Occurrence of synthetic phenolic antioxidants and transformation products in urban and rural indoor dust.

In this study, seven synthetic phenolic antioxidant (SPA) analogues were positively found in urban and rural indoor dust samples collected from Shandong province in China, among which the novel 2,4,6-tri-tert-butylphenol (AO 246), 2,6-di-tert-butyl-4-sec-butylphenol (DTBSBP), 2,4-di-tert-butylphenol (DBP) and 4,4'-butylidenebis (2-(1,1-dimethylethyl)-5- methyl-phenol) (AO 44B25) analogues accounted for 29% of total SPA concentrations (∑SPAs). Urban dust showed significantly higher ∑SPA levels (range: 1.56e3 - 2.03e4 ng/g) compared with those in rural indoor dust (668-4.39e3 ng/g, p < 0.05). 2,6-Di-tert-butyl-4-methylphenol (BHT) was the dominate analogue in the urban indoor dust, which constituted of 74% in ΣSPAs. While, varied composition profiles of SPAs were noticed in rural indoor dust, for instance, AO 246 (46%) and BHT (43%) had similar contributions to ∑SPAs. Three BHT transformation products (TPs) were also detected in most of the urban and rural dust samples (>97%), with individual residue level in the same order: 2,6-di-tert-butyl-1,4-benzoquinone (BHT-Q) > 2,6-di-tert-butyl-4-hydroxy- 4-methyl-2,5-cyclo-hexadienone (BHT-quinol) > 3,5-di-tert-butyl-4-hydroxybenzal-dehyde (BHT-CHO). Geometric mean values of total TP concentrations were 555 ng/g and 131 ng/g for urban and rural indoor dust samples, respectively. A preliminary estimated daily intake calculation at dust ingestion scenario suggested additional concerns might be paid to simultaneous exposure of several SPA analogues and TPs besides current focus on BHT exposure risks.