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PubMed1997

Synthesis and analysis of mixed chlorinated-fluorinated dibenzo-p-dioxins and dibenzofurans and assessment of formation and occurrence of the fluorinated and chlorinated-fluorinated dibenzo-p-dioxins and dibenzofurans.

Various mixtures of chlorinated-fluorinated dibenzodioxins (PCFDD), dibenzofurans (PCFDF) and biphenyls (PCFB) were synthesized. For trace analysis, we compared the behavior of PCFDD/PCFDF and chlorinated congeners in extraction, enrichment and clean-up steps. To establish GC/MS analysis, various columns were tested, temperature programs were optimized and for MS-identification specific masses were selected from the mass spectra. To evaluate the possibility of formation of these compounds in thermal processes, samples from the aluminum-producing industry and products of pyrolysis of chlorofluoro- hydrocarbons (FCKW) on a laboratory scale were analyzed. At present, the most important potential sources of fluorinated or mixed chlorinated-fluorinated dioxins, furans and biphenyls - combustion processes and large scale chemical production - do not cause significant environmental contamination at least in the areas considered. However, in a sample of filter dust from the refining process of aluminum using freon 12 we found high amounts (4.5 g/kg !) of chlorinated and chlorinated-fluorinated aromatic compounds including chlorinated-fluorinated dibenzofurans and biphenyls. Since the FCKW ban in Europe, this procedure was modified in 1992, replacing freon 12 by a mixture of chlorine and argon. The PFDD/PFDF concentration in the fluorophenols was between 0.45 and 120 micrograms/kg. The fluorobenzenes analyzed contained between 15 and 70 mg/kg fluorinated biphenyls.

Benzofurans↗
PubMed2002

Chlorine isotope fractionation during reductive dechlorination of chlorinated ethenes by anaerobic bacteria.

Chlorine isotope fractionation during reductive dechlorination of trichloroethene (TCE) and tetrachloroethene (PCE) to cis-1,2-dichloroethene (cDCE) by anaerobic bacteria was investigated. The changes in the 37Cl/35Cl ratio observed during the one-step reaction (TCE to cDCE) can be explained by the regioselective elimination of chlorine accompanied by the Rayleigh fractionation. The fractionation factors (alpha) of the TCE dechlorination by three kinds of anaerobic cultures were approximately 0.994-0.995 at 30 degrees C. The enrichment of 37Cl in the organic chlorine during the two-step reaction (PCE to cDCE) can be explained by the random elimination of one chlorine atom in the PCE molecule followed by the regioselective elimination of one chlorine atom in the TCE molecule. The fractionation factors for the first step of the PCE dechlorination with three kinds of anaerobic cultures were estimated to be 0.987-0.991 at 30 degrees C using a mathematical model. Isotope fractionation during the first step would be the primary factor for the chlorine isotope fractionation during the PCE dechorination to cDCE. The developed models can be utilized to evaluate the fractionation factors of regioselective and multistep reactions.

Bacteria, Anaerobic↗
PubMed2001

Effectiveness of the sulfur(IV) compound, sodium bisulfite, in reducing chlorine, chlorine dioxide, and chlorite toxicity to Daphnia magna in well water and pond water.

Flow-through toxicity tests were conducted with Daphnia magna to determine the residual toxicity of chlorine, chlorine dioxide, and chlorite after treatment with the sulfur(IV) compound sodium bisulfite. Daphnids were exposed separately to 0.5-mg/L concentrations of each of the three compounds without the addition of sodium bisulfite, with a low stoichiometric dose of sodium bisulfite, and with a high stoichiometric dose of sodium bisulfite. Tests were performed in well water with a low total organic carbon (TOC) content and pond water with a high TOC content. Analysis of results indicated that sodium bisulfite did not eliminate the toxicity of chlorine dioxide or chlorite to D. magna. Total residual oxidant (TRO) concentrations were reduced and survival times were extended, but acute toxicity persisted even with a S(IV) concentration 10.0 times the stoichiometric ratio of oxidant. Mortality occurred in chlorine dioxide treatments in which no TRO was detected, indicating that standard analytical (amperometric) techniques may be inadequate to detect toxicity. Sodium bisulfite did succeed in eliminating chlorine toxicity except in pond water receiving a low (3.0x) sodium bisulfite dose. Oxidant reactions with organic substrates may have produced chlorinated residuals that were resistant to S(IV) dechlorination.

