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Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

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Reference
Endpoint:
toxicity to aquatic algae and cyanobacteria
Type of information:
experimental study
Adequacy of study:
key study
Study period:
not specified
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: The study was conducted according to guideline.
Reason / purpose:
reference to same study
Reason / purpose:
reference to other study
Qualifier:
equivalent or similar to
Guideline:
other: EPA-660/3-75-009
Deviations:
no
Principles of method if other than guideline:
not applicable
GLP compliance:
no
Specific details on test material used for the study:
Details on properties of test surrogate or analogue material (migrated information):
Not applicable.
Analytical monitoring:
yes
Details on sampling:
Water samples were taken for analysis at intervals prior to and after the start of the test. During method development work it was shown that the water-soluble fraction of EPIKOTE 828 was composed principally of some species other than the major component of the test material as supplied. Mass spectrometry showed that, though this "water-soluble fraction" used as a standard was not pure, it contained a principal component which was probably a diol formed by hydrolysis of one of the two epoxide moieties present in the major component of EPIKOTE 828.

An analytical standard was obtained by preparative chromatography of EPIKOTE 828 to separate a quantifiable amount of the "water soluble fraction".

Three injections of EPIKOTE 828 in MTBE (3 x 100 mg EPIKOTE) were made on the following HPLC system:
Column: 25 cm x 9 mm I.D. stainless steel
Packing: Partisil 5 PAC
Mobile phase: MTBE + methanol (99.5 + 0.5 v/v)
Flow rate: 5 ml/min
Wavelength: 228 nm
(MTBE - methyl t-butyl ether)

Five fractions were collected following each injection. Fraction 5 co-chromatographed with the contents of the stock solutions and was used to produce analytical standard solutions for use on the following HPLC system:
Column: 25 cm x 4.6 mm I.D. stainless steel
Packing: Spherisorb 5 NH
Mobile phase: MTBE + methanol (92.5 + 7.5 v/v)
Flow rate: 1 ml/min
Wavelength: 228 nm
Retention time: "Water soluble fraction" ca 7.5 -8.2 min.
Vehicle:
no
Details on test solutions:
The "water soluble fraction" obtained from EPIKOTE 828 and used as an analytical standard in the aquatic tests was examined by mass spectrometry. Though it was not possible to characterize this material completely, the results suggested that a major component of the "water soluble fraction" was the diol presumably formed by hydrolysis of one of the two epoxide function of DGEBPA, the major component of EPIKOTE 828
Test organisms (species):
Scenedesmus capricornutum
Details on test organisms:
S. capricornutum were taken from the axenic laboratory culture. The culture is derived from a strain (ATCC 22662) obtained from the American Type Culture Collection, Maryland, U.S.A..
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
72 h
Post exposure observation period:
Study was stopped after 72 hours and no further observations made
Hardness:
no data
Test temperature:
24-25C
pH:
pH for the control group (which had not been passed through a chromosorb column) ranged from 7.1 at the start of the study to 8.6 at the end of the study. pH for the top concentrations ranged from 7.4 at the start of the study to 7.5 at the end of the study.
Dissolved oxygen:
no data
Salinity:
no data
Nominal and measured concentrations:
Nominal: 0 (control), 0 (chromosorb control), 2.2, 4.6, 10, 22, 46, 100
Measured: <0.01, <0.01, 0.18, 0.48, 1.1, 2.4, 4.2, 11
Details on test conditions:
A 3 day (72 h) growth test was carried out. A saturated stock solution of the water-soluble fraction of EPIKOTE 828 in algal growth medium was produced. Twenty-seven, 250 ml Erlenmeyer flasks were prepared. To five triplicate sets of these were added quantities of the stock solution and algal growth medium sufficient to produce, 46, 22, 10, 4.6 and 2.2% dilutions of the stock solution when made up to a final volume of 50 ml. A sixth set of three flasks was part filled with 50 ml of the undiluted stock solution. Two sets of control flasks were also prepared. The first set, consisting of six flasks, were part filled with 50 ml of algal growth medium. The second set, consisting of the remaining three flasks, were part filled with 50 ml of algal growth medium that had been circulated through a column packed with Chromosorb WHP that had not been coated with EPIKOTE 828. The latter also served as controls and are subsequently referred to as chromosorb controls.

