Toxicokinetic and Partial Mass Balance Assessment of ¹⁴C-Alpha Olefins in Rats

Higher olefins are a class of alkenes widely used as intermediates in the production of essential consumer and industrial products. This radiolabel disposition and partial mass balance study investigated the distribution and excretion of four ¹⁴C-radiolabelled alpha higher olefins (i.e., 1-octene, 1-decene, 1-hexadecene, and 1-eicosene) in male Wistar rats following a single oral dose (100 mg/kg). Blood, liver, kidney, adipose tissue, urine, and faeces were collected and analysed for total ¹⁴C-derived radioactivity. Urinary elimination was rapid, with approximately 70% and 90% of total radioactivity recovered in urinary excreted within 24 and 48 h, respectively. Excretion patterns showed a clear chain-length-dependent trend: shorter-chain olefins (C8, C10) exhibited higher urinary excretion, indicating greater systemic absorption, while longer-chain olefins (C16, C20) were primarily eliminated via faeces, suggesting limited intestinal uptake. Tissue distribution was minimal in blood, liver, and kidney, but adipose tissue retention increased with chain length. Total recovery of administered radioactivity in the analysed matrices was low, ranging from 17% to 60%. Importantly, because exhaled ¹⁴CO₂ and volatile parent compounds were not captured, the missing fraction cannot be quantified and the balance cannot be considered closed. All in all, the current study describes the partial disposition of higher olefins and highlights the influence of molecular size and lipophilicity on the biological fat, though further studies are required to fully characterise their metabolic profile and total elimination kinetics.