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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:
2011
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: Study carried out according to guideline and under GLP
Reason / purpose:
reference to same study
Qualifier:
according to
Guideline:
OECD Guideline 201 (Alga, Growth Inhibition Test)
Deviations:
yes
Remarks:
The algae were exposed to the water accomodated fraction according to OECD 2000.
Principles of method if other than guideline:
not applicable
GLP compliance:
yes (incl. certificate)
Analytical monitoring:
yes
Details on sampling:
no data
Vehicle:
no
Details on test solutions:
As the test material is considered to be poorly soluble, the organisms were exposed to the Water Accomodated Fraction (WAF). In this approach aquous media are prepared by by mixing the test item for a prolonged period of time. At completion of the mixing and settlement the test item phase is then separated and the organisms are exposed to the aquous phase or WAF. Exposures are expressed in terms of the original concentration of the test item in water at the start of the mixing period.
Test organisms (species):
Pseudokirchneriella subcapitata (previous names: Raphidocelis subcapitata, Selenastrum capricornutum)
Details on test organisms:
Liquid cultures of Pseudokirchnerella subcapitata were obtained from the culture collection of Algae and Potozoa (CCAP) SAMS Research services Ltd, Scottish Marine Institute, Oban, Argyll, Scotland.
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
72 h
Post exposure observation period:
not applicable
Hardness:
no data
Test temperature:
24 +/- 1
pH:
7.2 - 7.8
Dissolved oxygen:
no data
Salinity:
no data
Nominal and measured concentrations:
measured concentrations of 0 (control), 1.0, 3.2, 10, 32 and 100 mg/L.
Details on test conditions:
Exposure took place in 250 ml conical flasks.
Reference substance (positive control):
yes
Remarks:
potassium dichromate
Duration:
72 h
Dose descriptor:
EL50
Effect conc.:
9.6 mg/L
Nominal / measured:
meas. (geom. mean)
Conc. based on:
test mat.
Remarks:
Water Accomodated Fraction
Basis for effect:
growth rate
Remarks on result:
other: 95% CL: 7.8-12 mg/L
Duration:
72 h
Dose descriptor:
EL50
Effect conc.:
5 mg/L
Nominal / measured:
meas. (geom. mean)
Conc. based on:
test mat.
Remarks:
Water ACccomodated Fraction
Basis for effect:
cell number
Duration:
72 h
Dose descriptor:
NOELR
Effect conc.:
3.2 mg/L
Nominal / measured:
meas. (geom. mean)
Conc. based on:
test mat.
Remarks:
Water Accomodated Fraction
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
NOELR
Effect conc.:
3.2 mg/L
Nominal / measured:
meas. (geom. mean)
Conc. based on:
test mat.
Remarks:
Water Accomodated Fraction
Basis for effect:
cell number
Validity criteria fulfilled:
yes
Conclusions:
The 72hr EL50 based on the WAF of DBPP for Pseudokirchneriella subcapitata for growth rate was observed to be 9.6 mg/L (with an 95% CI of 7.8 - 12 mg/L), the NOELR was 3.2 mg/L. The 72hr EL50 based on the WAF of DBPP for Pseudokirchneriella subcapitata for Yield was observed to be 5.0 mg/L, the NOELR was 3.2 mg/L.
Executive summary:

An algal growth inhibition test was carried out with Pseudokirchneriella subcapitata exposed to dibutyl phenyl phosphate was carried out according to OECD guideline 201. The 72hr EL50 of DBPP for growth rate was observed to be 9.6 mg/L (based on the Water Accomodated Fraction) with a 95% CI of 7.8 - 12 mg/L, the NOELR was 3.2 mg/L (WAF). The 72 hr EL50 of DBPP for Pseudokirchneriella subcapati for Yield was observed to be 5.0 mg/L (based on the Water Accomodated Fraction). The NOELR was 3.2 mg/L (WAF).

Description of key information

Two algal studies are available, one carried out in 1978 according to then existing guidelines (Hollister and Shuba, 1978) and a recent study (2011) carried out according to existing guidelines and under GLP (Vrijenhoef and Mullee, 2011). The latter study is regarded as the key study and the results from that study is used in further risk assessment.

Key value for chemical safety assessment

EC50 for freshwater algae:
9.6 mg/L
EC10 or NOEC for freshwater algae:
3.5 mg/L

Additional information

The results of the studies are comparable, also taking the different exposure time into account. Though the setup of the studies was not entirely the same as were the evaluated of the endpoints. The endpoints of the most recent study are considered most appropriate for further use in the risk assessment. The most recent study used a WAF approach, however based on the water solubility of the substance the EL10/50 and a NOELR, can be regarded the same as the EC10/50 and NOEC. Therefore, the EC50 (72hr) is 9.6 mg/L, the EC10: 3.5 mg/L and the NOEC: 3.2 mg/L for growth rate.