Animals↗
PubMed2003

Chlorinated aromatics from combustion: influence of chlorine, combustion conditions, and catalytic activity.

Research on the formation of chlorinated aromatics in combustion processes has mainly taken place in the laboratory. Previous attempts to correlate observation data from commercial plants have been inconclusive. This study reports on the outcome of an industrial experiment in a full-scale afterburner. The influence of chlorine input, combustion temperature, and catalytic activity was investigated in a factorial design with two blocks. Polychlorinated benzenes, dibenzo-p-dioxins, and dibenzofurans were formed both at combustion temperatures and below 400 degrees C. The results show that all three experimental factors have statistically significant impact on the formation and release of these toxic byproducts. The quantitative dependence between chlorine input and the occurrence of chlorinated aromatics is of particular interest due to previous controversy. The purpose with this study was to ensure that the installation of a boiler for energy recovery would not cause elevated emissions of chlorinated aromatics. The experiment demonstrated that this risk is probably low, since the presence of catalytic material or an increase in chlorine input is required for this to happen. A general conclusion was that industrial experimentation employing the principles of statistical design could improve the validity in recommendations regarding commercial plant operation.

Air Pollutants↗
PubMed1996

Molecular chlorine generated by the myeloperoxidase-hydrogen peroxide-chloride system of phagocytes converts low density lipoprotein cholesterol into a family of chlorinated sterols.

Oxidation of low density lipoprotein (LDL) may be of critical importance in triggering the pathological events of atherosclerosis. Myeloperoxidase, a heme protein secreted by phagocytes, is a potent catalyst for LDL oxidation in vitro, and active enzyme is present in human atherosclerotic lesions. We have explored the possibility that reactive intermediates generated by myeloperoxidase target LDL cholesterol for oxidation. LDL exposed to the myeloperoxidase-H2O2-Cl- system at acidic pH yielded a family of chlorinated sterols. The products were identified by mass spectrometry as a novel dichlorinated sterol, cholesterol alpha-chlorohydrin (6beta-chlorocholestane-(3beta,5alpha)-diol), cholesterol beta-chlorohydrin (5alpha-chlorocholestane-(3beta, 6beta)-diol), and a structurally related cholesterol chlorohydrin. Oxidation of LDL cholesterol by myeloperoxidase required H2O2 and Cl-, suggesting that hypochlorous acid (HOCl) was an intermediate in the reaction. However, HOCl failed to generate chlorinated sterols under chloride-free conditions. Since HOCl is in equilibrium with molecular chlorine (Cl2) through a reaction which requires Cl- and H+, this raised the possibility that Cl2 was the actual chlorinating intermediate. Consonant with this hypothesis, HOCl oxidized LDL cholesterol in the presence of Cl- and at acidic pH. Moreover, in the absence of Cl- and at neutral pH, Cl2 generated the same family of chlorinated sterols as the myeloperoxidase-H2O2-Cl- system. Finally, direct addition of Cl2 to the double bond of cholesterol accounts for dichlorinated sterol formation by myeloperoxidase. Collectively, these results indicate that Cl2 derived from HOCl is the chlorinating intermediate in the oxidation of cholesterol by myeloperoxidase. Our observations suggest that Cl2 generation in acidic compartments may constitute one pathway for oxidation of LDL cholesterol in the artery wall.

Chloramines↗
PubMed2000

Influence of chlorine substituents on rates of oxidation of chlorinated biphenyls by the biphenyl dioxygenase of Burkholderia sp. strain LB400.

