The reused oil was high in acrolein which has been shown to have carcinogenic activity and changed the activity in 455 different genes in the livers of mice.

Additionally, reused soybean oil contains oxidized lipids and polymer molecules also accumulate. Typically, these standards permit restaurants to use oil containing up to 24-27% polar material. The reused oil in this study contained ~15% polar material, while fresh oil contains 2-4% or less.