Brian Bush

Decreases in dopamine concentrations in adult, non-human primate brain persist following removal from polychlorinated biphenyls.

Adult male non-human primates, Macaca nemestrina, were orally exposed for 20 weeks to 3.2 mg/kg per day of either Aroclor 1016 or Aroclor 1260 made up in corn oil. Following cessation of exposure, the animals were observed for either an additional 24 or 44 weeks. After killing, regional brain concentrations of biogenic amines and polychlorinated biphenyls were determined by high-performance liquid chromatography (HPLC) and gas chromatography (GC), respectively. Brain dopamine (DA) concentrations were significantly decreased, compared to controls, in all polychlorinated biphenyl-exposed animals. Most importantly, in spite of significant decreases in brain polychlorinated biphenyl concentrations observed following removal from exposure (an average decline of 60%), there was no statistically discernible relationship of the changes in brain DA concentrations to either time following removal from polychlorinated biphenyls or brain polychlorinated biphenyl concentrations. These findings demonstrate that sub-chronic exposure of the adult non-human primate to polychlorinated biphenyls results in long-lasting changes in brain DA concentrations.

Kinetics and products of the TiO2, photocatalytic degradation of 2-chlorobiphenyl in water

The light-induced degradation of 2-chlorobiphenyl (2-CB) under simulated solar irradiation has been investigated in aqueous solutions containing TiO2 suspensions as photocatalysts. The apparent quantum yield for an initial 2-CB concentration C0 = 3.8 micrograms/mL at the natural pH was ca. 0.005 The oxidation kinetics of 2-CB follows the Langmuir-Hinshelwood kinetic model at natural pH. The primary degradation of 2-CB follows a pseudo-first-order kinetics. Several reaction intermediates were identified using GC/FTIR/MS and ion chromatography. The products at the initial stage of the reaction were seven isomers of 2-chlorobiphenyl-ol and biphenyl-2-ol. These intermediates underwent further photocatalytic oxidation via aldehydes, ketones, and acids finally into CO2 and HCl. The formation and fate of some of these compounds under irradiation were also investigated. A reaction scheme involving hydroxyl radicals has been proposed.

Photocatalytic degradation of PCBs in TiO2 aqueous suspensions

A generator-column technique was used to prepare aqueous solutions of PCBs. The degradation of 2-chlorobiphenyl, Aroclor 1248, Aroclor mixture (1221, 1016, 1254, and 1260) and St. Lawrence River water by simulated sunlight or sunlight has been investigated in the presence of aqueous suspensions of TiO2. The effect of TiO2 concentration and pH on the degradation rate of PCBs have been studied. The reaction rate followed apparent first-order kinetics and increased with increasing TiO2 concentration. The half-life of the degradation process for 2-chlorobiphenyl is 20 minutes at pH 10 and 9 minutes at pH 3 in the presence of 25 mg/L of TiO2. Less chlorinated PCBs decomposed faster than higher chlorinated ones. The rate constants and half-lives of individual PCBs in the commercial PCB mixture and St. Lawrence River water were also measured.

Anaerobic biodegradation of polychlorinated biphenyls in hudson river sediments and dredged sediments in clay encapsulation

Abstract Anoxic Hudson River sediments and clay-encapsulated dredged sediments were investigated to determine whether anaerobic biodegradation of polychlorinated biphenyls (PCBs) occurred. Measured as a decrease in congener concentrations, clear evidence for anaerobic biodegradation of ambient PCBs was found in untreated Hudson River sediments incubated in the laboratory under an N 2 atmosphere. Of 10 different sediment treatments, which included amendments with biphenyl, yeast extract/trypticase mixture, live and sterilized anaerobic sewage sludges and inoculation with a mixed culture obtained with Aroclor 1221 enrichment, under either an N 2 or CO 2 /H 2 atmosphere, biphenyl enrichment in N 2 was most effective for both sediments. About 53% of the total PCBs (375 mg/kg sediment dry wt), mainly mono- to pentachlorobiphenyls, was degraded in the biphenyl-amended Hudson River sediments and 30% (281 mg/kg sediment) in biphenyl-amended Moreau sediments after 7 months, with the spectrum of congeners degraded much broader in Hudson River than Moreau sediments. Biphenyl amendment enhanced the disappearance of highly chlorinated congeners. Inoculation with the mixed culture showed positive results in Moreau sediments but not in Hudson River sediments. Regardless of treatments, no biodegradation occurred in a CO 2 /H 2 atmosphere. Moreau sediments incubated in situ (from November to June), showed little change in congener concentrations in all treatments, suggesting temperature as an important factor. The accumulation of less-chlorinated congeners as a result of reductive dechlorination of highly chlorinated ones was not observed.

Environmental occurrence and potential toxicity of planar, mono-, and Di-Ortho polychlorinated biphenyls in the biota

Four non-ortho-, eight mono-ortho-, and two di-ortho-chlorinated congeners have been determined in fresh water and salt water mussels, fish, snapping turtles, mallard, seals, and in human milk and adipose tissue. The planar PCB congeners are separated from the remainder of PCBs by activated carbon chromatography or HPLC on porous graphitic carbon followed by gas chromatography with electron capture detection. PCB toxic equivalency factors (TEFs) recommended by WHO [1] for 3 non-ortho, 8 mono-ortho, and 2 di-ortho PCBs and a TEF for congener 81 suggested by Harris et al. [2] were used for calculation of the contribution to dioxin-like toxicity to each life form. In all the biota examined, PCB congener IUPAC number 126 was the major contributor to PCB toxic equivalents. Congeners IUPAC number 118, 114, 105, 156, 157, 77, 81, and 170 also contributed significantly to PCB toxic equivalents. The ability to separate out planar PCBs from the majority of PCBs has allowed the use of TCDD toxicity equivalence to compare the relative dioxin-like potency of PCB residues in various species from different locations.

Production of aqueous PCB solutions for environmental toxicology

Abstract Studies investigating the toxicity of polychlorinated biphenyls (PCBs) to aquatic organisms demand a reliable method to produce aqueous PCB solutions. We evaluate the generator column method as a way of producing an aqueous solution containing a broad spectrum of PCB congeners. Solutions were created by pumping double distilled water through a column packed with glass beads coated with a standard Aroclor mix (1221, 1016, 1254, and 1260, 1:1:1:1). Water was passed through the column at a flow rate of 1.66 ml/min, well within the range of flow rates previously shown to produce saturated solutions for individual congeners. Solutions produced by the column were analyzed by high-resolution glass-capillary gas chromatography for 68 individual PCB-containing peaks. The total PCB concentration in three replicate solutions averaged 444 ± 10 μ g/ l . The aqueous PCB congener pattern produced was distinctly different from the pattern of the original Aroclor mixture. The concentration of the PCB congeners in solution decreased with increasing chlorine content. Two mono-chlorinated congeners (2- and 4-chlorobiphenyl) comprised greater than 65% of the total PCB concentration. The concentration of individual congeners in the solution were much lower than reported individual solubilities. This suggests that a partitioning of individual congeners between water and the oil phase, which is composed of the mixture of PCBs, is taking place rather than a simple dissolution. The generator column method is a rapid and reproducible technique for creating aqueous solutions containing a high concentration and broad spectrum of PCB congeners.