Reactionmass of octan-2-yl prop-2-enoate and octan-3-yl prop-2-enoate and octan-4-yl prop-2-enoate

Carcinogenicity

Description of key information

A carcinogenicity study was conducted on a structural analog of MTDID 44428. The results of the study were:

Not carcinogenic when tested according to via dermal exposure for 2 years.

Key value for chemical safety assessment

Carcinogenicity: via dermal route

Link to relevant study records

Reference

Reference 1

Endpoint:

carcinogenicity: dermal

Type of information:

experimental study

Adequacy of study:

key study

Study period:

April 1979 - may 1981

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Male mice only and one dose was tested. Dosing and evaluation is consistent with a 2 year dermal study.

Qualifier:

no guideline available

Principles of method if other than guideline:

No guidelines were referenced in the protocol or report; however, the study was conducted in accordance with carcinogenicity assays at that time. This was a 2 year dermal carcinogenicity assay that was reviewed by the Quality Assurance Unit at Bushy Run Research Center. The fur on the back of each mouse was clipped on Tuesday and Thursday of each week. 25 microliters of the test article were applied three times per week throughout the study, using an Eppendorf automatic pipette and spreading the aliquot up the back of each mouse. Animals were observed daily for mortality and monthly for skin leisons. All animals were necropisied at the end of the in-life phase; the necropsy included a careful examination of the skin and internal cavities and the recording of observations. All suspect tumors and the dorsal skin of all non-autolyzed mice, with or without tumors, were fixed in 10% neutral buffered formalin. Slides were prepared from the dorsal skin of all mice and any suspect internal tumors Histopathologic examinations were performed and reported.

GLP compliance:

no

Species:

mouse

Strain:

C3H

Sex:

male

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Jackson Laboratoris, Bar Harbor, Maine
- Age at study initiation: 74-9 Days
- Weight at study initiation: 21/1 to 27.5 g
- Fasting period before study:
- Housing: Group housing
- Diet (e.g. ad libitum): ad libitum
- Water (e.g. ad libitum): ad libitum
- Acclimation period: Two weeks
ENVIRONMENTAL CONDITIONS
- Temperature (°C):
- Humidity (%):
- Air changes (per hr):
- Photoperiod (hrs dark / hrs light):
IN-LIFE DATES: From: 9 April 1979 To: 1 May 1981

Route of administration:

dermal

Vehicle:

acetone

Details on exposure:

PREPARATION OF DOSING SOLUTIONS:
VEHICLE
- Justification for use and choice of vehicle (if other than water): Test article solubility
- Concentration in vehicle: 5% Test artcle in Acetone
TEST SITE
- Area of exposure: Back of mice
- % coverage:
- Type of wrap if used: None
- Time intervals for shavings or clipplings: Animals were clipped on Tuesdays and Thursdays
TEST MATERIAL
- Amount(s) applied (volume or weight with unit): 25 microliters
- Concentration (if solution): 5%
- Constant volume or concentration used: yes
VEHICLE
- Justification for use and choice of vehicle (if other than water): Test article solubility

- M/F ratio per cage: males Only

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

GC analysis was conducted to verify the dosing concentrations

Duration of treatment / exposure:

Test article was applied and was not washed after application

Frequency of treatment:

3 times per week

Remarks:

Doses / Concentrations:
A single 5% concentration was used which equals a 1.25 microliter dose
Basis:
other: applied to the skin

No. of animals per sex per dose:

40

Control animals:

yes, concurrent vehicle

Details on study design:

- Dose selection rationale: Based on dose finding study, the 5% dose resulted in slight skin irriation and did not result in weight loss.

Positive control:

None

Observations and examinations performed and frequency:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: Daily

DETAILED CLINICAL OBSERVATIONS: Yes
- Time schedule: Monthly
DERMAL IRRITATION (if dermal study): Yes
- Time schedule for examinations: Daily
BODY WEIGHT: No data

OPHTHALMOSCOPIC EXAMINATION: No

HAEMATOLOGY: No

CLINICAL CHEMISTRY: No

URINALYSIS: No

NEUROBEHAVIOURAL EXAMINATION: No

Sacrifice and pathology:

GROSS PATHOLOGY: Yes (see ATT 1)
HISTOPATHOLOGY: Yes (see ATT 2)

Other examinations:

