2-ethyl-2-[[(1-oxoallyl)oxy]methyl]-1,3-propanediyl diacrylate; 2,2-bis(acryloyloxymethyl)butyl acrylate; trimethylolpropane triacrylate

Carcinogenicity

Description of key information

The overall data base for carcinogenicity constitute a number of studies with different levels of reliability and qualities. The carcinogenic potential of TMPTA was evaluated for 80 weeks using topical application in C3H/HeJ male mice.(supportive study, Klimisch score 2) (Cytec, 1982). The U.S. National Toxicology Program (NTP) evaluated the carcinogenic potential of TMPTA in a short-term (6-month) bioassay using male and female transgenic Tg.AC mice (disregarded study, Klimisch score 3) and in chronic (2-year) bioassays in both sexes of F‐344/N rats and B6C3F1/N mice (disregarded study, Klimisch score 3). From the available data, summarised below and further evaluated in two expert opinions attached in the study entries (Exponent 2019 and John Cullen 2020), it is concluded that there is not sufficient evidence to classify TMPTA as carcinogenic.

Supporting study (Klimisch score 2) - 80 week dermal study by Cytec (1982):

Groups of C3H/HeJ male mice (50/dose) received topical application of 50 mg/kg bw of the test substance (5 % in white mineral oil) to shaved area of the back, twice weekly for 80 weeks (corresponding to an average daily dose of 24 mg/kg bw/day of TMPTA, which is 8 times more than the highest dose used in the 2-year NTP bioassay). The gross observations made at necropsy were dark red lesions in lungs, liver tumours, kidney haemorrhages, enlarged spleen, skin ulcers, flaky skin, enlarged and grey lymph nodes, haemorrhages in stomach, grey or yellow spots in adrenals. Non-neoplastic histopathologic lesions included ulcer, abscess, acanthosis, dysplasia, fibrosis, pigmentation, hyperkeratosis and retention cyst. The treatment resulted in skin ulcers in 11 mice, skin fibrosis in 38 and acanthosis in 46 of the treated mice, however, no tumours were observed in any of the animals after 80 weeks of treatment. The referenced study is an older study (1982) but is well documented, meets generally accepted scientific standards and described in sufficient details. The study is therefore used as supportive information, also because the study was performed with white mineral oil compared to the other referenced disregarded NTP studies perfomed with acetone (inappropriately vehicle due to drying, irritation,inflammation and hyperplasia of the skin).

In conclusion, TMPTA was considered not to be carcinogenic in mice as no carcinogenic potential was found. Thus, the data indicate no need for CLP classification.

Disregarded study (Klimisch score 3) - 6-month dermal NTP mice study (2005):

In the short-term NTP study, TMPTA was administered to Tg.AC mice at dose levels of 0, 0.75, 1.5, 3, 6, or 12 mg/kg body weight (bw)/day by skin painting for 28 weeks (5 days/week), using acetone as vehicle. Because of its high background incidence of skin tumours, high false positive rate, sensitivity to dermal irritation and other limitations, the Tg.AC mouse model is no longer used for assessing carcinogenicity. Further, acetone was inappropriately used as vehicle (see further commetns made for lifetime studies).

In conclusion, the study is therefore disregarded for further evaluation of the carcinogenicity of TMPTA.

Disregarded study (Klimisch score 3) - 2-year dermal NTP mice and rats studies (2012):

In the lifetime cancer bioassay, TMPTA was administered by dermal application at doses of 0, 0.3, 1.0, or 3.0 mg/kg bw/day for 5 days/week over a 2-year period to groups of 50 male and 50 female F‐344/N rats and B6C3F1/N mice. Acetone was used inappropriately as the dosing vehicle in the study, causing substantial epidermal chronic inflammation and hyperplasia in control mice, as well as destruction of the skin barrier and inflammation in both species at the mid and high doses of (1 and 3 mg/kg bw/day). Several limitations of the study were identified compromising the validity of the study as well the results. In particular, acetone was used inappropriately as the dosing vehicle which is a major factor to the conclusion that the study is disregarded. This has been further evaluated and reviewed upon by two independent expert opinions (Exponent 2019 and John Cullen 2020), and both concluded that not enough evidence to classify TMPTA as carcinogencic is available and that the observed incidences are not relevant. This is further discussed in the endpoints study entries and robust study summaries.

