reaction mass of isomers of: C7-9-alkyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate

Endpoint summary

Additional information

The test substance is a liquid under all environmental conditions and is of low solubility in water and is of low volatility (based on0.0015 Pa at 20 °C).  As the substance is a UVCB, assessment of affinity to soil / sludge is difficult to accomplish as standard tests for this endpoint are intended for single substances and are not appropriate for this complex substance. However, an assessment usingHPLC-screening method for the determination of the adsorption-coefficient on soil-comparison of different stationary phases", W Kordel, J Stutte and G Kotthoff, Fraunhofer-lnstitut fUr Umweltchemie und Okotoxikologie was undertaken. On the basis of the results of the calculation, a log Koc value of>4.3 was determined, indicating a highaffinity 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.A total of 6 different potential structures for C7, C8 and C9 components was evaluated in order to obtain an indication of possible values for the subtance as as whole. The results, expressed as a range, are as follows:

	Air (%)	Water (%)	Soil (%)	Sediment (%)
C7 derivatives	0.0741 - 0.12	5.84 - 7.73	58.2 - 63.5	30.4- 34.9
C8 derivatives	0.0912 - 0.149	6.65 - 9.32	61.5 - 63.1	28.2 - 31.8
C9 derivatives	0.104 - 0.182	8.03 - 12.5	68 - 72.8	14.5 - 24.1

It is proposed that the majority of the substance is modelled to distribute to the soil and sediment compartments within the constraints of the QSAR model. The substance displays a low ready biodegradability in that it achieved 2% biodegradation in a 28-day CO2 evolution ready biodegradation study, indicating that it is unlikely to achieve a half life of less than 40 or 60 days within fresh water attributed to ready biodegradation alone. Likewise, an assessment on the biodegradability of the substance using the C.9 (DIN 38409) biodegradation method indicated that it is also unlikely to be biodegradable by this route. However it is expected to hydrolyse slowly under normal environmental conditions.  Experimental studies on hydrolytic effects demonstrated that the substance does undergo hydrolysis at environmentally relevant pH’s, with a half life of 10.8 days at pH 4, 182 days at pH7 and 14.1 days at pH 9. As such, some minor degradation is anticipated via this route. 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 abiotic processes would 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 9.2 by calculation. The calculated 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 10, the substance is proposed not to bioaccumulate.  This is further confirmed via the use of QSAR; use of the US EPABCFBAF v3.01programme for bioaccumulation indicates that the substance is unlikely to bioaccumulate, with calculated values used for the assessment for6 different potential structures for C7, C8 and C9 components as follows:

	BCF value (L/kg wet-wt)	Log BCF value	Typical % w/w
C7 derivatives	648.4 - 5704	2.812 – 3.756	9.0
C8 derivatives	372.6 - 1887	2.571 – 3.276	>76.0
C9 derivatives	123 - 1178	2.090 – 3.071	15.0

Given the fact that the substance is subject to hydrolysis at biologically relevant pH’s (4 and 9), it is anticipated that bioaccumulation of the substance itself would not occur, as hydrolytic effects in association with metabolic effects would result in removal of the substance. In addition, the majority of the substance does not fall into a BCF range where classification is applicable. These 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. Assessment of the toxicity to earthworms indicates that the substance is not hazardous to terrestrial organisms, and as such, it is not predicted to pose a hazard overall to the environment.

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 will 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 thatAquatic 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. There is a chronic NOEC value available; however as this is a limit value, it is not possible to use this to quantify against water solubility. As such, the registrant accepts the current classification as listed in Annex VI to Regulation (EC) No 1272/2008; index reference 607-530-00-7 which is 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 or terrestrial organisms. Should release to the environment occur, it is proposed that it would persist for a short while, whilst degradation through the effects of hydrolysis would result in its eventual removal.