Mortality incidences were assessed by the product-limit method (Kaplan and Meire, 1958) and teh Mantel-Cox and Breslow statistics were used for testing the equality of teh survival curves (Mantel, 1966; Breslow, 1970)

Body weight and weight changes:

not specified

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:

not examined

Haematological findings:

not examined

Clinical biochemistry findings:

not examined

Urinalysis findings:

not examined

Behaviour (functional findings):

not examined

Organ weight findings including organ / body weight ratios:

not specified

Gross pathological findings:

effects observed, treatment-related

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Histopathological findings: neoplastic:

effects observed, treatment-related

Relevance of carcinogenic effects / potential:

The dermal carcinogenic potential of isooctyl acrylate was assessed by applying a 25 microliters of a 5% (v/v) dilution in acetone to the backs of 40 C3H/HeJ male mice. These mice were selected because of a low incidence of spontaneous skin tumors. A negative control group recieving acetone was dosed simultaneously. The dermal route of exposure was selected because this constitutes the most likely route of exposure to this substance.

A squamous cell carcinoma, not at the site of application, was found in the treated group of mice. In addition, an initially diagnosed dermal melanoma was found at the site of application in the treated group. Two nodules in the acetone control group in the acetone control group were diagnosed at a hematoma and fat necrosis. Skin alterations in the treatment group included hyperkeratosis, dermatitis and surface crusting.

The initially diagnosed melanoma wa reviewed by an additional pathologist who stated 'that the cells comprising this melanoma are well diifferentiated with no indication of nuclear or cytologic pleamorphism or atypia. The lesion is well circumscribed and confined to the dermis.' It was the pathologists opinion that this consttutes a benign lesion and would not be expected to invade or metastasize given non subsantative change in morphology if the animal had lived longer. (see attached letter)

The conclusion reached is that the test substance was not found to be carcinogenic.

Key result

Dose descriptor:

NOAEL

Effect level:

ca. 0.91 mg/kg bw/day

Based on:

test mat.

Sex:

male

Basis for effect level:

histopathology: neoplastic

Remarks on result:

other: Effect type: carcinogenicity (migrated information)

SEE ATT 1 : IOA Frequency of Gross Findings

SEE ATT 2: IOA Frequency of Histologic Findings

Conclusions:

The test substance, a 5% (v/v) Isooctyl acrylate in acetone, was not found to be carcinogenic in a two year dermal assay.

Executive summary:

40 C3H/HeJ mice were treated for two years by applying 25 microliters of a 5% (v/v) in acetone solution to the back. Treated animals exhibited surface crusting, moderate dermatitis, hyperkeratosis, epidermal hyperplasia and melanosis at the treatment site. A benign dermal melanoma was diagnosed in tissue taken from the treatment site of one animal in the treated group. Isooctyl acrylate was not found to be carcinogenic in this study.

Reference 2

Endpoint:

carcinogenicity: dermal

Type of information:

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

Adequacy of study:

key study

Justification for type of information:

REPORTING FORMAT FOR THE ANALOGUE APPROACH

1. HYPOTHESIS FOR THE ANALOGUE APPROACH
The target chemical (MTDID 44428, CASRN 87015-11-0) and the source chemical (isooctyl acrylate (IOA) CAS 29590-42-9) are isomers that contain the same functional acrylate moiety attached to primarily C8 alkyl hydrocarbon chains (C7-C9, C8 rich for the source chemical) with variable branching. The source chemical differs from the target chemical in both the degree and position of branching of the alkyl ester group with the source chemical being branched at the terminal end of the alkyl chain while the target chemical is branched near the acrylate functional group. The acrylate group is expected to be metabolized in the same manner in both substances and the remaining alkyl chain will be metabolized and excreted via the same pathway. The source chemical and target chemical have the same molecular weight and very similar log Kow values (Target: 4.7-4.8, Source: 4.5-4.7). Similar ADME profiles are expected between the two substances as the metabolic pathway of acrylate esters has been well characterized. Acrylate and methacrylate functionalities are electrophilic and both may participate in Michael addition reactions. Metabolism is expected to occur through the same pathways, hydrolysis by carboxylesterases into two metabolites, an alcohol and an acrylic acid moiety with minor conjugation to gluthathione. Hydrolysis is similar across the acrylate family and enhances the elimination of the chemical upon exposure (McCarthy & Witz, 1997). Studies with n-butyl acrylate and 2-ethylhexyl acrylate confirm that the acrylic acid metabolite enters aerobic oxidation and in completely metabolized to CO2 with only a minor proportion be conjugated to glutathione and excreted in the urine as a N-acetyl cysteine conjugate (Sanders, JM et. al, 1988; Gut, I, et al. 1988). The previously mentioned studies have also demonstrated that enzymatic hydrolysis kinetic constants for methacrylate and acrylate esters are similar.

