7,7,9(or 7,9,9)-trimethyl-4,13-dioxo-3,14-dioxa-5,12-diazahexadecane-1,16-diyl bismethacrylate

Endpoint summary

Description of key information

In accordance with Annex VIII, Column 1, Item 8.8.1, of Regulation (EC) 1907/2006 and ‘Guidance on information requirements and chemical safety assessment Chapter R.7c: Endpoint specific guidance’ (ECHA, 2017), an assessment of the toxicokinetic behaviour of the test substance is conducted to the extent that can be derived from the relevant available information. This comprises a qualitative assessment of the available substance specific data on physicochemical properties.

The test substance reaction mass of 7,7,9-trimethyl-4,13-dioxo-3,14-dioxa-5,12-diazahexadecane-1,16-diylbismethacrylate and 7,9,9-trimethyl-4,13-dioxo-3,14-dioxa-5,12-diazahexadecane-1,16-diylbismethacrylate (CAS No. 72869-86-4) is expected to be hydrolysed within the human body. Only low absorption via the dermal route is expected. The smaller molecule size of the hydrolysis products generated in the gastrointestinal tract facilitates the absorption. Any fraction of the parent molecule that is absorbed will be hydrolysed mainly in the liver. The absorbed hydrolysis products are readily distributed throughout the organism, with limited distribution in adipose tissue. Most of the hydrolysis products are expected to be rapidly conjugated and excreted via the urine or enter oxidation pathways, while the metabolite methacrylate will primarily be metabolised via the propionic acid enzymatic pathway and ultimately excreted via the exhaled air as CO₂. No bioaccumulation will take place, as the parent molecule and metabolites do not have lipophilic groups.

Key value for chemical safety assessment

Bioaccumulation potential:

no bioaccumulation potential

Additional information

Basic toxicokinetics

There are no studies available in which the toxicokinetic behaviour of reaction mass of 7,7,9-trimethyl-4,13-dioxo-3,14-dioxa-5,12-diazahexadecane-1,16-diyl bismethacrylate and 7,9,9-trimethyl-4,13-dioxo-3,14-dioxa-5,12-diazahexadecane-1,16-diylbismethacrylate (CAS No. 72869-86-4) was investigated. In accordance with Annex VIII, Column 1, 8.8.1, of Regulation (EC) 1907/2006 and with ‘Guidance on information requirements and chemical safety assessment Chapter R.7c: Endpoint specific guidance’ (ECHA, 2017), an assessment of the toxicokinetic behaviour of the reaction mass of 7,7,9-trimethyl-4,13-dioxo-3,14-dioxa-5,12-diazahexadecane-1,16-diyl bismethacrylate and 7,9,9-trimethyl-4,13-dioxo-3,14-dioxa-5,12-diazahexadecane-1,16-diylbismethacrylate was conducted to the extent that can be derived from the relevant available information. This comprises a qualitative assessment of the available substance specific data on physico-chemical and toxicological properties according to Guidance on information requirements and chemical safety assessment Chapter R.7c: Endpoint specific guidance (ECHA, 2017).

 

Physico-chemical properties

Reaction mass of 7,7,9-trimethyl-4,13-dioxo-3,14-dioxa-5,12-diazahexadecane-1,16-diyl bismethacrylate and 7,9,9-trimethyl-4,13-dioxo-3,14-dioxa-5,12-diazahexadecane-1,16-diylbismethacrylate is a multiconstituent substance, with mainly 2 isomers (7,7,9-trimethyl-4,13-dioxo-3,14-dioxa-5,12-diazahexadecane-1,16-diyl bismethacrylate and 7,9,9-trimethyl-4,13-dioxo-3,14-dioxa-5,12-diazahexadecane-1,16-diyl bismethacrylate).The substance has the molecular weight 470.56 g/mol.

It is a liquid at 20 °C with a water solubility of 11.29 ± 0.256 mg/L at 20 °C. The log Pow is 3.39 and the vapour pressure was calculated (by extrapolation from higher temperatures) to be 2.32 x 10E-6 Pa at 20 °C. 

