Estrogenic Properties and Removal of Tetrabromobisphenol-A (TBBPA) by UV Advanced Oxidation Bethany Taylor, Peter Ruiz-Haas Mary Baldwin University, Department of Chemistry and Physics, Staunton VA, 24401
Results Abstract UV Degradation and HPLC Analysis Experimental Methods
Tetrabromobisphenol-A (TBBPA) is a flame retardant added to various consumer products. Like other brominated flame retardants, there is concern High performance Liquid Chromatography about its ability to leach out of materials, its environmental persistence, and • Shimadzu SIL-10A system. ·3μm, 100 mm Restek Pinnacle II potential to be an endocrine disrupting compound (EDC). The estrogenic C-18 column. ·The mobile phase was 60% 0.1 mol/L acetate properties of TBBPA were examined with a yeast estrogen screen (YES) bioassay. Through this assay we determined a 20 mg/L (27 µM) TBBPA sample buffer (pH 3.0): 30% acetonitrile, 0.6 mL/min. to be 1x10-8 fold weaker than 17- β estradiol (E2). However, even the weak • Monitored at λ = 290 nm. estrogenic properties may still be of environmental or health concerns. • Calibration standards ranged from 2.5 – 20 mg/L. Following these experiments, we examined the photolysis of TBBPA by low pressure germicidal ultraviolet (LP-UV) light (254 nm). The breakdown of the Yeast Estrogen Screen (YES) compound was observed by HPLC at 290 nm. We observed about 61% removal of TBBPA in 25% v/v MeOH solutions after a UV dose of 368 mJ/cm2, or after 1 • The YES bioassay utilizes genetically modified yeast hour of exposure, via pseudo-first order kinetics. This increased to (Saccharomyces cerevisae) that incorporates the human approximately 71% destruction when spiked with 0.02 ppm H2O2. Furthermore, estrogen receptor – making the assay sensitive to preliminary studies suggest that performing the same experiment with treated estrogen and endocrine disrupting compounds (EDCs). wastewater instead of distilled water boasted approximately 99% destruction in the same amount of time. The direct-UV photolysis products of TBBPA were • Samples were added to a 96 deep well plate, with a 17- determined by LC-MS. Tribromobisphenol-a is produced in the distilled water Figure 1 Logarithmic relationship of the concentration of TBBPA Figure 2 Comparison of concentration of TBBPA after UV treatment β-estradiol (E2) as standard, and serially diluted. 2 experiments. The experiments with treated wastewater appear to produce and (mg/L) vs UV dosage (mJ/cm ) in aqueous mixtures of 25% (v/v) in distilled water and in treated wastewater. Samples in 25% (v/v) • A yeast suspension was added to the plates which were degrade the tribromobisphenol-a, but this has not yet been LC-MS verified. We MeOH and addition of 0.02 and 0.04 ppm H O . MeOH and 0.02 ppm H O . 2 2 2 2 then incubated for three days at 30˚C. are currently further examining the breakdown products of H2O2/UV AOP processes by LC-MS. Additional experiments are underway to assess the ability TBBPA Estrogenic Potency Percent Destruction Summary • After three days an ortho-Nitrophenyl-β-galactoside of advanced oxidation processes (AOPs) that employ UV in combination with (ONPG) assay buffer was added, producing a colored H O or O to generate OH-radicals. 2 2 3 substrate. The absorbance of the wells were read on a Table 1 Relative destruction of 20 mg/L TBBPA after microplate reader at 405 nm. (figure 4).
