Toxicological and environmental evaluation of the two-phase immersion cooling fluid HFO-153-10mczz-E

HFO-153-10mczz-E (decafluoro-3-hexene) is a volatile, nonflammable hydrofluoroolefin (HFO) developed as a dielectric fluid in heat transfer applications, such as two-phase immersion cooling (2-PIC). Its high vapor pressure and low water solubility indicate that inhalation is the primary route of exposure and that if released into the environment, the molecule would primarily partition into the air. The available toxicology dataset primarily comprises studies performed with Good Laboratory Practice (GLP) and under Organisation for Economic Co-operation and Development (OECD) test frameworks. This dataset includes acute, subacute, and subchronic inhalation studies, and reveals low systemic toxicity in rats at concentrations of up to approximately 3,000 ppm, with no treatment-related findings in reproductive or developmental endpoints. An in vitro and in vivo genotoxicity battery yielded no indication of genotoxicity. Additional studies illustrated no cardiac sensitization in dogs up to 5,000 ppm and no evidence of ocular/skin irritation or skin sensitization. Environmental testing across algae, invertebrates, and fish revealed no adverse effects in algae or daphnia, with the exception of acute toxicity in fish. However, interpretation was constrained by substantial volatility-related loss of the test material. Environmental partitioning, modeled bioaccumulation factors, and physicochemical properties collectively indicate a low bioaccumulation potential. Collectively, the empirical data characterize HFO-153-10mczz-E as a highly volatile fluorinated fluid with a well-defined toxicological profile, with available data suggesting a low human-health hazard and limited environmental exposure potential under plausible use conditions, though further studies may be warranted.