2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES)
Target Chemical
The target molecule, MTDID 44428 (CASRN 87015-11-0), is a multi-constituent substance defined as the reaction mass of octan-2-yl acrylate, octan-3-yl acrylate and octan-4-yl acrylate as represented by the following structures.
(see attached read-across justification document).
Molecular weight of the target chemical is 184.3
Source Chemical:
The source chemical, isooctyl acrylate (IOA) CAS 29590-42-9, is defined as a UVCB and is represented by the following structure (see attached read-across justification document).
The average molecular weight of the source substance is ca. 184.0. The source chemical differs from the target chemical in the degree and position of branching of the alkyl ester group with the source chemical having variable methyl branching along the alkyl chain while the target chemical is branched immediately adjacent to the acrylate functional group.

Purity and Impurities :
MTDID 44428 is a multi-constituent substance and the three acrylate constituents contribute >99% of the content. There are very low levels of residual reactants and reaction side products.
Isooctyl acrylate is a UVCB substance, based on the mixed-isomer nature of the material. As a UVCB substance, all components are considered part of the substance and the concept of impurities has little meaning. Acrylate ester content of IOA is >99 %, with very low levels of residual reactants and reaction side products. These non-acrylate components are substantially similar and do not impact the read-across of test results from IOA.
3. ANALOGUE APPROACH JUSTIFICATION
Analogue Approach Justification

The target chemical and source chemical are closely related alkyl acrylate compounds. They differ slightly in the structure of the alkyl ester portion of the molecule. MTDID 44428 contains a methyl, ethyl or propyl branch at the 1-carbon of the alkyl chain portion of the molecule, which is always C8 in total. IOA may have methyl or ethyl branches at one or more positions along the alkyl ester group. The carbon chain is predominantly C8 in total with lesser contributions of C7 and C9 (C8 on average).
The environmental toxicity of low molecular weight acrylate esters (aquatic mortality and immobilization) is by protein adduct formation via a Michael-type addition mechanism. In the environment, toxicity increases on a molar concentration basis with molecular weight (and concomitantly, hydrophobicity) due to increased ability of the molecule to reach its active site. The excess toxicity is mitigated in high molecular weight acrylate esters with log P > 5.

The mammalian toxicity of IOA and MTDID 44428 is also based on protein adduct formation via a Michael-type addition with the acrylate groups. Both the target and source chemical are weak dermal sensitizers (section 5) indicating that an equivalent mechanism of toxicity is at work for both substances based on identical functional groups and molecular weights and very similar log Kow values and water solubilities.

The number of hydrophobic carbons of IOA relative to MTDID 44428 is predicted to be similar resulting in very similar octanol water partition coefficient values. This was confirmed experimentally and the log Kow for IOA is 4.5-4.7 while the log Kow for MTDID 44428 is 4.7-4.8. Additionally, IOA and MTDID 44428 have very similar water solubility at 12.44 and 14.6 mg/L, respectively. IOA is expected to be metabolized via the same hydrolytic and enzymatic pathways as MTDID 44428, forming acrylic acid and isooctanol.

Similar mammalian metabolic pathways are expected for IOA and MTDID 44428 based on Sanders, et. al and Gut, et al. The source chemical and target chemical have the same molecular weight and very similar log Kow values. Similar ADME profiles are expected between the two substances as the metabolic pathway of acrylate esters has been well characterized. Acrylate and methacrylate functionalities are electrophilic and both may participate in Michael addition reactions. Metabolism is expected to occur through the same pathways, hydrolysis by carboxylesterases into two metabolites, an alcohol and an acrylic acid moiety with minor conjugation to gluthathione. Hydrolysis is similar across the acrylate family and enhances the elimination of the chemical upon exposure (McCarthy & Witz, 1997). Studies with n-butyl acrylate and 2-ethylhexyl acrylate confirm that the acrylic acid metabolite enters aerobic oxidation and in completely metabolized to CO2 with only a minor proportion be conjugated to glutathione and excreted in the urine as a N-acetyl cysteine conjugate (Sanders, JM et. al, 1988; Gut, I, et al. 1988). The previously mentioned studies have also demonstrated that enzymatic hydrolysis kinetic constants for methacrylate and acrylate esters are similar.