 

Absorption

Absorption is a function of the potential for a substance to diffuse across biological membranes. The most useful parameters providing information on this potential are the molecular weight, the octanol/water partition coefficient (log Pow) value and the water solubility. The log Pow value provides information on the relative solubility of the substance in water and lipids (ECHA, 2017).

 

Oral

In general, molecular weights below 500 and log Pow values between -1 and 4 are favourable for absorption via the gastrointestinal (GI) tract, provided that the substance is sufficiently water soluble (> 1 mg/L). Lipophilic compounds may be taken up by micellar solubilisation by bile salts, but this mechanism may be of particular importance for highly lipophilic compounds (log Pow > 4), in particular for those that are poorly soluble in water (≤ 1 mg/L) as these would otherwise be poorly absorbed (ECHA, 2017).

The physical state, log Pow and water solubility suggest the substance will be readily absorbed from the GI tract.

The available data on acute oral toxicity indicate the substance has low acute toxicity. However, since adverse effects were observed oral absorption might occur.

Two acute oral toxicity studies were performed with reaction mass of 7,7,9-trimethyl-4,13-dioxo-3,14-dioxa-5,12-diazahexadecane-1,16-diylbismethacrylate and 7,9,9-trimethyl-4,13-dioxo-3,14-dioxa-5,12-diazahexadecane-1,16-diylbismethacrylate. In the first, no mortality was observed in 5 male and 5 female rats administered 5000 mg/kg bw by gavage. 5/5 males and 5/5 females exhibited dyspnea on Day 1 until 5 h after dosing. Ruffled fur was observed in 5/5 males and 5/5 females 1 - 2 h after administration, and a curved body position was observed in 5/5 males and 5/5 females 1 - 3 h after dosing on Day 1. No clinical signs of toxicity were observed during the rest of the 14-day observation period, no effects on body weight were noted, and the gross necropsy showed no treatment-related macroscopic changes (Ullman, 1984). The LD50 value was > 5000 mg/kg bw. In the second acute oral toxicity study, 10 rats/sex were administered 20 mL/kg bw (equivalent to 22.24 g/kg bw, based on a density value of 1.112 g/mL) (Sterner, 1977). 1/10 males died on Day 7; during necropsy redness of the mucous membrane in the stomach and intestine was observed. A hard residue of the test substance was observed in the stomach. Slightly reduced activity and general response was noted 1 - 24 h after test substance administration in an unreported number of animals, in addition to increased abnormal gait 1 - 3 h after administration and piloerection until 24 h after dosing. Diarrhoea was observed in an undisclosed number of animals up to 7 days after test substance administration. The body weight of 1/10 females was reduced on Day 14, while the body weight gain of the remaining animals was within the expected range during the study period. None of the surviving rats showed any treatment-related effect during necropsy. 

Data of a subacute oral repeated dose toxicity study combined with a reproductive/developmental toxicity screening test indicate that oral absorption of the test substance might occur. The test substance was administered orally via gavage to male and female rats at doses of 0 (vehicle only), 100, 300 or 1000 mg/kg bw/day before and during mating as well as after mating (altogether 56 and 56, 57 or 64 days for males and females, respectively). Reversibility of any effects observed was assessed following a 14 day recovery period in additional animals of the control and high dose group. At the lowest dose (100 mg/kg bw/day) no treatment-related changes in any of the parameters were observed. An oral dose of 300 mg/kg bw/day induced pathological change in the liver of 1/12 male animal (pale liver) as well as hepatocellular change (hepatic lipidosis) in 3/12 male animals. At the highest dose pale liver as well as hepatic lipidosis was observed in males and females with high incidence. Therefore, oral absorption of the test substance is indicated.

The potential of a substance to be absorbed in the GI tract may be influenced by chemical changes taking place in GI fluids as a result of metabolism by GI flora, by enzymes released into the GI tract or by hydrolysis. These changes will alter the physicochemical characteristics of the substance and hence predictions based upon the physico-chemical characteristics of the parent substance may no longer apply or apply to a lesser extent (ECHA, 2017).

The ester bonds may be hydrolysed in the GI tract by esterases to form the corresponding alcohol and acid moieties. The rate of hydrolysis is unknown. The smaller molecules of the alcohol and acid moieties are likely to be absorbed faster than the parent molecule. 

