Triisobutyl phosphate

Endpoint summary

Key value for chemical safety assessment

Bioaccumulation potential:

no bioaccumulation potential

Additional information

Since no toxicokinetic studies are available for Triisobutyl phosphate the following assessment is based on the available physicochemical properties and results from other toxicological studies.

 

The substance is a colourless to yellowish liquid with characteristic odour and with a molecular weight of 266.31 g/mol. The calculated log Pow value is 3.7 at 25°C and the calculated solubility in water is 265 mg/L at 25°C. In case of low molecular weight substances (MW < 500 g/mol) the substance may pass through aqueous pores or be carried through the epithelial barrier by the bulk passage of water. Moderate log P values (between -1 and 4) are also favourable for absorption by passive diffusion. It is thus expected that the substance will be readily absorbed by the gastrointestinal tract. In the available 13-week rat feeding study clinical pathological changes (decrease in neutrophil counts, increase in cholesterol) suggest availability by the oral route (Monsanto, 1990).

Generally, moderate log P values (between -1 and 4) are favourable for absorption directly across the respiratory tract epithelium by passive diffusion. Signs of systemic toxicity were observed in the available oral toxicity study (Monsanto, 1990), so it is likely that the substance will also be absorbed if it is inhaled. The available experimental data concerning the respiratory hazard of Triisobutyl phosphate showed clinical signs suggestive of systemic availability. Overall it is therefore expected that the substance will be readily absorbed by inhalation.

The water solubility, between 100-10000 mg/L, suggests that dermal uptake is likely to be moderate to high. The Log P between 1 and 4 and the physical state (liquid) favour dermal absorption. Based on the available data the substance has been identified as a skin sensitizer, so some uptake must have occurred (BASF, 1989).

According to the route-specific information a ratio of 1 for oral to dermal absorption is provisionally suggested for the risk assessment of the substance.

Based on the partition coefficient the test substance is unlikely to bioaccumulate with the repeated intermittent exposure patterns normally encountered in the workplace but may accumulate if exposures are continuous. In the available repeated dose toxicity study alterations of clinical pathological parameters were observed, suggesting distribution of the substance (and/or its metabolites) (Monsanto, 1990). The results from several in vitro genotoxity studies with and without metabolic activation suggest that no genotoxic metabolite was formed after the addition of rat liver S9 mix (BASF, 1990; CCR, 1992; Monsanto, 1992; Harlan 2012).