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Administrative data

Link to relevant study record(s)

Description of key information

No studies are available. The molecular weight, physicochemical properties incl. water solubility and octanol-water partition coefficient of the substance suggest that oral, inhalative and dermal absorption occur. Widely distribution within the water compartment of the body after systemic absorption is because of lipophilicity of the test substance not expected. However, the distribution into cells particularly in fatty tissues is likely. Based on its log Pow the test substance is not considered to accumulate. The test substance might be metabolised after absorption. Excretion predominantly via the urine is expected.

Key value for chemical safety assessment

Bioaccumulation potential:
no bioaccumulation potential
Absorption rate - oral (%):
50
Absorption rate - dermal (%):
50
Absorption rate - inhalation (%):
100

Additional information

In accordance with Annex VIII, Column 1, Item 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, 2014), assessment of the toxicokinetic behaviour of the substance is conducted to the extent that can be derived from the relevant available information on physicochemical and toxicological characteristics. There are no studies available evaluating the toxicokinetic properties of the substance.

The test substance is a clear colourless liquid at 20°C with a molecular weight of 166.22 g/mol and a water solubility of 3.9 g/L at 20°C. The substance has a vapour pressure of 2.24 hPa at 20°C and the log Pow is 2.23 at 24.7°C.

 

Absorption

The major routes by which the test substance can enter the body are via the lung, the gastrointestinal tract, and the skin. To be absorbed, test substances must transverse across biological membranes either by active transport mechanisms or - as being the case for most compounds - by passive diffusion. The latter is dependent on compound properties such as molecular weight, lipophilicity, or water solubility (ECHA, 2014).

 

Oral

In general, low molecular weight (MW ≤ 500) and moderate lipophilicity (log Pow values of -1 to 4) are favourable for membrane penetration and thus absorption. The molecular weight of the test substance is relatively low with 166.22 g/mol, favouring oral absorption of the compound. This is supported by the determined log Pow values of 2.23, being advantageous for oral absorption. In addition the water solubility of 3.9 g/L leading to a ready dissolving of the compound in the gastrointestinal fluids favours oral absorption. Moreover, the observation of systemic toxicity following exposure by any route is an indication for substance absorption; however, this will not provide any quantitative information.

In an acute oral toxicity study conducted with the test substance in rats no mortalities were observed at 2000 mg/kg bw until the end of the study but slight signs of toxicity noted were abnormal gait. No abnormalities were noted at necropsy at termination of the study. In this acute oral toxicity study in rats a LD50 cut-off value of ≥ 5000 mg/kg bw was found.

Additionally, a repeated-dose oral toxicity study in rats was conducted with the test substance (2017). In a dose range-finding study, animals were treated at doses of 50, 200 and 800 mg/kg bw/day for 14 days. At 800 mg/kg bw/day salivation and soiled perineal region were observed and necropsy revealed increased liver weights in males and females. In the main study, animals were administered the test substance at dose levels of 60, 200 and 600 mg/kg bw/day. No substance- related mortality was observed within the study period. Increased liver weights in males at 600 mg/kg bw/day and in females at 200 and 600 mg/kg bw/day were noted. Hepatocellular hypertrophy was observed in animals of both sexes at 200 and 600 mg/kg bw/day. This effect was regarded as an adaptive response to the test substance and was considered not to be harmful to the animals. Based on available data from the acute oral and repeated dose toxicity study, slight toxicological signs and adaptive responses to the test substance were observed and thus absorption of the test substance via the gastrointestinal tract has evidently occurred.

 

Dermal

The dermal uptake of liquids and substances in solution is generally expected to be higher than that of dry particles. Molecular weights below 100 g/mol favour dermal uptake, while for those above 500 g/mol the molecule may be too large. Thus, for the molecular weight level of the test substance dermal uptake can be expected to be moderate. The Log Pow value of the test substance is optimal for dermal absorption. In addition, the water solubility is sufficiently high for partitioning from the stratum corneum into the epidermis indicating dermal uptake. The dermal permeability constant Kp of the substance was estimated to be 0.00555 cm/h using DermwinTM (v.2.01) and taking into account an estimated log Pow of 2.23 and the molecular weight of 166.22 g/mol. Thus the absorption of the test substance by the dermal route is anticipated to be moderate to high and comparable to oral absorption at most.

Data from an acute dermal toxicity study revealed no effects of the test substance up to the limit dose of 2000 mg/kg bw (2015).

 

Inhalation

Moderate log Pow values (between -1 and 4) are favourable for absorption directly across the respiratory tract epithelium by passive diffusion. The test substance has a vapour pressure of 2.24 hPa at 20 °C and therefore its volatility is considered low (< 500 Pa). Thus, under normal use and handling conditions, inhalation exposure and availability for respiratory absorption of the substance in the form of vapour can be considered low.

 

Distribution and Accumulation

No data are available regarding distribution. Distribution of a compound within the body depends on the physicochemical 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 (log Pow > 0), it is likely to distribute into cells and the intracellular concentration may be higher than extracellular concentration particularly in fatty tissues (ECHA, 2014).

Thus, due to the small molecular weight (166.22 g/mol) and a moderately lipophilic character (log Pow 2.23) distribution into cells and the intracellular concentration may be higher than the extracellular concentration particular in fatty tissues, if the substance is absorbed systemically. Substances with log Pow values of 3 or less would be unlikely to accumulate with the repeated intermittent exposure patterns normally encountered in the workplace but may accumulate if exposures are continuous.

 

Metabolism

No metabolism studies are available with the test substance itself. Prediction of compound metabolism based on physicochemical data is very difficult. Structure information gives some but no certain clue on reactions occurring in vivo. The potential metabolites following enzymatic metabolism were predicted using the QSAR OECD toolbox (v3.4, OECD, 2016). This QSAR tool predicts which metabolites may result from enzymatic activity in the liver and in the skin, and by intestinal bacteria in the gastrointestinal tract. 8 hepatic and 3 dermal metabolites were predicted for the test substance, respectively. Primarily, hydrolysis of the substance may occur in the liver. In general, the introduction of hydroxyl groups by hepatic phase I-metabolism leads to higher water solubility and makes the substances more susceptible to metabolism by phase II-enzymes. Up to 64 metabolites were predicted to result from all kinds of microbiological metabolism for the test substance. Most of the metabolites were found to be a consequence of the degradation of the molecule. There was no evidence for differences in genotoxic potencies due to metabolic changes in in vitro genotoxicity tests. The test substance did not induce gene mutations in the Ames test (King, 1999 and 2001) and at the HPRT locus in V79 cells with and without metabolic activation and did not induce micronuclei in human lymphocytes with and without metabolic activation (King, 2002 and Sokolowski, 2015).

 

Excretion

Only limited conclusions on excretion of a compound can be drawn based on physicochemical data. Due to metabolic changes, the finally excreted compound may have few or none of the physicochemical properties of the parent compound. In addition, conjugation of the substance may lead to very different molecular weights of the final product. The molecular weight (< 300 g/mol) and the water solubility of the molecule are properties favouring excretion via urine. Thus the test substance is expected to be excreted predominantly via the urine.

 

 

References

ECHA (2014): Guidance on information requirements and chemical safety assessment – Chapter 7c: Endpoint specific guidance. European Chemicals Agency, HelsinkiLiterature