF FOOD AND WATER QUALITY: No reported

Administration / exposure

Route of administration:

inhalation: vapour

Type of inhalation exposure:

whole body

Vehicle:

other: nitrogen

Details on inhalation exposure:

All groups were exposed in 15 m3 cubical stainless-steel and glass chambers with pyramidal tops. Atmospheres containing the test material were generated by heating maleic anhydride, which has a melting point of 53°C, and by transporting vapors from the melt to the chambers with a stream of nitrogen gas.

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

Concentrations in the chambers were monitored three times a day by drawing samples through Tenax (Supelco, Bellefonte, PA) columns and by quantifying the retained material, after thermal desorption into a nitrogen steam, using a gas chromatograph equipped with a flame ionization detector and a 5 x J-in. stainless-steel column packed with 1.5%OV-101 on 100-120 Chromosorb GHP (Supelco, Bellefonte, PA). The range of column and detector temperatures was 115 to 150°C and 205 to 220°C, respectively. Standards were prepared by thermally desorbing a known amount of maleic anhydride, which was applied in an acetone solution to a Tenax column, and quantifying the material by gas chromatography. Although this method measures maleic anhydride, it does not distinguish between maleic anhydride and maleic acid. Therefore, all concentrations are expressed in terms of total maleic.

Duration of treatment / exposure:

6 hours/day

Frequency of treatment:

5 days/week 6 months (132 to 136 days total)

Doses / concentrations

Doses / concentrations 1

Dose / conc.:

0 mg/m³ air (analytical)

Doses / concentrations 2

Dose / conc.:

1 mg/m³ air (analytical)

Doses / concentrations 3

Dose / conc.:

3 mg/m³ air (analytical)

Doses / concentrations 4

Dose / conc.:

10 mg/m³ air (analytical)

No. of animals per sex per dose:

15 male:15 female

Control animals:

yes, concurrent no treatment

Examinations

Observations and examinations performed and frequency:

Animals were observed before and after each exposure for signs of toxicity. Individual body weights were determined at weekly intervals and direct and indirect opthalmoscopic examinations were performed monthly on all test animals. Blood and urine were collected from control and high-dose rats and hamsters (5/sex/group) at 3 months, from all groups of rodents at 6 months and all monkeys at 0, 3, and 6 months. Tests performed on the appropriate samples included hematology (hemoglobin, hematocrit, total erythrocyte count, and total and differential leukocyte count), clinical chemistry (glucose, urea nitrogen, serum glutamic pyruvic transaminase activity, serum alkaline phosphatase activity, carbon dioxide, erythrocyte and plasma cholinesterase activity, and terminal brain chohnesterase activity) and urinalysis (volume, pH, specific gravity, description of color and appearance, qualitative tests for albumin, glucose, bilirubin, ketones, and occult blood, and microscopic examination of the sediment).
Pulmonary function tests were performed using a Pulmonary Mechanics Computer, Model 4 (Buxco Electronics, Sharon, CT) on all monkeys prior to exposure and after 3 and 6 months of exposure. These tests included respiratory rate, tidal volume, dynamic compliance, and resistance.

Sacrifice and pathology:

Complete necropsies were conducted on all animals that died on test and on all survivors. Organ weights and organ/body weight ratios were recorded for adrenals, brain, heart, kidneys, liver, lungs, spleen, pituitary, thyroid, and gonads from all survivors. 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, prostate, seminal vesicle, heart, aorta, skeletal muscle, submandibular (pharyngeal) lymph tissue, thoracic (mediastinal) lymph node, mesenteric lymphnode, spleen, trachea, lung, and any other tissue with grossly observable lesions. In addition, nasal turbinate sections from all species at all dose levels were taken immediately posterior to the upper incisors. All sections of the nasal turbinates were approximately 3 to 5 mm thick and contained primarily respiratory epithelium.

Statistics:

A statistical evaluation of the body weight data, terminal 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 was selected at p < 0.05

Results and discussion

Results of examinations

Clinical signs:

effects observed, treatment-related

Description (incidence and severity):

Nasal and ocular irritations were observed in rats at all test levels during this study. In the high-dose group, rats exhibited a red-tinged nasal discharge, isolated cases of ocular discharge, and sneezing. These effects were less severe in animals from the low and mid-dose groups.
A direct and indirect ophthalmoscopic examination, which was performed on all animals at monthly intervals during the study, revealed no treatment-related ophthalmologic abnormalities.

