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Assessment of the Toxicokinetic Behaviour

 

2-(phenylmethoxy)naphthalene (CAS-No. 613-62-7)

 

There were no studies available in which the toxicokinetic properties of 2-(phenylmethoxy)naphthalene were investigated.

 

2-(phenylmethoxy)naphthalene (molecular weight of 234.3 g/mol) is a fine white powder, which is almost insoluble in water (water solubility: 0.078 +/- 0.013 mg/L at 20 °C) and has a log Pow of 4.46 at 20 °C (Australian NICNAS file No. NA/272, 1999), indicating that a general accumulation of 2-(phenylmethoxy)naphthalene is possible.

 

Absorption

In an acute oral toxicity study, rats were administered 2000 mg 2-(phenylmethoxy)naphthalene per kg bw by gavage. No signs of systemic toxicity were observed (TNO-CIVO, 1990). Regarding the lipophilic character of the molecule, uptake via micellular solubilisation is considered as relevant mechanism rather than passive diffusion (ECHA GD 7c, 2008).

In an acute dermal toxicity study in rats, 2000 mg 2-(phenylmethoxy)naphthalene /kg bw did not cause any signs of systemic toxicity (TNO-CIVO, 1990). Additionally, since the water solubility is below 1 mg/L and the log Pow value is above 4 uptake into the stratum corneum will be high, but the rate of penetration may be limited by the rate of transfer between the stratum corneum and the epidermis (ECHA GD 7c, 2008). Taken together the experimental data and the considerations about the physical-chemical properties of the substance, dermal uptake of 2-(phenylmethoxy)naphthalene in humans is considered as limited.

2-(phenylmethoxy)naphthalene has a very low vapour pressure of < 0.01 Pa at 25°C (NICNAS, 1999); and the particle size is rather large (MMAD = 128 µm; 1.28% of the particles had a respirable size for alveoli (<= 10 µm; RCC, 2007). Therefore, human exposure via inhalation is considered as not relevant.

 

Metabolism

Potential metabolites were calculated by OECD toolbox 1.00. Here, the simulator tool for liver, GI tract and skin provided four potential metabolites of 2-(phenylmethoxy)naphthalene (smiles code cited below).

Studies on genotoxicity (Ames-Test, cytogenetic test in mammalian cells in-vitro, micronucleus assay in-vitro) gave no indications of a reactivity of 2-(phenylmethoxy)naphthalene or its metabolites under the test conditions (i.e. no increased mutagenicity or cytotoxicity in treatments with metabolic activation).

 

 

Excretion

The potential metabolites as well as the parent chemical have a molecular weight lower than 500 u. Therefore, 2-(phenylmethoxy)naphthalene and its metabolites are expected to be excreted predominantly via the urine; due to the lipophilic structure, biliary excretion is also possible especially fort he parent compound (ECHA GD 7c, 2008).

 

 

 

OECD Toolbox 1.00 (2010), potential liver metabolites following liver metabolism simulator (smiles codes):

c12c(cc(OCc3ccc(O)cc3)cc1)cccc2

c1(O)c(O)cc(COc2cc3c(cccc3)cc2)cc1

C1(=O)C(=O)C=C(COc2cc3c(cccc3)cc2)C=C1

c12c(cc(OCc3cc(O)ccc3)cc1)cccc2