More than Quaternary Ammonium Compounds: First Evidence of Tertiary Amine Compounds as Novel Contaminants Ubiquitously Present in Indoor Dust

Abstract Nitrogen-containing organic compounds have attracted global concern due to their widespread production and potential environmental risks. While the environmental occurrence of quaternary ammonium compounds (QACs) has been widely studied, research on tertiary amine compounds (TACs), another important class of toxic nitrogen-containing organic compounds with high production volumes, remains limited. In this study, 118 dust samples collected from residential homes in North China were analyzed for both QACs and TACs. Total concentrations of QACs in urban indoor dust ranged from 2.25 × 103 to 4.54 × 104 ng/g (median: 1.40 × 104 ng/g). Surprisingly, the previously overlooked TACs were detected in 80–100% of the urban dust samples, with comparable concentrations (range: 423–2.12 × 104 ng/g, median: 4.03 × 103 ng/g) to QACs, indicating their prevalence in indoor environments. Diethyldodecanamide (DEDA) and N-dodecyldiethanolamine were the dominant TACs in urban dust, with median concentrations of 2.25 × 103 and 395 ng/g, respectively. Both TAC and QAC concentrations were significantly higher in urban dust than in rural dust (p < 0.01). The toxicology priority index approach highlights that TACs warrant significant attention, as two TACs (DEDA and Stearyldiethanolamine) were identified as the highest priority compounds, even surpassing the detected QACs. To our knowledge, this is the first report of TACs in indoor environments, with 14 TACs detected in the environment for the first time, shedding light on the ubiquitous presence of TACs alongside QACs.