Mortality:

mortality observed, non-treatment-related

Description (incidence):

Survival was greater than 90% in all groups of rats.

Body weight and weight changes:

effects observed, treatment-related

Description (incidence and severity):

The body weights of male and female rats during the study are presented at monthly intervals in Table 1. No significant effect was observed at the low dose for either sex. In general, effects were observed transiently at short intervals in the mid-dose group and for more prolonged intervals in the high-dose group.
The body weights of male rats were significantly reduced in the mid-dose group only on Days 78, 92, 106, and 127 and in the high dose group on Days 40 through 189. The body weights of female rats were significantly reduced in the mid-dose group only on Days 54, 127, 134, 141, 148, 155, and 156 and in the high-dose group on Days 37, 47, 57, 71, 85-176, and 189.

Ophthalmological findings:

no effects observed

Description (incidence and severity):

No treatment-related effects were observed in clinical laboratory test results or opthalmoscopic examinations of all species.

Haematological findings:

effects observed, non-treatment-related

Description (incidence and severity):

Hematological and clinical chemistry results indicated a few statistically significant differences from control values. However, since these values either were within the range of normal values or did not exhibit a dose-response relationship, no biological significance was attributed to these changes and they were not considered to be treatment related. Urinalysis values were normal for male rats. Female rats in the low-dose group had a significantly reduced urine volume with an increased specific gravity. These observations were not dose related and thus not considered related to treatment.

Organ weight findings including organ / body weight ratios:

effects observed, non-treatment-related

Description (incidence and severity):

Organ weight changes were observed in rats (eight of nine tissues weighed). In rats, the only changes present in both the mid- and high-dose group were increased relative pituitary weight, increased relative adrenal weight, and reduced absolute and relative thyroid weight. Since the histopathology data did not provide evidence of tissue damage, these changes were not considered related to treatment.

Histopathological findings: non-neoplastic:

effects observed, non-treatment-related

Description (incidence and severity):

The nasal tissues were evaluated for histopathological changes. The changes were categorized as being hyperplastic, metaplastic, or inflammatory in nature. All changes were judged to be reversible (Table 2). The metaplastic changes in rodents represented a transitional stage in which the normal cuboidal to low columnar epithelium became hyperplastic and pseudostratified. This lesion, in addition, underwent further transformation to result in nonkeratinizing squamous-type epithelium. Hyperplastic changes, which ranged in grade of severity from trace to mild, were present at all dose levels for rats. Both the incidence and grade appeared dose related. Metaplastic changes were present in rats at all dose levels and the incidence increased in a nonlinear fashion.
Rats at all exposure levels exhibited a focal to multifocal infiltration of the nasal epithelium with neutrophils and eosinophils, which was generally graded as trace to mild. A luminal exudate was present only in one and three males from the mid- and high-dose groups, respectively.

Additional tissues were also examined for histopathological changes and the results are presented in Table 3. Although a variety of observations were noted, only those that occurred more frequently in treated animals were selected for presentation in these tables. The only observation whose incidence in treated animals was increased to a level that was statistically significant relative to control animals was an increased amount of hemosiderin pigment in the red pulp from spleens of female rats (Table 3).

Details on results:

Chamber Concentrations:
Individual chamber analyses were averaged to obtain a mean daily concentration for each group. In turn, these values were averaged to obtain a measure of the material each group was exposed to during the entire study.
Accordingly, animals were exposed to average daily concentrations ± SD of 1.1 ± 0.6, 3.3 ± 0.6, and 9.8 ± 1.8 mg/m3 of total maleic during the study.

Effect levels

Dose descriptor:

NOAEC

Effect level:

10 mg/m³ air (analytical)

Based on:

test mat.

Sex:

male/female

Basis for effect level:

body weight and weight gain

histopathology: non-neoplastic

Target system / organ toxicity

Critical effects observed:

not specified

Any other information on results incl. tables

TABLE 1. BODY WEIGHTS OF MALE AND FEMALE RATS EXPOSED TO ATMOSPHERES CONTAINING MALEIC ANHYDRIDE

Month	Total maleic (mg/m3)
	0		1.1		3.3		98
	M	F	M	F	M	F	M	F
0	268a	188	269	187	267	187	269	185
1	385	252	374	250	372	247	371	251
2	423	279	416	275	400	265	395b	263b
3	467	300	446	293	437b	285	417b	276b
4	480	312	471	303	456	293	430b	286b
5	500	326	495	318	480	302b	448b	294b
6	526	342	524	332	510	320	482b	320

a Mean gram/rat for 15 rats/group.

b Significantly different from control.

