Registration Dossier

Environmental fate & pathways

Endpoint summary

Administrative data

Description of key information

Additional information

Introduction

 

When a complex hydrocarbon substance is released into the environment, the hydrocarbon constituents distribute to the different environmental compartments according to individual physico-chemical properties (e.g. volatility, water solubility, partition coefficients). Exposure concentrations are further modulated by differential degradation rates between constituents and compartments. This makes it difficult to assess environmental exposure of UVCB hydrocarbon substances like the substance subject to the registration because measured concentrations of constituents or total hydrocarbons detected in the environment can no longer be directly related to the original hydrocarbon source substance. A further complication is multiple hydrocarbon sources, both man-made and natural, which may contribute to concentrations observed in each environmental compartment. Therefore, it is not possible to directly apply current risk assessment guidance developed for simple substances to complex hydrocarbon substances.

 

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 the highest % component substance between four environmental compartments (air, water, soil, sediment) at steady state in a unit world. QSAR estimates for other physico-chemical parameters have been conducted for some 70 proposed molecules in order to provide a range of likely values associated with the substance.  For the fugacity assessment the smallest and largest molecular weight substances were assessed to provide an indication of the complexity of the partitioning. 

 

On the basis of this modelling, partitioning as a range is detailed to be:

Component & compartment

Monomer

MW = 212.41

Tetramer (M-C16-C16-C16)

MW = 885.69

Mass amount (%)

Mass amount (%)

Air

6.9

1.33

Water

63.9

97.5

Soil

1.27

1.09

Sediment

28

<0.1

 

As can be seen, the partitioning is highly variable, and dependant on the physical characteristics of a specific component. The model predicts that 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 high partitioning values, these indicate that the majority of the substance would eventually partition to soil and sediment rather than water should it be released to the environment. This is confirmed by the calculated high soil adsorption values attained for the substance. Using the US EPA On-Line EPI Suite™ KOCWIN v2.00 model, the log Koc range is predicted to be 4.28 to 16.732.  This is anticipated to be appropriate, based on the predicted water solubility and hydrocarbon nature of the substance.

 

A study was attempted in order to determine the test substances adsorption coefficient. the intention was to estimate the adsorption coefficient Koc of test item using an HPLC method. This method is applicable for substances, which have log Koc value ranging from 0 to 6. During the test efforts were made to identify the appropriate analytical method which separates the test item and the pesticide standards. With the common HPLC eluents (acetonitrile or methanol) the pesticide standards were separated but the test item did not elute from the column. Stronger organic solvents were used which was enabled elution of the test item but the standards elute together and this prevents the calibration. The elution time is of the test item is much longer than the last eluting standard which means that the adsorption coefficient of the test item is higher than the last standard (DDT KOC=5.6).

 

Persistency

 

Degradation in the environment is a result of abiotic processes and biodegradation. The relative importance of these processes will depend upon the environmental compartment to which the individual components of the hydrocarbon UVCB substance partition. In general, abiotic processes are important in the atmosphere, whilst biodegradation is the principle mechanism of the breakdown of lower carbon chain length products in water and soil.Studies on direct phototransformation in water are not available but it is assumed on the basis of chemical structure and nature of use that direct photolysis is not expected to be a major degradation pathway for many of the hydrocarbon components in this UVCB substance. Likewise, hydrolysis is a reaction in which a water molecule or hydroxide ion substitutes for another atom or group of atoms present in a chemical resulting in a structural change of that chemical. Potentially hydrolyzable groups include alkyl halides, amides, carbamates, carboxylic acid esters and lactones, epoxides, phosphate esters, and sulfonic acid esters. The lack of a suitable leaving group renders compounds resistant to hydrolysis.

 

The chemical constituents that comprise the UVCB substance consist entirely of carbon and hydrogen and do not contain hydrolyzable groups. As such, they have a very low potential to hydrolyze. Therefore, this degradative process will not contribute to their removal from the environment.

 

Biodegradation studies on the substance are available for inspection as follows:

 

OECD 301B (in the presense of silica gel)

The test substance achieved the requirements for Ready Biodegradability by the OECD 301B standard, achieving 86.7% bidegradation. 60% biodegradation was achieved at 8.9 days; thus passing the 10 day window. The test material can be considered to be readily biodegradable under the conditions of the test.

 

OECD 301B (in the absence of silica gel)

The biodegradability - based on CO2 evolution - of TS2235 was calculated to be 78% and 88% of the theoretical value (ThCO2) after an incubation time of 28 and 56 days, respectively. The biodegradation of TS2235 reached 52% at the end of the 10-d window. Significant biodegradation of the test substance was observed after a lag phase of about 1 day. Whilst TS2235 did not reach the pass level of 60% for ready biodegradability in the CO2 Evolution Test within the 10-d window and cannot be termed as readily biodegradableit did reach the pass level of > 60% after 28 days.