exposure to one hour of UV light in diH2O. • The Estradiol Equivalent Quotient (EEQ) was calculated 2 Background and Objectives Sample % Destroyed R t1/2 (s) from the EC 50 and CF 50 and used to calculate a potency (figure 3). 100% MeOH 72 0.96 1.9 × 103 • Tetrabromobisphenol A UV Photolysis Experiments 50% MeOH 3 (TBBPA) is one of the 69 0.98 2.1 × 10 • A collimating apparatus with 4 most widely used 25% MeOH 3 61 0.97 2.6 × 10 LP-UV lights was employed as brominated flame * 7 8 0.02 ppm H O 3 described by Linden and Beil. retardants in the world. 1 Figure 4 96 well YES assay plate to 2 2 71 0.96 2.0 × 10 evaluate the potency of E2 and TBBPA. * • Test solutions of TBBPA were • It is most frequently -6 0.04 ppm H O 3 This plate assays a 1 × 10 mg/L E2 2 2 62 0.95 2.6 × 10 prepared in mixtures of MeOH:H O utilized in electronics, standard with 20 mg/L of TBBPA. 2 Figure 3 Reduction of estrogenic activity of TBBPA with because of poor solubility in water. * Prepared in 25% MeOH. paper, plastics, textiles, respect to E2 by UV dose as determined by the YES bioassay. and in chemical • UV irradiation experiments manufacturing. 2 conducted in solutions containing Discussion and Conclusions Future Work ~20 mg/L TBBPA in 100%, 50%, • TBBPA has been found in soil, water, river sediments, and in and 25% v/v MeOH. the atmosphere. The compound also is toxic to aquatic biota. In • The effect of UV/H O AOP was 2004, ~31-51 kilotons of TBBPA was used in materials where it • Due to low aqueous solubility, TBBPA was dissolved in various mixtures • Different levels of H2O2 2 2 had the potential to leach into the environment. 3,4 of H O:MeOH for the experiments to have HPLC detectable • Use O and other oxidizers as separately determined by addition 2 3 of 0.02 and 0.04 ppm H O . • TBBPA is an endocrine disrupting compound and has been concentrations. AOP sources. 2 2 found to cause uterine cancer in rats. 5 • Higher levels of MeOH show greater destruction of TBBPA (table 1), • Perform repeat experiments • 100 mL samples were placed in a 38 cm2 crystallization dish 40 cm • TBBPA has poor water solubility at neutral pH (0.0990 mg/L). 6 presumably due to solvent effects. using treated wastewater. from the light source • UV light is increasingly being used to destroy organic • Addition of H O to solutions containing 25% (v/v) MeOH:H O increase • Explore using lower 2 2 2 • UV dose (fluence) was measured contaminants in wastewater. the relative destruction of TBBPA (figure 1, table 1). concentrations of MeOH in with a potassium iodide chemical • Higher levels of H O did not correlate to higher degradation, due to treated wastewater samples • Addition of H2O2 produces OH· radicals that react 2 2 actinometer, which converts iodide non-selectively with most organic compounds: scavenging of OH-radicals by H O (figure 1). - - 2 2 (I ) to iodate (IO3 ) by exposure to H O +hυ →2OH· • Samples in 25% (v/v) MeOH:diH2O displayed ~60% destruction after 1 Figure 5 Schematic of UV apparatus. UV light. Fluence increases 2 2 hour of treatment with LP-UV light. This increases to ~70% with the proportionally with time. 7 • The UV/ H2O2 advanced oxidation process (AOP) is very effective in the elimination of organic pollutants. addition of 0.02 ppm H2O2 and further increases to ~99% in treated wastewater samples (figure 2, table 1) • Pseudo first order kinetics were observed for TBBPA decomposition in all References runs. (1) Chen, X.; Gu, J.; Wang, Y.; Gu, X.; Zhao, X.; Wang, X.; Ji, R. Environmental Pollution 2017, 227 , 526-533. Acknowledgements (2) National Institute of Environmental Health Sciences. Tetrabromobisphenol A [79-94-7] Review of Toxiological Literature; National Institute of Health: Durham, • The potency of TBBPA is ~1000x weaker than E2; TBBPA is weakly 2002. (3) Ronen, Z.; Abeliovich, A. Applied and Environmental Microbiology 2000, 66 ,2372-2377. a This research was supported by the General Program Undergraduate estrogenic. (4) European Chemicals Bureau Risk Assessment Report. 2006. Risk Assessment of 2,2',6,6'-Tetrabromo-4,4'-Isopropylidene Diphenol (Tetrobromobisphenol-A) (5) HSDB - PubChem Data Source https://pubchem.ncbi.nlm.nih.gov/source/HSDB Science Research Fellowship grant provided by the Virginia Foundation of • After UV exposure of 1 hr, TBBPA containing solutions show nearly a (6) Kuramochi, H.; Kawamoto, K.; Miyazaki, K.; Nagahama, K.; Maeda, K.; Li, X.; Shibata, E.; Nakamura, T.; Sakai, S. Environmental Toxicology and Chemistry Independent Colleges, the Arnold Travel Fund, the Mary Baldwin 1000-fold decrease in estrogenic activity, suggesting that UV treatment of 2008, 27, 2413. University Capstone Grant, and by the Mary Baldwin University (7)Linden, K.; Mofidi, A. Disinfection efficiency and dose measurement of polychromatic UV light; Water Environment Research Foundation: Alexandria, VA., 2004. (8) Beil, R. 2014 The Degradation of BPS under UV Light. Senior Thesis Mary Baldwin University. Department of Chemistry and Physics. TBBPA containing wastes may be a suitable treatment option (figure 3).