Chunyang Liao

Bisphenol S, a New Bisphenol Analogue, in Paper Products and Currency Bills and Its Association with Bisphenol A Residues

As the evidence of the toxic effects of bisphenol A (BPA) grows, its application in commercial products is gradually being replaced with other related compounds, such as bisphenol S (BPS). Nevertheless, very little is known about the occurrence of BPS in the environment. In this study, BPS was analyzed in 16 types of paper and paper products (n = 268), including thermal receipts, paper currencies, flyers, magazines, newspapers, food contact papers, airplane luggage tags, printing paper, kitchen rolls (i.e., paper towels), and toilet paper. All thermal receipt paper samples (n = 111) contained BPS at concentrations ranging from 0.0000138 to 22.0 mg/g (geometric mean: 0.181 mg/g). The overall mean concentrations of BPS in thermal receipt papers were similar to the concentrations reported earlier for BPA in the same set of samples. A significant negative correlation existed between BPS and BPA concentrations in thermal receipt paper samples (r = -0.55, p < 0.0001). BPS was detected in 87% of currency bill samples (n = 52) from 21 countries, at concentrations ranging from below the limit of quantification (LOQ) to 6.26 μg/g (geometric mean: 0.029 μg/g). BPS also was found in 14 other paper product types (n = 105), at concentrations ranging from <LOQ to 8.38 μg/g (geometric mean: 0.0036 μg/g; detection rate: 52%). The estimated daily intake (EDI) of BPS, through dermal absorption via handling of papers and currency bills, was estimated on the basis of concentrations and frequencies of the handling of papers by humans. The median and 95th percentile EDI values, respectively, were 4.18 and 11.0 ng/kg body weight (bw)/day for the general population and 312 and 821 ng/kg bw/day for occupationally exposed individuals. Among the paper types analyzed, thermal receipt papers were found to be the major sources of human exposure to BPS (>88%). To our knowledge, this is the first report on the occurrence of BPS in paper products and currency bills.

Bisphenol S in Urine from the United States and Seven Asian Countries: Occurrence and Human Exposures

As concern regarding the toxic effects of bisphenol A (BPA) grows, BPA in many consumer products is gradually being replaced with compounds such as bisphenol S (BPS). Nevertheless, data on the occurrence of BPS in human specimens are limited. In this study, 315 urine samples, collected from the general populations in the United States, China, India, Japan, Korea, Kuwait, Malaysia, and Vietnam, were analyzed for the presence of total BPS (free plus conjugated) concentrations by high-performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS). BPS was detected in 81% of the urine samples analyzed at concentrations ranging from below the limit of quantitation (LOQ; 0.02 ng/mL) to 21 ng/mL (geometric mean: 0.168 ng/mL). The urinary BPS concentration varied among countries, and the highest geometric mean concentration [1.18 ng/mLor 0.933 μg/g creatinine (Cre)] of BPS was found in urine samples from Japan, followed by the United States (0.299 ng/mL, 0.304 μg/g Cre), China (0.226 ng/mL, 0.223 μg/g Cre), Kuwait (0.172 ng/mL, 0.126 μg/g Cre), and Vietnam (0.160 ng/mL, 0.148 μg/g Cre). Median concentrations of BPS in urine samples from the Asian countries were 1 order of magnitude lower than the median concentrations reported earlier for BPA in the same set of samples, with the exception of samples from Japan. There were no significant differences in BPS concentrations between genders (male versus female), or among age groups (categorized as ≤ 19, 20-29, 30-39, 40-49, and ≥ 50 years), or races (Caucasian versus Asian). The daily intake (EDI) of BPS was estimated on the basis of urinary concentrations using a simple pharmacokinetic approach. The median EDI values of BPS in Japan, China, United States, Kuwait, Vietnam, Malaysia, India, and Korea were 1.67, 0.339, 0.316, 0.292, 0.217, 0.122, 0.084, and 0.023 μg/person, respectively. This is the first study to report the occurrence of BPS in human urine.