Biphenyl dioxygenase from Burkholderia (Pseudomonas) sp. strain LB400 catalyzes the first reaction of a pathway for the degradation of biphenyl and a broad range of chlorinated biphenyls (CBs). The effect of chlorine substituents on catalysis was determined by measuring the specific activity of the enzyme with biphenyl and 18 congeners. The catalytic oxygenase component was purified and incubated with individual CBs in the presence of electron transport proteins and cofactors that were required for enzyme activity. The rate of depletion of biphenyl from the assay mixture and the rate of formation of cis-biphenyl 2,3-dihydrodiol, the oxidation product, were almost equal, indicating that the assay accurately measured enzyme-specific activity. Four classes of CBs were defined based on their oxidation rates. Class I contained 3-CB and 2,5-CB, which gave rates that were approximately twice that of biphenyl. Class II contained 2,5,3',4'-CB, 2,3,2',5'-CB, 2,3,4,5-CB, 2,3,2',3'-CB, 2,4, 5,2',5'-CB, 2,5,3'-CB, 2,5,4'-CB, 2-CB, and 3,4,5-CB, which gave rates that ranged from 97 to 35% of the biphenyl rate. Class III contained only 2,3,4,2',5'-CB, which gave a rate that was 4% of the biphenyl rate. Class IV contained 2,4,4'-CB, 2,4,2',4'-CB, 3,4,5, 2'-CB, 3,4,5,3'-CB, 3,5,3',5'-CB, and 3,4,5,2',5'-CB, which showed no detectable depletion. Rates were not significantly correlated with the aqueous solubilities of the CBs or the number of chlorine substituents on the rings. Oxidation products were detected for all class I, II, and III congeners and were identified as chlorinated cis-dihydrodiols for classes I and II. The specificity of biphenyl dioxygenase for the CBs examined in this study was determined by the relative positions of the chlorine substituents on the aromatic rings rather than the number of chlorine substituents on the rings.

Burkholderia↗
PubMed2005

Membrane damage and microbial inactivation by chlorine in the absence and presence of a chlorine-demanding substrate.

The relationship between cell inactivation and membrane damage was studied in two gram-positive organisms, Listeria monocytogenes and Bacillus subtilis, and two gram-negative organisms, Yersinia enterocolitica and Escherichia coli, exposed to chlorine in the absence and presence of 150 ppm of organic matter (Trypticase soy broth). L. monocytogenes and B. subtilis were more resistant to chlorine in distilled water. The addition of small amounts of organic matter to the chlorination medium drastically increased the resistance of both types of microorganisms, but this effect was more marked in Y. enterocolitica and E. coli. In addition, the survival curves for these microorganisms in the presence of organic matter had a prolonged shoulder. Sublethal injury was not detected under most experimental conditions, and only gram-positive cells treated in distilled water showed a relevant degree of injury. The exposure of bacterial cells to chlorine in distilled water caused extensive permeabilization of the cytoplasmic membrane, but the concentrations required were much higher than those needed to inactivate cells. Therefore, there was no relationship between the occurrence of membrane permeabilization and cell death. The addition of organic matter to the treatment medium stabilized the cytoplasmic membrane against permeabilization in both the gram-positive and gram-negative bacteria investigated. Exposure of E. coli cells to the outer membrane-permeabilizing agent EDTA increased their sensitivity to chlorine and caused the shoulders in the survival curves to disappear. Based on these observations, we propose that bacterial envelopes could play a role in cell inactivation by modulating the access of chlorine to the key targets within the cell.

Cell Membrane↗
PubMed1975

Photochemical technique for the elimination of chlorinated aromatic interferences in the gas-liquid chromatographic analysis for chlorinated paraffins.

A method is described for eliminating chlorinated aromatic interferences in the analysis for the more volatile chlorinated paraffins. Sample extracts are irradiated in aliphatic hydrocarbon solvents with high intensity ultraviolet light prior to detection of the chlorinated paraffin by microcoulometric gas-liquid chromatography. Chlorinated aromatic and unsaturated materials, including DDT and polychlorinated biphenyls, are selectively degraded to compounds containing little or no chlorine. Cycloaliphatic pesticides such as toxaphene, chlordane, and mirex are only partially degraded. Analysis of fish fillets fortified with 1 and 5 ppm of a chlorinated paraffin gave recoveries greater than 90%.

