Letter Cite This: Environ. Sci. Technol. Lett. XXXX, XXX, XXX−XXX
pubs.acs.org/journal/estlcu
Synthetic Phenolic Antioxidants and Transformation Products in Human Sera from United States Donors Runzeng Liu* and Scott A. Mabury Department of Chemistry, University of Toronto, 80 St. George Street, Toronto M5S 3H6, Ontario, Canada S Supporting Information *
ABSTRACT: Synthetic phenolic antioxidants (SPAs) make up a group of widely used anthropogenic additives, whose potential for toxicity has received more attention in recent years. Although SPAs can reach humans through many exposure pathways, few data on the concentrations of SPAs in humans are available. In this study, five SPAs were quantified, at significant concentrations, in 50 individual serum samples collected from donors in the United States. The measured total SPA concentrations [0.46−34.7 ng/mL, geometric mean (GM) of 7.77 ng/mL] were dominated by 2,6-di-tert-butyl-4-methylphenol (BHT) and 2,4-di-tert-butylphenol (DBP), which contributed 42 and 57% on average to the total concentrations, respectively. Four putative biotransformation products (TPs) of BHT [2,6-di-tert-butyl-4(hydroxymethyl)phenol (BHT-OH), 3,5-di-tert-butyl-4-hydroxybenzaldehyde (BHT-CHO), 2,6-di-tert-butyl-1,4-benzoquinone (BHT-Q), and 2,6-di-tert-butyl-4-hydroxy-4-methyl-2,5-cyclohexadienone (BHT-quinol)] were also detected, with total concentrations ranging from below the method quantification limits to 3.66 ng/mL (GM of 0.77 ng/mL). Five pooled serum samples, each containing sera from at least 1000 donors, were also included in this study. The concentrations of the SPAs (GM of 24.5 ng/mL) and TPs (GM of 10.4 ng/mL) were even higher in pooled sera than in individual samples, indicating the prevalent human burdens of SPAs in a large population. To the best of our knowledge, this is the first analysis of a wide range of SPAs and TPs in human sera.
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prevalent in indoor environments globally.8 Besides BHT, other single-ring phenolic antioxidants, such as 2,4-di-tert-butylphenol (DBP) and 3-tert-butyl-4-hydroxyanisole (BHA), were also frequently detected in dust samples collected from urban and rural residential houses.9 It should be noted that DBP is a degradation product of tris(2,4-di-tert-butylphenyl)phosphite (known as Irgafos 168), which is largely used as an antioxidant in plastics.10 Furthermore, 11 SPAs were identified in sewage sludge collected from 20 Chinese provinces.11 4-tert-Octylphenol (4-tOP), which is mainly used to manufacture alkylphenol ethoxylates, was also detected along with the SPAs in the environment.11,12 The environmental ubiquity of these SPAs is of concern because of their toxicity effects. BHA has been shown to disrupt the endocrine system,13,14 and its carcinogenicity in rodents has been established.15 4-tert-Octylphenol (4-tOP) has been reported to have estrogenic effects in both in vivo and in vitro studies.16,17 Endocrine-disrupting effects have been reported for DBP using in vitro assays.18,19 In contrast, the toxicity effects of BHT itself remain controversial: some studies identified a potential relationship between BHT exposure and cancer,
INTRODUCTION Synthetic phenolic antioxidants (SPAs) make up a family of anthropogenic chemicals that are used as radical trapping agents in plastics, fireproofing plasticizers, elastomers, synthetic fibers, lubricants, fuels, and even foods.1−3 Most SPAs have a basic common molecular structure characterized by phenolic rings representatively substituted with hindered alkyl groups in ortho positions.4,5 Among the synthetic phenols, single-ring phenolic antioxidants such as 2,6-di-tert-butyl-4-methylphenol (BHT) are the most frequently used congeners. Currently, several SPAs, including BHT, are included on the U.S. Environmental Protection Agency high-production volume (HPV) list. In the year 2000, BHT use was distributed among a wide variety of end applications as follows: rubber (27%), plastics (27%), mineral oil/fuel additive (17%), foodstuff/pharmaceuticals/cosmetics (12%), animal feed/pet food (11%), and printing inks/miscellaneous (6%).6 The massive production and widespread use of SPAs in the past several decades have led to public concern about environmental contamination.1 BHT has received the most attention in this regard. A nontargeted analysis found BHT to be ubiquitously present in surface water and soil samples collected from rice fields in Columbia.7 A recent study reported the frequent presence of BHT in indoor dust samples collected from 12 countries, indicating that BHT contamination is © XXXX American Chemical Society
Received: April 24, 2018 Accepted: May 2, 2018 Published: May 2, 2018 A
DOI: 10.1021/acs.estlett.8b00223 Environ. Sci. Technol. Lett. XXXX, XXX, XXX−XXX
Letter
Environmental Science & Technology Letters
glass tube. The extraction was performed three times. The combined hexane was dried to 0.5 mL under a stream of nitrogen and separated into 0.1 and 0.4 mL aliquots. The 0.1 mL sample was analyzed for BHT, 2,6-di-tert-butyl-pbenzoquinone (BHT-Q), 2,4,6-tri-tert-butylphenol (AO 246), and 2,6-di-tert-butyl-4-s-butylphenol (DTBSBP) by gas chromatography and mass spectrometry (GC−MS). The 0.4 mL sample had 6 ng of BPA-d16 added to it, was further dried under a stream of nitrogen, and then was solvent exchanged into 0.4 mL of methanol. The 0.4 mL sample was then centrifuged at 3000 rpm for 5 min to remove the suspended particles. Finally, after centrifugation, a 2 μL aliquot was injected into an ultrahigh-performance liquid chromatography−tandem mass spectrometry (UPLC−MS/MS) instrument to detect the other target congeners. The details of the instrumental analysis are given in Tables S3 and S4. Quality Assurance/Quality Control. To ensure that three extractions were sufficient, a fourth extraction was performed on five randomly selected serum samples. Quantifiable amounts of the target SPAs and TPs were not found in the fourth extraction, indicating that the first three cycles achieved maximum recoveries for the target analytes. As shown in Table S5, recoveries of the target analytes in matrix-spiked samples (2 ng/mL) varied from 76 to 103%. The relative standard deviations (n = 3) were all