In conclusion, the study is therefore disregarded for further evaluation of the carcinogenicity of TMPTA.

Overall, based on the results of the 80-week study by Cytec (1982) using dermal application of TMPTA formulated in white mineral oil (not acetone), it is concluded that TMPTA should not be classified for carcinogenicity.

Key value for chemical safety assessment

Carcinogenicity: via oral route

Endpoint conclusion

Endpoint conclusion:

no study available

Carcinogenicity: via inhalation route

Endpoint conclusion

Endpoint conclusion:

no study available

Carcinogenicity: via dermal route

Link to relevant study records

Reference

Endpoint:

carcinogenicity

Remarks:

other: Dermal

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

Not reported

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:

The referenced study is an older study (1982) but is well documented, meets generally accepted scientific standards and described in sufficient details. The protocol is though outdated and does not contain as many detailed information as included in studies performed in accordance to latest versions of carcinogenic testing guidelines. The study is therefore used as supportive information, but considered relevant in an overall discussion of the carcinogenic potential of TMPTA as the study was performed with white mineral oil compared to the other referenced studies perfomed with acetone (inappropriately vehicle due to drying, irritation,inflammation and hyperplasia of the skin).

Principles of method if other than guideline:

A group of 50 C3H/HeJ male mice received topical application of 50 mg of C-92 (5 % in white mineral oil) to shaved area of the back, twice weekly for 80 weeks. A group of solvent control and positive control (0.05% benzo(a)pyrene in mineral oil) were also maintained along with no-treatment control group in the study. Parameters evaluated included clinical signs, mortality, body weight, gross pathology and histopathological (neoplastic and non-neoplastic) examinations.

GLP compliance:

not specified

Species:

mouse

Strain:

other: C3H/HeJ

Sex:

male

Details on test animals or test system and environmental conditions:

- Source: Jackson Laboratory, Bar Harbor, Maine
- Age at study initiation: 6-8 wk
- Housing: Five animals per cage housed in stainless steel suspended cages
- Diet: Ad libitum
- Water: Ad libitum
- Acclimation period: 2 wk

Route of administration:

other: Dermal

Vehicle:

paraffin oil

Details on exposure:

TEST SITE
- Area of exposure: Interscapular region at the back
- Time intervals for shavings or clipplings: Shaved bi-weekly

TEST MATERIAL
- Amount(s) applied (volume or weight with unit): 50 mg twice/ wk
- Concentration (if solution): 5 % solution prepared in white mineral oil (paraffin oil)
- Constant volume or concentration used: Yes

VEHICLE
- Justification for use and choice of vehicle (if other than water):
a) Nontoxic, noncarcinogenic and non-cocarcinogenic
b) Test material remain in suspension long enough so that a uniform dose could be applied

Analytical verification of doses or concentrations:

no

Details on analytical verification of doses or concentrations:

Not applicable

Duration of treatment / exposure:

80 weeks

Frequency of treatment:

Twice a wk

Post exposure period:

None

Remarks:

Doses / Concentrations:
50 mg
Basis:
other: nominal, per mouse per application

No. of animals per sex per dose:

50 males/dose

Control animals:

yes, concurrent no treatment

yes, concurrent vehicle

Details on study design:

- Dose selection rationale: As confirmed by pilot study
- Rationale for animal assignment: Random assignment

Positive control:

0.05 % benzo(a)pyrene in mineral oil

Observations and examinations performed and frequency:

CAGE SIDE OBSERVATIONS: Yes
- Time schedule: Daily

DETAILED CLINICAL OBSERVATIONS: No
- Time schedule: Daily

DERMAL IRRITATION (if dermal study): Yes
- Time schedule: Weekly observed for skin conditions and tumors

