Registration Dossier

Environmental fate & pathways

Endpoint summary

Administrative data

Description of key information

Additional information

The test substance is a solid under all environmental conditions and is of low solubility in water (<0.0067 mg/l) and is of low volatility (based on0.667 kPa at 20 °C).  The substance was determined to have a log Koc value of 6.54, indicating a high affinity for soil/sediment. As such, any environmental release will result in virtually all of the substance compartmentalising into soil/sediment compartments, with little release directly to atmosphere or compartmentalising to water compartments.

Any potential exposure to the environment is predicted to result in redistribution to both water and soil; however due to its low volatility, low water solubility and partitioning values, these indicate that the majority of the substance would eventually partition to soil rather than the water compartment should it be released to the environment. 

A Level III fugacity model was conducted in the US EPA EPISUITE (Mackay,) which assumes steady-state but not equilibrium conditions. The Level III model in EPI Suite predicts partitioning between air, soil, sediment and water using a combination of default parameters and various input parameters. This model has been used to calculate the theoretical distribution of a range of components present in the substance between four environmental compartments (air, water, soil, sediment) at steady state in a unit world. The results obtained from modelling are as follows:

Air (%)

Water (%)

Soil (%)

Sediment (%)

0.036

2.07

2.86

95

It is proposed that the majority of the substance is modelled to distribute to the sediment compartments within the constraints of the QSAR model. As such, and given the low solubility, the soil and sediment compartments are proposed to the areas to which partitioning would occur.

The substance displays a low ready biodegradability in that it achieved 29% biodegradation in a 28-day CO2 evolution ready biodegradation study, and 5% in atwo-phase closed bottle test. This indicates that the substance isunlikely to achieve a half-life of less than 40 or 60 days within fresh water attributed to ready biodegradation alone, but could potentially biodegrade over time. No data on hydrolysis is available; however given the structure, some hydrolysis slowly over time under normal environmental conditions could be anticipated.   Studies on direct phototransformation in water are not available, but it is assumed on the basis of chemical structure and nature of use that the substance is not degraded by direct photolysis. It is concluded, therefore, that biotic and abiotic processes could contribute to the depletion of the substance within the environment, although this is likely to be a slow process.

The substance has been demonstrated to have a very high partition coefficient value which demonstrates that the potential for this substance to accumulate biologically is limited, given that it is a high value of log P = 7.90 ± 1.22 (25°C, pH = 6.9). The high log Pow is considered to be more a consequence of poor water solubility issues than a lipophilic tendency and is considered to be not indicative of the tendency to bioaccumulate in lipid tissues of aquatic organisms. This is based on literature data which demonstrates a tendency for the Bioconcentration Factor (BCF) to decrease as Log Pow increases above 6. At a high value of 7.9, the substance is proposed not to bioaccumulate.  This is further confirmed via the use of the following QSAR tools:

 

·       CAESAR BCF Read-Across (version 1.0.0)

·       US EPA On-Line EPI Suite™v3.01 model BCFBAF

 

Which indicates that the substance is unlikely to bioaccumulate, with calculated values as follows:

 

BCF value (L/kg wet-wt)

Log BCF value

BCF Read-Across (version 1.0.0)

888

2.95

US EPA On-Line EPI Suite™v3-01 model BCFBAF

1245

3.095

 

This QSAR prediction is supported by a radiolabelled toxicokinetic study on the substance. Within this study,14C radiolabelled test material was not extensively distributed into tissues of rats after an oral dose. The substance did not demonstrate high absorption from the gastrointestinal tract. And after 72h, the concentrations in the majority of tissues had decreased significantly. The above factors indicate that bioaccumulation within body tissues is unlikely. 

Adsorption to soil is deemed to be high, based on the high associated test results. Such potential indicates that the substance is likely to bind tightly to soils and sediments and not partition at high levels in water. As such, significant exposure related effects to water dwelling organisms are considered to be negligible. It is proposed that the substance is not hazardous to terrestrial organisms, and as such, should not pose a hazard overall to the environment.  This statement will be confirmed by the completion of a study to assess these overall effects.

Based on its low water solubility, high partition coefficient and biodegradation rate it can be concluded that it is likely that the substance could potentially be persistent within the environment. Abiotic effects within the environment could result in eventual removal from the environment. Given the low toxicity and predicted bioaccumulation potential, it is expected that effects on organisms in the food chain can considered to be minimised. 

Finally, the substance demonstrates low acute toxicity in mammalian studies. As it also is not anticipated to bioaccumulate, based on QSAR assessments and hydrolysis effects, in the event of exposure to higher level organism via ingestion of environmental organisms, effects due to secondary poisoning can be excluded.

Reliability.

The studies have all been ranked reliability 1 according to the Klimish et al system. This ranking was deemed appropriate because the studies were all conducted to GLP in compliance with recognised guidelines.

Justification for classification or non classification

 

The CLP Regulation (EC No 1272/2008) states that Aquatic Chronic 4 is applicable to substances in:

 

Cases when data do not allow classification under the above criteria but there are nevertheless some grounds for concern. This includes, for example, poorly soluble substances for which no acute toxicity is recorded at levels up to the water solubility (note 3), and which are not rapidly degradable and have an experimentally determined BCF≥500 (or, if absent, a log Kow≥4), indicating a potential to bioaccumulate, will be classified in this category unless other scientific evidence exists showing classification to be unnecessary. Such evidence includes chronic toxicity NOECs > water solubility or > 1 mg/l, or evidence of rapid degradation in the environment.

The substance fulfills this criteria in that no actual scientific data apart from QSAR exists to dispute the bioaccumulation potential assigned to the substance. As such, the registrant has self classified as follows:

CLP Regulation (EC No 1272/2008): Aquatic Chronic 4; H413: May cause long lasting harmful effects to aquatic life.

Dangerous Substance Directive (67/548/EEC): R53 May cause long-term adverse effects in the aquatic environment.

It should be noted however that the substance does not cause toxicity to aquatic organism at the limit of solubility in water. Should release to the environment occur, it is proposed that it would persist whilst degradation effects would result in its eventual removal.