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HCSC Category 4 - C14-C20 Aliphatics (2-30% Aromatics) (September 2017)

Justifications and discussions

Category definition:
The C14-C20 Aliphatic [2-30% Aromatics] Hydrocarbon Solvents Category is comprised of multi-constituent aliphatic hydrocarbons with predominant carbon numbers in the range of C14 to C20. The primary constituents are straight chain (n-), branched (iso-) and cyclic aliphatic hydrocarbons and 2% to 30% aromatics. The substances included in this category are hydrocarbon solvents.

The carbon number and initial distillation point (IBP) characterize the substances in the C14-C20 Aliphatic [2-30% Aromatics] Hydrocarbon Solvents Category. The distillation range, approximately 230°C to 350°C, is similar to the boiling ranges of certain petroleum substances, i.e., C9-C16 Hydrodesulfurized Kerosene (CAS No. 64742-81-0) and C11-C25 Hydrodesulfurized Middle Distillates; however, petroleum substances tend to have wider boiling ranges and be less highly refined than the hydrocarbon solvents, and they are intended for different end uses. The benzene and sulphur contents of hydrocarbon solvents substances in the C14-C20 Aliphatic [2-30% Aromatics] Hydrocarbon Solvents category are low; benzene levels for example are typically < 1 ppm benzene, since benzene and sulphur are intentionally removed from hydrocarbon solvents.

The toxicology and environmental fate and effects data show that substances in this category have similar hazard properties, also supporting the grouping of these substances as a category. Table 2 summarizes the typical toxicological and environmental fate properties of substances in the C14-C20 Aliphatic [2-30% Aromatics] Hydrocarbon Solvents Category.

The C14-C20 aliphatics (2-30% aromatics) Category members are distinguished by HSPA (Hydrocarbon Solvents Producers Association) according to the following nomenclature:

Hydrocarbons, C14-C18, n-alkanes, isoalkanes, cyclics, aromatics (2-30%)
Hydrocarbons, C16-C20, n-alkanes, isoalkanes, cyclics, aromatics (2-30%)
Category order description:
Not specific for a UVCB category
Category rationale:
(1) Similarity of Production Methods – Hydrocarbon solvents in this category are separated from wide boiling hydrocarbon streams by a refining process known as atmospheric distillation. The resulting hydrocarbon streams are fractionated by boiling range and further refined, usually by hydrogenation to reduce levels of sulphur- and nitrogen-containing constituents.

(2) Similarity of Use – Substances in this category are liquids at room temperature and produced for use as solvents. The technical properties for which these solvents are intended require that the constituents be of relatively low volatility (high carbon number/molecular weight), have very low levels of sulphur- and nitrogen-containing substances, and may also limit the total content of aromatic constituents.

(3) Similarity of Composition – Constituents of solvents in this category are hydrocarbons of the 4 structural types: n-alkanes, iso-alkanes, cycloalkanes and/or aromatics with carbon numbers that predominantly range from C14-C20. Any molecules other than hydrocarbons are contaminants which are only present at extremely low levels.

(4) Similarity of Functional Groups – The substances in this class are comprised of aliphatic and aromatic hydrocarbon constituents. The only functional groups which these constituents contain are alkyl side chains that 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. The physical/chemical endpoints available in IUCLID 5 for the individual substances in C14-C20 Aliphatic [230% Aromatics] Hydrocarbon Solvent Category are summarized in Table 1b of the category justification document.

(6) Similarity of Metabolism – Hydrocarbon molecules in this range are rapidly metabolized and excreted. However, an evaluation of the representative hydrocarbon structures indicates that some constituents may bioaccumulate.

(7) Similarity of Mammalian Toxicity – The C14-C20 Aliphatic (2-30% aromatic) Hydrocarbon Solvents have similar toxicological properties as shown in Table 2 of the category justification document. Where there is a lack of data for an endpoint, data from another category member can be used to predict the likely result. The full results, as compiled by IUCLID 5, of the data are attached to the substance dossier (labeled as “MATRIX Report for Category 4 - C14-C20 Aliphatic, 2-30pt Aromatic.html”).

(8) Similarity of Environmental Toxicity and Fate Properties – The C14-C20 Aliphatics (2-30% aromatic) have similar environmental effects and fate properties as shown in Table 4a of the category justification document. The environmental and ecotoxicological endpoints available in IUCLID 5 for the individual substances in C14-C20 Aliphatic [2-30% Aromatics] Category is demonstrated in Table 4b of the category justification document.

(9) Similarity in Health Effects and Mechanism of Toxic Action – One potential health effect associated with substances in this category is that if these substances are taken into the lung in a liquid state, chemical pneumonitis may develop. This is a common effect shared by most hydrocarbon solvents.

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 interference with biological membrane function, and the differences between their toxicities can be explained by the differences between the target tissue-partitioning behavior of the individual hydrocarbons. There are no toxicological properties of category member constituents that are specific and distinguish them from each other or from other constituents of these hydrocarbon solvents.