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PubMed2005

Theoretical study of hydrogen-bonded complexes of chlorophenols with water or ammonia: Correlations and predictions of pKa values.

A simple practical method for predicting the acidity constants (as pKa values) of chlorophenols is proposed based on density functional theory calculations of a series of hydrogen-bonded complexes of phenol and 19 different congeners of chlorophenol, with a single probe molecule, either water or ammonia. Relevant structural parameters and molecular properties of these complexes, primarily involving the acidic hydroxyl group, are examined and plotted against the known pKa values of 14 chlorophenols and phenol. Strong linear correlations are found for these compounds. Such correlations are used to determine the pKa values of five chlorophenols whose experimental acidities have large uncertainties. Similar predicted pKa values are obtained by using different structural parameters and molecular properties for the complexes with either probe molecule. The study may be extended to determine the acidity of other compounds with a single acidic functional group.

Algorithms↗
PubMed2006

An investigation of chlorophenol proton affinities and their influence on the biological activity of microorganisms.

The proton affinities of 15 chlorophenols are calculated by ab initio methods. Straight correlation between proton affinities and changes in the electronic structure is observed. The proton affinities decrease linearly with the electronic density gain on the chlorine atoms, as the liberation of the proton increases. To confirm the importance of the proton affinities on the toxicity of chlorophenols, calorimetric responses of these molecules and related ones where the acid proton is changed to a methyl group (anisol and its chlorinated derivatives) were used to verify their effects on Chromobacterium violaceum. The results confirmed that the chlorophenols are more toxic than the respective chloroanisols and suggest that high proton affinities are associated with low toxic activity. The toxicity of the chlorophenols can be associated with the respiratory mechanism in some microorganisms.

Anti-Bacterial Agents↗
PubMed2004

Bacterial degradation of chlorophenols: pathways, biochemica, and genetic aspects.

Chlorophenols belong to the group of toxic and persistent to microbial attack xenobiotics. Nevertheless, due to the adaptation microorganisms acquire the ability to use chlorophenols as the sole source of carbon and energy. The present review describes the diversity of aerobic pathways for the utilization of halogenated phenols by bacteria with the emphasis on the main reactions and intermediates formed, enzymes responsible for these reactions and their genetic basis. Taking into account (i) the fact that enzymes degrading chlorophenols are similar to the ones involved in the conversion of other (chloro)aromatic compounds and (ii) that present numerous publications describing the properties of separated enzymes or encoding their genes are published, this review was planned as the attempt to present both, the most general and specific aspects in chlorophenols degradation with the emphasis on the literature of the last ten years.

Aerobiosis↗
PubMed1998

Occupational chlorophenol exposure and soft tissue sarcoma risk among men aged 30-60 years.

To evaluate the association of chlorophenol exposure with soft tissue sarcoma risk independent of phenoxyherbicide exposure, the authors analyzed data from the Selected Cancers Study, a population-based case-control study that included 295 male soft tissue sarcoma cases, aged 32-60 years, from eight population-based cancer registries and 1,908 male controls. Chlorophenol exposure was assigned using both an intensity and a confidence estimate by an industrial hygienist based on verbatim job descriptions. Seventeen percent of the jobs rated as high intensity involved wood preservation, while 82% involved cutting oils. Soft tissue sarcoma risk, modeled using conditional logistic regression, was significantly associated with ever having high-intensity chlorophenol exposure (odds ratio = 1.79, 95% confidence interval 1.10-2.88). A duration-response trend was evident among more highly exposed subjects (p for trend < 0.0001). For subjects with 10 or more years of substantial exposure, the odds ratio was 7.78 (95% confidence interval 2.46-24.65). These results suggest that chlorophenol exposure independent of phenoxyherbicides may increase the risk of soft tissue sarcoma. Because of the large number of machinists in the exposed group and the complex composition of cutting fluids, it is possible that another exposure involved in machining is responsible for the observed excess risk.

Adult↗
PubMed1983

Degradation of chlorophenols by a defined mixed microbial community.

Synthetic sewage containing phenol, acetone, and alkanols plus 4-chlorophenol or a mixture of isomeric chlorophenols is completely degraded by a defined mixed culture with Pseudomonas sp. strain B13 as a chlorocatechol-dissimilating member of the community. Total degradation of the organic carbon was indicated by release of stoichiometric amounts of chloride and low content of dissolved organic carbon in the cell-free effluents. During adaptation to high loads of chlorophenols the initial meta-cleavage activity was completely replaced by ortho-cleavage activity of type I and II. In the fully acclimated culture, hybrid strains such as Alcaligenes sp. strain A7-2 were detected, which are more competitive than Pseudomonas sp. strain B13 with respect to chlorophenol degradation.

