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Classification & Labelling & PBT assessment

PBT assessment

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PBT assessment: overall result

PBT status:
the substance is not PBT / vPvB

Whole substance screening level data are available for the assessment of biodegradation and bioaccumulation for rosin adduct esters. However, assessing the substances as a whole is not considered to be the most appropriate method for assessing the PBT potential of complex UVCB substances such as these, as different constituents will have different environmental fate properties.

Whole substance ready biodegradation studies are available, and based on the results from these studies category members are not considered to be readily biodegradable. However, as different constituents within a UVCB substance are likely to have differing biodegradation potential these studies are not considered to be appropriate for assessing the persistence potential of the substances. Instead an assessment based review of individual constituents within the UVCB substances is considered to be more appropriate.

The rosin adduct ester category consists of fumarated and maleated esters of glycerol and pentaerythritol. The substances consist of ester constituents (mono-, di- and tri- glycerol esters and mono-, di-, tri- and tetra- pentaerythritol esters), and free resin acids. QSAR predictions and measured data for the constituents has been assessed. It should be noted that some of the di and tri ester structures are outside the structural domains of some of the Episuite models, but the predictions are still able to give an indication of the potential for biodegradation and bioaccumulation.

QSAR predictions conducted with Episuite’s BIOWIN model show that di- and tri- adduct ester constituents screen as potentially persistent (BIOWIN 3 value <2.2 and BIOWIN 6 or BIOWIN 2 <0.5). Tetra ester constituents are also considered to be potentially P, however, these constituents could not be run through the model due to issues processing the SMILES notation. In addition, the tetra-ester constituents are outside the model domain. Mono-ester constituents do not screen as persistent based on BIOWIN results. Resin acids are the main components of rosin (>85%) and based on measured ready biodegradation studies with rosin these constituents are considered to be readily biodegradable and not persistent. Based on this QSAR assessment and the measured data for resin acids, mono-ester constituents and free resin acids are not considered to be persistent (P). Di-, tri- and tetra- ester constituents are potentially P.

Measured log Kow values for category members range from 2.44 - >6.5. The wide range of measured Kow values are considered to reflect the differences in partitioning behaviour between constituents. Based on QSAR predictions using Episuite’s KOWWIN and BCFBAF models, di- and tri- ester constituents are not considered to be bioaccumulative as their large molecular size and very high predicted log Kow values (9.82 – 16.51) mean that these constituents are unlikely to be taken up by organisms. This is reflected in the low predicted BCF values (3.16 L/kg ww, log BCF 0.5, regression-based estimate). Structures for tetra ester constituents could not be run through the model, but as these constituents have an even larger molecular size than the di-and tri-esters they are also unlikely to bioaccumulate. Mono-ester constituents are considered to be potentially bioaccumulative based on predicted log Kow values (log Kow 3.75 – 4.23), although predicted BCF values for these constituents are still low (3.16 L/kg ww, log BCF 0.5, regression-based estimate). Based on measured bioaccumulation data for mussels and fish, free resin acids are not considered to bioaccumulate. Based on this QSAR assessment and measured data resin acids, di-, tri- and tetra- esters and free resin acids are not considered to be bioaccumulative (B). Mono-ester constituents are potentially B, based on predicted Kow values.

Measured toxicity data are available for Daphnia magna for all category members, for algae for resin acids and rosin acids, fumarated esters with glycerol and resin acids and rosin acids, maleated esters with pentaerythritol and for fish for resin acids and rosin acids, maleated, esters with pentaerythritol. In all studies the EL50 value was determined to be above the highest concentration tested. Rosin adduct esters are therefore not considered to be toxic (T).

None of the substances included in H4R Category 4 are classified as carcinogenic (cat. 1A or 1B), germ cell mutagenic (cat. 1A or 1B), toxic to reproduction (cat. 1A, 1B or 2), STOT RE 1, or STOT RE 2. Assessing rosin adduct esters based on constituents within the UVCBs, mono adduct esters are considered to be not P but potentially B and therefore not PBT or vPvB. Di-, tri- and tetra- adduct ester constituents are potentially P but not B and therefore not PBT or vPvB. Free resin acids are not P or B. Based on whole substance data none of the substances in the category are T. Therefore, none of the constituents in rosin adduct ester substances are PBT or vPvB.