Octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate

Biodegradation in water: screening tests

Description of key information

Not readily biodegradable (according to OECD criteria); inherently biodegradable

Additional information

Based on the studies as presented in this chapter, octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate seems to be hydrolysed in a biotic process to benzenepropanoic acid, 3,5-bis(1,1-dimethylethyl)-4-hydroxy- (“Metilox acid” CAS: 20170-32-5) and 1-octadecanol (CAS: 112-92-5).

 

3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate reached a mineralisation of 32 % in 29 days in an OECD 301B–test (CO2-evolution, CIBA 1984). Another test, reports, that up to 47 % of the substance was degraded in 35 days in an OECD 302B –test (RL3, CIBA 1991).

 

CERI (1996) has also reported on a ready biodegradability test (OECD 301C). With 100 mg/l test concentration, 21-39 % mineralization was observed after 28 days (measured as BOD) and metilox acid was observed to be formed. Primary degradation was based on metilox acid formation 62-93 % of the parent substance concentration. 1-Octadecanol was not detected suggesting that it was further degraded.

 

A ready biodegradation test according to OECD 301A (DOC Die away) has been conducted by RCC Ltd. (2006). A test concentration of 0.1 mg/l and predominantly domestic sludge (final conc. 30 mg/l SS) were used and degradation was measured by means of monitoring the concentration of the parent compound and the anticipated degradation product metilox acid with LC-MS (LOQ = 0.003 mg/l for the parent compound, LOQ = 0.001 mg/ for metilox acid). Only the inoculum and procedure controls were followed by means of DOC. Acetone was used as solvent. Removal of the parent compound was 85 % in 10 days. Primary degradation was observed as Metilox acid was detected in the same samples analysed for the parent compound, and the concentrations increased from 0.005 mg/l on day 1 to mean concentrations between 0.024 mg/l and 0.037 mg/l on days 2 to 10. In the abiotic control, the concentration of the test item decreased by 47 % over the incubation period of 10 days. However, no quantifiable concentrations of metilox acid were found. Loss of the parent compound could therefore probably be attributed to sorption to the glass walls.

Fischer et al. (1999) investigated the degradation of 14C-octadecyl 3-(3,5-di-tert-butyl-4 -hydroxyphenyl)propionate (50 μg/L) after incubation for five days at 25°C with constant stirring by activated sludge. The overall mass balance was low at 76.9% based on the initial amount of 14C added. Ca. 0.1% of the applied radioactivity was recovered as CO2, 69.8% as extractable products and 7.0% as non-extractable products. The extractable products were found to contain around 10.5% of 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionic acid methyl ester, 7.7% unchanged octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate and 53.6% unknown products.

In conclusion, 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate is not readily biodegradable. However, significant biodegradation was observed under ready biodegradability conditions. Therefore the substance can be considered as inherently biodegradable.