 

OECD 302 C Inherent biodegradability: Modified MITI Test (II)

The substances inherent biodegradability was assessed using an automated closed-system oxygen consumption measuring apparatus (BOD-meter) for 28 days. The biodegradation was then calculated on the basis of BOD and supplemental chemical analysis factoring residual test substance. Under the conditions of the study, the percentage biodegradation of the test substance on day 28 which was calculated by BOD was 11 .0%, the primary biodegradation which was calculated with the residual test substance was 11.1 %.

 

OECD 301 C Ready biodegradability: Modified MITI Test (I)

Biodegradability based on the measurement of biochemical oxygen demand for the test substance was 26-27% in 28 days. Under the conditions of the study it was noted that some of the test item had biodegraded and that four converted products which had not biodegraded were detected in the quantitative analysis (LC-MS), however these were not quantifiable as it was not possible to separate these under the analytical conditions. It is to be presumed that these converted products are not that of a water soluble product as DOC was not detected during qualitative analysis.

 

OECD 301 F Ready biodegradability: Modified MITI Test (II)

The percentage biodegradation of the test substance did not reach 60% at 10d-window under the conditions of the study presently performed, so the test substance cannot be considered to be readily biodegradable. O2 consumption 49% in 28 days (mean %)

 

It is considered on the basis of these results that the substance shows significant biodegradation, and can be considered to be biodegradable under normal conditions. The lighter fractions are expected to be readily biodegradable. Heavier fractions (majority by mass) are predicted to be inherently biodegradable.

 

Bioaccumulation.

 

A full bioaccumulation study in accordance with Japanese Guidelines provided the following results:

Bioconcentration test

BCF

Level 1 (0.1 mg/L)

Peak 1: <63 L/kg

Peak 2: <2.0 L/kg

Peak 3: <29 L/kg

Level 2 (0.01 mg/L)

Peak 2: <10 L/kg

It was evaluated that a steady-state was reached within 28 days because all BCFs were less

than 100 L/kg.

The substance is a hydrocarbon UVCB. Assessment using the US EPA On-Line EPI Suite™ KOWWIN version 1.68 model, the log Kow range is predicted to be 7.49 to 31.33.As the substance shows log Kow values in the main of > 10,it is proposed that the substance is not indicative of being potentially bioaccumulative, on the basis of the partition coefficient values observed.

The substance is, however, considered to be not bioavailable to aqueous organisms as demonstrated by the lack of toxicity. Furthermore, the high log Kow is considered to be more a consequence of poor water solubility 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 in part on an evaluation of literature data which demonstrates a tendency for the Bioconcentration Factor (BCF) to decrease as Log Pow increases above 6. This assumption is further confirmed by the data set available on the substance which demonstrates that it is poorly absorbed, both on the basis of the toxicity (or lack of) observed, plus the absorption study which demonstrated the lack significant absorption in the rat.

The above opinion is also confirmed via use of the EPIWIN BCFBAF v3.01 for assessment of bioaccumulation. The smallest and largest theoretical molecular weight substances were assessed and all evaluated values are less that <2000, indicating that the substance is not proposed to be bioaccumulative.

 Evaluation of predicted molecular size data indicates that approximately 29% of the molecules are of a Dmax average of greater than 17 Å (1.7 nm) plus a molecular weight of greater than 700 (Da). 

 Taking into account the following:

·       The actual test data.

·       Demonstrated lack of absorption

·       Demonstrated lack of persistency

·       High predicted log Kow value.

·       Demonstrated lack of bioaccumulation potential

·       Molecular size data not being indicative of the propensity towards bioaccumulation.

 This indicates, within a weight of evidence approach and with expert judgment, that NovaSpec Renewable White Oil is deemed to not be bioaccumulative in aquatic organisms.

 

Overall Conclusion

 

The substance is a hydrocarbon UVCB. Assessment using the US EPA On-Line EPI Suite™ KOWWIN version 1.68 model, the log Kow range is predicted to be 7.49 to 31.33. As the substance shows log Kow values in the main of > 10, it is proposed that the substance is not indicative of being potentially bioaccumulative, on the basis of the partition coefficient values observed. This is confirmed by the experimentally derived BCF of < 100 L/kg ww and calculated values.

 

The substance is not proposed to be toxic. No evidence of general toxicity was noted in any of the mammalian studies conducted on the substance and its analogues. The substance is not acutely or chronically toxic, not is it proposed to be carcinogenic. There are no mutagenic or reproductive toxicant activity ascribed to the substance. Furthermore, there is no evidence that, as a mineral hydrocarbon, the substance would be significantly absorbed via the oral, dermal or inhalation routes. With the exception of being an “aspiration hazard” ( a physical effect based on viscosity), the substance is not classified.

 

Based on the available data used in support of the registration, the substance is not proposed to be non-toxic and non-bioaccumulative. In the event of significant environmental exposure, the substance is proposed to partition mainly to soil / sediment compartments, where it is predicted not to be toxic. The substance displays ready biodegradation hence this route of degradation will result in eventual removal of the substance from the environmental compartment of interest.