N-(2-nitrophenyl)phosphoric triamide

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:

2005-02-07 - 2005-08-12

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 201 (1984)

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

yes

Vehicle:

no

Details on test solutions:

Test solutions of the chosen concentrations were prepared by mixing a stock solution of the test item with test medium and inoculum culture.

Before test initiation, a stock solution was prepared by dissolving the test item in the test medium. Then, adequate volumes of the stock solution were mixed with test medium to obtain the desired test concentrations. The test solutions were prepared just before introduction of the algae (= test initiation). The same volume of algal inoculum was added to each test solution.

Test organisms (species):

Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)

Details on test organisms:

freshwater green algae - Desmodesmus subspicatus

source: Albrecht-v.-Haller-Institut fur Pflanzenwissenschaften; Sammlung von Algenkulturen Nikolausberger Weg 18, D-37073 Gottingen
strain: 86.81 SAG

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

72 h

Post exposure observation period:

no

Test temperature:

23.5 - 24.1 degree C

pH:

8

Nominal and measured concentrations:

nominal (mg/l): 3.13, 6.25, 12.5, 25.0, 50.0, 100.0

Reference substance (positive control):

not required

Key result

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

6.25 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

test mat.

Basis for effect:

growth rate

Key result

Duration:

72 h

Dose descriptor:

LOEC

Effect conc.:

12.5 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

test mat.

Basis for effect:

growth rate

Key result

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

51.4 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

test mat.

Basis for effect:

growth rate

Key result

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

22 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

test mat.

Basis for effect:

growth rate

Validity criteria fulfilled:

yes

Conclusions:

The growth rate in the 100 mg/l treatment as 92% inhibited compared to the control. A NOEC of 6.25 mg/l and a LOEC of 12.5 mg/l have been estimated for the parameters cell growth and growth rate. The EC50 was calculated as 28.3 mg/l (cell growth) and 51.4 mg/l (growth rate).

Executive summary:

The test was performed according to the recommendations of the OECD Guideline 201 (1984).

The purpose of this study was to determine the inhibitory effect of the test item on the growth of the fresh water unicellular green alga Desmodesmus subspicatus. Exponentially growing cultures of this algal species were exposed to various concentrations of the test item under defined conditions. The aim of the test was to determine the EbC50 (cell biomass), ErC50 (growth rate), LOEC and NOEC for the endpoint based on D. subspicatus growth (cell number) over a period of 72 hours. Other endpoints included cell size, colour differences or aggregation of alga cells.

The growth rate in the 100 mg/l treatment as 92% inhibited compared to the control. A NOEC of 6.25 mg/l and a LOEC of 12.5 mg/l have been estimated for the parameters cell growth and growth rate. The EC50 was calculated as 28.3 mg/l (cell growth) and 51.4 mg/l (growth rate).

Description of key information

OECD 202 guideline study, GLP: NOEC: 6.25 mg/l

Key value for chemical safety assessment

EC50 for freshwater algae:

51.4 mg/L

EC10 or NOEC for freshwater algae:

6.25 mg/L

Additional information

A study was performed to assess the effect of the test material on the growth of the green alga Scenedesmus subspicatus. The method followed that described in the OECD Guidelines for Testing of Chemicals (1984) No 201, "Alga, Growth Inhibition Test".

The growth rate in the 100 mg/l treatment as 92% inhibited compared to the control. A NOEC of 6.25 mg/l and a LOEC of 12.5 mg/l have been estimated for the parameters cell growth and growth rate. The EC50 was calculated as 28.3 mg/l (cell growth) and 51.4 mg/l (growth rate).