Hexadecyl acetate

Biodegradation in water: screening tests

Description of key information

The test item attained 73 % biodegradation after 14 days in the key study and satisifed the 10 -day window validation criterion whereby 60 % biodegradation must be attained within 10 days of the biodegradation exceeding 10 % (OECD 301 F).

Key value for chemical safety assessment

Biodegradation in water:

readily biodegradable

Additional information

METHODOLOGY

Low water solubility of the test item (< 1.14E-05 g/L of solution at 20.0 ± 0.5 °C) combined with low vapour pressure (4.8E-03 Pa at 25 °C) results in a high value for the Henry's Law constant. This was relevant with respect to air bubbles passed through the jars during investigation of ready biodegradation using OECD Guideline 301 B because the test item partitions to air even though vapour pressure is low. Expert advice was therefore accepted and investigation of ready biodegradation was undertaken in accordance with OECD Guideline 301 F and reported as the key study

KEY STUDY

The study was performed to assess the ready biodegradability of the test item in an aerobic aqueous media. The method followed was designed to be compatible with the OECD Guidelines for Testing of Chemicals (1992) No. 301 F "Ready Biodegradability; Manometric Respirometry Test" referenced as Method C.4 -D of Commission Regulation (EC) No. 440/2008 and US EPA Fate, Transport and Transformation Test Guidelines OCSPP 835.3110 (Paragraph (q)).

 

METHODS

 

The test item at a concentration of 20 mg/L was exposed to sewage treatment microorganisms with mineral medium in sealed culture vessels in diffuse light at temperatures between 22 and 23 °C for 14 days. The study was terminated after 14 days with the sponsor's approval as degradation of the test item had reached a plateau for at least three determinations and hence the test item could be considered to be readily biodegradable.

 

Following the recommendations of the International Standards Organisation (ISO 1995), the test item was dissolved in an auxiliary solvent prior to being absorbed onto a filter paper and subsequent dispersal in test media. High shear mixing was also applied to break up the filter paper containing the test item. Using this method the test item was evenly distributed throughout the test medium and the surface area of test item exposed to the test organisms was increased thereby increasing the potential for biodegradation.

 

Biodegradation of the test item was assessed by measurement of daily oxygen consumption values on Days 0 to 14. Control solutions with inoculum and reference item (aniline) together with a toxicity control were used for validation purposes.

 

RESULTS

 

The test item attained 73 % biodegradation after 14 days and satisfied the 10 -day window validation criterion whereby 60 % biodegradation must be attained within 10 days of the biodegradation exceeding 10 %.

 

CONCLUSION

 

The test item can be considered to be readily biodegradable under the strict terms and conditions of OECD Guideline No 301 F.

SUPPORTING STUDY

GUIDELINE

A study was performed to assess the ready biodegradability of the test item in an aerobic aqueous medium. The method was designed to be compatible with OECD Guidelines for Testing of Chemicals (1992) No 301B "Ready Biodegradability; CO2 Evolution Test" referenced as Method C.4 -C of Commission Regulation (EC) No 440/2008 and US EPA Fate, Transport, and Transformation Test Guidelines OCSPP 835.3110 (Paragraph m).

METHOD

The test item at a concentration of 10 mg carbon/L was exposed to activated sewage sludge micro-organisms with mineral medium in sealed culture vessels in the dark at 19 to 22 °C for 28 days.

The biodegradation of the test item was assessed by determination of carbon dioxide produced. Control solutions with inoculum and the reference item, sodium benzoate, and a toxicity control were used for validation purposes.

RESULTS

The test item attained 30 % biodegradation after 28 days and cannot be considered to be readily biodegradable under the strict terms and conditions of OECD Guideline No 301 B.