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Toxicity to aquatic algae and cyanobacteria

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Description of key information

Key value for chemical safety assessment

EC50 for freshwater algae:
1.75 mg/L

Additional information

For this endpoint, in total 3 studies are available, one klimisch 1 study and two Klimisch 2 studies.

In the GLP compliant Klimisch 1 study from Ágh (2012), the toxicity of Camphene, technical grade, solid to Pseudokirchneriella subcapitata was determined according to OECD 201, EU method C.3 and the US EPA OPPTS 850.5400 in a static test. The test item has a purity of 82.6 % by weight and contains 12.4 % Tricyclene as impurity. A supersaturated solution (nominal loading: 1000 mg/L) was first prepared by mixing an excess of the test item in dilution water (OECD medium). This mixture was shaken overnight and then the non-dissolved test material was separated to give the stock solution at the limit of solubility level in the test medium. This stock solution was further diluted with dilution water to result in following dilutions: 19.8, 29.6, 44.4, 66.7 and 100 % v/v saturated solution.

The concentration of Camphene was experimentally determined. and following geometric mean measured concentrations were obtained: < LOQ (Control), 0.06, 0.07, 0.12, 0.29 and 0.28 mg/L. After 72 hours, 3.3, 5.5, 13.7, 17.1 and 19.4% inhibition of the growth rate relative to the control was determined at mean measured concentrations of 0.06, 0.07, 0.12, 0.29 and 0.28 mg/L. The NOEC for growth rate was determined to be 0.07 mg/L. The ErC50 was extrapolated to 1.75 mg/L (the highest mean measured concentration was 0.29 mg/L).

Overall the inhibition of the growth rate was with < 20% low and therefore extrapolation to ErC50 values is problematic. However, since several measures (sealing of test vessels, preconditioning of test vessels) were taken to avoid a loss of test material, the obtained test concentrations must be considered as the maximum of concentration which could be obtained under the conditions of the algal test. Therefore the results from the extrapolation are considered relevant.

It was tried to minimize the loss of test item by sealing the test vessels and b preconditioning the test vessels. However, the loss of test material was significant already during the first 24 hours. Calculation of the 48 hours effect concentrations (NOEC, ErC50) resulted in less conservative values and hence the 72 hour values were reported.

The results of this study are considered relevant and reliable for the risk assessment.

In the Klimisch 2 study from Noack (1992) the toxicity of Camphene to aquatic algae was studied with Scenedesmus subspicatus for 72 hours according to OECD Guideline 201. Various concentrations were tested: 32, 58, 100, 180, 320, 580 and 1000 mg/L. Since the substance is insoluble in water, DMSO was used as vehicle. In all concentrations it was found that the concentration at the beginning was less than 10% of the nominal concentration. The unsatisfactory recovery of camphene is due both to the water insolubility as well as the high vapor pressure. A concentration-effect relationship could not be established. The cell density was determined by chlorophyll fluorescence and converted into cell numbers. The EC50 was greater than 1000 mg/L (basis for effect: growth rate). All tested concentrations were above the limit of water solubility.

The results of this study were not used for the risk assessment since testing was performed only above the limit of water solubility, the biological data were based on nominal concentrations and dose verification was not able to show that the concentrations were maintained within 80 - 120 % of the nominal concentrations. Furthermore, the obtained result from Noack (1992) is less conservative than the result from Ágh (2012).

In the second Klimisch 2 study from Noack (1992) the toxicity of Camphene to aquatic algae was studied with Scenedesmus subspicatus for 72 hours according to OECD Guideline 201. Various concentrations were tested: 32, 58, 100, 180, 320, 580 and 1000 mg/L. Since the substance is insoluble in water, Tween 80 was used as vehicle. In all concentrations it was found that the concentration at the beginning was less than 10% of the nominal concentration. The unsatisfactory recovery of camphene is due both to the water insolubility as well as the high vapor pressure. A concentration-effect relationship could not be established. Between 58 and 320 mg/L, proliferation of algal cell was observed. The vehicle (Tween 80) showed an inhibition on the algal cell proliferation at the highest tested concentration (100 mg / L). The cell density was determined by chlorophyll fluorescence and converted into cell numbers. The EC50 was greater than 1000 mg/L (basis for effect: growth rate).

The results of this study were not used for the risk assessment since testing was performed only above the limit of water solubility, the biological data were based on nominal concentrations and dose verification was not able to show that the concentrations were maintained within 80 - 120 % of the nominal concentrations. Furthermore, the obtained result from Noack (1992) is less conservative than the result from Ágh (2012).