Widespread Occurrence of Bisphenol A in Paper and Paper Products: Implications for Human Exposure

Bisphenol A (BPA) is used in a variety of consumer products, including some paper products, particularly thermal receipt papers, for which it is used as a color developer. Nevertheless, little is known about the magnitude of BPA contamination or human exposure to BPA as a result of contact with paper and paper products. In this study, concentrations of BPA were determined in 15 types of paper products (n = 202), including thermal receipts, flyers, magazines, tickets, mailing envelopes, newspapers, food contact papers, food cartons, airplane boarding passes, luggage tags, printing papers, business cards, napkins, paper towels, and toilet paper, collected from several cities in the USA. Thermal receipt papers also were collected from Japan, Korea, and Vietnam. BPA was found in 94% of thermal receipt papers (n = 103) at concentrations ranging from below the limit of quantitation (LOQ, 1 ng/g) to 13.9 mg/g (geometric mean: 0.211 mg/g). The majority (81%) of other paper products (n = 99) contained BPA at concentrations ranging from below the LOQ to 14.4 μg/g (geometric mean: 0.016 μg/g). Whereas thermal receipt papers contained the highest concentrations of BPA (milligram-per-gram), some paper products, including napkins and toilet paper, made from recycled papers contained microgram-per-gram concentrations of BPA. Contamination during the paper recycling process is a source of BPA in paper products. Daily intake (DI) of BPA through dermal absorption was estimated based on the measured BPA concentrations and handling frequency of paper products. The daily intake of BPA (calculated from median concentrations) through dermal absorption from handling of papers was 17.5 and 1300 ng/day for the general population and occupationally exposed individuals, respectively; these values are minor compared with exposure through diet. Among paper products, thermal receipt papers contributed to the majority (>98%) of the exposures.

Urinary Bisphenol A Concentrations and Their Implications for Human Exposure in Several Asian Countries

Bisphenol A (BPA) is an industrial chemical used in the manufacture of polycarbonate plastics and epoxy resins. Due to the potential of this compound to disrupt normal endocrinal functions, concerns over human exposure to BPA have been raised. Although several studies have reported human exposure to BPA in Western nations, little is known about exposure in Asian countries. In this study, we determined total urinary BPA concentrations (free plus conjugated) in 296 urine samples (male/female: 153/143) collected from the general population in seven Asian countries, China, India, Japan, Korea, Kuwait, Malaysia, and Vietnam, using high-performance liquid chromatography (HPLC) tandem mass spectrometry (MS/MS). On the basis of urinary BPA concentrations, we estimated the total daily intake. The results indicated that BPA was detected in 94.3% of the samples analyzed, at concentrations ranging from <0.1 to 30.1 ng/mL. The geometric mean concentration of BPA for the entire sample set from seven countries was 1.20 ng/mL. The highest concentration of BPA was found in samples from Kuwait (median: 3.05 ng/mL, 2.45 μg/g creatinine), followed by Korea (2.17 ng/mL, 2.40 μg/g), India (1.71 ng/mL, 2.09 μg/g), Vietnam (1.18 ng/mL, 1.15 μg/g), China (1.10 ng/mL, 1.38 μg/g), Malaysia (1.06 ng/mL, 2.31 μg/g), and Japan (0.95 ng/mL, 0.58 μg/g). Among the five age groups studied (≤ 19, 20-29, 30-39, 40-49, and ≥ 50 years), the highest median concentration of BPA was found in urine samples from the age group of ≤ 19 years. There was no significant difference in BPA concentrations between genders (male and female) or domicile of residence (rural and urban). The estimated median daily intakes of BPA for the populations in Kuwait, Korea, India, China, Vietnam, Malaysia, and Japan were 5.19, 3.69, 2.90, 2.13, 2.01, 1.80, and 1.61 μg/day, respectively. The estimated daily intake of BPA in the seven Asian countries was significantly lower than the tolerable daily intake recommended by the U.S. Environmental Protection Agency. This is the first study to document the occurrence of and human exposure to BPA in several Asian countries.