BODY WEIGHT: Yes
- Time schedule: Animals were weighed weekly during the first month of the study and thereafter every two weeks

Sacrifice and pathology:

GROSS PATHOLOGY: Yes
HISTOPATHOLOGY: Yes

Other examinations:

None

Statistics:

No data

Clinical signs:

effects observed, treatment-related

Mortality:

mortality observed, treatment-related

Body weight and weight changes:

not specified

Food consumption and compound intake (if feeding study):

not examined

Food efficiency:

not examined

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

not examined

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 examined

Gross pathological findings:

effects observed, treatment-related

Histopathological findings: non-neoplastic:

effects observed, treatment-related

Histopathological findings: neoplastic:

no effects observed

Details on results:

CLINICAL SIGNS AND MORTALITY: Nearly all the mice survived the first three months of exposures. Percent survival after 78 week was 60.

GROSS PATHOLOGY: Dark red lesions in lungs, liver tumors, kidney haemorrhages, enlarged spleen, skin ulcers, flaky skin, enlarged and gray lymph nodes, haemorrhages in stomach, gray or yellow spots in adrenals

HISTOPATHOLOGY: NON-NEOPLASTIC: Lesions include ulcer, abscess, acanthosis, dysplasia, fibrosis, pigmentation, hyperkeratosis, retention cysts

HISTOPATHOLOGY: NEOPLASTIC (if applicable):
No-treatment group: Liver carcinoma (18 mice), lymphadenitis (0 mice)
Solvent control group: Liver carcinoma (13 mice), lymphadenitis (2 mice)
Treatment group (C-92): Liver carcinoma (2 mice), lymphadenitis (2 mice) but no skin tumors

Relevance of carcinogenic effects / potential:

The low incidence of neoplasms in this investigation strongly suggests that the test substance is non-carcinogenic in mice. In the event of similar exposures to humans, it appears that good, appropriate personal hygiene measures should be undertaken to prevent repeated exposures to the test substance .

Dose descriptor:

dose level:

Effect level:

50 other: mg

Based on:

test mat.

Sex:

male

Basis for effect level:

other: gross pathology; histopathology (neoplastic and non-neoplastic)

Remarks on result:

other:

Remarks:

Effect type: other: non-carcinogenic (migrated information)

None

Conclusions:

A group of 50 male C3H/HeJ mice received topical doses on the clipped interscapular region of the skin of 50 mg of 5% TMPTA in white mineral oil (not acetone as previously used for NTP studies) twice weekly for 80 weeks to shaved area of the back. The dose corresponds to an average daily dose of 24 mg/kg bw/day of TMPTA), which is 8 times more than the highest dose used in the 2 -year NTP bioassay (disregarded study due to the use of acetone as vehicle). A group of solvent control and positive control (0.05% benzo(a)pyrene in mineral oil) were also maintained along with no-treatment control group in the study. The treatment resulted in skin ulcers in 11 mice, skin fibrosis in 38 and acanthosis in 46 of the treated mice, however, no tumours were observed in any of the animals after 80 weeks of treatment. Thus, TMPTA was considered to be non-carcinogenic in mice and thus no need for CLP classification.

Executive summary:

A study was conducted to assess the carcinogenic potential of the test substance trimethylolpropane triacrylate (TMPTA) in C3H/HeJ male mice (females not tested). Groups of C3H/HeJ male mice (50/dose) received topical application of 50 mg of 5% TMPTA in white mineral oil (not acetone as previously used for NTP studies) twice weekly for 80 weeks to shaved area of the back. The dose corresponds to an average daily dose of 24 mg/kg bw/day of TMPTA, which is 8 times higher than the highest dose used in the 2-year bioassay. A group of solvent control and positive control (0.05% benzo(a)pyrene in mineral oil) were also maintained along with no-treatment control group in the study.

