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Short-term toxicity to aquatic invertebrates

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Reference
Endpoint:
short-term toxicity to aquatic invertebrates
Type of information:
experimental study
Adequacy of study:
key study
Study period:
19.12-5.1.2017
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study with acceptable restrictions
Qualifier:
according to
Guideline:
OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test)
Version / remarks:
FINAS accredited inhouse method “EC001 Akuutti toksisuus vesikirpulla” which is based on international test standard ISO 6341:2012, Water quality – Determination of the inhibition of the mobility of Daphnia magna Straus (Cladocera, Crustacea) – Acute toxicity test.
Deviations:
no
Principles of method if other than guideline:
The test concentrations were established following the OECD guidance document No 23 (OECD 2000) for testing of difficult substances and mixtures. The target was to produce Water Accomodated Fraction (WAF) of tar. Tar is made of several substances of which some are volatile and some hydrophobic.
GLP compliance:
not specified
Remarks:
Accredited testing laboratory without GLP certificate
Analytical monitoring:
not specified
Vehicle:
yes
Remarks:
beakers
Details on test solutions:
The test water followed the recipe in the ISO standard and was made of four salts (CaCl2 x 2H2O, MgSO4 x 7H2O, NaHCO3 and KCl) dissolved to MilliQ pure water. The pH was set to 7,8 and O2 was above 8 mg/L.
Test organisms (species):
Daphnia magna
Details on test organisms:
The water flea (Daphnia magna) culture originates from a Japanese laboratory and have been cultured in SYKE laboratories for years. The culture media (Elendt M7) and culture practises follow the instructions of ISO standard (6341:2012).The test concentrations were established following the OECD guidance document No 23 (OECD 2000) for testing of difficult substances and mixtures. The target was to produce Water Ac-comodated Fraction (WAF) of tar.
Test type:
not specified
Water media type:
freshwater
Limit test:
no
Total exposure duration:
48 h
Hardness:
The test water followed the recipe in the ISO standard and was made of four salts (CaCl2 x 2H2O, MgSO4 x 7H2O, NaHCO3 and KCl) dissolved to MilliQ pure water.
Test temperature:
20˚C ± 1˚C
pH:
The pH remained between 7,6 and 7,9 in treatments and controls
Dissolved oxygen:
O2 was above 8,9 mg/L in treatments and controls
Salinity:
not measured
Conductivity:
not measured
Nominal and measured concentrations:
In the EC50-24h test, series of tar concentrations were established by weighing appropriate amounts of tar to each beaker to obtain five concentrations of tar (mg/L). In the EC50-48h test, one tar solution was prepared and dilutions from this solution were prepared to create other four test concentrations (five altogether).
Details on test conditions:
The parent water fleas were let to reproduce in the four salt test water and neonates from at least of second brood and less than 24 h old were selected for tests. Neonates were exposed in five concentrations either in four (EC50-48h) or five replicates (EC50-24h) each having five water fleas. Volume of single test vessel was 20 ml filled full and closed with a lid and kept wrapped in aluminum foil in room temperature (20˚C ± 1˚C). Immobilized ne-onates were counted at designated time points. Control vessels had only pure test water.
Reference substance (positive control):
yes
Remarks:
potassium dichromate
Key result
Duration:
24 h
Dose descriptor:
EC50
Effect conc.:
>= 237 mg/L
Nominal / measured:
meas. (initial)
Conc. based on:
test mat. (dissolved fraction)
Basis for effect:
mobility
Key result
Duration:
48 h
Dose descriptor:
EC50
Effect conc.:
>= 56 mg/L
Nominal / measured:
meas. (initial)
Conc. based on:
test mat. (dissolved fraction)
Basis for effect:
mobility
Details on results:
The EC50 values were calculated using probit regression anal-yses of the statistical package SPSS ver. 23.
EC50-24h: 237 mg tar/L (184 – 362 mg/L; 95% confidence limits).
EC50-48h: 56 mg tar/L (47 – 64 mg/L; 95% confidence limits).
Results with reference substance (positive control):
The recent (29.11.2016) positive control test with potassium dichromate gave EC50-24h as 0,7 mg/L (95% confidence limits 0,6 – 0,8 mg/L) that falls between the validity limits of 0,6 – 2,1 mg/L (additional re-quirement of ISO 6341:2012).
Validity criteria fulfilled:
yes
Conclusions:
In both tests control mortality was below 10% and oxygen concentration was ≥ 3 mg/L (requirement of OECD 2004). The recent (29.11.2016) positive control test with potassium dichromate gave EC50-24h as 0,7 mg/L (95% confidence limits 0,6 – 0,8 mg/L) that falls between the validity limits of 0,6 – 2,1 mg/L (additional requirement of ISO 6341:2012). The results were: EC50 -24 h: 237 mg/L. EC50 -48 h: 56 mg/L
Executive summary:

The tests were successful fulfilling the requirements of both ISO and OECD standard. The calculated EC50 estimates most likely reliably describe the level of exposure leading to acute toxicity to standard water flea species. The OECD guidance document nro 23 (OECD 2000) suggests to spike test waters individually, “where possible”. This procedure was applied in the EC50-24h test. EC50 -24 h: 237 mg/L. EC50 -48 h: 56 mg/L.

Description of key information

The test concentrations were established following the OECD guidance document No 23 (OECD 2000) for testing of difficult substances and mixtures. The tests were successful fulfilling the requirements of both ISO and OECD standard. The calculated EC50 estimates most likely reliably describe the level of exposure leading to acute toxicity to standard water flea species. The EC50 values were calculated using probit regression analyses of the statistical package SPSS ver. 23. The results were: EC50 -24 h: 237 mg/L. EC50 -48 h: 56 mg/L.

Key value for chemical safety assessment

EC50/LC50 for freshwater invertebrates:
56 mg/L

Additional information