Fate of PBDEs during food processing: Assessment of formation of mixed chlorinated/brominated diphenyl ethers and brominated dioxins/furans.

The aim of this study was to evaluate effects of food processing on PBDE levels, in particular influence of heat treatment on degradation of PBDEs, including possible formation of chlorinated diphenyl ethers or brominated dioxins/furans as degradation products. It was shown that PBDEs heated in the presence of chlorine (from either organic or inorganic sources) formed mixed chlorinated/brominated diphenyl ethers. However, no PCDEs were formed in the presence of lipids. Lipid medium increased stability of PBDEs exposed to UV irradiation. Profile of congeners formed in result of the debromination reaction was significantly different than profiles observed by some other authors in aliphatic organic solvents. Grilling processes increased concentrations (calculated on the fresh product basis) of the studied compounds by 4-8/22-34% for electric/coal grill, respectively. Depending on the congener and on the applied heat treatment, PBDE mass in pork meat after grilling dropped by 26-53%. No detectable quantities of either brominated dioxins or furans were formed during thermal processing of food containing typical levels of PBDEs.

Photodegradation of dioxin in contaminated soil in the presence of solvents and nanoscale TiO2 particles.

Decomposition of 2,3,7,8-Tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD) present in soil under ultraviolet (UV) illumination (350-400nm) was investigated using a combination of nontoxic solvents mixed in soil and nanoscale anatase TiO2 (nTiO2) distributed on 2mm top soil surface. Three types of UV-exposure experiments were conducted: intermittent exposure (8 h/day) for 90 days and 120 days, sequential intermittent (120 days) and continuous (24 h/day) for the next 55 days, and continuous exposure for 55 days. The influence of several factors on dioxin photodegradation efficiency was investigated, including the UV absorption by the targeted dioxin, presence of catalytic nTiO2 on soil surface, solvent evaporation rate, as well as vertical gradients of solvents added into the soil columns. Results of dioxin analysis for the soil samples collected at the end of every experiment condition show that the photodegradation enhanced by the nTiO2 presence on the soil surface considerably increased the dioxin removal. Higher removal efficiencies were found for treatments with 15%wt of nTiO2 mixed in the 2-mm surface soil as compared to the 5%wt nTiO2 treatments. The highest removal efficiency (79.6%) was for the sequential intermittent-continuous UV-exposure experiment with nTiO2. Dechlorinated products of 2,3,7,8-TCDD were generally not detected which suggests degradation of targeted dioxin by C-Cl cleavage was negligible. Further modifications to improve removal efficiencies were proposed. Large-scale engineered systems may employ this integrated treatment approach which can also incorporate the reuse of the top soil containing nTiO2 and solvent vapours. With the utilization of natural sunlight such systems would be promisingly suitable for tropical conditions.

Ionization of liquids by radiation: measurement by a clearing field.

A method has been developed for determining the yield of free ions formed by irradiation of a liquid with high-energy x-rays. Contrary to expectation, branched-chain paraffins produce many more free ions than straight-chain paraffins do, and the ether 1,4-dioxane produced only a third as many free ions as its hydrocarbon analog, cyclohexane.

Effects of UV-B in biological and chemical systems: equipment for wavelength dependence determination.

The thinning of the stratospheric ozone layer has prompted a large number of studies of UV-B-induced effects in biological and chemical systems. The wavelength dependency of such effects is of interest from mechanistic, physiological or economic points of view. Here, we describe an apparatus for determining the wavelength dependency of UV-B effects in biological and chemical systems. The apparatus consists of a high intensity UV radiation source and narrow bandpass filters to produce UV radiation in even intervals (between 280 and 360 nm). The usefulness of the equipment is demonstrated in two different systems: 1) Chalcone synthase (CHS) gene is up-regulated by UV-B radiation. Therefore quantitative analysis of the CHS gene expression was chosen in the present investigation for studies of the wavelength dependency of gene expression regulation in plants. Maximum induction of CHS expression was found at 300 nm with a 12-fold induction compared with the control; 2) The wavelength dependency of formation of dioxin-like photoproducts from the brominated flame retardant decabrominated diphenyl ether (DeBDE) is described. This is an example of UV-B-induced conversion of non-toxic species into a number of products of which some may be toxic in the environment. In the UV interval studied, the highest dioxin-like activity was found in the sample irradiated at 330 nm and therefore this wavelength is most important for the mechanism involved in photoconversion of DeBDE.

DNA photocleavage and biological activity of a pyrene dihydrodioxin.

A pyrene dihydrodioxin has been synthesized, shown to bind to duplex DNA by intercalation, and cleave the phiX 174 supercoiled plasmid upon irradiation with UV light. This compound also exhibits cytotoxic activity at the micromolar range in a number of human cancer cell lines.

Decomposition of toxic and environmentally hazardous 2,3,7,8-tetra-chlorodibenzo-p-dioxin by gamma irradiation.

The decomposition of the toxic and environmentally hazardous 2378-TCDD by gamma irradiation was studied and successfully used to decontaminate laboratory wastes containing small quantities of this chemically and biologically stable compound. The method makes use of gamma irradiation from a commercial 60cobalt facility at high dose levels (1000 kGy) to break down the compound into nontoxic products. Irradiation also decomposed 2378-TCDD in contaminated soil from the Seveso accident.