As can be seen in the table in section 5, the source and target substances have very similar environmental and mammalian hazard profiles for endpoints where each substance has experimental data. This further supports the hypothesis that the target and source substances are expected to behave similarly in mammalian and environmental systems with the same mechanism of action and that read-across of the data for higher-tier endpoints is appropriate in an effort to reduce unnecessary animal testing.

4. DATA MATRIX
See 'Other Information Including Tables' or attached justification.

Supporting References
Gut, I, Vodička, Cikrt, M, Sapota, A, and Kavan, I (1988) Distribution and elimination of (14C)-2-ehtylheyxyl acrylate radioactivity in rats. Archives of Toxicology 62:346-350.
McCarty, TJ and Witz, G (1997) Structure-activity relationships in the hydrolysis of acrylate and methacrylate esters by carboxylesterase in vitro. Toxicology 116: 153-158.

Reason / purpose for cross-reference:

read-across source

Body weight and weight changes:

not specified

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:

not examined

Haematological findings:

not examined

Clinical biochemistry findings:

not examined

Urinalysis findings:

not examined

Behaviour (functional findings):

not examined

Organ weight findings including organ / body weight ratios:

not specified

Gross pathological findings:

effects observed, treatment-related

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Histopathological findings: neoplastic:

effects observed, treatment-related

Relevance of carcinogenic effects / potential:

The dermal carcinogenic potential of isooctyl acrylate was assessed by applying a 25 microliters of a 5% (v/v) dilution in acetone to the backs of 40 C3H/HeJ male mice. These mice were selected because of a low incidence of spontaneous skin tumors. A negative control group recieving acetone was dosed simultaneously. The dermal route of exposure was selected because this constitutes the most likely route of exposure to this substance.

A squamous cell carcinoma, not at the site of application, was found in the treated group of mice. In addition, an initially diagnosed dermal melanoma was found at the site of application in the treated group. Two nodules in the acetone control group in the acetone control group were diagnosed at a hematoma and fat necrosis. Skin alterations in the treatment group included hyperkeratosis, dermatitis and surface crusting.

The initially diagnosed melanoma wa reviewed by an additional pathologist who stated 'that the cells comprising this melanoma are well diifferentiated with no indication of nuclear or cytologic pleamorphism or atypia. The lesion is well circumscribed and confined to the dermis.' It was the pathologists opinion that this consttutes a benign lesion and would not be expected to invade or metastasize given non subsantative change in morphology if the animal had lived longer. (see attached letter)

The conclusion reached is that the test substance was not found to be carcinogenic.

Key result

Dose descriptor:

NOAEL

Effect level:

ca. 0.91 mg/kg bw/day (nominal)

Based on:

test mat.

Sex:

male

Basis for effect level:

