Neodecanoic acid, iron salt

Toxicity to aquatic algae and cyanobacteria

Link to relevant study record(s)

Reference

Endpoint:

toxicity to aquatic algae and cyanobacteria

Remarks:

Inhibition of Growth to the Alga Pseudokirchneriella subcapitata

Type of information:

experimental study

Adequacy of study:

key study

Study period:

06th June 2017 to 12th November 2017

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Alga, Growth Inhibition Test)

Version / remarks:

OECD Chemicals Testing Guideline No.201 Alga, Growth Inhibition Test (adopted 23 March 2006, Annex 5 corrected 28 July 2011)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Specific details on test material used for the study:

Batch Number: E01133-065
Purity: 100%
Receipt Date 06 March 2017
Retest Date: 31 July 2019
Storage on Receipt: Refrigerated under nitrogen

Analytical monitoring:

yes

Remarks:

Chemical analysis showed the TI was stable over the 72-hour test period. However, as media was prepared as a saturated solution (based on behaviour of compound in test water and test substance purity), results were based on mean measured concentrations.

Details on sampling:

Measured test concentrations were determined from samples of test solution from treatment and control groups at the beginning of the test (new media) and the test end (old media).

Vehicle:

no

Remarks:

Initial solubility work was conducted under study number 3201780. It was concluded that saturated solution preparations were most appropriate for the test substance, based on behaviour of test substance in test water and 100% purity.

Details on test solutions:

Initial solubility work was conducted under study number 3201780. It was concluded that saturated solution preparations were most appropriate for the test substance, based on behaviour of test substance in test water and 100% purity.

Test organisms (species):

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

Details on test organisms:

The test organism, Pseudokirchneriella subcapitata (Strain 278/4), was originally obtained from the Culture Collection of Algae and Protozoa (CCAP) and is a representative species of the freshwater aquatic phytoplankton. This species is recommended for testing in accordance with the OECD regulatory guidelines.

Prior to testing, duplicate starter cultures were prepared and incubated under test conditions (as detailed in the attached Appendix 3) to obtain sufficient algal cells in exponential growth and to achieve a starting algae cell density of 1 × 104 cells/mL.

Test type:

static

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

72 h

Test temperature:

Temperatures remained within 21–24 ºC, and were maintained within ± 2 ºC range established for the test, temperature range during the test was 22.0–23.1 °C.

pH:

The pH of the control and test solutions ranged from 7.96 to 7.97 at test initiation in solutions without algae. The pH tended to increase relative to increases in algal densities, which is typical for tests conducted with P. subcapitata. The pH in the control increased by a maximum of 1.51 units, which exceeds the OECD 201 guideline requirement of an increase, not greater than 1.5 units. This change in pH was not considered to be detrimental to this study since increases in pH of greater than 1.5 units are commonly observed and this change had no impact on the growth of the control, which met the established validity criteria for the test.

Nominal and measured concentrations:

Analysis of the freshly prepared test solutions at 0 hours showed measured concentration of 1.15 mg/L (mean of two results).
Analysis of the 72-hour test solutions showed measured concentration of 1.20 mg/L (mean of two results).
Chemical analysis showed the test item was stable over the 72-hour test period. However, as media were prepared as a saturated solution (based on behaviour of test substance in test water and test substance purity), results were based on geometric mean measured concentrations.

Reference substance (positive control):

yes

Remarks:

See attached Annex 1

Key result

Duration:

72 h

Dose descriptor:

other: EyC50, EbC50 and ErC50 values

Effect conc.:

> 1.18 mg/L

Nominal / measured:

nominal

Conc. based on:

other: Based on mean measured concentrations

Basis for effect:

growth rate

Remarks on result:

other: All validity criteria were met therefore the test was considered valid.

Key result

Duration:

72 h

Dose descriptor:

NOEC

Remarks:

values for yield, biomass and specific growth rate after 72 hours

Effect conc.:

ca. 1.18 mg/L

Nominal / measured:

nominal

Conc. based on:

other: Based on mean measured concentrations

Basis for effect:

growth rate

Remarks on result:

other: The corresponding NOEC values for yield, biomass and specific growth rate after 72 hours were ~1.18 mg/L, ~1.18 mg/L and 1.18 mg/L, respectively.

Key result

Duration:

72 h

Dose descriptor:

other: ErC10

Effect conc.:

> 1.18 mg/L

Nominal / measured:

nominal

Conc. based on:

other: Based on mean measured concentrations

Basis for effect:

growth rate

Remarks on result:

other: The 72 hour ErC10 value was calculated to be >1.18 mg/L.

Range-finder test

Key results from the range-finding test are summarised in the attached table 1.

At the start of the test, the control and each test concentration were observed to be colourless solutions. At 72 hours, the control and each test concentrations were observed to be green, non-homogenous hazy dispersions of algal cells.

Chemical analysis was not conducted during the range-finder test.

The results of the range-finding test suggested that the 72-hour EC50 values for yield, specific growth rate and area under the curve (biomass) were likely to be greater than 100% saturated solution.

Definitive Test

Chemical Analysis

The results of the chemical analysis are presented in the attached table 2. Example chromatograms of test samples, standard solution and a typical calibration line are presented in the attached Appendix 4. The limit of quantification (LOQ) was 0.3 mg/L.

