Benzenesulfonamide, N-(4-hydroxyphenyl)-

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

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

not specified

Details on test solutions:

The test water used for the range-finding and definitive tests was deionized reverse osmosis water containing less than 1 mg/L Dissolved Organic Carbon (DOC).

Test organisms (species):

activated sludge of a predominantly domestic sewage

Details on inoculum:

A mixed population of activated sewage sludge micro-organisms was obtained on 10 September 2015 for the range-finding test and on 5 October 2015 for the definitive test from the aeration stage of the Severn Trent Water Plc sewage treatment plant at Loughborough, Leicestershire, UK which treats predominantly domestic sewage.

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

3 h

pH:

The pH of the test item dispersions were measured after stirring using Hach HQ40d Flexi handheld meter (see Table 6) and adjusted to between pH 7.0 to pH 8.0.

Nominal and measured concentrations:

Nominal amounts of test item (5, 16, 50, 160 and 500 mg (in triplicate)) were each separately dispersed in approximately 200 mL of deionized reverse osmosis water and subjected to ultrasonication for approximately 15 minutes followed by magnetic stirring for 24 hours, at temperatures of between 20 °C and 21 °C, in order to maximize the dissolved test item concentration. All test vessels were shielded from the light during mixing. Synthetic sewage (16 mL), activated sewage sludge (250 mL) and water were added to a final volume of 500 mL to give the required concentrations of 10, 32, 100, 320 and 1000 mg/L (3 replicates).

Details on test conditions:

A synthetic sewage of the following composition, was added to each test vessel to act as a respiratory substrate:

16 g Peptone
11 g Meat extract
3g Urea
0.7 g NaCl
0.4 g CaCl2.H2O
0.2 g MgSO4.7H2O
2.8 g K2HPO4
dissolved in a final volume 1 liter of water with the aid of ultrasonication.

In the range-finding test, the pH of the synthetic sewage stock was pH 7.1. In the definitive test, the pH of the synthetic sewage stock used to feed the activated sewage sludge was pH 7.3 and the pH of the synthetic sewage stock used for the definitive test was pH 7.3. The pH values were measured using a Hach HQ40d Flexi handheld meter.

Reference substance (positive control):

yes

Remarks:

3,5-Dichlorophenol

Duration:

3 h

Dose descriptor:

EC10

Effect conc.:

72 mg/L

Duration:

3 h

Dose descriptor:

EC50

Effect conc.:

220 mg/L

Reported statistics and error estimates:

The percentage inhibition values were plotted against concentration, a line fitted using the Xlfit software package (IDBS) and the EC10, EC20, EC50 and EC80 values determined from the equation for the fitted line.
95% confidence limits were calculated for the reference item EC50 value using the method of Litchfield and Wilcoxon (Litchfield and Wilcoxon, 1949).
One way analysis of variance incorporating Bartlett's test for homogeneity of variance (Sokal and Rohlf, 1981) and Dunnett's multiple comparison procedure for comparing several treatments with a control (Dunnett, 1955) was carried out on the oxygen consumption data for the range- finding test after 3 hours for the control and all test concentrations to determine any statistically significant differences between the test and control groups. All statistical analyses were performed using the SAS computer software package (SAS, 1999 - 2001).

Validity criteria fulfilled:

yes

Conclusions:

The effects of the test item on the respiration of activated sewage sludge was tested. A 3-Hour EC10 value of 72 mg/L and a 3-Hour EC50 value of 220 mg/L was determined. The reference item gave a 3-Hour EC50 value of 11 mg/L, 95% confidence limits 8.6 to 14 mg/L.

Description of key information

An EC50 of 220 mg/L and an EC10 of 72 mg/L were determined with a OECD 329 test.

Key value for chemical safety assessment

EC50 for microorganisms:

220 mg/L

EC10 or NOEC for microorganisms:

72 mg/L