In conclusion, based on the available information, reaction mass of 7,7,9-trimethyl-4,13-dioxo-3,14-dioxa-5,12-diazahexadecane-1,16-diylbismethacrylate and 7,9,9-trimethyl-4,13-dioxo-3,14-dioxa-5,12-diazahexadecane-1,16-diylbismethacrylateis predicted to undergo enzymatic hydrolysis in the GI tract and absorption of the hydrolysis products rather than (or in addition to) the parent substance is likely. The absorption rate of the hydrolysis products is expected to be high. Due to the limited information on the breakdown products of the target substance, as a worst-case approach the oral absorption potential is assumed to be high.  

Dermal

The dermal uptake of liquids and substances in solution is higher than that of dry particulates, since dry particulates need to dissolve into the surface moisture of the skin before uptake can begin. Molecular weights below 100 g/mol favour dermal uptake, while for those above 500 g/mol the molecule may be too large. Dermal uptake is anticipated to be low if the water solubility is < 1 mg/L; low to moderate if it is between 1-100 mg/L; and moderate to high if it is between 100-10000 mg/L. Log Pow values in the range of 1 to 4 (values between 2 and 3 are optimal) are favourable for dermal absorption, in particular if the water solubility is high. For substances with a log Pow above 4, the rate of penetration may be limited by the rate of transfer between the stratum corneum and the epidermis, but uptake into the stratum corneum will be high. Log Pow values above 6 reduce the uptake into the stratum corneum and decrease the rate of transfer from the stratum corneum to the epidermis, thus limiting dermal absorption (ECHA, 2017).

The test substance reaction mass of7,7,9-trimethyl-4,13-dioxo-3,14-dioxa-5,12-diazahexadecane-1,16-diylbismethacrylate and 7,9,9-trimethyl-4,13-dioxo-3,14-dioxa-5,12-diazahexadecane-1,16-diylbismethacrylate is moderately water soluble (11.29 ± 0.256 mg/L) indicating a moderate potential for dermal absorption. Furthermore, the log Pow is in the range indicating dermal absorption is likely to occur. The molecular weight of the test substance (470.56 g/mol) is on the border to be too large to be absorbed (ECHA, 2017).

The available data on acute dermal toxicity indicate the substance has low acute toxicity.

An acute dermal toxicity study was performed with reaction mass of 7,7,9-trimethyl-4,13-dioxo-3,14-dioxa-5,12-diazahexadecane-1,16-diylbismethacrylate and 7,9,9-trimethyl-4,13-dioxo-3,14-dioxa-5,12-diazahexadecane-1,16-diylbismethacrylate. No mortality and no clinical signs or signs of local irritation were observed in 5 male and 5 female rats treated with 2000 mg/kg bw under semi-occlusive conditions. No treatment-related effects on body weight or body weight gain were noted, and the gross necropsy showed no treatment-related macroscopic changes (Holalagoudar, 2016). The LD50 value was > 2000 mg/kg bw.

The dermal permeability coefficient (Kp) can be calculated from log Pow and molecular weight (MW) applying the following equation described in US EPA (2004):

log(Kp) = -2.80 + 0.66 log Pow – 0.0056 MW

QSAR calculations regarding the molecular weight, log Kow and water solubility, estimated the following dermal absorption rates (calculated with DERMWIN, v.2.01, 2011, modified considering the Fick´s first law): 6.34 × 10 ^-4cm/h. Considering the water solubility (0.0113 mg/cm³), the dermal flux is estimated to be 0.00716 µg/cm²/h. This indicates a very low dermal absorption potential.

If a substance shows skin irritating or corrosive properties, damage to the skin surface may enhance penetration. There is no in vivo data on the effects of acute or long-term dermal exposure to the test substance. The available skin irritation data on the test substance showed none or very mild skin irritating effects in the rabbit (Sterner, 1977; Ullmann, 1984). No skin irritating effects were noted in the skin sensitisation study (LLNA) performed on the mouse with the test substance (Vogel, 2009). Additionally, no signs of local effects were noted in the acute dermal toxicity study (Holalagoudar, 2016). Therefore, no enhanced penetration of the substance due to skin damage is expected.

