2-hydroxyethyliminodi(acetic acid)

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

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)

Specific details on test material used for the study:

Chemical Name: (2-hydroxyethylimino) diacetic acid, disodium salt
Synonym: HEIDA
Appearance: Clear liquid
Identification: 53053-35
Chemical Purity: 40% (wtlwt.)
Solubility: miscible in water
Dow Registry No.: 001 8-5342
CAS No: 135-37-5
Molecular Formula: C6H9Na2NO5

Analytical monitoring:

yes

Details on sampling:

Bulk dose solutions were sampled and analyzed on day 0 (from 1000-mL volumetric flask) and day 4 (from fourth "test vessel" of each level, incubated without
algae). Each of the triplicate test vessels, inoculated with algae (including control vessels) were analyzed on day 4. The bulk dosing solutions of the 4, 12,37, and 11 1 mgk test levels were sampled in essentially the same manner on both day 0 and day 4 by transferring a 2-mL aliquot from each vessel to a 1-dram autosampler vial (blank AAM, without algae, was analyzed on day 0 only).

Vehicle:

no

Details on test solutions:

Bulk dose solutions were prepared in 1000-mL volumetric flasks on day 0 of the study at each of six target exposure concentrations (4 , 12, 37, 1t 1, 333, and 1000 mg HEIDA/L of algal assay medium). Test vessels were set in triplicate at each treatment level, including an AAM control. After dividing three aliquots (100 mL) from the bulk stock among the test vessels (250-mL Erlenmeyer flasks), all replicate vessels at each level, including controls, were inoculated with the
freshwater algal culture. A fourth vessel containing only a lOernL aliquot of the dosing solution, but no algae, was also prepared at each test level and subjected to. the same exposure conditions as the treatment flasks. The tcst solutions were maintained at 24 ± 1 "C throughout the study.

Test organisms (species):

other:

Details on test organisms:

Selenastnun capriconuctum Printz (strain 1648)

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

48 h

Test temperature:

24 ± 1 C

pH:

7.0-7.5

Reference substance (positive control):

no

Duration:

96 h

Dose descriptor:

EC50

Effect conc.:

> 45 - < 166 mg/L

Nominal / measured:

nominal

Conc. based on:

act. ingr. (total fraction)

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

> 80 - < 385 mg/L

Nominal / measured:

nominal

Conc. based on:

act. ingr. (total fraction)

Basis for effect:

growth rate

Duration:

96 h

Dose descriptor:

EC50

Effect conc.:

> 55 - < 281 mg/L

Nominal / measured:

nominal

Conc. based on:

act. ingr. (total fraction)

Basis for effect:

other: inhibition

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

> 38 - < 1 665 mg/L

Nominal / measured:

nominal

Conc. based on:

act. ingr. (total fraction)

Basis for effect:

other: inhibition

Duration:

96 h

Dose descriptor:

NOEC

Effect conc.:

12 mg/L

Nominal / measured:

nominal

Conc. based on:

act. ingr. (total fraction)

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

37 mg/L

Nominal / measured:

nominal

Conc. based on:

act. ingr. (total fraction)

Basis for effect:

growth rate

Details on results:

Preliminam Test: Two preliminary range-finding tests were set in order to establish the
concentration range for the definitive test. The objective was to select a range of treatment levels
that would result in both inhibition in algal growth and no inhibition or observable effect in
growth. The first test was carried out by exposing algae to five target exposure concentrations:
1000, 100, 10, 1 and 0.1 mg/L, and an algal assay medium control group (negative group), with
each dose group set in triplicate; the solutions were made via serial dilution of the 1000 mg/L
primary stock and a carrier solvent was not used during testing. The estimated May ECso value
fell between 100 and 1000 mg/L. However, based on the lack of suitable growth in the control
group the data generated was considered unreliable. Therefore, a second probe was set with five
concentrations ranging from 100 mg/L to 0.01 mglL separated by an order of magnitude, and algal
assay medium control p u p (negative group), with each dose group set in triplicate. The .
solutions were made via serial dilution of the 100 mg/L primary stock and a carrier solvent was
not used during testing. The results from this probe indicate that the estimated 4day ECs value
was greater than the top dme of 100 mg/L.
Definitive Test: Based on the results from the preliminary tests, the definitive test was set with
nominal concentrations ranging from 4 to 1000 mg/L. The test was started on January 13, 1997
and terminated on January 17, 1W. The six nominal exposures were set in a geometric series
using a progression factor of -3. The 1000 mg/L bulk dosing solution was prepared
volumetrically. The calculation used to &tennine the amount of HEIDA required to yield this
concentration was based on the laboratory-derived density for the neat test material of 1.245
g/mL. The remahhg concentrations were achieved via serial dilution of this primary stock
solution. Three replicates were set of each test concentration, and six replicates were set:in the
control group. Each test flask was then dosed with an inoculum of approximately 10,000 algal
ceIls/mL. A counting blank was included with each test concentration; these blanks contained
growth medium and the appropriate amount of test substance but no algae. The definitive test
was carried out aseptically under static conditions for 4 days. The test flasks were placed in an
incubator with the temperahue controller set to maintain 24 ± 1°C with continuous light at
approximately 4300 ± 1100 lux.

Validity criteria fulfilled:

yes

Conclusions:

The 3- and 4day HEIDA EC50 values and their 95% confidence intervals for algal growth and percent inhibition of growth were 175 (80-385) mg/L and 86 (45-166) mg/L for
growth, respectively, and 251 (38-1665) mg/L and 124 (55-281) mg/L respectivcly for inhibition. The 3- and 4 -day NOEC values for algal growth were 37 mg/L and 12 mg/L,
respectively.

Executive summary:

The 3- and 4day HEIDA EC50 values and their 95% confidence intervals for algal growth and percent inhibition of growth were 175 (80-385) mg/L and 86 (45-166) mg/L for growth, respectively, and 251 (38-1665) mg/L and 124 (55-281) mg/L respectivcly for inhibition. The 3- and 4 -day NOEC values for algal growth were 37 mg/L and 12 mg/L, respectively.

Description of key information

The 3- and 4day HEIDA EC50 values and their 95% confidence intervals for algal growth and percent inhibition of growth were 175 (80-385) mg/L and 86 (45-166) mg/L for

growth, respectively, and 251 (38-1665) mg/L and 124 (55-281) mg/L respectivcly for inhibition. The 3- and 4 -day NOEC values for algal growth were 37 mg/L and 12 mg/L,

respectively.

Key value for chemical safety assessment

EC50 for freshwater algae:

86 mg/L