Chlordan↗
PubMed1988

In vitro characterization of monoaspartyl chlorin e6 and diaspartyl chlorin e6 for photodynamic therapy.

The characteristics of two new chlorin photosensitizers were studied in cell culture by determining phototoxicity, subcellular localization, and photophysical properties. Monoaspartyl chlorin e6 (MACE) and diaspartyl chlorin e6 (DACE) are new photosensitizers that show promise for use in photodynamic therapy. These chlorins are pure, monomeric compounds as determined by high-pressure liquid chromatography. Both compounds absorb substantially at a longer wavelength (664 nm) than does dihematoporphyrin ether-ester (DHE). Tumor diagnosis with the use of fluorescence should be facilitated due to the purity of the compounds and the single fluorescence emission peak. Phototoxicity dose-response curves of the sensitizers were completed using a standard clonogenic assay to determine cell viability. The chlorins showed good sensitizing capabilities with light. In addition, subcellular localization of MACE, DACE, and DHE was studied using fluorescence microscopy. Whereas DHE was located throughout the cytoplasm, the primary site of localization of the chlorins appeared to be in the lysosome. The results demonstrate that MACE and DACE are effective photosensitizing agents in vitro and compare favorably to DHE.

Cell Line↗
PubMedDate not supplied

Breast-feeding exposure of infants to environmental contaminants--a public health risk assessment viewpoint: chlorinated dibenzodioxins and chlorinated dibenzofurans.

Exposure of children to chlorinated dibenzodioxins and chlorinated dibenzofurans via breast-feeding has been well-documented in industrialized countries. Recent studies indicate a possible link between development of subtle health effects in children and their exposure to dioxin-like chemicals from maternal milk. Some examples of the effects are lower vitamin K levels, increased thyroxine levels, and mild changes in liver enzymes. The projected daily intakes of chlorinated dibenzodioxins and chlorinated dibenzofurans are compared with minimal risk levels for intermediate duration oral exposure (15-365 days) derived for these chemicals. Public health recommendations for future actions related to infant intake of chlorinated dibenzodioxin- and chlorinated dibenzofuran-contaminated breast milk are also addressed.

Benzofurans↗
PubMed1985

Mechanism of chloroform formation by chlorine and its inhibition by chlorine dioxide.

Chlorination of drinking waters leads to the formation of trihalomethanes arising from the reaction of chlorine and organic substances. Therefore, chlorine dioxide (ClO2) which does not produce trihalomethanes is being considered as an alternative disinfectant. It has been reported that rat blood chloroform levels were significantly decreased after treatment with ClO2. Studies were conducted to investigate the mechanisms of chloroform formation by chlorine (HOCl) and its inhibition by ClO2 (5 mg/liter) in the presence of HOCl (5, 10, 20 mg/liter) using sodium citrate (1 mM) as an organic substance. When citrate was reacted with HOCl, beta-ketoglutaric acid, monochloroacetone, dichloroacetone, and trichloroacetone were produced as reaction intermediates and chloroform as a final product. There was a linear relationship between the concentrations of HOCl and the formation of chloroform. When ClO2 was substituted for HOCl, neither chloroform was formed nor citrate concentration was changed. Further, chloroform formation was inhibited by ClO2 in the presence of HOCl and citrate and the degree of inhibition depends on the ratio of ClO2/HOCl. Gas chromatograph/mass spectrometer analysis indicates that this inhibition is related to the reaction of ClO2 with beta-ketoglutaric acid to form malonic acid. Chlorine dioxide also oxidizes other intermediates such as monochloroacetone and dichloroacetone to acetic acid. These studies indicate that ClO2 inhibits chloroform formation from citrate and HOCl by the oxidation of the intermediates which were involved in the reaction of chloroform formation.

Acetone↗
PubMed2000

Chlorine, chloramine, chlorine dioxide, and ozone susceptibility of Mycobacterium avium.