The test substance reaction mass of 7,7,9-trimethyl-4,13-dioxo-3,14-dioxa-5,12-diazahexadecane-1,16-diylbismethacrylate and 7,9,9-trimethyl-4,13-dioxo-3,14-dioxa-5,12-diazahexadecane-1,16-diylbismethacrylatewas identified as a skin sensitiser, which shows that some uptake must have occurred, although it may only have been a small fraction of the applied dose.

 

Hydrolysis of the ester bonds may take place in the skin, although at a lower rate than via the oral route due to the lower amount of enzymes present in the skin. For the fraction of ester that is absorbed into the skin, the ester bond will be hydrolysed and the hydrolysis products may enter the blood circulation.

Taking all the available information into account, the dermal absorption potential of the test substance is considered to be low.

 

Inhalation

Reaction mass of7,7,9-trimethyl-4,13-dioxo-3,14-dioxa-5,12-diazahexadecane-1,16-diylbismethacrylate and 7,9,9-trimethyl-4,13-dioxo-3,14-dioxa-5,12-diazahexadecane-1,16-diylbismethacrylateis a liquid with low vapour pressure (2.32 x 10E-06 Pa at 20 °C), and therefore very low volatility. Consequently, under normal use and handling conditions, inhalation exposure and availability for respiratory absorption of the substance in the form of vapour, gases or mists is not significant (ECHA, 2017). However, the substance may be available for absorption after inhalation of aerosols, if the substance is sprayed (e.g. as a formulated product). In humans, particles with aerodynamic diameters below 100 μm have the potential to be inhaled. Particles with aerodynamic diameters below 50 μm may reach the thoracic region and those below 15 μm the alveolar region of the respiratory tract. Particles deposited in the nasopharyngeal/ thoracic region will mainly be cleared from the airways by the mucocilliary mechanism and swallowed. The log Pow and water solubility indicate that the target substance may be absorbed across the respiratory tract epithelium to a certain extent. However, the high molecular weight may have a limiting effect on the absorption rate. There is no experimental data on the effects of acute or long-term inhalation exposure to the target substance.

Due to the limited information available a worst case approach is applied, and absorption via inhalation is assumed to be as high as via the oral route.

Distribution and accumulation

Distribution of a compound within the body depends on the physico-chemical properties of the substance; especially the molecular weight, the lipophilic character and the water solubility. In general, the smaller the molecule, the wider is the distribution. If the molecule is lipophilic, it is likely to distribute into cells and the intracellular concentration may be higher than extracellular concentration, particularly in fatty tissues (ECHA, 2017).

The transient clinical signs observed in the acute oral toxicity studies indicate that the target substance is systemically available. The macroscopic examination during necropsy did not show any target organ for acute toxicity and no lasting effects were seen on any parameters.

As discussed under oral absorption, reaction mass 7,7,9-trimethyl-4,13-dioxo-3,14-dioxa-5,12-diazahexadecane-1,16-diylbismethacrylate and 7,9,9-trimethyl-4,13-dioxo-3,14-dioxa-5,12-diazahexadecane-1,16-diylbismethacrylateis expected to undergo enzymatic hydrolysis in the GI tract prior to absorption. After being absorbed, the hydrolysis products are expected to be widely distributed due to the relatively small size and the functional groups, which are characteristics that increase the water solubility. The substances absorbed from the GI tract will be transported via the portal vein to the liver, where further metabolism can take place. Substances that are absorbed through the pulmonary alveolar membrane or through the skin enter the systemic circulation directly before transport to the liver where metabolism will take place. The substances are not expected to accumulate in adipose tissue due to the lack of lipophilic groups. 

 

Metabolism

Reaction mass of 7,7,9-trimethyl-4,13-dioxo-3,14-dioxa-5,12-diazahexadecane-1,16-diylbismethacrylate and 7,9,9-trimethyl-4,13-dioxo-3,14-dioxa-5,12-diazahexadecane-1,16-diylbismethacrylate has functional groups that are suitable for undergoing phase I reactions. The ester bonds may be enzymatically hydrolysed by esterases. The hydrolysis products may be conjugated (e.g. glucuronidation) to form a polar molecule suitable for excretion or metabolism. The methacrylate group that may be derived by ester bond hydrolysis is expected to be rapidly metabolised, as literature shows that in rats administered methyl methacrylate, the substance will be metabolised to methacrylic acid, which in turn will rapidly be metabolised via the oxidation pathway of propionate catabolism to acetyl-CoA and CO₂ (Cosmetic Ingredient Review, 2005).

