Trimethylbenzene Mixed Isomers

Trimethylbenzene mixed isomers (CAS 25551-13-7) are a blend of 1,2,3-, 1,2,4-, and 1,3,5-trimethylbenzene arising from the aromatic fraction of petroleum naphtha. They appear in detailing products as minor constituents of petroleum-distillate co-solvents (Stoddard solvent, mineral spirits) at sub-1% concentrations rather than as deliberate standalone additions. At the substance level, the harmonized REACH/CLP classification is Flam. Liq. 3 (H226) and Aquatic Chronic 2 (H411). In finished detailing products where the isomer mixture is present at 0.5–<1%, the concentration is below the mixture-classification threshold that would trigger product-level health hazard codes — the classification contribution to a finished product is the aquatic chronic flag, which informs the product's environmental profile rather than health PPE. The primary environmental concern is aquatic toxicity: the aromatic component of petroleum naphtha is the dominant driver of aquatic chronic classifications in Stoddard solvent-containing products. At trace product concentrations the environmental load per application is low, but cumulative drain discharge from wash-stage products deserves noting given the weekly application cycle typical of maintenance detailing products.