Diisotridecyl adipate

Endpoint summary

Additional information

Stability

 

Hydrolysis

Tests need not be conducted, as diisotridecyl adipate is highly insoluble in water (see Sect. 4.8) (Annex VIII, Nr 9.2.2.1.)

In addition using the calculation program US EPA EPI Suite v4.00, the half-life of diisotridecyl adipate at 25°C and under neutral conditions was estimation to be 4.6 years.

 

Biodegradation

Biodegradation in water: screening tests

The test substance diisotridecyl adipate was demonstrated to be readily biodegradable in three OECD guideline 301-tests.

An OECD 301F-study (Flach, 2014, key study) (guideline suitable for poorly soluble and volatile substances) with the test substance has been conducted, showing that DITA is readily biodegradable (69 % biodegradation based on ThOD after 28 days). The inoculum used in this study was neither adapted, nor pre-exposed (confirmation of the test institute attached). Two more studies (OECD 301B) are available, showing that DITA is readily biodegradable. In the first OECD 301B study, 81 % biodegradation were achieved within 28 d, fulfilling the 10d-window criterion (although not required for an UVCB). A second OECD 301B-test resulted in a biodegradation extent of 69.6 % after 28 days. The other studies reported for DITA clearly indicate the ready biodegradability of the substance, by almost reaching the 60% biodegradation threshold. In the respective study according to OECD guideline 301B, a biodegradation of 56.6% within 28 days was obtained with DITA. Similar biodegradation was found in the other 301F study (58.53% biodegradation within 28 days). Supporting all these findings, the read-across substance diisotridecyl dodecanedioate was found readily biodegradable in an OECD 301B-test.

Biodegradation in water and sediment: simulation tests

In accordance with column 2 of REACH Annex IX Nr 9.2.1.2, the study does not need to be conducted as the substance is regarded as readily biodegradable and to be highly insoluble in water (see Sect. 4.8). DITA is readily biodegradable and therefore a sediment simulation test is not required. The available studies on the biodegradation behavior of DITA, particularly the key study of Flach (2014), clearly show that the substance fulfills the criteria for Ready biodegradability. The inoculum used in these studies was neither adapted, nor pre-exposed. This also applies to the latest OECD 301F study with DITA (Flach, 2014) and was confirmed by the respective test institute (please see attachment: " issue2_OECD301FcommentsInoculum_diisotridecyladipate __studyno892. pdf"). Based on the data, direct and indirect sediment deposition is unlikely.

 

Biodegradation in soil

In accordance with column 2 of REACH Annex IX Nr 9.2.1.2, the study does not need to be conducted as the substance is regarded as readily biodegradable. DITA is readily biodegradable and therefore a soil simulation test is not required. The available studies on the biodegradation behavior of DITA, particularly the key study of Flach (2014), clearly show that the substance fulfills the criteria for Ready biodegradability. The inoculum used in these studies was neither adapted, nor pre-exposed. This also applies to the latest OECD 301F study with DITA (Flach, 2014) and was confirmed by the respective test institute (please see attachment: " issue2_OECD301FcommentsInoculum_diisotridecyladipate __studyno892. pdf"). It is expected that direct and indirect soil exposition is unlikely.

 

Bioaccumulation

 

Bioaccumulation: aquatic/sediment

The log BCF of diisotridecyl adipate (log Pow = 13.03) was estimated to be 1.17 (BCF 14.8) using the program US EPA EPI Suite v4.00. In addition, a log BAF (upper trophic) of -0.008 (BAF = 0.982) was calculated using the method of Arnot-Gobas. The low BCF/BAF values indicate a low potential of diisotridecyl adipate for bioaccumulation in aquatic organisms (MWC, 2010).

 

Transport and Distribution

 

Adsorption/Desorption

Based on a calculated log Koc of 7.08 (MCI method) or 8.00 (log Kow method) diisotridecyl adipate is expected to have a high potential for accumulation in soil and sediment (MWC, 2010).

 

As additional information, the Koc of butyric acid was estimated to be 45.5 at pH 7 (log Koc = 1.66) (OXEA, 2010) indicating high mobility in soil.

 

Henrys Law constant

The Henry's law constant (HLC) of diisotridecyl adipate at 25°C was estimated by calculation methods (program US EPA EPI Suite v4.00) (MWC 2010).

Bond contribution method: HLC (25°C) = 89.9 Pa*m3/mol

Group contribution method: HLC (25°C) = 68.3 Pa*m3/mol

Diisotridecyl adipate will volatilize from water.

 

Distribution modelling

Estimates obtained from Level III fugacity distribution modeling using US EPA EPI Suite v4.00, indicate that emissions of diisotridecyl adipate will distribute mostly in soil (84.9%) and to a lesser extend in water (14.8%). The fractions in air (0.28%) and in sediment (0.02%) are minimal. The estimated persistence time is 1310 hr (ca. 55 days) (MWC 2010).

 

Other distribution data

Volatilization from Water

Using the calculated Henry's Law Constant (HLC) of 8.89 Pa*m³/mol at 25 °C, diisotridecyl adipate volatilization half-lifes from a model river and a model lake were estimated to 4.3 and 236 hours (ca. 0.2 and 10 days), respectively (MWC 2010).