4,4'-oxydianiline

Endpoint summary

Description of key information

4,4’-ODA in not readily biodegradable (7.6 % biodegradation in a 28-day study closed bottle test).

Experimental studies on hydrolytic effects demonstrated that the substance is hydrolytically stable at neutral and alkaline pH, but hydrolyses fairly rapidly under acidic conditions (pH 4) and such effects are increased at raised temperatures. However, such conditions are unlikely to be found within the environment.

4,4’-ODA has a measured log Pow of 0.72. Bioaccumulation in the food chain is not anticipated. This is supported bythe use of the US EPA EPIWIN programme BCFBAF v 3.00, which provides a predicted BCF value of 2.763 – 3.667L/kg by calculation.  

A screening organic carbon-water partitioning coefficient (Koc) shows a log Koc value of1.66 at 25 °C with Koc of 45 L/kg. As such, adsorption to soil is deemed to be low.

Additional information

The test substance, 4,4’-ODA, is a solid under all environmental conditions and only sparingly soluble in water. It has a low volatility (based on a vapour pressure result of 0.09 kPa at 20 °C). As such, any environmental release will result in virtually all of the substance compartmentalising into soil and water compartments, with little release directly to atmosphere.

 

Any potential exposure to the environment would result in rapid redistribution from soil and waterdue to its volatility and low adsorption to soil (based on the soil adsorption study, discussed below). This is supported by a Level III fugacity model in the US EPA EPISUITE (Mackay,) whichassumes steady-state but not equilibrium conditions.  The Level III model in EPI Suite predicts partitioning between air, soil, sediment and water using a combination of default parameters and various input parameters . This model has beenused to calculate the theoretical distribution of 4,4’-ODA between four environmental compartments (air, water, soil, sediment) at steady state in a unit world. Partitioning is detailed to be:

 

Air                         0.523 %

Water                   30.1 %

Soil                       68.6 %

Sediment             0.743 %

 

It should be noted that although the majority of the substance distributes to the soil compartment; due to the low soil adsorption profile, the substance is predicted not to remain within this compartment. Instead, removal will occur, possibly via dilution to soil pore water over a period of time.

 

4,4’-ODA displays a low ready biodegradability in that it achieved 7.6 % biodegradation in a 28-day study closed bottle test, indicating that it is unlikely to achieve a half life of less than 40 or 60 days within fresh water.

 

4,4’-ODA is not expected to hydrolyse under normal environmental conditions.  Experimental studies on hydrolytic effects demonstrated that the substance is hydrolytically stable at neutral and alkaline pH, but hydrolyses fairly rapidly under acidic conditions (pH 4) and such effects are increased at raised temperatures. However, such conditions are unlikely to be found within the environment, detailing that hydrolysis under environmental conditions is not anticipated. Studies on direct phototransformation in water are not available but it is assumed on the basis of chemical structure that the substance is not degraded by direct photolysis. It is concluded, therefore, that abiotic processes do not contribute significantly to the depletion of the substance in the aquatic environment.

 

4,4’-ODA has a measured log Pow of 0.72. This value indicates that possible bioaccumulation in the food chain is not anticipated. This is supported bythe use of the US EPA EPIWIN programme BCFBAF v 3.00, which provides a predicted BCF value of 2.763 – 3.667L/kg by calculation. This, in conjunction with the low Log Pow indicates that bioaccumulation will not occur. 

 

A screening organic carbon-water partitioning coefficient (Koc) is available for the substance, using a HPLC Estimation method. This resulted on a log Koc value of 1.66 at 25 °C with Koc of 45L/kg. As such, adsorption to soil is deemed to be low, based on this study assessment.

 

Based on its limited water solubility, biodegradability and lack of hydrolysis under environmental conditions, it can be concluded that 4,4’-ODA could potentially be persistent within the environment. However, significant contact with the organisms in the food chain can considered to be negligible. This is based on the fact that the substance is not anticipated to be bioaccumulative, based on calculated BCF values and actual log Pow values. 

4,4’-ODA also demonstrates lack of absorption and relatively rapid excretion of metabolites in mammalian studies. Finally, the substance is hydrolytically unstable at acidic pH’s, hence is unlikely to exist within the digestive systems of organisms for a significant length of time.

 

The above is reported for the “neat” test substance and is included for information purposes only. The substance is imported into the EU only in a polymerised form, and hence exposure to the “neat” form is not anticipated.