4-chloro-o-cresol

Toxicity to aquatic plants other than algae

Administrative data

Endpoint:

toxicity to aquatic plants other than algae

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: The study is performed to current guidelines and is GLP compliant.

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2010

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 221 (Lemna sp. Growth Inhibition Test)

GLP compliance:

yes (incl. QA statement)

Test material

Test material information

Constituent 1

Reference substance name:

PCOC

IUPAC Name:

PCOC

Details on test material:

Test material supplied by Nufarm UK Limited

Sampling and analysis

Analytical monitoring:

yes

Details on sampling:

Samples of the test solutions were taken at the start of the test, on fresh and aged solutions when replaced on days 2 and 5, and on termination of the test on day 7.

Test solutions

Details on test solutions:

The definitive test solutions were prepared at 0 (control), 6.3, 12.5, 25, 50 and 100mg/L.

Test organisms

Test organisms (species):

Lemna gibba

Details on test organisms:

TEST ORGANISM
- Common name: Lemna minor
- Source (laboratory, culture collection): Blades Biological Limited

ACCLIMATION
- Acclimation period: 7 days
- Culturing media and conditions: Swedish Standard (SIS) Lemna growth medium.

Study design

Test type:

semi-static

Water media type:

freshwater

Total exposure duration:

7 d

Test conditions

Hardness:

No details specified

Test temperature:

The temperature was monitored throughout the test. The minimum and maximum temperatures recorded were 22.9 and 24.3° C respectively. The temperatures recorded on specific days are tabulated below.

Temperature (°C)
Day 0 Day 2 Day 5 Day 7
24.3 23.6 23.6 23.5

pH:

The pH of the aged and fresh solutions was recorded on days 0, 2, 5 and day 7. The details are tabulated below.

Nominal pH
Concn Day 0 Day 2 Day 2 Day 5 Day 5 Day 7
(mg/L) Fresh soln Aged soln Fresh soln Aged soln Fresh soln Aged soln
0 6.4 6.6 6.4 7.2 6.4 7.0
6.3 6.4 6.6 6.4 7.0 6.4 6.8
12.5 6.4 6.6 6.4 6.8 6.4 6.8
25 6.4 6.5 6.4 6.5 6.4 6.5
50 6.4 6.5 6.4 6.4 6.4 6.5
100 6.4 6.5 6.4 6.4 6.4 6.5

Dissolved oxygen:

No details specified

Salinity:

No details specified

Nominal and measured concentrations:

The details are tabulated below.

Nominal Exposure Period
Concn of
PCOC Day 0 Day 2 Day 2 Day 5 Day 5 Day 7 (mg/L) Fresh soln Aged soln Fresh soln Aged soln Fresh soln Aged soln
Control 0.00 0.00 0.00 0.00 0.00 0.00
6.3 10.02 9.11 6.76 5.94 6.53 5.82
12.5 12.91 11.77 13.70 11.93 13.39 12.07
25 25.64 23.32 27.31 24.18 27.03 24.68
50 52.05 48.06 55.28 48.54 54.77 50.09
100 108.14 100.03 111.58 99.66 112.04 103.30

Details on test conditions:

TEST SYSTEM
- Incubation chamber used: yes
- Test vessel: 250ml beaker
- Fill volume: 100ml
- Renewal rate of test solution (frequency/flow rate): Test solutions renewed on days 2 and 5.
- No. of fronds per vessel: 12 in total
- No. of fronds per colony: no more than 3
- No. of vessels per concentration (replicates): 3
- No. of vessels per control (replicates): 6

GROWTH MEDIUM
- Standard medium used: yes, Swedish Standard (SIS) Lemna growth medium.

OTHER TEST CONDITIONS
- Photoperiod: Constant
- Light intensity and quality: Between 6500 and 10000 lux.

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
- Determination of frond number: Frond numbers were recorded at the beginning of the test and on days 2, 5 and 7. Changes in plant development were also recorded.
- Determination of biomass: [dry weight / fresh weight] The initial dry weight was determined from colonies of the inoculum culture at the start of the definitive test. The final dry weight was determined from the total fronds in each control or exposure solution at the end of the test.

RANGE-FINDING STUDY
- Test concentrations: 0.1, 1, 10, 100 mg/L
- Results used to determine the conditions for the definitive study:

Nominal Concn Percent Inhibition (0-7 days)
(mg/L) Growth Rate Yield
0.1 -4 -12
1 3 7
10 3 7
100 100 100

Data from the preliminary study identified the 7 day EC50 as being between 10 and 100mg/L.

Reference substance (positive control):

no

Results and discussion

Effect concentrations

Duration:

7 d

Dose descriptor:

EC50

Effect conc.:

ca. 15.7 mg/L

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

biomass

Details on results:

Throughout the study all fronds in the controls were observed to be large, green and healthy.
The observations made of the plant development are tabulated below.

Nominal Concentration Observations of Lemna Minor Development after 7 days exposure to PCOC.
(mg/L)
0 No abnormal observations
6.3 No abnormal observations
12.5 No abnormal observations
25 Indication of chlorosis
50 Indication of necrosis
100 Indication of necrosis


The percentage inhibition compared to the control based on frond number and dry weight are summarised in Tables 1 and 2 respectively below.
An overall summary of the calculated results is presented in Table 3 below.

Any other information on results incl. tables

Table 1. Percentage inhibition compared to the control based on frond number.

Nominal concentration	Percentage Inhibition (0 to 7 days)
(mg/L)	Growth Rate	Yield
6.3	9	21
12.5	12	28
25	41	68
50	99	100
100	100	100

Table 2. Percentage Inhibition based on dry weight.

Nominal concentration	Percentage Inhibition (0 to 7 days)
(mg/L)	Growth Rate	Yield
6.3	9	19
12.5	13	26
25	52	74
50	100	100
100	100	100

Table 3. Summary of calculated EC50 and NOEC values.

Period of Eposure	ErC50 value (mg/L)	EyC50 value (mg/L)
(Days)	(95% Confidence Limits)	(95% Confidence Limits)
0 to 7 Frond Number	22.9 (10.4 -54.9)	15.9 (9.4 - 25.2)
0 to 7 Dry Weight	21.0 (12.0 - 38.7)	15.7 (10.1 - 23.6)
NOEC	< 7.2 mg/L (0 -7 days) by growth rate	< 7.2 mg/L (0 -7 days) by yield

Applicant's summary and conclusion

Conclusions:

The ErC50 (growth rate) was determined to be 22.9mg/L by frond number and 21.0 mg/L by dry mass. The EyC50 (yield) was determined to be 15.9mg/L by frond number and 15.7mg/L by dry mass.

The NOECr(0-7days) and NOECy(0-7days) were both estimated (by the Dunnett’s Test, using frond number data) to be <7.2 mg/L

Executive summary:

Lemna minor plants, initially 12 fronds, were exposed to PCOC in a semi-static study at nominal concentrations 0 (control), 6.3, 12.5, 25, 50 and 100mg/L for 7 days. The test vessels were maintained at 24±2ºC and kept under constant illumination with white light of 6500 – 10000Lux. Changes of the test media occurred on day 3 and 5 of the study.

Inhibtion of growth was determined by frond number and by dry mass; results were collated on days 3, 5 and 7 of the study.

The E_rC₅₀ was determined to be 22.9mg/L by frond number and 21.0 mg/L by dry mass. The EyC₅₀was determined to be 15.9mg/L by frond number and 15.7mg/L by dry mass.

The NOEC_r(0-7days) and NOECy(0-7days) were both estimated (by the Dunnett’s Test, using frond number data) to be <7.2 mg/L.