Use of scalp hair as indicator of human exposure to heavy metals in an electronic waste recycling area

Scalp hair samples were collected at an electronic waste (e-waste) recycling area and analyzed for trace elements and heavy metals. Elevated levels were found for Cu and Pb with geometric means (GMs) at 39.8 and 49.5 microg/g, and the levels of all elements were found in the rank order Pb > Cu >> Mn > Ba > Cr > Ni > Cd > As > V. Besides Cu and Pb, Cd (GM: 0.518 microg/g) was also found to be significantly higher compared to that in hair samples from control areas. Differences with age, gender, residence status and villages could be distinguished for most of the elements. The high levels of Cd, Cu and Pb were likely found to be originated from e-waste related activities, and specific sources were discussed. This study shows that human scalp hair could be a useful biomarker to assess the extent of heavy metal exposure to workers and residents in areas with intensive e-waste recycling activities.

Bisphenol analogues in sediments from industrialized areas in the United States, Japan, and Korea: spatial and temporal distributions.

Bisphenol analogues are used in the production of polycarbonate plastics and epoxy resins. Despite the widespread use of bisphenols, few studies have reported the occurrence of compounds other than bisphenol A (BPA) in sediment. In this study, concentrations and profiles of eight bisphenol analogues were determined using high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) in sediments collected from several industrialized areas in the United States (U.S.), Japan, and Korea. The total concentrations of bisphenols (ΣBPs; sum of eight bisphenols) in sediment ranged from below the limit of quantitation (LOQ) to 25,300 ng/g dry weight (dw), with a mean value of 201 ng/g dw. Sediment samples from Lake Shihwa, Korea, contained the highest concentrations of both individual and total bisphenols. Among individual bisphenols, BPA and bisphenol F (BPF) were the predominant compounds, accounting for 64% and 30% of the total bisphenol concentrations in sediment. We also examined vertical profiles of concentrations of bisphenol analogues in sediment cores from the U.S. and Japan. Sediment cores from the U.S. showed a gradual decline in the concentrations of bisphenols as compared to the past decade. BPA concentrations were found to decline in a sediment core from Tokyo Bay, but bisphenol S (BPS) was more frequently detected in core sections that represent the most recent decade, which is consistent with the replacement of BPA with BPS in some applications since 2001 in Japan.

Determination of Free and Conjugated Forms of Bisphenol A in Human Urine and Serum by Liquid Chromatography–Tandem Mass Spectrometry

Exposure of humans to bisphenol A (BPA), a widely used industrial chemical, is well-known. In humans and animals, conjugation of BPA molecule with glucuronide or sulfate is considered as a mechanism for detoxification. Nevertheless, very few studies have directly measured free, conjugated (e.g., glucuronidated), and substituted (e.g., chlorinated) forms of BPA in human specimens. In this study, free, conjugated (BPA glucuronide or BPAG and BPA disulfate or BPADS), and substituted (chlorinated BPA; mono- [BPAMC], di-[BPADC], and trichloride [BPATrC]) forms of BPA were determined in human urine and serum samples, using solid-phase extraction (SPE) and liquid chromatography-tandem mass spectrometry (LC-MS/MS) techniques. The instrumental calibration for each of the target compounds ranged from 0.01 to 100 ng/mL and showed excellent linearity (r > 0.99). The limits of quantification (LOQs) were 0.01 ng/mL for free BPA and 0.05 ng/mL for the conjugated and substituted BPA. Respective recoveries of the six target compounds spiked into water blanks and sample matrices (urine and serum), and passed through the entire analytical procedure, were 96 ± 14% and 105 ± 18% (mean ± SD) for urine samples and 87 ± 8% and 80 ± 13% for serum samples. The optimal recoveries of BPAG and BPADS in the analytical procedure indicted that no deconjugation occurred during the SPE procedure. The method was applied to measure six target chemicals in urine and serum samples collected from volunteers in Albany, New York. BPA and its derivatives were found in urine samples at concentrations ranging from < LOQ to a few tens of ng/mL. In serum, free and conjugated BPA were detected at sub ng/mL concentrations, whereas BPA chlorides were not detected. The urine and serum samples were also analyzed by enzymatic deconjugation and liquid-liquid extraction (LLE) for the determination of total BPA, and the results were compared with those measured by the SPE method. To our knowledge, this is the first report on the occurrence of BPAG and BPADS in human serum.

