Polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs) in municipal and industrial effluents

Polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs) were quantified in 45 effluent samples in the Houston Ship Channel (HSC) system in Texas. Total PCDD/F concentrations ranged from 0.16 to 13.23 pg L(-1) in the dissolved phase and from 0.79 to 682.27 pg L(-1) in the suspended phase. Generally, industrial facilities contained more PCDD/F contamination than municipal wastewater treatment plants or refuse facilities. World Health Organization Toxic Equivalents (WHO-TEQs) ranged from 0.007 to 0.279 pg L(-1) in the dissolved phase and 0.021-1.851 pg L(-1) in the suspended phase. The major TEQ contributor was 2,3,7,8-TCDD and overall, TEQs were greatest in industrial effluents. A correlation between high solids and high PCDD/F concentrations was observed and based on the results obtained in this study, the abundance of suspended solids may have largely contributed to high PCDD/F contamination in the suspended phase. Homolog profiles revealed that PCDD/F contamination increased with increasing chlorination and the highest concentrations were primarily from the octa-chlorinated congeners (OCDD/F) in both the dissolved and suspended phase.

Theoretical study on the degradation reaction of octachlorinated dibenzo-p-dioxin with atomic oxygen O((3)P) in dielectric barrier discharge reactor

Dielectric barrier discharges (DBD) have been used in the degradation of dioxins due to the large number of excimers and free radicals produced in discharge process. In this article, the density functional theory (DFT) is used to study the degradation mechanism of octachlorinated dibenzo-p-dioxin (OCDD) with the atomic oxygen O((3)P) in DBD reactor. The reactants, intermediates, transition states and products are optimized at the MPWB1K/6-31+G(d,p) level. The vibrational frequencies have been calculated at the same level. The reaction pathways and mechanisms are analyzed in detail. The effect of removing the chlorine atom on environment also has been discussed.

Characterization and fate of polychlorinated biphenyls, polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans in soils and sediments at the Portsmouth Gaseous Diffusion Plant, Ohio

The U.S. Department of Energy Portsmouth Gaseous Diffusion Plant is in the early stages of decommissioning and decontamination. During operations, the site drew a large amount of electric power and had multiple large switchyards on site. These are a source of polychlorinated biphenyls (PCB) contamination to both on-site and off-site streams. Some soil remediation has been completed in the main switchyard. During 2011 and 2012, fifteen sites were sampled at the surface (<10 cm) and subsurface (20-30 cm) to characterize the extent of PCB contamination, to identify weathering and migration of PCB contamination and to explore potential polychlorinated dibenzo-p-dioxins (PCDD) and polychlorinated dibenzofurans (PCDF) contamination due to transformer fires and explosions in the 1950s and 1960s. Stagnant sites tended to exhibit more migration of contamination to deeper sediments than sites with fast-moving waters, and the highest concentrations were found at the bottom of a settling pond. A signature set of five dioxin-like PCBs were consistently found across the site with higher concentrations in carbon rich surface sediments. PCB concentrations had a significant inverse correlation with clay content, suggesting that PCBs did not bind to clays at this site. Remediation has reduced PCB concentrations throughout the site compared to levels found in previous studies and long-term upkeep of sediment lagoons is necessary to retain PCB and dioxin-rich sediments. The flow regimen, organic carbon and clay content play a very important role in the fate of PCBs in the environment at the surface as well as downward migration.

Levels of PCDDs, PCDFs, and dioxin-like PCBs in human milk among Hong Kong mothers

Dioxins are a family of persistent organic pollutants (POPs) listed under the Stockholm Convention, and include PCDDs, PCDFs, and dioxin-like PCBs. These toxic chemicals are carcinogenic, widely dispersed, and have long half-lives. They have contaminated the food web and, being fat-soluble, accumulate in adipose tissues and milk in the human body. To assess human exposure, we collected breast milk samples from 137 first-time mothers recruited from around Hong Kong. Samples were analysed by HRGC-HRMS in four pools, according to the subject's age and length of residency. Exposure was related to age, duration of stay, and possibly diet. Generally, older mothers, and mothers with a longer stay in Hong Kong, had higher levels of dioxins in their milk. This pattern was clearest for the PCBs, although deviations were observed for some of the PCDD/Fs. Mean concentrations, measured per gram of lipid weight in terms of WHO toxic equivalents (WHO-TEQs), were 7.48 pg/g for PCDD/Fs and 3.79 pg/g for PCBs, giving a total of 11.27 pg/g for PCDD/Fs and PCBs combined. Compared to an earlier Hong Kong study we conducted in 2002, the mean WHO-TEQ values in our latest findings were about 9% lower overall for PCDD/Fs and 19% lower for PCBs, with the mean total WHO-TEQ for PCDD/Fs and PCBs being around 13% lower in this study. This indicates a general declining trend in the levels of POPs in Hong Kong. However, our levels were still high when compared to those in some other Asian-Pacific countries. More stringent policies on reducing and eliminating POPs should help to lower these. Continued surveillance for POPs in human milk, as well as in common foodstuffs, will provide us with important information on human exposures that will be necessary for tracking our progress, and making future health risk assessments.

Global DNA hypermethylation is associated with high serum levels of persistent organic pollutants in an elderly population

Dioxin exposure has experimentally been associated with changes in DNA methylation, an epigenetic change that is associated with disease. The present study aims to investigate if serum levels of dioxin and other persistent environmental pollutants are related to global DNA methylation in a human sample. In the population-based Prospective Investigation of the Vasculature in Uppsala Seniors (PIVUS) study (all aged 70), global DNA methylation was measured by the Luminometric Methylation Assay in 524 subjects. Twenty-three different POPs, including 16 PCBs, five pesticides, one dioxin (OCDD) and one brominated flame retardant (BDE47) were analysed by HRGC/HRMS. Ten single nucleotide polymorphisms (SNPs) in the Aryl hydrocarbon (Ah)-receptor were analysed by mini-sequencing. High levels of toxic equivalency (TEQ) for PCBs and dioxin were associated with DNA hypermethylation (p=0.030). This was mainly attributed to coplanar non-ortho PCBs. While no significant associations were found between DNA methylation and SNPs in the Ah-receptor, an interaction was found between the SNP rs2237297 and TEQ so that TEQ was associated with hypermethylation (p=0.009) only in subjects with one G-allele (n=103). Also high levels of the PCB126 congener, the OCDD, and the pesticide metabolite p,p'-DDE were related to DNA hypermethylation (p=0.01, 0.03 and 0.003, respectively). In conclusion, in a sample of elderly subjects, high TEQ including PCBs and the dioxin OCDD and high serum levels of PCB126, OCDD, and p,p'-DDE were related to global DNA hypermethylation in a cross-sectional analysis.