Bis(p-methoxyphenyl)iodonium bromide

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:

15 January 2019 - 19 March 2019

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Freshwater Alga and Cyanobacteria, Growth Inhibition Test)

Version / remarks:

Annex 5 corrected: 28 July 2011

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

yes

Details on sampling:

Based on the results of the preliminary range-finding test five test concentrations in a geometric series with a spacing factor of 2.5 were used in the main test. A concurrent control ran parallel.
The measured concentrations deviated more than 20 % from the nominal during the experiment therefore the geometric mean of the measured concentrations were calculated to determine exposure concentrations.
Biological results and endpoints are based on the measured geometric mean concentrations.

Vehicle:

no

Test organisms (species):

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

Test type:

static

Water media type:

freshwater

Total exposure duration:

72 h

Hardness:

The reconstituted water (ISO medium) has an approximate theoretical total hardness of 249 mg/L (as CaCO3).

Test temperature:

The test temperature was in the range of 21.1 – 21.7°C measured in the test vessels during the test. The additionally measured ambient temperature within the climate chamber was between 20.5 – 21.8°C.

pH:

The pH of the test solution was not adjusted and not varied by more than 1.5 units in any one test. The pH was in the range of 7.39 – 7.94 during the test.

Dissolved oxygen:

The dissolved oxygen concentration was in the range of 6.98 – 7.68 mg/L during the test.

Salinity:

Reconstituted water (ISO medium, according to OECD 202) was used as dilution water in the experiment. Separate stock solutions of individual substances are first prepared in deionised water (prepared in TOXI-COOP ZRT. by MILLIPORE ELIX 3 water purification system). The ISO medium is prepared by adding 25 mL from each of four stock solutions to one litre deionised water.

Nominal and measured concentrations:

The test solutions used in the test were prepared by mechanical dispersion. A stock solution was first prepared by dissolving an amount of 0.0107 g test item in 1070 mL dilution water (OECD medium) resulting a nominal concentration of 10 mg/L. Test solutions of chosen test concentrations were prepared by appropriate dilution of this stock solution (see the Table below). After the formulation procedure the algal cells were immediately introduced into the test solution.

Table: Preparation of the test solutions

Nominal Stock ISOMedium
concentration [mg/L] Solution [mL] [mL]
10.0 300–
5.7 171 q.s. ad 300
3.3 98 q.s. ad 300
1.9 56 q.s. ad 300
1.1 32 q.s. ad 300
q.s. ad = quantum sufficiat ad (a sufficient quantity to make)

Reference substance (positive control):

yes

Key result

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

0.04 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat. (total fraction)

Basis for effect:

growth rate

Key result

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

> 0.33 - < 0.5 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat. (dissolved fraction)

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

EC20

Effect conc.:

> 0.13 - < 0.22 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat. (dissolved fraction)

Basis for effect:

growth rate

Key result

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

>= 0.07 - <= 0.15 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat. (dissolved fraction)

Basis for effect:

growth rate

Details on results:

Six different concentrations arranged in a geometric series with a spacing factor of 2.5 and a concurrent control was tested in the main experiment.
The measured concentrations deviated more than 20 % from the nominal therefore the exposure concentrations were calculated as the geometric mean of the start and end concentrations.
As the concentration was below the Limit of Detection (LOD) in the lowest test concentration (0.05 mg/L nominal) at the end of the test, the end concentration was taken as the Limit of Detection (LOD = 0.03 mg/L) according to the recommendation of OECD 23 Guidance document [6].

Validity criteria fulfilled:

yes

Conclusions:

The results of the statistical evaluation show that the 0-72 h average specific growth rate was statistically significantly different from the untreated control value in the concentrations of 0.10, 0.29, 0.77, 1.91 and 3.71 mg/L (measured) and not significantly different in the concentration of 0.04 mg/L (measured).
Accordingly the 72-h NOEC based on growth rate was determined to be 0.04 mg/L.
The 72 h ErC50 value was determined to be 0.40 mg/L (95 % confidence limits: 0.33 – 0.50 mg/L).

Executive summary:

Test item:
DIMETHOXYDIPHENYL-IODONIUMBROMID (Batch No.: B486663)
Test species:
Raphidocelis subcapitata (formerly known as Pseudokirchneriella subcapitata); Strain number: 61.81 SAG
Exponentially-growing cultures; preculture was incubated for four days before the test.
Dilution water: OECD medium, prepared in the laboratory of TOXI-COOP ZRT.
Concentrations: Nominal concentrations of 0.05, 0.13, 0.32, 0.80, 2.00 and 5.00 mg/L were investigated in the main study. Concurrent control ran.
The measured concentrations deviated more than 20 % from the nominal during the experiment therefore the geometric mean of the measured concentrations were calculated to determine exposure concentrations.
The corresponding calculated geometric mean concentrations were the followings: 0.04, 0.10, 0.29, 0.77, 1.91 and 3.71 mg/L.
Biological results and endpoints are based on the measured geometric mean concentrations.
Test design:
Exponentially-growing cultures of Raphidocelis subcapitata were exposed to the test item under defined conditions. The algal growth in relation to a control culture was determined over a fixed test period of 72 hours and, thus, over several algal generations. The test design included three replicates at each test concentration and six replicates for the untreated control. The alga cell concentration was approximately 104 cells/mL at the start of the test in all of the test cultures. Glass flasks with total capacity of 250 mL were used as test vessels. The volume of the test liquid in the vessels was 100 mL. The alga cell concentration was determined by manual cell counting by microscope in each testing flask during the 72-hour test, in 24-hour intervals.
Analytics: For determination of the test item concentrations, samples were taken from each concentration level and control at the start and at the end of the test. Concentrations were determined using HPLC method with UV detection.
Endpoints: EC10, EC20, EC50, NOEC and LOEC for both response variables (i.e. average specific growth rate and yield).
Statistics: For the determination of the LOEC and NOEC, ANOVA and Dunnett’s tests, for determination of the ECx values Probit analysis was used.
Validity:
All validity criteria were met and therefore the study can be considered as valid.

 

A 72-h NOEC based on growth rate was determined to be 0.04 mg/L.
The 72 h ErC50 value was determined to be 0.40 mg/L (95 % confidence limits: 0.33 – 0.50 mg/L).

Description of key information

Growth Inhibition Test  on Algae (Raphidocelis subcapitata) OECD Guideline for Testing of Chemicals, Section 2, No. 201: "Freshwater Alga and Cyanobacteria, Growth Inhibition Test", adopted 23rd March, 2006 (Annex 5 corrected: 28 July 2011).

Key value for chemical safety assessment

EC50 for freshwater algae:

0.4 mg/L