Alcaligenes↗
PubMed1978

Influence of growth rate and nutrient limitation on the gross cellular composition of Pseudomonas aeruginosa and its resistance to 3- and 4-chlorophenol.

Concentrations of 3-chlorophenol and 4-chlorophenol below their minimal inhibitory concentrations were found to increase the permeability of Pseudomonas aeruginosa cells to protons. Levels of such activity were assessed in suspensions of cells prepared from chemostat-grown cultures, limited by either magnesium (Mg-lim) or glucose (G-lim), with the use of five growth rates. Drug concentrations required to produce the same levels of proton translocation varied with the growth rate and the nutrient limiting growth. Fast-growing cultures were more sensitive than slower-growing ones, and G-lim cells were generally more sensitive than Mg-lim ones. 3-Chlorophenol had greater activity than 4-chlorophenol at slow growth rates, but at faster rates of growth their activity was similar. Variation in these iso-effective concentrations for different cells probably reflected an alteration in the ease of drug penetration of the outer envelope. Uptake of the compounds by cells in suspension varied, drug-sensitive bacteria absorbing more than resistant ones. This variation in uptake persisted when bacteria were solvent-extracted to remove readily extractable lipids (REL). Since no significant alteration in cell size was observed among the growth conditions studied, variation in absorption probably resulted from an altered affinity of the cells to the drug, with little involvement of REL. Overall REL content did not alter significantly with growth rate or nutrient limitation. However, total phospholipid content decreased and fatty acid content increased with increasing growth rate. For G-lim and Mg-lim cultures phosphatidylcholine content remained constant, yet phosphatidylethanolamine and phosphatidylglycerol content decreased with increasing growth rate. Diphosphatidylglycerol content decreased with increasing growth rate for Mg-lim cultures and remained relatively constant for G-lim cultures. Lipopolysaccharide content of the cells was higher in Mg-lim than in G-lim cultures and decreased with increasing growth rate in both cases. Lipopolysaccharide content correlated significantly with drug uptake and sensitivity, and it appeared to determine the degree of penetration of the cell envelope by these chlorinated phenols.

Chlorophenols↗
PubMed2001

[Study on the quantitative structure toxicity relations of chlorophenols in some aquatic species].

The quantitative structure-activity relations between electronic structure of chlorophenols and their toxicity to Bluegill and Guppy were were studied. The electronic structure parameters of fourteen chlorophenols were calculated by using CNDO/2 method. The quantitative structure-activity relationships between electronic structure parameter of chlorophenols and their toxicity to Bluegill and Guppy were were discussed respectively by step regression analysis. Two linear equations were obtained as follows: (1) for Bluegill, LC50 = -122.493 + 20.334 sigma Q pi R; (2) for Guppy DLC50 = -100.263 + 16.639 sigma Q pi R. The results showed that the toxicity of chlorophenols to Bluegill and Guppy were increased as the sum of pi-charge (sigma Q pi R) at the carbon atom on benzene ring increased.

Animals↗
PubMed2003

2-Chlorophenol oxidation kinetic by photo-assisted Fenton process.

Experimental data are presented to test and validate a kinetic model for the oxidation of 2-chlorophenol wastewater by photo-assisted Fenton process. The data showed that this process had produced good effects under acidic conductions. Up to 90% 2-chlorophenol was removed after 90-minute reaction time with H2O2 of 25% COD(Cr, in), while in UV/H2O2 system only 16.8% 2-chlorophenol was removed after one hour treatment. The optimal pH in this reaction occurred between pH 3.0 and pH 4.0. The reaction kinetics for photo-assisted Fenton process experimented in this research was investigated. Kinetic models were proposed for the treatment of 2-chlorophenol wastewater. The reaction was found to follow the 2nd order. The equations of reaction kinetics are as follows: -d[RH]/dt = K(RH) [RH] [H2O2]0 exp(-K(H2O2) t); -d[COD(Cr)]/dt = K(COD(Cr)) [COD(Cr)] [H2O2]0 exp(-K' t). The prediction of the models was found to be in a good agreement with experimental results, thus confirming the proposed reaction mechanism.