Each flask was inoculated with sufficient S. capricornutum cells to give an initial nominal cqncentration of 10 000 cells ml-. The flasks: were then closed with a loose fitting aluminium cap and incubated in a cooled orbital incubator (100 cycles/min) under constant illumination (~3000 lux) at a nominal temperature of 22-26°C for 3 days (72 h). At 0 h and then at 24 h intervals after the start of incubation cell counts were made using a Coulter Multisizer. The pH in the control and highest concentration test solutions were determined at the start and conclusion of the test. The incubation temperature was monitored throughout the test.

Samples of the freshly prepared and 72 h old test and control solutions were analysed to determine the concentration of the water-soluble fraction of EPIKOTE 828.
Reference substance (positive control):
no
Duration:
48 h
Dose descriptor:
EC50
Effect conc.:
9.1 mg/L
Nominal / measured:
meas. (arithm. mean)
Conc. based on:
other: water soluble fraction
Basis for effect:
biomass
Remarks on result:
other: 5.6 - 42 mg/L
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
9.4 mg/L
Nominal / measured:
meas. (arithm. mean)
Conc. based on:
other: water soluble fraction
Basis for effect:
biomass
Remarks on result:
other: 5.3 - 40
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
2.4 mg/L
Nominal / measured:
meas. (arithm. mean)
Conc. based on:
other: water soluble fraction
Basis for effect:
biomass
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
4.2 mg/L
Nominal / measured:
meas. (arithm. mean)
Conc. based on:
other: water soluble fraction
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
> 11 mg/L
Nominal / measured:
meas. (arithm. mean)
Conc. based on:
other: water soluble fraction
Basis for effect:
growth rate
Details on results:
Inhibition of the growth of S. capricornutum by more than 50% was only detected at the highest test concentration when the data were analysed in terms of the area under the growth curves (A) and then only after 48 and 72 hours of exposure.

The highest concentration in which growth of S. capricornutum was not inhibited over the 72 hour test period was 2.4 mg/L when growth was expressed in terms of A and 4.2 mg/L when growth was expressed in terms of the average specific growth rate (u).
Results with reference substance (positive control):
no data
Reported statistics and error estimates:
see above

The 48 and 72 hour EC50 values were 9.1 and 9.4 mg/L, respectively.

Validity criteria fulfilled:
yes
Conclusions:
The 48 and 72 hour EC50(biomass) values were 9.1 and 9.4 mg/L, respectively.
Executive summary:

The toxicity of EPIKOTE 828 to S. capricornutum was determined in a 72 h growth test. Based upon analyses of the test results in terms of the area under the culture growth curves the 48 and 72 EC50 values were calculated to be 9.1 and 9.4 mg/L, respectively, when expressed in terms of the concentration of the water-soluble fraction of EPIKOTE 828.

Description of key information

In a growth inhibition test with Scenedesmus capricornutum, the 72-hour ErC50 for BADGE and BADGE-related resins was determined to be > 11 mg/L, which was the limit of solubility for BADGE.  The 72-hour NOEC (based on growth rate) for BADGE and BADGE-related resins was determined to be 4.2 mg/L.

Key value for chemical safety assessment

EC50 for freshwater algae:
11 mg/L
EC10 or NOEC for freshwater algae:
4.2 mg/L

Additional information

Two toxicity tests were assessed for this endpoint, and these studies were found to be of good quality and reliable for use in the risk assessment process. The two algal toxicity studies that were deemed of good quality and reliable for use in risk assessment (Klimisch score = 1 or 2) measured both growth rate (r) and biomass (y) as indicators of growth inhibition over 72 hours of exposure.  One of these reliable studies tested BADGE with Scenedesmuscapricornutum and reported the NOEC and ErC50 for growth rate as 4.2 and >11 mg/L BADGE, respectively. The 72-hour ErC50 value (based on growth rate) could not be exactly determined since no significant effects were noted at the limit of solubility for the test material. The 72-hour NOEC and EyC50 (based on biomass) in this same study with S. capricornutum were reported as 2.4 and 9.4 mg/L BADGE, respectively. In the other reliable algal toxicity test with Pseudokirchneriella subcapitata, the 72-hour ErC10 and ErC50 for growth rate was reported as 4.51 and >100 mg/L BADGE, respectively. As in the previous study, the ErC50 value for the specific growth rate could not be exactly determined due to effects occurring above the limit of solubility.  The 72-hour EyC10 andEyC50 based on biomass was reported as 1.96 and 13.81 mg/L BADGE, respectively, for P. subcapitata. Since the use of the average specific growth rate for estimating toxicity is scientifically preferred (OECD 201, 2006), this endpoint was used to select the key parameter, and the data from the algal toxicity test with S. capricornutumwas used since the toxicity values in this study were lower than the reported values for P. subcapitata.