Environmental and patient isolates of Mycobacterium avium were resistant to chlorine, monochloramine, chlorine dioxide, and ozone. For chlorine, the product of the disinfectant concentration (in parts per million) and the time (in minutes) to 99.9% inactivation for five M. avium strains ranged from 51 to 204. Chlorine susceptibility of cells was the same in washed cultures containing aggregates and in reduced aggregate fractions lacking aggregates. Cells of the more slowly growing strains were more resistant to chlorine than were cells of the more rapidly growing strains. Water-grown cells were 10-fold more resistant than medium-grown cells. Disinfectant resistance may be one factor promoting the persistence of M. avium in drinking water.

AIDS-Related Opportunistic Infections↗
PubMed2006

Relationship between chlorine consumption and chlorination by-products formation for model compounds.

The objective of this research is to investigate the relationship between chlorine decay and the formations of disinfection by-products (DBP), including trichloromethane (TCM) and chloroacetic acid (CAA) in the presence of four model compounds, i.e., resorcinol, phloroglucinol, p-hydroxybenzoic acid, and m-hydroxybenzoic acid. The chlorine degradation in model compounds with OH and/or COOH functional groups were rapid after chlorination. The TCM yields of carboxylic group substituted compounds (3-hydroxybenzoic acid [3-HBA], 4-hydroxybenzoic acid [4-HBA]) were found to be lower than that of the m-dihydroxy substituted compounds. Phloroglucinol, with one more OH substitution group than resorcinol, tends to form significant amounts of CAA after chlorination. However, it was observed that with the COOH substitution of 3-HBA and 4-HBA tend to exhibit more CAA formation potential than resorcinol. The developed parallel second and first-order reaction model for chlorine demand has been successfully utilized for TCM, CAA and DBP formation modeling. A high correlation between CAA and TCM was observed for the model compounds.

Acetates↗
PubMed2005

Formation of chloroform and chlorinated organics by free-chlorine-mediated oxidation of triclosan.

The widely used antimicrobial agent triclosan (5-chloro-2-(2,4-dichlorophenoxy)phenol) readily reacts with free chlorine under drinking water treatment conditions. Overall second-order kinetics were observed, first-order in free chlorine and first-order in triclosan. Over the pH range of 4-11.5, the kinetics were pH sensitive as a result of the pH dependent speciation of both triclosan and free chlorine. Using a Marquardt-Levenberg routine, it was determined that this pH effect indicates that the dominant reaction in this system is between the ionized phenolate form of triclosan and hypochlorous acid (HOCl). The overall second-order rate coefficient was determined to be kArO- = 5.40 (+/- 1.82) x 10(3) M(-1) s(-1). Three chlorophenoxyphenols and two chlorophenols were identified by gas chromatographic-mass spectroscopic analysis. The chlorophenoxyphenol compounds include two monochlorinated triclosan derivatives (5,6-dichloro-2-(2,4-dichlorophenoy)phenol and 4,5-dichloro-2-(2,4-dichlorophenoxy)phenol) and one dichlorinated derivative (4,5,6-trichloro-(2,4-dichlorophenoxy)phenol); these species form via bimolecular electrophilic substitution of triclosan. 2,4-Dichlorophenol was detected under all reaction conditions and forms via ether cleavage of triclosan. In experiments with excess free chlorine, 2,4,6-trichlorophenol was formed via electrophilic substitution of 2,4-dichlorophenol. Chloroform formation was observed when an excess of free chlorine was present. A Hammett-type linear free-energy relationship (LFER) using Brown-Okamoto parameters (sigma+) was established to correlate the reactivity of HOCI and the phenolate forms of triclosan and other chlorophenols (log kArO- = -(10.7 +/- 2.2)Sigmasigma(+)o,m,p + 4.43). This LFER was used to obtain estimates of rate coefficients describing the reactivity of the intermediates 5,6-dichloro-2-(2,4-dichlorophenoy)phenol (kArO- approximately equal to 6 x 10(2)), 4,5-dichloro-2-(2,4-dichlorophenoxy)phenol (kArO- approximately equal to 3 x 10(2)), and 4,5,6-trichloro-(2,4-dichlorophenoxy)phenol (kArO- approximately equal to 4 x 10(1)).

