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Category name:
HCSC Category 8 - C9-14 Aliphatics (≤ 2% aromatic) (October 2017)

Justifications and discussions

Category definition:
The C9-C14 Aliphatics [<2% Aromatics] Hydrocarbon Solvents Category is comprised of aliphatic hydrocarbon solvents with predominant carbon numbers in the range of C9 to C14. The constituents of these solvents could be single isomers as well as mixed solvents of which the primary constituents are straight chain (n-), branched chain (iso-), and cyclic aliphatic hydrocarbons. Aromatic constituents, if present, represent less than 2% of the total volume and are normally C9 aromatics (trimethyl benzenes and ethyl toluenes).The carbon numbers, typically C9-C14, and initial distillation points (IBP) characterize the substances in Category. The distillation range is approximately 110°C to 280°C although some solvents may contain higher boiling material. The benzene and sulphur contents of substances in this category are low, benzene levels for example are typically <3 ppm. Category members are distinguished by HSPA according to the following nomenclature:
Hydrocarbons, C9-C10, n-alkanes, isoalkanes, cyclics, <2% aromatics
Hydrocarbons, C9-C11, n-alkanes, isoalkanes, cyclics, <2% aromatics
Hydrocarbons, C10-C13, n-alkanes, isoalkanes, cyclics, <2% aromatics
Hydrocarbons, C11-C14, n-alkanes, isoalkanes, cyclics, <2% aromatics
Hydrocarbons, C13-C15, n-alkanes, isoalkanes, cyclics, <2% aromatics
Hydrocarbons, C12-C16, isoalkanes, cyclics, <2% aromatics
Hydrocarbons, C9-C11, isoalkanes, cyclics, <2% aromatics
Hydrocarbons, C10-C13, isoalkanes, cyclics, <2% aromatics
Hydrocarbons, C11-C14, isoalkanes, cyclics, <2% aromatics
Hydrocarbons, C10-C12, isoalkanes, <2% aromatics
Hydrocarbons, C11-C12, isoalkanes, <2% aromatics
Hydrocarbons, C11-C13, isoalkanes, <2% aromatics
Isododecane
Hydrocarbons, C9-C11, cyclics, <2% aromatics
Hydrocarbons, C8-C10, n-alkanes, <2% aromatics
Hydrocarbons, C10-C13, n-alkanes, <2% aromatics
Hydrocarbons, C11-C14, n-alkanes, <2% aromatics
Decane
Undecane
Dodecane
Tridecane
Tetradecane
Category order description:
Not specific for a UVCB category
Category rationale:
There are a number of unifying considerations, which together justify the inclusion of members within the C9-C14 Aliphatic [<2% Aromatics] Hydrocarbon Solvents Category. These include:

1) Similarity of Production Methods – Hydrocarbon solvents in this category can be produced in several ways, but in each case the manufacturing process leads to aliphatic solvents within a relatively narrow range of carbon numbers and with an overall low (<2%) aromatic hydrocarbon content.
• The “mixed” solvents, i.e., the de-aromatized grades, are typically manufactured by a process in which the feed streams are initially separated from wide boiling hydrocarbon streams by a refining process known as atmospheric distillation. The resulting hydrocarbon streams are further refined, usually by hydrogenation to reduce levels of aromatic constituents to below 2%. Sulphur - and nitrogen-containing substances are also removed by the hydrogenation process. These streams are then fractionated by boiling range to produce finished solvents with the desired technical properties.
• The isoparaffinic solvents are manufactured by an alkylation process in which olefinic feed streams are reacted in the presence of acid to produce nearly pure isoparaffinic hydrocarbons. These streams are then separated by distillation to produce finished solvents with the desired technical properties
• The normal paraffinic solvents are produced by sieving of feedstreams produced by atmospheric distillation of wide boiling hydrocarbon streams. This process results in relatively pure n-paraffins of specified molecular weights.
• The cycloparaffinic streams are produced by hydrogenation of aromatic streams. The hydrogenation process is optimized to saturate the aromatic constituents, converting them from aromatics to cycloparaffins.

2) Similarity of Use – Substances in this category are liquids at room temperature and are produced for use as solvents. The technical properties for which these solvents are intended require that the constituents have well defined rates of evaporation which is related to the carbon number distribution, to limit the aromatic content, and to also have very low levels of sulphur- and nitrogen-containing constituents.

3) Similarity of Composition – Constituents of solvents in this category can include n-alkanes, iso-alkanes, or cycloalkanes or combinations thereof with carbon numbers ranging from approximately C9-C14. However, the aromatic content of these solvents does not exceed 2%.

4) Similarity of Functional Groups – The substances in this class are comprised almost entirely of aliphatic constituents. The only functional groups are alkyl side chains, which are found on most if not all constituents other than the n-alkanes.

5) Similarity of Physical / Chemical Properties – The similarity of physical / chemical properties for these substances is demonstrated in Table 1a of the attached category justification document. The physical/chemical endpoints available in IUCLID 5 for the individual substances in C9-C14 Aliphatic <2% Aromatics Hydrocarbon Solvents Category are summarized in Table 1b of the attached category justification document..

6) Similarity of Metabolism – Hydrocarbon molecules in this range are not well absorbed from the intestinal tract and very poorly absorbed through the skin. However, once absorbed, these molecules are relatively rapidly metabolized and excreted. They do not bioaccumulate.

7) Similarity of Mammalian Toxicity – The constituents of this class have similar toxicological properties as shown in Table 2 of the attached category justification document. They are not acutely toxic, irritating to the eyes or skin or sensitizing. They do not produce systemic effects (other than male rat-specific kidney changes) in repeated dose studies. They are not mutagenic, and as above, do not produce carcinogenic effects other than those related to male rat-specific kidney effects. They do not produce developmental toxicity, and there is no evidence that they are toxic to the reproductive system.

Additionally, data is available for most of the toxicological endpoint for each substance in the category (Table3 of the attached category justification document). Where there is a lack of data for an endpoint, data from another category member can be used to interpolate the likely result. The full results, as compiled in IUCLID 5, of the data are attached to the substance dossier (labeled as "Matrix Report, Category 8, C9-C14 Aliphatics, <2pt aromatics.html").

(8) Similarity of Environmental Toxicity and Fate Properties – The substances in this category have similar environmental effects properties as shown in Table 4a of the attached category justification document. The environmental effects data are similar for most category members in that most members do not exhibit acute aquatic toxicity due to their low water solubility. However, some members do exhibit acute and chronic aquatic toxicity. The environmental and ecotoxicological endpoints available in IUCLID 5 for the individual substances in C9-C14 Aliphatic, <2% Aromatics Hydrocarbon Solvents Category is demonstrated in Table 4b of the attached category justification document.

(9) Similarity in Health Effects and Mechanism of Toxic Action – There are two general potential health effects associated with substances in this category, acute central nervous system (CNS) depression and, if taken into the lung in a liquid state, chemical pneumonitis. Both of these are common effects shared by all hydrocarbon solvents. It should be noted, however, that the vapor pressures of hydrocarbons with more than 9 carbons are so low that acute effects on the central nervous system are not produced even at saturated vapor concentrations.

Additionally, category member constituents are neutral organic hydrocarbons that share a similar mode of action for aquatic organisms, nonpolar narcosis. The mechanism of short-term toxicity for these chemicals is disruption of biological membrane function, and the differences between their toxicities can be explained by the differences between the target tissue-partitioning behaviours of the individual hydrocarbons. There are no toxicological properties of category member constituents that are specific and distinguish them from each other or from constituents of most other hydrocarbon solvents.