2-ethylhexyl 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 information.

 

Physical and chemical properties

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

• Molecular weight – 192 g/mol
• Water solubility – 0.052 mg/L
• Log Kow – 5.87
• Vapour pressure – 26.6 Pa

 

Absorption

2EHDPP 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 for absorption, also based on the low water solubility and low molecular weight. In a Range Finding Acute Oral Toxicity study at autopsy there were haemorrhagic areas of the liver, lungs, and kidneys, and intestinal inflammation found (Birch, Melvin D., 1969). This indicates that oral absorption has occurred. Acute toxicity tests give little 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. Based on acute inhalation toxicity study an LC50 of 2.1 mg/L (6hr) has established, indicating that 2EHDPP is classified as harmful by inhalation. This confirms that respiratory absorption of the substance has occurred and might be the main exposure route.

 

Because of its highly lipophilic character the dermal penetration of 2EHDPP 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 elimination

There is no information about the distribution, metabolism, excretion, bioavailability and accumulation of 2EHDPP. 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 stratum corneum.

No specific target organ has been identified. The effects of repeated exposure to 2EHDPP are investigated in two studies. Both studies report hypertrophy of the liver as key finding. Brain and adrenal weight was significantly increased for the high dose males, showing a dose-related response. Kidney, testes and caecum (empty) weight was significantly increased for the mid and high dose group, also indicating a dose-related response. This was also seen for the liver, but here all treated males had a significantly increased weight.

 

Conclusion:

2EHDPP can be absorbed after oral exposure, but respiratory exposure might be the main exposure route. The amount of absorption cannot be predicted. Dermal absorption is considered to be very low. No information is available about the distribution, metabolism and excretion.