Determination of 16 polycyclic aromatic hydrocarbons in seawater using molecularly imprinted solid-phase extraction coupled with gas chromatography-mass spectrometry

A method of solid-phase extraction (SPE) using molecularly imprinted polymers (MIPs) as adsorbent coupled with gas chromatography-mass spectrometry (GC-MS) was developed for the determination of 16 types of polycyclic aromatic hydrocarbons (PAHs) in seawater samples. The MIPs were prepared through non-covalent polymerization by using the 16 PAHs mixture as a template based on sol-gel surface imprinting. Compared with the non-imprinted polymers (NIPs), the MIPs exhibited excellent affinity towards 16 PAHs with binding capacity of 111.0-195.0 μg g(-1), and imprinting factor of 1.50-3.12. The significant binding specificity towards PAHs even in the presence of environmental parameters such as dissolved organic matter and various metal ions, suggested that this new imprinting material was capable of removing 93.2% PAHs in natural seawater. High sensitivity was attained, with the low limits of detection for 16 PAHs in natural seawater ranging from 5.2-12.6 ng L(-1). The application of MIPs with high affinity and excellent stereo-selectivity toward PAHs in SPE might offer a more attractive alternative to conventional sorbents for extraction and abatement of PAH-contaminated seawater.

Epigenetic Responses Following Maternal Dietary Exposure to Physiologically Relevant Levels of Bisphenol A

Animal studies have linked perinatal bisphenol A (BPA) exposure to altered DNA methylation, but little attention is given to analyzing multiple physiologically relevant doses. Utilizing the viable yellow agouti (Avy) mouse, we examine the effects of developmental exposure through maternal diet to 50 ng BPA/kg (n = 14 litters), 50 μg BPA/kg (n = 9 litters), or 50 mg BPA/kg (n = 13 litters) on global and candidate gene methylation at postnatal day 22. Global methylation analysis reveals hypermethylation in tail tissue of a/a and Avy/a offspring across all dose groups compared with controls (n = 11 litters; P < 0.02). Analysis of coat color phenotype replicates previous work showing that the distribution of 50 mg BPA/kg Avy/a offspring shifts toward yellow (P = 0.006) by decreasing DNA methylation in the retrotransposon upstream of the Agouti gene (P = 0.03). Maternal exposure to 50 μg or 50 ng BPA/kg, however, results in altered coat color distributions in comparison with control (P = 0.04 and 0.02), but no DNA methylation effects at the Agouti gene are noted. DNA methylation at the CDK5 activator‐binding protein (CabpIAP) metastable epiallele shows hypermethylation in the 50 μg BPA/kg offspring, compared with controls (P = 0.02). Comparison of exposed mouse liver BPA levels to human fetal liver BPA levels indicates that the three experimental exposures are physiologically relevant. Thus, perinatal BPA exposure affects offspring phenotype and epigenetic regulation across multiple doses, indicating the need to evaluate dose effects in human clinical and population studies. Environ. Mol. Mutagen. 2012.

A functional graphene oxide-ionic liquid composites–gold nanoparticle sensing platform for ultrasensitive electrochemical detection of Hg2+

A simple and sensitive electrochemical assay strategy of stripping voltammetry for mercury ions (Hg(2+)) detection is described based on the synergistic effect between ionic liquid functionalized graphene oxide (GO-IL) and gold nanoparticles (AuNPs). The AuNPs-GO-IL modified onto glassy carbon electrode (GCE) resulted in highly enhanced electron conductive nanostructured membrane and large electroactive surface area, which was excellently examined by scanning electron microscopy and cyclic voltammetry. After accumulating Hg(2+), anodic stripping voltammetry (ASV) was performed, and differential pulse voltammetry (DPV) was employed for signal recording of Hg(2+). Several main experimental parameters were optimized, i.e., deposition potential and time of AuNPs were -0.2 V and 180 s, respectively, and accumulation potential and time of Hg(2+) were -0.3 V and 660 s, respectively. Under the optimal conditions, this AuNPs-GO-IL-GCE sensor attained a good linearity in a wide range of 0.1-100 nM (R = 0.9808) between the concentration of the Hg(2+) standard and peak current. The limit of detection was estimated to be 0.03 nM at a signal-to-noise ratio of 3σ. A variety of common coexistent ions in water samples were investigated, showing no obvious interferences on the Hg(2+) detection. The practical application of the proposed sensor has been carried out and demonstrated as feasible for determination of trace levels of Hg(2+) in drinking and environmental water samples.