Faculty Bibliography

Concentrations of 12 hydroxylated polycyclic aromatic hydrocarbons (OH-PAHs) were determined in 306 urine samples collected from seven Asian countries (China, India, Japan, Korea, Kuwait, Malaysia, and Vietnam) by high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). The total concentrations of OH-PAHs found in the seven Asian countries were in the following increasing order: Malaysia (median: 2260 pg/mL) < Japan (4030 pg/mL) < China (5770 pg/mL) < India (6750 pg/mL) < Vietnam (8560 pg/mL) < Korea (9340 pg/mL) < Kuwait (10170 pg/mL). The measured urinary concentrations of 1-hydroxypyrene (1-PYR) in samples from Malaysia, Korea, and Japan (∼ 100 pg/mL) were similar to those reported for North America and Western Europe. The concentrations of 1-PYR in urine samples from China, India, and Vietnam were 4-10 times higher than those reported for other countries, thus far. Among the 12 OH-PAH compounds analyzed, hydroxynaphthalene (NAP: sum of 1-hydroxynaphthalene and 2-hydroxynaphthalene) was the dominant compound (accounting for 60-90% of total OH-PAHs), followed by hydroxyphenanthrene (PHEN: sum of 2-hydroxyphenanthrene, 3-hydroxyphenanthrene, 4-hydroxyphenanthrene, and 9-hydroxyphenanthrene [3-16%]), 2-hydroxyfluorene (3-20%), and 1-PYR (2-8%). The total daily intakes (DIs) of PAHs were estimated based on the urinary concentrations of their metabolites. The DIs of naphthalene were found to be higher for populations in Korea, Kuwait, and Vietnam (> 10 μg/day) than those of the other countries studied (∼ 5 μg/day). The DIs of phenanthrene and pyrene (> 10 μg/day) in the populations of China, India, and Vietnam were higher than those estimated for the populations in the other countries studied (∼ 5 μg/day).

Perfluoroalkyl substances (PFAS) have been globally detected in various environmental matrices, yet their fate and transport to the Arctic is still unclear, especially for the European Arctic. In this study, concentrations of 17 PFAS were quantified in two ice cores (n=26), surface snow (n=9) and surface water samples (n=14) collected along a spatial gradient in Svalbard, Norway. Concentrations of selected ions (Na(+), SO4(2-), etc.) were also determined for tracing the origins and sources of PFAS. Perfluorobutanoate (PFBA), perfluorooctanoate (PFOA) and perfluorononanoate (PFNA) were the dominant compounds found in ice core samples. Taking PFOA, PFNA and perfluorooctane-sulfonate (PFOS) as examples, higher concentrations were detected in the middle layers of the ice cores representing the period of 1997-2000. Lower concentrations of C8-C12 perfluorocarboxylates (PFCAs) were detected in comparison with concentrations measured previously in an ice core from the Canadian Arctic, indicating that contamination levels in the European Arctic are lower. Average PFAS concentrations were found to be lower in surface snow and melted glacier water samples, while increased concentrations were observed in river water downstream near the coastal area. Perfluorohexanesulfonate (PFHxS) was detected in the downstream locations, but not in the glacier, suggesting existence of local sources of this compound. Long-range atmospheric transport of PFAS was the major deposition pathway for the glaciers, while local sources (e.g., skiing activities) were identified in the downstream locations.

Thyroid hormones (THs) are essential for brain development, and iodine is required for TH synthesis. Environmental chemicals that perturb the thyroid axis result in modest reductions in TH, yet there is a paucity of data on the extent of neurological impairments associated with low-level TH disruption. This study examined the dose-response characteristics of marginal iodine deficiency (ID) on parameters of thyroid function and neurodevelopment. Diets deficient in iodine were prepared by adding 975, 200, 125, 25, or 0 µg/kg potassium iodate to the base casein diet to produce five nominal iodine levels ranging from ample (Diet 1: 1000 μg iodine/kg chow, D1) to deficient (Diet 5: 25 µg iodine/kg chow, D5). Female Long Evans rats were maintained on these diets beginning 7 weeks prior to breeding until the end of lactation. Dams were sacrificed on gestational days 16 and 20, or when pups were weaned on postnatal day (PN) 21. Fetal tissue was harvested from the dams, and pups were sacrificed on PN14 and PN21. Blood, thyroid gland, and brain were collected for analysis of iodine, TH, and TH precursors and metabolites. Serum and thyroid gland iodine and TH were reduced in animals receiving two diets that were most deficient in iodine. T4 was reduced in the fetal brain but was not altered in the neonatal brain. Neurobehavior, assessed by acoustic startle, water maze learning, and fear conditioning, was unchanged in adult offspring, but excitatory synaptic transmission was impaired in the dentate gyrus in animals receiving two diets that were most deficient in iodine. A 15% reduction in cortical T4 in the fetal brain was sufficient to induce permanent reductions in synaptic function in adults. These findings have implications for regulation of TH-disrupting chemicals and suggest that standard behavioral assays do not readily detect neurotoxicity induced by modest developmental TH disruption.

