4-(4-isopropoxyphenylsulfonyl)phenol

Toxicity to aquatic algae and cyanobacteria

Link to relevant study record(s)

Reference

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

experimental study

Adequacy of study:

key study

Study period:

from 1993-02-15 to 1993-09-27

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Alga, Growth Inhibition Test)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

yes

Details on sampling:

Samples of aqueous test media containing d-8 were diluted to equate HPLC mobile phase to within the concentration range of 0.4 to 4 mg/L. The concentrations of D-8 in the diluted samples were then determined by high performance liquid chromatography using a spectrophotometric detector.

Vehicle:

no

Details on test solutions:

Test media were prepared from aqueous stock preparations, in which the test material was added directly to water, with the aid of sonication.

Test organisms (species):

Raphidocelis subcapitata (previous names: Pseudokirchneriella subcapitata, Selenastrum capricornutum)

Details on test organisms:

TEST ORGANISM
- Common name: green algae
- Strain: CCAP number 278/4
- Source: CCAP Culture Centre for Algae and Protozoa; Freshwater Biological Association; Ferry House; Far Sawrey, Ambleside, Cumbria
- Method of cultivation: Axenic, uni-algal slope cultures were incubated in OECD medium to result stock cultures. Subcultures were prepared by aseptic transfer of aliquots into fresh OECD medium and incubation for several days until required cell density has been achieved.

ACCLIMATION
- Acclimation period: not indicated
- Culturing media and conditions: temperature-controlled illuminate orbital incubator; at 20 - 25 °C; shaking speed: 175 rpm; light intensity: approx. 16000 lux
- Any deformed or abnormal cells observed: not indicated

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

72 h

Test temperature:

Start of test: 21.9 - 22.3 °C
after 72 h: 23.3 - 23.8 °C

pH:

start of test: 7.9 - 8.1
after 72 h: 7.8 - 8.1

Nominal and measured concentrations:

Nominal: 0.32; 1; 3.2; 10 and 32 mg/L
Measured: 0.162; 0.461, 1.90; 4.63 and 16.7 mg/L (unfiltered media)

Details on test conditions:

Triplicate algal cultures with a cell count of 1E04/mL were exposed to D-8 in mineral salts medium at nominal concentrations 0.32, 1, 3.2, 10 and 32 mg/L, selected following a preliminary range finding test. Test media were prepared from aqueous stock preparations, in which test material was added directly to water, with the aid of sonication. The cell density of each culture was measured, using a haemocytometer, at 24-hour intervals. Growth rate (the rate of change in cell number with time) and biomass (the number of cells per mL) were both calculated.

Reference substance (positive control):

no

Key result

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

5.62 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other: 95 % CI: 4.63 - 16.7 mg/L

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

2.22 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

test mat.

Basis for effect:

biomass

Remarks on result:

other: 95 % CI: 1.90 - 4.63 mg/L

Key result

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

0.461 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

test mat.

Basis for effect:

other: growth rate and biomass

Details on results:

Exposure to D-8, at measured levels in unfiltered samples at and above 1.90 mg/L, caused a significant reduction in the average specific growth rates and biomass of Raphidocelis subcapitata cultures (p > 0.05). Thus, the no-observed-effect concentration (NOEC) for growth rate and biomass was 0.461 mg/L.
The 50 % effect concentrations for average specific growth rate (ErC50) and mean biomass (EbC50) respectively were found to be 5.62 mg/L (95 % confidence limits 4.63 and 16.7 mg/L) and 2.22 mg/L (95 % confidence limits 1.90 and 4.63 mg/L).

Reported statistics and error estimates:

Statistical comparisons of average specific growth rates in control and test cultures were carried out using Dunnett's multi-comparison test. In this test, a multiple t-test compares each treatment with the control group using a common estimate of experimental error, and then uses Dunnett's t-Statistic tables to assess significance at the 95 % level of probability.
Statistical comparisons of the area under the growth curve in control and test groups were again carried out using Dunnett's multi-comparison test.

Table 1. Analytical determination of D-8

Sampling time, h		Nominal D-8 concentrations, mg/L
	0	0.32	1	3.2	10	32
Unfiltered samples
0 h	nd	0.161 (50)	0.476 (48)	2.08 (65)	4.44 (44)	17.3 (54)
72 h	nd	0.162 (51)	0.446 (45)	1.71 (53)	4.81 (48)	16.0 (50)
% of t0	-	101	94	82	108	92
Overall mean	-	0.162 (51)	0.461 (46)	1.90 (59)	4.63 (46)	16.7 (52)
Filtered media
0 h	nd	0.0193 (6)	0.0540 (5)	0.355 (11)	1.05 (11)	7.23 (23)
72 h	nd	0.0066 (2)	0.0603 (6)	0.371 (12)	1.91 (19)	8.16 (26)
% of t0	-	34	112	105	182	113
Overall mean	-	0.013 (4)	0.057 (6)	0.363 (11)	1.48 (15)	7.70 (24)

nd: not detected
(): meas. Concentrations expressed as percentage of the nominal value
% of t0: mean meas. Concentrations after 72 hours, expressed as a percentage of the mean starting conc.

