ORIGINAL ABSTRACT

Soybean is a vital global protein source but raises growing concerns over herbicide co-formulant residues. Polyethoxylated tallow amine (POEA), a common surfactant in glyphosate-based herbicides, is up to 167 times more toxic than glyphosate alone. However, data on its occurrence and dietary risk in soybeans remain scarce. To fill this gap, we established a sensitive QuEChERS-UPLC-MS/MS method to analyze POEA homologs in 101 domestic and imported soybean samples. POEA was detected in all samples, with total concentrations of 57.1-522 μg/kg (median 207 μg/kg). Residues in imported soybeans (392-522 μg/kg, median 497 μg/kg) were more than twice those in domestic samples (57.1-439 μg/kg, median 203 μg/kg). Glyphosate isopropylamine salt formulations (e.g., Roundup, containing 80,505 μg/g POEA) were the major source of contamination for imported soybeans. For domestic soybeans, intercropping systems had the highest residues (250 μg/kg), followed by conventional (154 μg/kg) and green cultivation (77.6 μg/kg). Non-glyphosate pesticides (0.43-4349 μg/g POEA) may also contribute to residues in domestic soybeans. Dietary risk assessments indicated minimal acute and chronic intake risks for the general population (0.006-0.12%). However, children were the most susceptible group, requiring increased attention. This study provides the first evidence of widespread POEA contamination in soybeans and highlights its low but age-dependent dietary risks.