The potential metabolites following enzymatic metabolism of the test substance main isomers were predicted using the QSAR OECD toolbox (OECD, 2014). This QSAR tool predicts which metabolites of the test substance may result from enzymatic activity in the liver and in the skin, and by intestinal bacteria in the gastrointestinal tract. Two dermal metabolites and 20 hepatic metabolites were predicted for each of the main components. The metabolites are mainly the result of hydrolysis of the ester bonds and of a hydroxyl group being added to, or substituted with, a methyl group, and furthermore the hydrolysis of the amino bond. In general, the hydroxyl groups make the substances more water-soluble and susceptible to metabolism by phase II-enzymes. The smaller molecules resulting from hydrolysis of the ester bond are also expected to have higher water solubility. The metabolites formed in the skin are relatively few, compared with the liver, due to the lower level of enzymes in the skin. The skin metabolites and any absorbed parent substance will enter the blood circulation and have the same fate as the hepatic metabolites. Up to 98 metabolites were predicted to result from microbiological metabolism. The high number includes many minor variations in the c-chain length and number of carbonyl- and hydroxyl groups; reflecting the many microbial enzymes identified. Not all of these reactions are expected to take place in the human GI-tract.

It is unclear whether reaction mass of7,7,9-trimethyl-4,13-dioxo-3,14-dioxa-5,12-diazahexadecane-1,16-diylbismethacrylate and 7,9,9-trimethyl-4,13-dioxo-3,14-dioxa-5,12-diazahexadecane-1,16-diylbismethacrylatehas mutagenic activity. The Ames test was negative, with and without metabolic activation (Paulus, 2009). The result of an in vitro HPRT test performed in mammalian cells (Chinese hamster lung fibroblasts) without metabolic activation was likewise negative (Schweikl, 2001). The result of an in vitro micronucleus test in mammalian cells (Chinese hamster lung fibroblasts) was ambiguous, as slightly increased numbers of micronuclei were reported at cytotoxic concentration levels (>= 24 µg/mL), without metabolic activation (Schweikl, 2001). No experiment was performed with metabolic activation. The result may indicate the target substance is cytogenic.

 

Excretion

The hydrolysis products of reaction mass of 7,7,9-trimethyl-4,13-dioxo-3,14-dioxa-5,12-diazahexadecane-1,16-diylbismethacrylate and 7,9,9-trimethyl-4,13-dioxo-3,14-dioxa-5,12-diazahexadecane-1,16-diylbismethacrylatewillbe conjugated with e.g. glutathione to form more water-soluble molecules and excreted via the urine or metabolised. The metabolite methacrylate will primarily be excreted via the exhaled air as CO₂.

The fraction of the target substance that is not absorbed in the GI tract will be excreted via the faeces. If microbial metabolism occurs (as predicted in the OECD QSAR Toolbox, see above under ‘Metabolism’), then the smaller metabolites may be absorbed; thereby entering the systemic circulation. The metabolites are expected to be conjugated as described above and excreted via the urine.

A detailed reference list is provided in the technical dossier (see IUCLID, section 13).

References

ECHA (2017). Guidance on information requirements and chemical safety assessment, Chapter R.7c: Endpoint specific guidance. Version 2.0.

Cosmetic Ingredient Review. Final Report of the Safety Assessment of Methacrylic Acid, International Journal of Toxicology, 24(Suppl 5):33-51, 2005

OECD (2014). (Q)SAR Toolbox v3.3. Developed by Laboratory of Mathematical Chemistry, Bulgaria for the Organisation for Economic Co-operation and Development (OECD). Prediction performed 21 June 2016.http://toolbox.oasis-lmc.org/?section=overview

US EPA (2014).Estimation Programs Interface Suite™ for Microsoft® Windows, v 4.11. United States Environmental Protection Agency, Washington, DC, USA.Downloaded from: http://www.epa.gov/oppt/exposure/pubs/episuite.htm