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Category 1 - Rosin, Hydrogenated Rosin and their Salts (April 2018)

Justifications and discussions

Category definition:
The substances within this category consist of rosin, hydrogenated rosin and mono-, di-, and trivalent salts of rosin’. This is a series of structurally related compounds, each of which is present to a greater or lesser extent in every grade of material. The main constituents of all the category members share the same basic chemistry, primarily resin acids, consisting of diterpenic monocarboxylic acids (85 – 95%), and a neutral fraction. None of the individual constituents are present at concentration >10 %. The organic structures of the mono, di and tri-valent salts are identical to the equivalent free acids. There is a high degree of similarity in the constituents of the whole category. It is therefore expected that the substances will act in in a very similar manner within biological systems.
Category order description:
Not specific for a UVCB category
Category rationale:
This category includes rosin, hydrogenated rosin and mono, di and trivalent salts of rosin. They are composed primarily of resin acids, a class of tricyclic carboxylic acids, but also contains minor amounts of dimerized rosin and unsaponifiable matter. It also includes oligomers of Rosin and Rosin formaldehyde adducts, both of which have higher levels of higher molecular weight dimers and trimers.

The chemistry of Rosin and its derivatives is highly complex. H4R has produced a reference document on analytical aspects. It also provides an insight into this chemistry. A copy is also given in the registration dossier.

Physico-Chemical
The molecular weight and salt cations of these compounds differ and, therefore, some differences in physico-chemical properties are expected. All the substances in this category are solids at ambient temperature, with similar densities and vapour pressures. The melting points are lower for the rosins than the salts, but all category members decompose before boiling. The major variation in physico-chemical properties between category members is the water solubility. The rosins and divalent salts have low solubility, whilst the monovalent salts are highly soluble in water.

Environmental
Ready biodegradation studies are available for a number of different category members, covering rosin, monovalent and divalent salts of rosin and hydrogenated variants. Although there is some variation in the amount of degradation demonstrated in these studies, likely to be due to the low solubility of the test items and difficulties with ensuring bioavailability of the test item, the weight of evidence demonstrates that substances in this category are readily biodegradable. An enhanced ready biodegradation study and an inherent biodegradation study are also available for category members, and also indicate that these substances are unlikely to be persistent.

Measured BCF values obtained from a bioaccumulation study with Oncorhynchus mykiss are available for nine resin acids (abietic, dehydroabietic, chlorodehydroabietic, dichlorodehydroabietic, neoabietic, pimaric, isopimaric, sandaracopimaric and palustric acids) and these show a range of BCFs between 23 and 129. BCF values in mussels (Hyridella menziesi) for the individual resin acids ranged from 110 to 330 L/kg. Resin acids are the main constituents in rosin and rosin salts, and these BCF values are far below the bioaccumulation threshold, therefore rosin and rosin salts are not considered to be bioaccumulative. In addition, QSAR predictions have been conducted for a representative structure of rosin dimers and based on the predictions these constituents are considered to have a low potential for bioaccumulation due to their large molecular size and very high log Kow (log Kow >10), meaning that they are unlikely to be taken up by organisms. Overall, members of the category rosin and rosin salts are not considered to be bioaccumulative.

Acute ecotoxicity results are available for members of the rosin and rosin salts category, covering rosin, monovalent and divalent salts of rosin and hydrogenated variants. The lowest LC50 value is 1.6 mg/L for Daphnia magna, for category member resin acids and rosin acids, hydrogenated, potassium salts.

In addition to the rosin component of the substances, for the salts within the category environmental toxicity may also be affected by the cation (Na, K, Ca, Mg, Zn, Mn or Al). The cations that do not have environmental classifications (Na, K, Ca, Mg and Al) are not considered to contribute to the toxicity of the substances. Some soluble zinc and manganese substances are classified for the environment, therefore these need to be considered in the environmental assessment. There are ecotoxicity data available for resin acids and rosin acids, calcium zinc salts, which indicates that this substance is not toxic at the limit of solubility in an acute study (EL50 >100 mg/L for Daphnia magna). Based on data for the substance itself, it does not therefore require classification for environmental endpoints.

Environmental Hazard Assessment
There are no hazardous properties for classification for the environment.

Conclusion for PBT/vPVB
Members of the category rosin and rosin salts are not considered to be PBT or vPvB.

PACT assessments were conducted by the Finnish competent authority for category members rosin, rosin, hydrogenated and resin acids and rosin acids, sodium salts (Tukes 2015). The assessments state that the conclusions can, in principle, be applied to all members of the category. Tukes based their assessment on the available measured data and EPISuite predictions conducted based on abietic, isopimaric and neoabietic acids, as representative structures. The assessments conclude that “… the
substance is not considered to meet the PBT/vPvB criteria based on the available, mainly screening level, information. This conclusion covers the relevant constituents.

Mammalian Toxicity
Based on the molecular weights, chemical structures, and Kow values for Rosins and Rosin salts, this category of substances is expected to be poorly absorbed and minimally toxic. This is confirmed by toxicokinetic information which demonstrates negligible uptake from the gastrointestinal tract. In addition, Rosins and Rosin salts are not acutely toxic, not irritating to skin, and do not induce or elicit allergic skin conditions. The monovalent salts are irritating to the eye, whereas the divalent and trivalent salts are not.

Rosin (CAS # 8050-09-7) is classified according to EU Classification, Labelling and Packaging of Substances and Mixtures (CLP) Regulation (EC) No. 1272/2008 as “Skin Sensitiser Category 1” and assigns the hazard statement H317: May cause an allergic skin reaction. As noted in Section 1.3.2 of the Category Justification Document, subsequent evaluation determined that the single positive study for Rosin was conducted with an oxidized form of the test material. When the same un-oxidized Rosin esters were re-tested no sensitisation responses were observed. Consequently, the oxidized form of Rosin should be considered a skin sensitiser. Based on the available evidence, the H4R Consortium made a recommendation to declassify non-oxidized Rosin (CAS # 8050-09-7).

The monovalent salts are irritating to the eye, whereas the divalent and trivalent salts are not. Results of in vitro genotoxicity testing reveal no activity toward microbial or mammalian cells both in the absence and presence of exogenous metabolic activation.

Several key Guideline (OECD 408, 414, 421, & 422) studies that investigated the oral (dietary) repeated dose toxicity potential in rats of Rosin; Rosin, hydrogenated; Rosin, oligomers; and Rosin, reaction products with formaldehyde are available. The results of these studies showed that none satisfy the CLP hazard classification criteria for specific target organ toxicity following repeated oral exposure (STOT RE). Rosin, Hydrogenated Rosin and their Salts are not classified for reproductive or developmental toxicity according to EU Classification, Labelling and Packaging of Substances and Mixtures (CLP) Regulation (EC) No. 1272/2008 or UN Globally Harmonized System of Classification and Labelling of Chemicals (GHS).