Synthetic phenolic antioxidants and their major metabolites in human fingernail

Synthetic phenolic antioxidants (SPAs) have been widely used in foods, polymers, and cosmetics, but very limited information is available about their occurrence in human tissues. In this study, five SPAs, namely 2,6-di-tert-butyl-4-methylphenol (BHT), 2-tert-butyl-4-hydroxyanisole (BHA), propyl-, octyl-, and dodecyl-gallate (PG, OG, and DG), and four major metabolites of BHT, including 3,5-di-tert-butyl-4 -hydroxybenzaldehyde (BHT-CHO), 2,6-di-tert-butyl-4-(hydroxymethyl) phenol (BHT-OH), 3,5-di-tertbutyl-4-hydroxybenzoic acid (BHT-COOH), and 2,6-di-tert-butyl-1,4-benzoquinone (BHT-Q), were determined in human fingernail samples collected from Nanjing, China. Total concentrations of the nine target analytes (∑₉SPAs) were 523-14,000 ng/g. BHT was the predominant SPA compound and detected in all samples at a range of 309-11,400 ng/g. The ∑₉SPAs was negatively correlated with age of fingernail donors (p < 0.05). In addition, indoor dust samples from the living places of the fingernail providers were collected with aim to better understand the SPA exposure pathways. A positive correlation (p < 0.05) was found only for DG concentrations between paired fingernail and dust samples, while not for other SPAs, suggesting that SPAs accumulated in fingernails may not be mainly from indoor dust. SPAs were measured for the first time in human fingernail, and the elevated concentrations in fingernail suggest that the health risk of SPAs should be paid more attention due to their bioaccumulation potential in human body. Further studies are warranted about exposure pathway, distribution and metabolism of SPAs in human body.