Chlorophenols↗
PubMed2006

[Determination of chlorophenols in drinking water by headspace solid phase microextraction and gas chromatography].

OBJECTIVE: To study the method for determination of chlorophenols in drinking water by headspace solid phase microextraction and gas chromatography. METHODS: Chlorophenols in water samples was extracted using optimized SPME technology, separated by HP-5 chromatigraphic column and the concentration of chlorophenols was determined by electron capture detector (ECD). RESULTS: The detection limit of MCP, DCP, TCP, PCP were 60.0 microg/L, 2.64 microg/L, 0.15 microg/L and 0.84 microg/L. The correlation coefficient(r) were 0.999, 0.997, 0.997, 0.995. When adding standard material of MCP, DCP, TCP, PCP at low, middle, high concentrations, the recovery rates were 95.3% - 107%, 93.6% - 102%, 92.4% - 102%, 91.5% -99.1% and the RSD (n = 6) were 1.0% - 8.1%,1.6% - 6.6%, 2.9% - 8.6%, 2.0% - 8.2%. CONCLUSION: The method was simple, sensitive and without solvent, which was an ideal method for determination of chlorophenols in drinking water.

Chlorophenols↗
PubMed1994

[Chlorophenols in urine as an environmental medicine monitoring parameter].

Chlorophenols occur ubiquitously in the environment. They are taken up as such in man or are formed in intermediary metabolism e.g. from chlorobenzenes. In particular pentachlorophenol (PCP) is one of those chemical substances used up to the early 70's as a component of wood preservatives also indoors; for many years it has been at the centre of discussion about the environment. Mono, di, tri and tetrachlorophenols as well as pentachlorophenol occur in the urine in the general population often in surprisingly high concentrations. An increased chlorophenol excretion under certain circumstances also indicates an increased dioxin exposure (pre-dioxins). Possible sources of emission and routes of absorption for corresponding organochlorine compounds can be found in industry, agriculture and also private households. Environmental analysis in the air, in earth or dust do not allow any evaluation of health risks. Only biological monitoring with qualitative and quantitative determination of the actual concentration of the substance taken up by the organism allows a reliable estimation of the individual health risk. The background exposure of the general population not occupationally exposed to organochlorine compounds can be used for the determination of so-called norm values. For the determination of the chlorophenol spectrum 50 ml urine are necessary. The following values can be given as reference values for the most important chlorophenols: 4-monochlorophenol: 7.5 micrograms/l, 2.4-dichlorophenol and 2.5-dichlorophenol: 33.6 micrograms/l, 2.4.6-trichlorophenol: 4.7 micrograms/l, 2.4.5-trichlorophenol: 4.5 micrograms/l, 2.3.4.6-tetrachlorophenol and 2.3.5.6-tetrachlorophenol: 22.0 micrograms/l, pentachlorophenol 9.0 micrograms/l urine.

Chlorophenols↗
PubMed2003

Effects of ultrasound on adsorption-desorption of p-chlorophenol on granular activated carbon.

The aim of this work is the evaluation of the effects of ultrasound on p-chlorophenol adsorption-desorption on granular activated carbon. Adsorption equilibrium experiments and batch kinetics studies were carried out in the presence and the absence of ultrasound at 21 kHz. Results indicate that the adsorption of p-chlorophenol determined in the presence of ultrasound is lower than the adsorption observed in the absence of ultrasound. Desorption of p-chlorophenol from activated carbon with and without the application of ultrasound was studied. The desorption rates were favoured by increased ultrasound intensity. This rise is more noticeable as temperature increases. The addition of ethanol or NaOH to the system causes an enhancement of the amount of p-chlorophenol desorbed, especially in the presence of ultrasound. A synergetic enhancement of the desorption rate was observed when ultrasonic irradiation was coupled with ethanol chemical regeneration.