Parameters evaluated included clinical signs, mortality, body weight, gross pathology and histopathological (neoplastic and non-neoplastic) examinations. The gross observations made at necropsy were dark red lesions in lungs, liver tumours, kidney haemorrhages, enlarged spleen, skin ulcers, flaky skin, enlarged and grey lymph nodes, haemorrhages in stomach, grey or yellow spots in adrenals. Non-neoplastic histopathologic lesions included ulcer, abscess, acanthosis, dysplasia, fibrosis, pigmentation, hyperkeratosis and retention cyst. The treatment resulted in skin ulcers in 11 mice, skin fibrosis in 38 and acanthosis in 46 of the treated mice, however, no tumours were observed in any of the animals after 80 weeks of treatment. No skin tumours were found in any of the treated animals.

In conclusion, no neoplastic hepatic lesions identified in C3H/HeJ male mice in this study, even though the C3H/HeJ strain of mice is considered more susceptible to hepatocellular liver tumor formation than B6C3F1 mice as used in the 2-year NTP bioassay (disregarded study due to the use of acetone as vehicle). In conclusion, TMPTA was considered not to be carcinogenic in mice as no hepatic carcinogenic potential was found. Thus, the data indicate no need for CLP classification.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Study duration:

chronic

Species:

mouse

Quality of whole database:

The referenced study (Cytec, 1982) is well documented, meets generally accepted scientific standards and described in sufficient details. The protocol is though outdated and does not contain as many detailed information as included in studies performed in accordance to latest versions of carcinogenic testing guidelines. The study is therefore only used as supportive information, but considered relevant in an overall discussion of the carcinogenic potential of TMPTA as the study was performed with white mineral oil compared to the other referenced studies perfomed with acetone (inappropriately vehicle due to drying, irritation,inflammation and hyperplasia of the skin).

Mode of Action Analysis / Human Relevance Framework

The available data for a mode of action analysis is the data from the Cytec study (1982) using dermal application of TMPTA formulated in white mineral oil. The two NTP studies, the short-term (2005) and the 2-year bioassay (2012) are disregarded due to the inappropriately use of acetone as vehicle.

In the Cytec study (1982), the gross observations made at necropsy were dark red lesions in lungs, liver tumours, kidney haemorrhages, enlarged spleen, skin ulcers, flaky skin, enlarged and grey lymph nodes, haemorrhages in stomach, grey or yellow spots in adrenals. Non-neoplastic histopathologic lesions included ulcer, abscess, acanthosis, dysplasia, fibrosis, pigmentation, hyperkeratosis and retention cyst.The treatment resulted in skin ulcers in 11 mice, skin fibrosis in 38 and acanthosis in 46 of the treated mice, however, no tumours were observed in any of the animals after 80 weeks of treatment.No skin tumours were found in any of the treated animals.

In relation to genotoxicity, the mutagenic, clastogenic, and aneugenic properties of TMPTA were adequately investigated both in vitro and in vivo. In vitro, TMPTA primarily induced clastogenicity in cytotoxic concentrations, but such an effect was not evident in vivo in micronucleaus studies (OECD test guideline compliant studies). Moreover, the in vivo comet assay is believed to be a reliable indicator assay for detecting gene mutagens as well as clastogens and this assay was negative with TMPTA. Thus, the database is sufficient to comprehensively assess the genotoxicity of TMPTA. Based on the available data, it is concluded that although TMPTA is an in vitro clastogen at cytotoxic concentrations, no such activity is likely to occur under normal in vivo conditions because of the cellular protective mechanisms operating in an intact animal. Thus, TMPTA is concluded not to be genotoxic. Thus, a genotoxic mode of action in realtion to a carcinogenic potential can be excluded.

Justification for classification or non-classification

The only available valid study evaluating the carcinogenicity of TMPTA is the Cytec study (1982) in which no tumour increase was observed in mice after 80 weeks of exposure by dermal route. Based on this study, no classification for carcinogenicity is required for TMPTA according to the Regulation EC n°1272/2008.