bis(O,O-2-ethylhexyl-thiophosphoryl)polysulfide

Toxicity to aquatic algae and cyanobacteria

Administrative data

Endpoint:

toxicity to aquatic algae and cyanobacteria

Data waiving:

study scientifically not necessary / other information available

Justification for data waiving:

other:

Justification for type of information:

JUSTIFICATION FOR DATA WAIVING

According to REACH Annex VII column 2, 9.1.2. Growth inhibition study aquatic plants (algae preferred), the study does not need to be conducted if there are mitigating factors indicating that aquatic toxicity is unlikely to occur for instance if the substance is highly insoluble in water or the substance is unlikely to cross biological membranes.

In general, there is no legal limit value available defining a substance as poorly water soluble or insoluble under REACH. However, in ECHA’s Guidance document Chapter R.7b: Endpoint specific guidance Version 3.0 – February 2016, it is stated: „poorly water soluble substances (e.g. water solubility below 1 mg/L or below the detection limit of the analytical method of the test substance)“. Further, poorly soluble substances are defined by OECD (2000 OECD SERIES ON TESTING AND ASSESSMENT, Number 23, GUIDANCE DOCUMENT ON AQUATIC TOXICITY TESTING OF DIFFICULT SUBSTANCES AND MIXTURES, ENV/JM/MONO(2000)6) as substances with a limit of solubility <100 mg/l although technical problems are more likely to occur at <1mg/l as defined in TGD (1996). Very low water solubility (i.e. in the low μg/l range) could be used as a reason to significantly modify a standard test or to test non-pelagic organisms preferentially.
ECHA’s Guidance document Chapter R.7c: Endpoint specific guidance Version 3.0 – June 2017 further says: „As indicated in the OECD TG 305, for strongly hydrophobic substances (log Kow > 5 and a water solubility below ~ 0.01-0.1 mg/L), testing via aqueous exposure may become increasingly difficult. However, an aqueous exposure test is preferred for substances that have a high log Kow but still appreciable water solubility with respect to the sensitivity of available analytical techniques, and for which the maintenance of the aqueous concentration as well as the analysis of these concentrations do not pose any constraints.

The logPow was determined to be >7.2, and the water solubility is < 4.5 µg/L, so the criteria mentioned above are met. Further, the criterion for “below the detection limit of the analytical method of the test substance” is also met. The establishment and validation of the analytical method was properly performed.
The limit of quantification (LOQ) is defined as the lowest concentration level at which an accuracy in the range 70-110% and a repeatability of ≤ 20% is demonstrated. The LOQ was obtained from the data of the accuracy and repeatability test. The limit of quantification (LOQ) was assessed at a test item concentration of 10 µg/L in water.
The calibration curve was constructed excluding the data points in the concentration range 0.0400 - 0.250 µg/L since no reliable duplicate results and no linear or quadratic relationship between response of disulfide (n=0) and test item concentration was observed.
In the concentration range 0.450 – 5.00 µg/L, the calibration curve was constructed excluding one data point since a deviation was observed in the response factor. There was a quadratic relationship between response of disulfide (n=0) and test item concentration in the range of 0.450 – 5.00 µg/L (in end solution). Since the coefficient of correlation (r) was > 0.99 and the back calculated accuracies of the remaining data points were in the range 85-115% the calibration line was accepted. Pretreatment of the samples however required a dilution by a factor of 10 with 2-propanol, which does not allow a quantification in these low limits.
Ecotoxicity tests are performed in media containing various supplements and biological material, which is expected to lower the sensitivity of the analytical method. Hence, quantification of the test item up to its water solubility in ecotoxicity test media could like not be performed at all. So, the required analytics for ecotoxicity testing, are technically not feasible, and testing does not need to be conducted.

Based on the available information it can be stated that, as outlined in the first waiving possibility under REACH, the substance is highly insoluble in water, and hence, aquatic toxicity is unlikely to occur. The latter conclusion is supported by available studies conducted prior to REACH implementation, i.e. a study for toxicity against Brachydanio rerio. In this study, the following LC-values (Mortality, effective concentrations) were determined: LC100 = 12.0 mg/L; LC50 = 2.38 mg/L; LC0 = 0.64 mg/L; NOEC = 0.64 mg/L, which are way above the possible water solubility of the registered substance. With regard to fish, adequate information for environmental classification and labelling is available, as the noted effects were above the water solubility and trigger classification as Aquatic Chronic Cat. 4, so omitting this test would not result in an underestimation of the actual hazard.

Hence, an additional study of the acute toxicity of the registered substance to algae does not need to be conducted, as it is considered both not technically feasible and no additional information on classification and labelling could be retrieved, and the study can be omitted.

Cross-reference

Reason / purpose for cross-reference:

data waiving: supporting information

Remarks:

water solubility

Reference

Endpoint:

water solubility

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2017-05-11 - 2017-10-19 (experimental phase)

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Reason / purpose for cross-reference:

reference to same study

Remarks:

Partition coefficient

Reason / purpose for cross-reference:

reference to same study

Remarks:

Adsorption / Desorption

Qualifier:

according to guideline

Guideline:

EU Method A.6 (Water Solubility)

Version / remarks:

EC Guideline A.6. Water Solubility. March 19, 2014

Deviations:

no

Qualifier:

according to guideline

Guideline:

OECD Guideline 105 (Water Solubility)

Version / remarks:

OECD Guideline 105. Water Solubility. July 27, 1995

Deviations:

no

Qualifier:

according to guideline

Guideline:

EPA OPPTS 830.7840 (Water Solubility)

Version / remarks:

EPA Product Properties Test Guideline OPPTS 830.7840: Water Solubility: Column Elution Method; Shake Flask Method. March 1998

Deviations:

no

GLP compliance:

yes

Type of method:

flask method

Remarks:

slow-stirring

Specific details on test material used for the study:

SOURCE OF TEST MATERIAL
- Source and lot/batch No.of test material: sponsor

STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL
- Storage condition of test material: In refrigerator (2-8°C)

Key result

Water solubility:

< 0 g/L

Conc. based on:

test mat.

Loading of aqueous phase:

10 other: µl/l

Incubation duration:

>= 24 - <= 72 h

pH:

>= 7.3 - <= 7.4

Remarks on result:

other: water solubility is below the LOQ

Conclusions:

The study was performed according to OECD TG 105 under GLP on the substance to be registered itself, the test procedure is well documented and therefore reliability of Klimisch 1 has been assigned. The analytical method was properly established. The limit of quantification (LOQ) was assessed at a test item concentration of 10 µg/L in water. The response of the test samples was lower than the response of the lowest calibration solution (0.450 µg/L). The analyzed concentration in the test samples was determined to be < 4.5 µg/L taking a dilution factor of 10 into account. In conclusion it can only be stated that the water solubility of the test item at 20°C was < 4.5 * 10E-6 g/L, making a quantification in e.g. ecotoxicity test impossible as the test item must be regarded as practically insoluble in water.

Executive summary:

The water solubility of the test item was determined according to EC A.6, OECD 105, and OPPTS 830.7840 under GLP at 20°C by the slow-stirring flask method as < 4.5 x 10E-6 g/L.