Registration Dossier

Environmental fate & pathways

Endpoint summary

Administrative data

Description of key information

Additional information

The substance is a UVCB liquid under all environmental conditions and is of low solubility in water and is of low volatility (based on 0.0015 Pa at 20 °C).  

Any potential exposure to the environment would result in rapid redistribution from soil and water due to its volatility.  The high adsorption to soil (based on the soil adsorption study, discussed below) indicates that the majority of the substance will partition to soil and sediment rather than water should it be released to the environment. This is supported by a Level III fugacity model 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 the substance, based on the theoretical lowest and highest molecular weight compounds as follows:

 

 

Air (%)

Water (%)

Soil (%)

Sediment (%)

All derivatives

0.00522 - 0.0612

0.701 - 18.4

38.7 - 80.7

0.835- 60.6

It should be noted that as the majority of the substance distributes to the soil compartment; and the low solubility in water, this indicates that the substance is likely to persist in this compartment rather than distribute to the soil pore water.It is proposed therefore 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 is anticipated to display a low ready biodegradability. The substance is a substituted diphenylamine UVCB substance.  Substituted Diphenylamines, which are used as antidegradants in rubber, foamed polymers and high-temperature functional fluids (lubricants, gear oils, hydraulic fluids), are defined as amines with various substitutions. Their use in these applications requires stability at high temperatures, low biodegradation, low water solubility and low vapor pressure.Substituted Diphenylaminesas a group have been assessed under the US HPV programme in the “Substituted DiphenylaminesCategory”, sponsored by the American Chemistry Council’s Rubber and Plastic Additives Panel (RAPA). Utilising read across to an analogous substance, it is proposed that the substance is not readily biodegradable. The analogue achieved 8% biodegradation in a OECD Guideline 301 E Ready biodegradability: Modified OECD Screening Test, 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.  No experimental studies on hydrolytic effects are available on the substance, as the solubility and UVCB natures precludes experimental analysis. Some minor degradation may be anticipated via this route on the basis of structure; however this is proposed to be minimal. 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 whilst abiotic processes could contribute to the depletion of the substance within the environment, this is likely to be a slow process.

The substance has been demonstrated to have a relatively high partition coefficient value (Log Kow of 5.2) which demonstrates that there is the potential for this substance to accumulate biologically. However, given the UVCB nature of the substance, it is difficult to assess the substance using a standard test. Therefore an assessment was undertaken utilizing recognised QSAR derivation software as follows:

·       BCF model (CAESAR) (version 2.1.11)

·       BCF model (Meylan) (version 1.0.0)

·       BCF Read-Across (version 1.0.0)

·       US EPA On-Line EPI Suite™v4.0 model BCFBAF

 

An assessment of 50 potential structures that could be present was undertaken. These were selected at random for the purposes of the exercise. On the basis of a weight of evidence approach, there is sufficient information available to state that the substance is not bioaccumulative. Whilst it is not possible to provide a definitive BCF value for the substance, due to the variation in the results, none of the values determined via QSAR are above the threshold value quoted in the Regulation of 2000 or 5000 which indicates the potential to bioaccumulate. A geometric mean BCF is therefore applied for the purposes of hazard assessment.

 

Endpoint study

Result (BCF) [geometric mean]

EPIWIN BCFBAF Results [L/kg]

36.60

BCF Read-Across (version 1.0.0) [L/kg]

348.83

BCF model (CAESAR) (version 2.1.11) [L/kg]

1274.0

BCF model (Meylan) (version 1.0.0)

95.0

Geometric Mean BCF overall

1754.04

 

Whilst this mean result is presented as only a general indication, this supports the overall conclusion that the substance is not considered to be bioaccumulative. The substance is not considered to be “bioaccumulative” or “very bioaccumulative” on the basis of the available data.  The available mammalian repeat dose data on the Substituted Diphenylamines as a group would also generally support the fact that bioaccumulation does not occur, as no significant results were noted in these studies.

A screening organic carbon-water partitioning coefficient (Koc) is available for the substance, using a HPLC Estimation method. This resulted on a log Koc value of 5.48 at 35 °C with Koc of 300000. Adsorption to soil is therefore 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. 

Three studies with terrestrial organisms are available for read-across substances. Results are as follows: OECD Guideline 208 (Terrestrial Plants Test: Seedling Emergence and Seedling Growth Test): Lowest NOEC: 63 mg/kg [Lycopersicon esculentum (tomato)] ; OECD Guideline 216 (Soil Microorganisms: Nitrogen Transformation Test): 28-d EC50 > 2500 mg substance/kg dry soil; OECD Guideline 222 (Earthworm Reproduction Test (Eisenia fetida/Eisenia andrei)): NOEC 62.5 mg/kg dry soil based on the numbers of juveniles produced. As can be seen, the effects on terrestrial organisms are not indicative of hazard to these types of organisms.

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 mammalian 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, 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 or 2 according to the Klimish et al system. This ranking was deemed appropriate because although not all the studies were conducted to GLP in compliance with recognised guidelines, in the context of a group approach forSubstituted Diphenylamines, the data is consistent across the group.

Justification for classification or non classification

The substance fulfils the persistency criteria in that the Substituted Diphenylamines are not biodegradable and that no actual scientific data apart from QSAR exists to dispute the bioaccumulation potential assigned to the substance. As the substance also demonstrated effects on the mysid shrimp in an acute toxicity test, the following classification is applicable.

CLP Regulation (EC No 1272/2008): Aquatic Chronic 2; H411: Toxic to aquatic life with long lasting effects.

A study was conducted in accordance with OECD Guideline 211 to determine the effects of read-across substance, 4-(1-methyl-1-phenylethyl)-N-[4-(1-methyl-1-phenylethyl)phenyl]aniline, on the survival, growth and reproduction of the cladoceran, Daphnia magna, during a 21-day exposure period under flow-through test conditions. The 21-day EC10 value based on the mean number of live neonates produced per adult at the beginning of the test was 16 μg a.i./L. Since the 95% confidence interval was outside of the data range used for the calculation, it was not reported. However, the EC10 value was not meaningful because the mean number of live neonates produced per adult at the beginning of the test in the 21 μg a.i./L did not follow a dose-response pattern. The EC50 value based on the mean number of live neonates produced per adult at the beginning of the test was >38 μg a.i./L, the highest concentration tested.