4-aminophenol

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:

2010-09-08 to 2010-09-28

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

no

Vehicle:

no

Details on test solutions:

Volume of the 500 mL test medium
Composition of 1 mg/L:test medium
200 mL inoculum
16 mL synthetic waste water
234 mL autoclaved tap water
50 mL test item stock solution

3.2 mg/L:
200 mL inoculum
16 mL synthetic waste water
124 mL autoclaved tap water
160 mL test item stock solution

10 - 320 mg/L:
200 mL inoculum
16 mL synthetic waste water
34 mL autoclaved tap water
Test item suspension (250 mL)

Test organisms (species):

activated sludge of a predominantly domestic sewage

Details on inoculum:

A fresh sample of activated sludge taken from the sewage plant Sarstedt was used for the test procedure. It was washed twice and adjusted with autoclaved tap water to a dry sludge concentration of 4.0 g/L ± 10

Test type:

static

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

3 h

Test temperature:

21°C

pH:

pH value of the activated sludge 6.67
Dry sludge concentration [g/L] 4.19

Details on test conditions:

TEST METHOD Static
Test duration 3 hours
Replicates One per concentration and two controls
Test vessels 500 mL Erlenmeyer flasks, DIN 12380
Nutrient solution Synthetic waste water according to OECD Guideline 209
Volume of the 500 mL test medium
Aeration Permanent

Reference substance (positive control):

yes

Remarks:

Copper (II) sulphate pentahydrate p.a.

Duration:

3 h

Dose descriptor:

EC50

Effect conc.:

29.9 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Remarks on result:

other: 95% CL

Duration:

3 h

Dose descriptor:

EC10

Effect conc.:

2.65 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Details on results:

VALIDITY CRITERIA The difference between the two control respiration rates should be not more than 15 %.

The EC50 of the reference item should be in the range of
54 - 156 mg/L. The range of validity (EC50  3 SD) of copper (II) sulphate pentahydrate is calculated from the mean of all reference tests (n = 298) from 1991 - 2010.

Results with reference substance (positive control):

EC50 = 135 mg/L
This is in the recommended confidence range of 54 - 156 mg/L.

Reported statistics and error estimates:

The EC-values and confidence intervals of the test item were calculated by linear regression using software GraphPad Prism5, GRAPHPAD SOFTWARE, INC.

The EC50-value of the reference item was calculated with probit analysis using software SIGMAPLOT (Windows), SPSS CORPORATION. Probit values were taken from WEBER (1986).

Table2:    Inhibitions in the Preliminary Tests

Nominal Test Item Concentration	Inhibition [%]
	1^ststudy	2^ndstudy	3^rdstudy
[mg/L]	No stirring	24 h stirring	1 h stirring
1	–	–	- 7
10	17	2	52
100	45	41	81
1000	- 5	34	2

Table3:   Respiration Rates and Inhibition of Respiration of Test and Reference Item Concentrations

	Concentration	Respiration rate	Inhibition
	[mg/L]	[mgO2/(L×h)]	[%]
Test item		320		9.2		42
		100		4.4		72
		32		8.0		49
		10		10.8		32
		3.2		14.0		11
		1		16.4		-4
Control 1		–		16.4		–
Control 2		–		15.2		–
Reference item		180		5.6		65
		100		10.8		32
		58		12.8		19

	EC-values	Confidence interval
	[mg/L]	P = 95 [%] [mg/L]
EC20	4.85	-
EC50	29.9	23.6 - 39.3
EC80	n.d.	-

Solubility of the Test Item

 

After stirring for 1 h all test item concentrations were dissolved. The colours of the solutions were slightly brown (10 mg/L stock solution and 10 mg/L), brown (32 mg/L and 100 mg/L) and colourless to slightly yellow (320 mg/L).

Validity criteria fulfilled:

yes

Conclusions:

The EC 50 of the test item p-Aminophenol is 29.9 mg/L and EC10 is 2.65 mg/L to activated sludge of a municipal sewage treatment plant.

Description of key information

One key experimental study was reported,  Respiration Inhibition Test with Activated Sludge with EC50 of 29.9 mg/L.

Key value for chemical safety assessment

EC50 for microorganisms:

29.9 mg/L

EC10 or NOEC for microorganisms:

2.65 mg/L

Additional information

For short-term toxicity to micro-organisms, there is one key study conducted in 2010, Respiration Inhibition Test with Activated Sludge according to OECD 209 with an EC50 of 29.9 mg/L.