The results of cell counts in control and test flasks are given in Table 2:

Table 2. Cell numbers in individual control and test cultures

Measured test material conc. (mg/l)	Flask number	Cell numbers per mL (x1E4)
		24 hours	48 hours	72 hours
0 (control)	1	9.4	25.3	141.5
	2	8.3	45.0	149.3
	3	10.4	43.4	147.0
	4	7.3	59.4	214.8
	5	10.0	54.8	181.3
	6	7.8	44.6	156.0
0.162	7	10.6	45.5	133.3
	8	8.4	27.9	102.5
	9	10.4	35.8	141.8
0.461	11	9.3	33.1	109.8
	12	10.5	49.8	151.3
	13	7.6	30.3	109.5
1.90	15	9.3	27.4	78.3
	16	7.6	29.1	83.1
	17	8.4	32.0	94.0
4.63	19	3.0	7.0	16.8
	20	2.4	7.0	32.1
	21	2.1	9.9	28.6
16.7	23	1.0	0.4	0.8
	24	0.8	0.6	0.9
	25	1.1	0.8	0.9

 Note: Cell numbers are quoted to one decimal place.

The average specific growth rates and biomass in test and control cultures are given in Table 3:

Table 3. Average specific growth rates and biomass (0 – 72 hours) in test and control cultures

Measured test material conc. (mg/l)	Flask number	Average specific growth rate x 10^-2	Mean x 10^-2	Biomass x10^4	Mean x10^4
0 (control)	1	6.878	7.076	2469	3221
	2	6.952		3009
	3	6.931		2994
	4	7.458		4116
	5	7.222		3669
	6	7.014		3069
0.162	7	6.795	6.702	2886	2558
	8	6.430		2040
	9	6.881		2748
0.461	11	6.525	6.673	2274	2546
	12	6.971		3201
	13	6.522		2163
1.90	15	6.055	6.168	1758	1872
	16	6.139		1820
	17	6.310		2037
4.63	19	3.914	4.464	381	501
	20	4.819		551
	21	4.659		572
16.7	23	-0.400	-0.257	-18	-13
	24	-0.185		-17
	25	-0.185		-5

Note: Growth rate – values are quoted to three decimal places.

Biomass - values are quoted to the nearest whole number.

Determination of algistatic/algicidal effect:

Sub-cultures (established in freshly prepared medium) from test cultures containing D-8 at 4.63 mg/L showed normal growth after seven days of incubation indicating that, at this level, the material was algistatic. At 16.7 mg/L, no growth occured after ten days of incubation indicating that D-8 at this concentration was algicidal.

Validity criteria fulfilled:

yes

Conclusions:

The 50 % effect concentrations for average specific growth rate (ErC50) and mean biomass (EbC50) for D-8, respectively, were found to be 5.62 mg/L (95 % confidence limits 4.63 and 16.7 mg/L) and 2.22 mg/L (95 % confidence limits 1.90 and 4.63 mg/L). The no-observed-effect concentration (NOEC) for growth rate and biomass was 0.461 mg/L.

Executive summary:

D-8 was tested for algal toxicity to Raphidocelis subcapitata in a 72-h test for average specific growth rate and mean biomass in accordance to OECD 201. D-8 was tested at concentration levels of 0.32, 1, 3.2, 10 and 32 mg/L. Exposure to D-8, at measured levels in unfiltered samples at and above 1.90 mg/L, caused a significant reduction in the average specific growth rates and biomass of Raphidocelis subcapitata cultures (p > 0.05). The no-observed-effect concentration (NOEC) for growth rate and biomass was 0.461 mg/L. The 50 % effect concentrations for average specific growth rate (ErC50) and mean biomass (EbC50) respectively were found to be 5.62 mg/L (95 % confidence limits 4.63 and 16.7 mg/L) and 2.22 mg/L (95 % confidence limits 1.90 and 4.63 mg/L). D-8 at 4.63 mg/L showed normal growth after seven days of incubation indicating that, at this level, the material was algistatic. At 16.7 mg/L, no growth occurred after ten days of incubation indicating that D-8 at this concentration was algicidal.

Description of key information

The 50 % effect concentrations for average specific growth rate (ErC50) and mean biomass (EbC50) for D-8, respectively, were found to be 5.62 mg/L (95 % confidence limits 4.63 and 16.7 mg/L) and 2.22 mg/L (95 % confidence limits 1.90 and 4.63 mg/L). The no-observed-effect concentration (NOEC) for growth rate and biomass was 0.461 mg/L.

Key value for chemical safety assessment

EC50 for freshwater algae:

5.62 mg/L

EC10 or NOEC for freshwater algae:

0.461 mg/L

Additional information

D-8 was tested for algal toxicity to Raphidocelis subcapitata in a 72-h test for average specific growth rate and mean biomass in accordance to OECD 201. D-8 was tested at concentration levels of 0.32, 1, 3.2, 10 and 32 mg/L. Exposure to D-8, at measured levels in unfiltered samples at and above 1.90 mg/L, caused a significant reduction in the average specific growth rates and biomass of Raphidocelis subcapitata cultures (p > 0.05). The no-observed-effect concentration (NOEC) for growth rate and biomass was 0.461 mg/L. The 50 % effect concentrations for average specific growth rate (ErC50) and mean biomass (EbC50) respectively were found to be 5.62 mg/L (95 % confidence limits 4.63 and 16.7 mg/L) and 2.22 mg/L (95 % confidence limits 1.90 and 4.63 mg/L). D-8 at 4.63 mg/L showed normal growth after seven days of incubation indicating that, at this level, the material was algistatic. At 16.7 mg/L, no growth occurred after ten days of incubation indicating that D-8 at this concentration was algicidal.