2,2'-(2-methylpropylidene)bis[4,6-xylenol]

Endpoint summary

Description of key information

Oral

In the acute oral toxicity study and the repeated dose toxicity study there were treatment-related effects noted that resulted in classification for exposure via this route. This implies that the substance is absorbed following oral ingestion, and hence oral availability of the substances is relatively high. The test substance has water solubility of 0.203 mg/L at 20 °C and a log Kow value 5.60. The absorption of highly lipophilic substances (log Kow ≥ 4) may be limited by the inability of such substances to dissolve in gastrointestinal fluids and therefore make contact with the mucosal surface. However, the absorption of such substances will be increased if they undergo micellular solubilisation by bile salts. As a worst case, for risk assessment purposes the oral absorption of the test substance is set at 100%.

Dermal

The results of the acute dermal toxicity study with the test substance and the skin irritation and skin sensitisation studies with provide no evidence to support significant skin absorption or subsequent retention.

The log Kow value of the test substance 5.60 therefore the dermal absorption of the substance is expected to be limited based on the high log Kow value. At log Kow values 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.. Maximum dermal absorption is often associated with values of log Kow between +1 and +2 (ECETOC (European Centre for Ecotoxicology and Toxicology of Chemicals). Monograph No, 20; Percutaneous absorption. August 1993). In addition, the substance must be sufficiently soluble in water to partition from the stratum corneum into the epidermis. The test substance has an estimated water solubility of 0.203 mg/L at 20 °C therefore dermal uptake is likely to be low. In conclusion, dermal absorption of the substance is expected to be low. In addition, the relatively large molecular weight is approaching the value where absorption in precluded. In the absence of significant absorption, for risk assessment purposes the dermal absorption of the test substance is set at 10%.

Inhalation

The substance has a low vapour pressure (2.5 x 10 E-6 Pa at 20°C) therefore a significant inhalation exposure to vapours is not expected. The substance has a relatively high percentage of small particulates (62.13% < 10.00 μm) and hence is potentially respirable; however exposure to such dusts is strictly controlled at the site of manufacture. Moderate log Kow values (between -1 and 4) are favourable for absorption directly across the respiratory tract epithelium by passive diffusion. The test substance has a high log Kow value (5.60) therefore it may be taken up by micellular solubilisation particularly as the substance is poorly soluble in water (0.203 mg/L at 20 °C). As a worst case, for risk assessment purposes the inhalation absorption of the test substance is set at 100%.

Key value for chemical safety assessment

Bioaccumulation potential:

low bioaccumulation potential

Absorption rate - oral (%):

100

Absorption rate - dermal (%):

10

Absorption rate - inhalation (%):

100