histopathology: neoplastic

READ-ACROSS DATA MATRIX

	Target substance	Source substance
CHEMICAL NAME	Reaction mass of octan-2-yl acrylate, octan-3-yl acrylate and octan-4-yl acrylate	Isooctyl acrylate
CAS#	44914-03-6	29590-42-9
Molecular formula	C11H20O2	C11H20O2 (on average)
Molecular Weight	184.3	184.3 (on average)
Melting Point	Experimental: <-35 °C	Experimental: < -90 °C at 1004 hPa
Boiling Point	Experimental: 217.6 °C (normalized)	Experimental: 196.8 °C at 1016 hPa
Density	Experimental: 0.8665 at 23 °C	Experimental: 0.885 g/cm3 at 20.0 °C
Vapour Pressure	Experimental: .06 hPa at 18 °C	Experimental: 1 hPa at 20 °C
Partition Coefficient (log KOW)	Experimental: 4.7-4.8	Experimental: 4.5 - 4.7
Water Solubility	Experimental: Individual isomers had solubilites of 4-5 mg/L, total was 14.6 mg/L	Experimental: 12.44 mg/L at 23.1 °C
Stability in Water	Experimental: t1/2at 25 °C, pH 9, 37.7-116 days t1/2at 25 °C, pH 7, 137 days - not determinable t1/2at 25 °C, pH 4, 154 days - not determinable. Hydrolysis product could be detected at pH 9 but not pH 7 and 4. Half-life increased from 2-octyl < 3-octyl < 4-octyl isomers.	Adaptation, readily biodegradable
Aerobic Biodegradation	Experimental: 54.7% after 28 days, biodegradation essentially stopped at day 11 (OECD 301F)   67% after 28 days. No residual material could be detected in test chambers on day 28. In abiotic control, residual test material was 4.8% of initial result (OECD 302C)	Experimental: 93-95% after 28 days (OECD 301D)
Bioconcentration		Not bioaccumulative (Extensive metabolism)
Transport and Distribution	Experimental: Koc 630 (OECD121)	Experimental: Koc 650-3900 (OECD121)
Henry's Law constant	NDA	Experimental: 1780 Pa*m3/mol at 23.1 °C
Acute Toxicity to Fish  (P. promelasunless noted)	NDA	Experimental: 96-hour LC50 0.67 mg/L (OECD 202)
Chronic Toxicity to Fish	NDA	Waived
Acute Toxicity to Aquatic Invertebrates (D. magna)	NDA	Experimental: 48-hour EC50 0.4 mg/L (OECD 202)
Long-Term Toxicity to Aquatic Invertebrates (D. magna)	NDA	Experimental: 28-day NOEC 0.065 mg/L (OECD 202 rev 1984)
Toxicity to Algae and Aquatic Plants (P. subcapitata)	NDA	QSAR result not read across
Toxicity to Microorganisms (activated sludge respiration)	Experimental: 3-hour EC50 >1000 mg/L (OECD 209)	Experimental: 3-hour EC50 >1000 mg/L (OECD 209)
Acute Oral Toxicity	Experimental: Rat oral LD50 > 2,000 mg/kg	Experimental: Rat oral LD50 > 5,000 mg/kg
Acute Dermal Toxicity	Read-across from source: Rabbit dermal LD50 > 2,000 mg/kg	Experimental: Rabbit dermal LD50 > 2,000 mg/kg
Acute Inhalation Toxicity	Read-across from source: NDA	Experimental: NDA
Skin Irritation	Experimental: Irritating (GHS Cat. 2)	Experimental: Not irritating
Eye Irritation	Experimental: Not Irritating	Experimental: Not irritating
Skin Sensitization	Experimental: Weak sensitizer (GHS Category 1B)	Experimental: Weak sensitizer (GHS Category 1B)
Ames Assay	Experimental: Non-mutagenic	Experimental: Non-mutagenic
in vitroChromosome Aberration	Read-across from source: Clastogenic at cytotoxic concentrations	Experimental: Clastogenic at cytotoxic concentrations
in vitroMouse Lymphoma Assay	Read-across from source: Non-mutagenic	Experimental: Non-mutagenic
28 Day Oral Toxicity	Read-across from source: NOAEL = 1,000 mg/kg/day	Experimental: NOAEL = 1,000 mg/kg/day
90 Day Oral Toxicity	Read-across from source: NOAEL = 600 mg/kg/day	Experimental: NOAEL = 600 mg/kg/day
Reproductive/Developmental Screening Study (Dermal)	Read-across from source: NOAEL = 20% Dermal Exposure	Experimental: NOAEL = 20% Dermal Exposure
Prenatal Developmental Study (Oral)	Read-across from source: NOAEL = 1,000 mg/kg/day	Experimental: NOAEL = 1,000 mg/kg/day
Carcinogenicity (Dermal)	Read-Across from source: Not Carcinogenic	Experimental: Not Carcinogenic (5% Dermal Exposure)

Conclusions:

Reading-across the results from the source substance (IOA), the target substance (MTDID 44428) is not carcinogenic.

Executive summary:

The similarities between the structural, physical & chemical, toxicity, and predicted metabolic properties of the source and target substances presented above support the read-across hypothesis for genetic toxicity. The data are adequate and reliable scientific information to support the hypothesis. Therefore, based upon the data and considerations presented in the above sections, it can be concluded that the results of the carcinogenicity study with source substance will accurately predict the results for the target substance and are considered as adequate to fulfil the information requirement of Annex VIII, of the REACH Regulation for the target substance.

Justification for classification or non-classification

Based on the results of the study conducted on a structural analog, MTDID 44428 does not meet the criteria for classification.