1,2,4-Benzenetricarboxylic acid, mixed lauryl and octyl triesters

Endpoint summary

Description of key information

Biodegradation in water: screening tests

Two key studies for 1,2,4-Benzenetricarboxylic acid, mixed dodecyl and octyl triesters are reported for biodegradation:

The study from Chen Xiaoqian (2015 ) reports that 1,2,4-Benzenetricarboxylic acid, mixed dodecyl and octyl triesters was not readily biodegradable under the present test conditions.

 

The study from Zhang Jingji (2015) report that 1,2,4-Benzenetricarboxylic acid, mixed dodecyl and octyl triesters was primarily biodegradable, but not ultimately biodegradable. Therefore, the test substance was inherently biodegradable according the OECD definition.

Biodegradation in water, sediment and soil simulation tests

Simulation studies are not required due to the fact microbial pathways exist for the degradation of 1,2,4-Benzenetricarboxylic acid, mixed dodecyl and octyl triesters, the degradation of substance will be limited due to limited bioavailability.  Biodegradation Pathway  A microbial pathway (ester hydrolysis) does exist in nature for degradation of esters (Otton et al., 2008).  According to the trimellitate category test plan for the US EPAs HPV Chemical Challenge Program, the degradation of the trimellitates is expected to precede through the step-wise hydrolysis of the ester groups to free alcohols and mellitic acid (ExxonMobil Biomedical Sciences, 2001). Further, the test plan states that these metabolites are known to rapidly degrade and not persist.  Evidence of the biodegradation potential for  1,2,4-Benzenetricarboxylic acid, mixed dodecyl and octyl triesters, can be observed with the results from two OECD 301B ready biodegradability studies of the structural related substance 1,2,4-Benzenetricarboxylic acid, mixed decyl and octyl triesters .  In both studies there is an extended time lag (14 to 24 days) before biodegradation begins to occur.  However, once biodegradation is initiated, the substance is significantly degraded (>70%) within 48 days.  Limited Bioavailablity  1,2,4-Benzenetricarboxylic acid, mixed dodecyl and octyl triesters is an extremely hydrophobic substance that will have limited bioavailability to microorganisms living in soil.  The limited bioavailability of the substance will also limit the amount of biodegradation that can occur in the soil.  The measured log Koc value of the structural related substance 1,2,4-Benzenetricarboxylic acid, mixed dodecyl and octyl triesters was greater than 5.67 (the log Koc of the most hydrophobic standard).  Using the KOCWIN Program v2.00 embedded in the US EPAs EPI Suite software (EPIWEB 4.0), the calculated log Koc values for 1,2,4-Benzenetricarboxylic acid, mixed dodecyl and octyl triesters ranged from 8.4 (estimated from the log Pow) to 8.98 (estimated from MCI).  The equivalent calculated Koc values were 260600000 L/kg to 9470000000 L/kg.  Based on these results, 1,2,4-Benzenetricarboxylic acid, mixed decyl and octyl triesters is expected to be immobile in soil (Koc >5000, classification according to McCall et al., 1980).  Conclusion  The data requirement for further biodegradation studies is waived based on the weight of evidence supporting the conclusion that, while pathways exist for the degradation of 1,2,4-Benzenetricarboxylic acid, mixed decyl and octyl triesters, the degradation of substance will be limited due to limited bioavailability.