6-tert-butyl-2,4-xylenol

Toxicity to microorganisms

Link to relevant study record(s)

Reference

Endpoint:

activated sludge respiration inhibition testing

Type of information:

experimental study

Adequacy of study:

key study

Study period:

15 - 16 June 1992

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study without detailed documentation

Qualifier:

according to guideline

Guideline:

OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test

Deviations:

not specified

GLP compliance:

no

Specific details on test material used for the study:

No further details specified in the study report.

Analytical monitoring:

not specified

Details on sampling:

Concentrations:
Range Finding Study: 10, 100, 1000 mg/l
Definitive Study: 10 mg/l

Vehicle:

no

Details on test solutions:

Method of Preparation: Direct dispersion in water.

Test organisms (species):

activated sludge of a predominantly domestic sewage

Details on inoculum:

Inoculum: A mixed population of activated sewage sludge microorganisms.
Source: The aeration Stage of Severn Trent PLC Sewage Treatment Plant, Belper, Derbyshire.

Test type:

static

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

3 h

Post exposure observation period:

No post exposure observation period specified.

Hardness:

Not specified

Test temperature:

21°C

pH:

pH 7.1

Dissolved oxygen:

Not specified

Salinity:

Not applicable

Conductivity:

Not specified

Nominal and measured concentrations:

Nominal concentrations

Details on test conditions:

The sample was maintained at 21°C with continuous aeration and used on the day of collection. The pH was buffered to pH 7.1 with sodium hydroxide solution and the suspended solids level adjusted to 4.0 g/l prior to use.

Reference substance (positive control):

yes

Remarks:

3,5-dichlorophenol

Key result

Duration:

3 h

Dose descriptor:

EC50

Effect conc.:

> 10 - < 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Results with reference substance (positive control):

Reference Material : EC50 (3 hour contact time) = 12 mg/l

Range Finding Study – Date: 15 June 1992

Concentration (mg/l)		O2consumption rates mg O2/l/min 3 hour contact time	% Inhibition
Control	R1	0.44	-
	R2	0.42	-
Test	10	0.43	0
	100	0.13	70
	1000	0.02	95
Reference	3.2	0.42	2
	32	0.06	86

Variation between controls: ± 2%

 

Definitive Study – Date: 16 June 1992

Concentration (mg/l)			O2consumption rate mg O2/l/min 3 hour contact time	% Inhibition
Control	R1		0.36	-
	R2		0.28	-
Test	10	R1	0.28	13
	10	R2	0.28	13
	10	R3	0.31	3
Reference	3.2		0.28	13
	32		0.07	78

R₁– R₃: Replicates R₁– R₃

Variation between controls: ±11%

Conclusions:

Phenol-(1,1-dimethylethyl)-4,6-dimethyl- : EC50 (3 hour contact time) >10 mg/l

Executive summary:

Phenol-(1,1-dimethylethyl)-4,6-dimethyl- : EC50 (3 hour contact time) >10 mg/l

Description of key information

Key value determined using OECD guideline 209.

Key value for chemical safety assessment

EC50 for microorganisms:

10 mg/L

Additional information

Phenol-(1,1-dimethylethyl)-4,6-dimethyl- : EC50 (3 hour contact time) >10 mg/l.