Tall oil, potassium salt

Toxicity to microorganisms

Link to relevant study record(s)

Reference

Endpoint:

toxicity to microorganisms, other

Remarks:

Manometric respirometry test (OECD 301F)

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Reason / purpose for cross-reference:

reference to same study

Qualifier:

according to guideline

Guideline:

other: OECD Guideline 301F

Deviations:

not applicable

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

yes

Remarks:

measurement of oxygen consumption value

Details on sampling:

Daily from Day 0 to Day 28

Vehicle:

no

Test organisms (species):

activated sludge of a predominantly domestic sewage

Details on inoculum:

A mixed population of sewage treatment micro-organisms was obtained on 18 March 2019 from the final effluent stage of the Severn Trent Water Plc sewage treatment plant at Loughborough, Leicestershire, UK, which treats predominantly domestic sewage. The sample of effluent was filtered through coarse filter paper (first approximate 200 mL discarded) and maintained on aeration in a temperature controlled room at 21 ±1 °C prior to use.

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

28 d

Test temperature:

Between 20 and 22°C

pH:

7.2-7.9

Dissolved oxygen:

Mean BOD of the inoculum control was 18 mg O2/L

Nominal and measured concentrations:

100 mg/L

Details on test conditions:

The test substance was dissolved in an auxiliary solvent prior to being adsorbed onto a filter paper and subsequent dispersal in test media. Using this method the test substance was evenly distributed throughout the test medium and the surface area of test substance exposed to the test organisms was increased thereby increasing the potential for biodegradation. The biodegradation of the test substance was assessed by the measurement of daily oxygen consumption values on Days 0 to 28. Control solutions with inoculum and the reference substance aniline, and a toxicity control were used for validation purposes.

Reference substance (positive control):

yes

Remarks:

Aniline

Key result

Duration:

28 d

Dose descriptor:

NOEC

Effect conc.:

100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Validity criteria fulfilled:

yes

Conclusions:

Under the study conditions, the NOEC of the test substance in sewage microorganisms was determined to be a nominal level of 100 mg/L.

Executive summary:

A study was conducted to assess the toxicity of the test substance on the total respiration of sewage microorganisms according to the OECD Guideline 301F (Manometric respirometry method) under GLP conditions. The test substance at a concentration of 100 mg/L was exposed to sewage treatment microorganisms with mineral medium in sealed culture vessels in diffuse light at temperatures between 20 and 22ºC for 28 days. The inoculum was sourced from a sewage treatment plant treating predominantly domestic sewage. The test substance was dissolved in an auxiliary solvent prior to being adsorbed onto a filter paper and subsequent dispersal in test media. Using this method the test substance was evenly distributed throughout the test medium. The biodegradation of the test substance was assessed by the measurement of daily oxygen consumption from Days 0 to 28. Control solutions with inoculum, the reference substance, aniline, and a toxicity control were used for validation purposes. The test substance attained 72% biodegradation after 28 days. Aniline attained 62% biodegradation after 14 days with greater than 60% degradation being attained in a 10-Day window and 72% biodegradation in 28 days. No inhibition of respiration of sewage microorganisms was observed as the toxicity control attained 58% biodegradation after 14 days and 68% biodegardation after 28 days. Under the study conditions, the NOEC of the test substance in sewage microorganisms was determined to be a nominal level of 100 mg/L (Best, 2019).

Key value for chemical safety assessment

EC10 or NOEC for microorganisms:

100 mg/L

Additional information

A study was conducted to assess the toxicity of the test substance on the total respiration of sewage microorganisms according to the OECD Guideline 301F (Manometric respirometry method) under GLP conditions. The test substance at a concentration of 100 mg/L was exposed to sewage treatment microorganisms with mineral medium in sealed culture vessels in diffuse light at temperatures between 20 and 22ºC for 28 days. The inoculum was sourced from a sewage treatment plant treating predominantly domestic sewage. The test substance was dissolved in an auxiliary solvent prior to being adsorbed onto a filter paper and subsequent dispersal in test media. Using this method the test substance was evenly distributed throughout the test medium. The biodegradation of the test substance was assessed by the measurement of daily oxygen consumption from Days 0 to 28. Control solutions with inoculum, the reference substance, aniline, and a toxicity control were used for validation purposes. The test substance attained 72% biodegradation after 28 days. Aniline attained 62% biodegradation after 14 days with greater than 60% degradation being attained in a 10-Day window and 72% biodegradation in 28 days. No inhibition of respiration of sewage microorganisms was observed as the toxicity control attained 58% biodegradation after 14 days and 68% biodegardation after 28 days. Under the study conditions, the NOEC of the test substance in sewage microorganisms was determined to be a nominal level of 100 mg/L (Best, 2019).