Anti-Infective Agents, Local↗
PubMed1992

Chlorination, chlorination by-products, and cancer: a meta-analysis.

OBJECTIVES: Individual epidemiological investigations into the association between chlorination by-products in drinking water and cancer have been suggestive but inconclusive. Enough studies exist to provide the basis for a meaningful meta-analysis. METHODS: An extensive literature search was performed to identify pertinent case-control studies and cohort studies. Consumption of chlorinated water, surface water, or water with high levels of chloroform was used as a surrogate for exposure to chlorination by-products. Relative risk estimates were abstracted from the individual studies and pooled. RESULTS: A simple meta-analysis of all cancer sites yielded a relative risk estimate for exposure to chlorination by-products of 1.15 (95% CI: 1.09, 1.20). Pooled relative risk estimates for organ-specific neoplasms were 1.21 (95% CI: 1.09, 1.34) for bladder cancer and 1.38 (95% CI: 1.01, 1.87) for rectal cancer. When studies that adjusted for potential confounders were pooled separately, estimates of relative risks did not change substantially. CONCLUSIONS: The results of this meta-analysis suggest a positive association between consumption of chlorination by-products in drinking water and bladder and rectal cancer in humans.

Case-Control Studies↗
PubMed2002

Relationships between tissue concentrations of chlorinated hydrocarbons (polychlorinated biphenyls and chlorinated pesticides) and antioxidative responses of marine mussels, Perna viridis.

Marine mussels, Perna viridis, were transplanted from a reference site to various polluted sites around Hong Kong. After 30 d of exposure, antioxidative responses in the gills and hepatopancreas and tissue concentrations of chlorinated hydrocarbons [polychlorinated biphenyls (PCBs) and chlorinated pesticides (CPs)] were determined for individual mussels. Glutathione S transferase (GST) and glutathione (GSH) were positively correlated with tissue PCB concentrations. Only one of the enzymatic antioxidants, glutathione peroxidase (GPx), showed significant response to tissue PCB. No significant correlation was found between tissue concentrations of chlorinated hydrocarbons and other enzymatic antioxidants (superoxide dismutase (SOD), catalase (CAT), glutathione reductase (GR) and NADPH DT-diaphorase (DT-d). Oxidative stress, measured as thiobarbituric acid reactive substances, was correlated with chlorinated pesticide concentrations in tissues. This study demonstrated a correlation between GST/ GSH and chlorinated hydrocarbons. The apparent lack of correlation between trace organic pollutants and some of the enzymatic antioxidants may be due to the inhibitory effects caused by these chemicals. The above results suggest that more investigations are needed before these enzymes can be used as biomarkers.

Animals↗
PubMed2001

Photochemical and electrochemical properties of zinc chlorin-C60 dyad as compared to corresponding free-base chlorin-C60, free-base porphyrin-C60, and zinc porphyrin-C60 dyads.

The photochemical and electrochemical properties of four chlorin-C60 or porphyrin-C60 dyads having the same short spacer between the macrocycle and the fullerene are examined. In contrast with all the previous results on porphyrin-fullerene dyads, the photoexcitation of a zinc chlorin-C60 dyad results in an unusually long-lived radical ion pair which decays via first-order kinetics with a decay rate constant of 9.1 x 10(3) x s(-1). This value is 2-6 orders of magnitude smaller than values reported for all other porphyrin or chlorin donor-acceptor of the molecule dyad systems. The formation of radical cations of the donor part and the radical anion of the acceptor part was also confirmed by ESR measurements under photoirradiation at low temperature. The photoexcitation of other dyads (free-base chlorin-C60, zinc porphyrin-C60, and free-base porphyrin-C60 dyads) results in formation of the ion pairs which decay quickly to the triplet excited states of the chlorin or porphyrin moiety via the higher lying radical ion pair states as is expected from the redox potentials.

Carbon↗