Hydroxybenzoic acid esters (parabens) are used as preservatives in foods, cosmetics, and pharmaceuticals, which results in the exposure of humans to these compounds. Parabens and its metabolite, p-hydroxybenzoic acid (p-HB) are excreted from urine in free and conjugated forms. In this study, free and total forms (free plus conjugated) of parabens and their common metabolite, p-HB, were measured in urine samples collected from U.S. children (n = 40), Chinese children (n = 70), and Chinese adults (n = 26). The median concentrations of the sum of 6 parabens (Σparabens) in urine from U.S. and Chinese children were 54.6 and 10.1 ng/mL, respectively. The median concentration of urinary parabens measured for Chinese adults was 33.2 ng/mL, which was lower than that reported for U.S. adults. Elevated concentrations of parabens (1000-10,000 ng/mL) were found in urine from some Chinese adult females. Parabens were present predominantly (>90%) as conjugated species in urine. Among the six parabens analyzed, methyl paraben (MeP) and propyl paraben (PrP) were the predominant compounds, which accounted for 57-98% and 1.4-12%, respectively, of the total concentrations. A significant positive correlation was found between the concentrations of MeP and PrP. The geometric mean (GM) concentration of p-HB was 1380 and 2370 ng/mL for Chinese children and adults, respectively. The GM concentrations of p-HB in urine from U.S. children were 752 ng/mL for girls and 628 ng/mL for boys, which were 2-3 times lower than the concentrations determined for Chinese children. There was a significant difference in the ratios of concentrations of Σparabens and p-HB between demographic groups, which suggested the existence of various exposure routes to parabens. Based on the concentrations of urinary parabens and p-HB, the daily intake (DI) of MeP and PrP was estimated. The GM DI(MeP) estimated for Chinese children was 0.5-0.7 mg/day, which was similar to those determined for U.S. children. The GM DI(PrP) (0.2-0.5 mg/day) estimated for Chinese children was 20- to 50-fold higher than the value determined for U.S. children (0.01 mg/day). The highest exposure to parabens was found for Chinese adult females, with GM DI(MeP) and DI(PrP) of 5.9 and 1.2 mg/day, respectively. Elevated exposure to PrP was found in some Chinese adult females (27 mg/day) and children (11 mg/day).

The occurrence and fate of 5 cyclic (D3 to D7) and 12 linear (L3 to L14) siloxanes were investigated in raw and treated wastewater (both particulate and dissolved phases) as well as in sludge from a wastewater treatment plant (WWTP) in Athens, Greece. Cyclic and linear siloxanes (except for L3) were detected in all influent wastewater and sludge samples at mean concentrations of (sum of 17 siloxanes) 20 μg L(-1) and 75 mg kg(-1), respectively. The predominant compounds in wastewater were L11 (24% of the total siloxane concentration), L10 (16%), and D5 (13%), and in sludge were D5 (20%) and L10 (15%). The distribution of siloxanes between particulate and dissolved phases in influents differed significantly for linear and cyclic siloxanes. Linear siloxanes showed higher solid-liquid distribution coefficients (log K(d)) than did cyclic compounds. For 10 of the 16 compounds detected in influents, the removal efficiency was higher than 80%. Sorption to sludge and biodegradation and/or volatilization losses are important factors that affect the fate of siloxanes in WWTPs. The mean total mass of siloxanes that enter into the WWTP via influent was 15.1 kg per day(-1), and the mean total mass released into the environment via effluent was 2.67 kg per day(-1).

Widespread exposure to the endocrine active compound, bisphenol A (BPA), is well documented in humans. A growing body of literature suggests adverse health outcomes associated with varying ranges of exposure to BPA. In the current study, we measured the internal dose of free BPA and conjugated BPA and evaluated gene expression of biotransformation enzymes specific for BPA metabolism in 50 first- and second-trimester human fetal liver samples. Both free BPA and conjugated BPA concentrations varied widely, with free BPA exhibiting three times higher concentrations than conjugated BPA concentrations. As compared to gender-matched adult liver controls, UDP-glucuronyltransferase, sulfotransferase, and steroid sulfatase genes exhibited reduced expression whereas β-glucuronidase mRNA expression remained unchanged in the fetal tissues. This study provides evidence that there is considerable exposure to BPA during human pregnancy and that the capacity for BPA metabolism is altered in the human fetal liver.