Environmental Conditions

The results of the environmental conditions and pH determined during the test are presented in the attached table 3.

The light intensity was measured at the start and end of the test; 6715 Lux at the start and 7325 Lux at the end of the test (mean of two readings carried out at each time point).

Test Media Descriptions

The freshly prepared test media at 0 hours appeared as colourless solutions.

The appearance of the test media following the 72-hour exposure period are summarised in the table below.

Chart 1. Test media descriptions at the end of the definitive test

Nominal Concentrations (% saturated solution)                             Colour of inoculated test medium                            State of test medium

Control                                                                                           green                                                              Non-homogenous hazy dispersion of algal cells

100                                                                                                  green                                                              Non-homogenous hazy dispersion of algal cells

Growth Test

Individual replicate data for cell density and mean treatment cell density are presented in the attached table 4. Results of the growth test, as specific growth rate, area under curve and yield are presented in the attached table 5 to table 7.

Growth curves of Pseudokirchneriella subcapitata exposure to the test item are presented in the attached Figure 1. 

Validity criteria fulfilled:

yes

Remarks:

All validity criteria were met therefore the test was considered valid.

Conclusions:

Based on mean measured concentrations, the 72-hour EyC50, EbC50 and ErC50 values were calculated to be > 1.18 mg/L, respectively.
The corresponding NOEC values for yield, biomass and specific growth rate after 72 hours were ~1.18 mg/L, ~1.18 mg/L and 1.18 mg/L, respectively.
The 72 hour ErC10 value was calculated to be >1.18 mg/L.

Executive summary:

The objective of the study was to determine the effects of the test substance against algal growth by exposing the green alga, Pseudokirchneriella subcapitata, at the exponential growth phase to the test substance during a 72-hour test period.

The test was conducted in accordance with OECD Chemicals Testing Guideline No. 201.

The definitive limit test was conducted at a nominal test concentration of 100% saturated solution. Six replicate vessels were prepared for the control and 100% saturated solution test group.

Test vessels (250 mL conical flasks) were prepared containing 100 mL of the appropriate test or control medium. Each test vessel was inoculated with

1 × 10⁴ algae cells/mL and incubated at 21 - 24°C (under 4440 - 8880 Lux light intensity) for 72 hours with cell counts at 24-hour intervals.

Measured test concentrations were determined from samples of test solution from treatment and control groups at the beginning of the test (new media) and the test end (old media).

Analysis of the test samples at 0 and 72 hours are summarised in the table below.

Nominal Concentration (% saturated solution)		Measured Concentration (mg/L)
		0 hours (New)	72 hours (Old)	Mean Measured Concentration (mg/L)
Control		-	-	-
	100	1.15	1.20	1.18
-	None found

Chemical analysis showed the test item was stable over the 72-hour test period. However, as media was prepared as a saturated solution (based on behaviour of compound in test water and test substance purity), results were based on mean measured concentrations.

The 72-hour yield (EyCx), area under the growth curve (EbCx) and growth rate (ErCx) toxicity values, with corresponding no observed effect concentration (NOEC) and lowest observed effect concentration (LOEC) values, are presented in the table below.

Toxicity values mg/L

Parameter                     72 hours                                             Confidence limits                                                                Statistical test

(LCL-UCL)

Growth Rate

ErC10                          >1.18                                                             NC

ErC20                          >1.18                                                             NC                                                                        Linear Interpolation

                                                                                                                                                                                                   (ICPIN)

ErC50                          >1.18                                                              NC

NOEC                         ~1.18                                                              NC                                                                       Equal variance t Two

Sample

Yield

EyC10                         0.336                                                      0.27-0.434

EyC20                         0.785                                                      0.612-1.05                                                                    Linear Interpolation

(ICPIN)

EyC50                         >1.18                                                                NC

NOEC                         ~1.18*                                                              NC                                                                      Equal variance t Two

Sample

Area Under

the Curve

(Biomass)

EbC10                         0.365                                                      0.280-0.521

EbC20                         0.864                                                      0.637-NC                                                                      Linear Interpolation

(ICPIN)

EbC50                          >1.18                                                             NC

NOEC                         ~1.18*                                                            NC                                                                        Equal variance t Two

Sample

NC = Not calculated

LCL = Lower confidence limit

UCL = Upper confidence limit

* 25% inhibition is considered to be natural variation, and therefore, it is not considered a significant effect if 25% inhibition is observed, therefore, as yield and area under curve resulted in 26.9% and 25.0% inhibition, respectively it was considered that the NOEC for these end-points were close to 1.18 mg/L. As these are secondary end-points this was not considered to impact on the study integrity.

Description of key information

Based on mean measured concentrations, the 72-hour EyC50, EbC50 and ErC50 values were calculated to be > 1.18 mg/L, respectively.

The corresponding NOEC values for yield, biomass and specific growth rate after 72 hours were ~1.18 mg/L, ~1.18 mg/L and 1.18 mg/L, respectively.

The 72 hour ErC10 value was calculated to be >1.18 mg/L.

Key value for chemical safety assessment

EC10 or NOEC for freshwater algae:

1.18 mg/L