Isodecyl diphenyl phosphate

Endpoint summary

Additional information

No toxicokinetic studies are available. The available toxicity studies provide no or little information. Therefore the assessment is primarily based on physicochemical properties, supported by some toxicological indications.

 

Physical/chemical parameters

The physical/chemical properties that are of importance to assess the toxicokinetics behaviour of IDDPP are:

• Molecular weight - 390 g/mol
• Water solubility - 0.011 mg/L
• Log Kow - 6.11
• Vapour pressure - 66.5 Pa

 

Absorption

IDDPP is highly lipophilic (based on log Kow) and therefore oral/GI-absorption by passive diffusion is expected to be limited. If any absorption occurs, micellular solubilisation will be the major mechanism, also based on the low water solubility and moderate low molecular weight of 390 g/mol. In a 90-day repeated dose toxicity oral feeding study (Naylor, M.W., 1986), IDDPP was found to cause significant effects on several haematology parameters at the lowest dose level of 140 ppm. In the mid and high dose, effects were observed on liver-related clinical parameters, relative liver weight, and histopathology of the liver. This indicates that oral absorption has occurred. . Acute toxicity tests give no additional information.

 

The same absorption patterns are considered to be applicable for respiratory absorption, although exposure via this route is unlikely based on the low vapour pressure. However, information from toxicology studies via this route is available. In one respiratory exposure study (Younger Fred M., 1968) male rats died 3-4 days after an 6h exposure (nominal exposure 1.74 mg/L). This indicates that respiratory absorption has occurred, although it gives no indication of the amount of absorbed substance.

 

Because of its highly lipophilic character the dermal penetration of IDDPP into the stratum corneum will be high. However, because of its very low water solubility the rate of penetration from the stratum corneum into the epidermis is likely to be low and therefore dermal absorption is considered to be low.

 

Distribution, metabolism and excretion

There is no information about the distribution, metabolism, excretion, bioavailability and accumulation of IDDPP. Based on the physical chemical properties the substance is likely to be distributed into cells and to a lower extent into the extracellular spaces. Since its highly lipophilic character it is anticipated that it tends to be accumulated in adipose tissues and in lipophilic layers like the stratum corneum. In the 90-day repeated dose toxicity oral feeding study (Naylor, M.W., 1986), IDDPP was found to cause increased liver weights and hepatocellular hypertrophy/hyperplasia and hepatocellular brown pigment were seen this might indicate that IDDPP is metabolized in the liver.

 

Conclusion:

IDDPP can be absorbed after oral and respiratory exposure, but the amount of absorption cannot be predicted. Dermal absorption is considered to be very low, however, accumulation in the stratum corneum is possible. No information is available about the distribution, metabolism and excretion.