A field study on the photolysis of perfluoroalkyl substances (PFASs) was conducted at high altitudes in Mt. Mauna Kea (Hawaii, USA; 4200 m) and Mt. Tateyama (Toyama, Japan; 2500 m). Results of photolysis of PFASs in the field were further confirmed in laboratory studies. Perfluorooctanesulfonate (PFOS), which is perceived as a non-degradable chemical in the environment, can undergo photolysis. Long chain PFASs can be successively dealkylated to short chain compounds such as perfluorobutyric acid (PFBA) and perfluorobutane sulfonate (PFBS), but the short chain compounds were relatively more resistant to photodegradation. These results suggest that environmental levels of short chain PFASs would increase both due to their formation from photolysis of long chain PFASs and from direct releases. Earlier studies on photolysis of PFASs were focused on the formation of perfluorocarboxylic acids (PFCAs) and perfluorosulfonic acids (PFSAs) from precursor compounds (such as fluorotelomer alcohols) under laboratory conditions. Our study suggests that PFSAs and PFCAs themselves can undergo photodegradation in the environment.

Polybrominated diphenyl ethers (PBDEs), used as flame retardants (BFRs), are incorporated in plastics of most electronic equipment. Among BFR mixtures, deca-BDE is the most widely used commercial additive in the polymer industry and the use of deca-BDE is currently not subject to any restrictions in China. However, debate over environmental and health risks associated with deca-BDE still remains. Regulatory agencies in developed countries have adopted and/or established environmentally sound strategies for the management of potential threat posed by PBDEs to the environment and human health. No regulations or management policies for PBDEs currently exist in China at either central or provincial government levels. Large amounts of plastics containing PBDEs are still in use and must be disposed of after their lifetimes, creating outdoor reservoirs for the future dispersal of PBDEs into the environment. Concerted action is needed not only to regulate the production and use of PBDEs but also to find ways to effectively manage waste electrical and electronic products that contain PBDEs. This article is the first to investigate the policy issues and current problems related to the use of PBDEs in China. In addition, we estimate the mass flows of PBDEs contained in Waste Electrical and Electronic Equipment (WEEE) in China. We suggest alternatives to PBDEs and sound management of plastics used in electrical and electronic equipment (EEE) that contain PBDEs.

Concentrations of polybrominated diphenyl ethers (PBDEs) were determined in commonly consumed seafood and house dust collected from Korea. Total concentrations of PBDEs in seafood and house dust samples were in the ranges of 0.06 to 6.25 ng/g wet weight and 80 to 16,000 ng/g dry weight, respectively. Predominant congeners in seafood were BDEs 47, 99 and 100 and those in dust samples were BDE 209. Estimated daily intakes (EDIs) of PBDEs through seafood consumption and dust ingestion for adults (>20 years) and toddlers (<2 years) were 1.83 and 11.4 ng/kg body weight/day, respectively. In comparison with the EDIs reported for PBDEs by general population in several countries, the contribution of seafood consumption to PBDE intake in Korea was the highest. Seafood consumption and dust ingestion contributed equally to the total PBDE intakes in Korean adults, while dust ingestion was the major contributor to toddlers. This study was the first to assess exposure of humans to PBDEs through two major exposure pathways.

Benzotriazole (BTR) and benzothiazole (BTH) derivatives are used in a wide variety of industrial and consumer products and have been reported to occur in the environment. Owing to a lack of analytical methods, human exposure to BTR and BTH is still unknown. In this study, a liquid chromatography-electrospray ionization tandem mass spectrometry (LC-ESI(+)MS/MS) method was developed for simultaneous determination of five 1,2,3-benzotriazoles and five 1,3-benzothiazoles in human urine. The target benzotriazoles were 1H-benzotriazole, 1-hydroxy-benzotriazole, tolyltriazole, xylyltriazole (or 5,6-dimethyl-1H-benzotriazole), and 5-chloro-benzotriazole, and the target benzothiazoles were benzothiazole, 2-hydroxy-benzothiazole, 2-methylthio-benzothiazole, 2-amino-benzothiazole, and 2-thiocyanomethylthio-benzothiazole. Urine specimens were enzymatically deconjugated with β-glucuronidase and extracted by a solid-phase extraction (SPE) procedure for the measurement of total concentrations (i.e., free + conjugated forms) of BTRs and BTHs. Additionally, a liquid-liquid extraction (LLE) method was developed for comparison of extraction efficiencies between SPE and LLE. The limits of detection (LODs) ranged from 0.07 (2-amino-benzothiazole) to 4.0 ng/mL (benzothiazole) for the SPE method and from 0.04 (tolyltriazole) to 6.4 ng/mL (benzothiazole) for the LLE method. A total of 100 urine specimens, collected from Athens, Greece, were analyzed by enzymatic deconjugation and SPE. Benzothiazole and tolyltriazole were found frequently, and their concentrations were on the order of a few ng/mL. To our knowledge, this is the first study on the occurrence of 10 BTR and BTH compounds in human urine.