Bis(2,4-di-tert-butyl-6-methylphenyl)ethyl phosphate

Endpoint summary

Additional information

There were no studies available in which the toxicokinetic properties of the test substance were investigated.

The test substance (molecular weight: 514.73 g/mol) is a white powder (Ciba-Geigy Ltd., 1982) with a log Pow = 11 (calculated, ACD/Labs software V11.02, BASF 2011), a water solubility of < 0.000021 g/L (Ciba-Geigy Ltd., 1993), and a vapour pressure of 0.000004 Pa at 25°C (Ciba-Geigy Ltd., 1992).

 

Absorption

Based on the physico-chemical properties, (very low water solubility and a log Pow of 11), the substance is not thought to be taken up by gastro-intestinal fluids very efficiently. In a subchronic capsule feeding study with dogs (Covance, 1999), the substance caused a functional adaption of the liver reflected in liver/gall bladder weight increases correlating with elevated alkaline phosphatase activity and centrilobular to diffuse hepatocellular hypertrophy (Ciba-Geigy, 1984). No other organs showed any effects up to the highest dose administered (1000 mg/kg). In a subchronic study with rats (C.I.T. 1994), the test substance did not cause any effects of toxicological relevance up to the highest dose tested (1000 mg/kg). The results from these two studies indicate a poor systemic availability of the test substance. In conclusion, the substance is not expected to be absorbed very well after oral administration. However, as indicated by the study performed in dogs, the substance has the potential to reach the liver at least partially, where it is probably eliminated as indicated by lack of toxic effects in both studies.

In an acute dermal toxicity study (Ciba-Geigy, 1992) and in a guinea pig maximization assay (Ciba-Geigy, 1993), no indications of systemic availability after dermal application were detected. Highly lipophilic substances that come into contact with the skin can readily penetrate the lipid rich stratum corneum but are not well absorbed systemically. Although they may persist in the stratum corneum, they will eventually be cleared as the stratum corneum is sloughed off. Furthermore, dermal uptake of chemicals with a molecular weight >500 is not favored (ECHA GD 7c, 2008). In conclusion, a dermal uptake of the test substance is expected to be low.

No reliable inhalation studies are available. However, given its very low vapor pressure and low water solubility, systemic availability after exposure to vapors or dust particle of the test substance is expected to be low.

Excretion

In view of the absence of relevant findings, it can be assumed that the test substance and its metabolites are rapidly excreted upon absorption after oral administration and liver passage. Since the test substance has a molecular weight larger than 500 g/mol and a low solubility in water, it is expected to be excreted predominantly via the faeces (ECHA GD 7c, 2008).