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Classification & Labelling & PBT assessment

PBT assessment

Administrative data

PBT assessment: overall result

PBT status:
the substance is not PBT / vPvB
Justification:

The competent authority (CA) in France (BERPC before REACH enactment, ANSES afterwards) has designated A104 as a potential PBT or vPvB based on data presented in the original 1992 new substance notification and subsequent dossier updates. These relied, in part, on initial experimental results obtained from relatively simple standard and older methodologies: specifically water solubility < 0.85 mg/L, Log Kow > 6.1, and several unsuccessful biodegradation tests.

Several ready biodegradation studies have been conducted on A104 in an attempt to characterize or assess potential persistence. The latest biodegradation test (adhering to OECD 301B) was conducted using14C-radiolabelled A104. This concluded that approximately 13% of the test material mineralised during 61 days of exposure (based on radiochemical measurements), and no toxic effect on the biota present at 30 and 300 mg/L was evident). The bioavailable amount of radioactivity and, therefore, potentially the biodegradation rates were substantially reduced as a result of the radioactivity dosed into the test system strongly adhering to the glassware and was not removed during the course of the study. Overall, the study was inconclusive due to a lower than 90% recovery of total radioactivity added to the test system, but these results do reveal that A104 is biodegradable to some extent. As a result, the assessment of persistence potential from the biodegradability tests conducted to date is inconclusive.

In terms of toxicity, A104 has shown low acute toxic effects to aquatic organisms (Fish LL50 between 10 to 20 mg/L, Daphnia 6.8 mg/L, and green alga 12.5 mg/L). Also chronic toxicity tests conducted on reproduction of earthworms and on higher terrestrial plants (results not shown here, but reported in the last dossier update) indicate that A104 is not chronically toxic. While there is no chronic toxicity data on aquatic organisms, A104 is not expected to be a concern. Albeit indirect, toxicokinetics information from a 28 repeat dose study in rats also supports this notion (see details in Appendix). Hence based on the toxicity data currently available, A104 does not warrant the T categorization under the PBT profile.

In discussions in November 2013 ANSES suggested that a “block approach” might be appropriate for elucidating the properties of A104. According to this approach the P, B and T properties of all the main constituents can be considered separately in order to build up a picture of the properties of the entire substance.

With the exception of the Ethomeen monomer and Naphthenic base oil (which are registered under REACH by their manufacturers (not our company) and which are data-rich), none of the other constituents of A104 have data for physico-chemical, environmental fate, and toxicity endpoints. Hence other estimation methods, e.g. QSAR models, read-across, chemical stability, published data on environmental fate of same or similar compounds, etc., have to be used to further evaluate the potential PBT or vPvB properties in more detail.  QSAR modelling suggests that the main constituents of Additiv 104 have the following properties:

 

Structures 1 – 4: insoluble in water, no ready biodegradation (except Structure 1), highly hydrophobic, low bioaccumulation potential

Structures 5 & 6 (the main Mo-containing constituents): insoluble in water, no ready biodegradation, highly hydrophobic, low bioaccumulation potential

Ethomeen Monomer: insoluble in water, readily biodegradable, hydrophobic, low bioaccumulation potential

Ethomeen Dimer: insoluble in water, no ready biodegradation, highly hydrophobic, low bioaccumulation potential

Ethomeen Trimer: insoluble in water, no ready biodegradation, highly hydrophobic, low bioaccumulation potential

 

Inspection of the structure of these molecules suggests that they are generally susceptible to known pathways for relatively fast biotransformation (linear alkyl groups, hydroxyl/alcohol groups). These chemical structures are drastically different from chemicals known to have slow rates of biotransformation and high bioaccumulation (i.e., highly halogenated and branched molecules). The best available predictions for the biotransformation for the Ethomeen monomer suggest that the chemical is relatively quickly biotransformed in fish and thus bioconcentration and bioaccumulation is low.

Furthermore the Mo containing species (Structures 1 -6) are likely to hydrolyse (via metal alkoxide disproportionation) in the absence of oil and presence of moisture or bulk water, conditions which are particularly relevant to aqueous systems, such as sewage treatment plants, and in biological systems. These reactions lead to the formation of Ethomeen dimer, with concomitant generation of structures with increasing Mo/O content. Ultimately such reactions will lead to the breakdown of Additiv 104 to Ethomeen dimer and Molybdenum trioxide (MoO3). The latter has a low potential for bioaccumulation.

[Update May-18] Newly conducted hydrolysis experiments reported in Section 5.1.2 suggest that, contrary to the prediction made in the above paragraph, that hydrolysis of the Mo-containing species is slow under normal conditions. Nevertheless it is still believed that these constituents have a low potential for bioaccumulation.