TABLE 2. HISTOPATHOLOGICAL OBSERVATIONS IN NASAL TISSUE FROM ANIMALS EXPOSED TO ATMOSPHERES CONTAINING MALEIC ANHYDRIDE

Histopathological observation	Total Maleic (mg/m3)
	0	9.8	0	9.8
	Male		Female
Mucosa, epithelial hyperplasia focal/multifocal, septum/turbinates
Male	0/0a	13/40	7/93	0/80
Female	0/0	40/33	27/67	0/93
Mucosa, squamous metaplasia focal/multifocal, septum/turbinates
Male	0b	13	13	73
Female	0	0	13	87

a Percentage of animals with trace grade/percentage of animals with mild grade. Tissues from 15 rats, 15 hamsters, and 3 monkeys/sex/group were examined.

b Percentage of animals with observation. Tissues from 15 rats, 15 hamsters, and 3 monkeys/sex/group were examined.

TABLE 3. HISTOPATHOLOGLCAL OBSERVATION IN TISSUES FROM RATS EXPOSED TO ATMOSPHERES CONTAINING MALEIC ANHYDRIDE

Histopathological observation	Total Maleic (mg/m3)
	0	9.8	0	9.8
	Male		Female
Lung
Peribronchial/peribronchiolar lymphoid hyperplasia—Slight	11 (73)a	7 (47)	5 (33)	8 (53)
Perivascular lymphoid infiltrates—Slight	2 (13)	0 (0)	0 (0)	1 (7)
Alveolar hemorrhage—Slight	3 (20)	3 (20)	1 (7)	3 (20)
Interstitial inflammatory cell infiltrates—Slight	1 (7)	3 (20)	1 (7)	2 (13)
Atelectasis—Slight	2 (13)	0 (0)	1 (7)	2 (13)
Spleen
Increased amount of hemosiderin pigment in red pulp—Slight	1 (7)	2 (13)	2 (13)	7 (47)b
Increased amount of hemosiderin pigment in red pulp—Moderate	0 (0)	0 (0)	5 (33)	3 (20)
Liver
Periportal/sinusoidal mononuclear cell infiltrates—Slight	2 (13)	4 (27)	3 (20)	1 (7)
Sinusoidal congestion—Slight	0 (0)	0 (0)	0 (0)	1 (7)
Kidneys
Acute to subacute pyelonephritis—Moderate	0 (0)	1 (7)	0 (0)	0 (0)
Acute to subacute pyelitis—Moderate	0 (0)	0 (0)	0 (0)	1 (7)
Urinary bladder
Acute cystitis - Slight	0 (0)	1 (7)	0 (0)	0 (0)
Acute cystitis - Moderate	0 (0)	0 (0)	0 (0)	1 (7)
Mucosal hyperplasia	0 (0)	1 (7)	0 (0)	0 (0)
Testes
Testicular degeneration—Moderate	0 (0)	1 (7)	-	-
Prostate
Interstitial lymphoid infiltrates—Slight	0 (0)	3 (20)	-	-
Acute prostatitis—Slight	0 (0)	1 (7)	-	-

a Number of rats affected (% of total affected). Tissues from 15 rats/sex/group were examined.

b Significantly different from control (X2 test)

Applicant's summary and conclusion

Conclusions:

The purpose of this study was to determine if the current TLV for maleic anhydride of 1 mg/m3, which is based on irritation, could be supported with specific toxicity information. Although signs of nasal and ocular irritation were present in our study, no systemic toxicity was observed in any of the species exposed to concentrations of maleic anhydride equivalent to the current TLV and PEL. Furthermore, no systemic effects, which were directly attributed to maleic anhydride, were observed at levels that were nearly 10 times this value. Although results of this study support the current TLV and PEL regarding systemic toxicity, continuous exposure at this level during the day may produce irritation in the occupational setting, as suggested by the work of others (ACGIH, 1981)