Journal Article↗
PubMed2000

Sonochemical degradation of chlorophenols in water

Sonochemical degradation of dilute aqueous solutions of 2-, 3- and 4-chlorophenol and pentachlorophenol has been investigated under air or argon atmosphere. The degradation follows first-order kinetics in the initial state with rates in the range 4.5-6.6 microM min-1 under air and 6.0-7.2 microM min-1 under argon at a concentration of 100 microM of chlorophenols. The rate of OH radical formation from water is 19.8 microM min-1 under argon and 14.7 microM min-1 under air in the same sonolysis conditions. The sonolysis of chlorophenols is effectively inhibited, but not completely, by the addition of t-BuOH, which is known to be an efficient OH radical scavenger in aqueous sonolysis. This suggests that the main degradation of chlorophenols proceeds via reaction with OH radicals; a thermal reaction also occurs, although its contribution is small. The addition of appropriate amounts of Fe(II) ions accelerates the degradation. This is probably due to the regeneration of OH radicals from hydrogen peroxide, which would be formed from recombination of OH radicals and which may contribute a little to the degradation. The ability to inhibit bacterial multiplication of pentachlorophenol decreases with ultrasonic irradiation.

Journal Article↗
PubMed2005

FTIR investigation of 2-chlorophenol chemisorption on a silica surface from 200 to 500 degrees C.

The time-dependent chemisorption of 2-chlorophenol on a fumed silica surface was studied in situ from 200 to 500 degrees C using a temperature-controlled dosing cell and FTIR absorption spectroscopy. 2-Chlorophenol was found to chemisorb at isolated and geminal surface hydroxyl sites. 2-Chlorophenol chemisorption and subsequent surface oxidation resulted in a mixture of chlorophenolate and partial oxidation products, such as formates and acetates. The rates of chemisorption were measured, and the activation energy of adsorption was found to be 15 +/- 4 kJ mol(-1) for a fast, initial reaction and 22 +/- 2 kJ mol(-1) for a slower reaction at higher surface coverage. This work was motivated by the observation that combustion-generated fly ash mediates the formation of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/F) at temperatures between 250 and 450 degrees C. Although transition metals such as copper are known to catalyze or mediate this reaction, silica is the major component of fly ash and chemisorption at higher concentration surface sites of silica must have a significant impact on the surface-mediated PCDD/F formation on fly ash surfaces.

Journal Article↗
PubMed2004

Chlorophenol exposure in harbor workers exposed to river silt aerosols.

OBJECTIVES: While dredging the river Elbe in the harbor of Hamburg, workers are potentially exposed to river silt aerosols containing organic compounds. The aim of this cross-sectional study was to determine the internal load of chlorophenols in exposed workers. METHODS: Eighty-four exposed workers and eighty-four unexposed office workers were examined. Urinary samples were analyzed for dichlorophenols, trichlorophenols, tetrachlorophenols, and pentachlorophenol (PCP). RESULTS: For exposed workers, more than 2/3 of the urinary samples were above detection limit for 2,5-dichlorophenol, 2,4/3,4-dichlorophenol, 2,4,6-trichlorophenol, and PCP. Harbor workers had significantly higher median levels of 2,5-dichlorophenol (0.6 vs. 0.4 microg/g creatinine) and PCP (1.4 vs. 1.0 microg/g creatinine) as compared to unexposed subjects. These differences remained statistically significant after adjustment for age, smoking habits, and fish consumption. CONCLUSION: Harbor workers in the harbor of Hamburg have a statistically significant higher internal load of chlorophenols than the general population. However, the internal load is within the range of exposure reported from the general population. Therefore, even though chlorophenols are found in the river silt these exposures do not seem to be the major source of the internal load among workers in the harbor of Hamburg.

Adult↗
PubMed2006

In-capillary solid-phase extraction-capillary electrophoresis for the determination of chlorophenols in water.

A novel CE method combined with SPE in a single capillary was developed for analysis of chlorophenols in water. A frit of 0.5 mm was first made by a sol-gel method, followed by packing a SPE sorbent in the inlet end of the capillary. Two phenol derivatives, 2,4-dichlorophenol and 2,4,5-trichlorophenol, were used as the model compounds. By loading sample solutions into the capillary, the two chlorophenols were extracted into the sorbent. They were desorbed by injecting only about 4 nL of methanol. Finally, the analytes were separated by conventional CE. The technique provided a concentration enhancement factor of over 4000-fold for both chlorophenols. The detection limits (S/N = 3) of 2,4-dichlorophenol and 2,4,5-trichlorophenol were determined to be 0.1 ng/mL and 0.07 ng/mL, respectively. For replicate analyses of 5 ng/mL of 2,4-dichlorophenol, within-day and between-day RSDs of migration time, peak height and peak area were in the range of 1.8-2.0%, 4.0-4.4% and 4.1-4.6%, respectively. The method shows wide linear range, acceptable reproducibility and excellent sensitivity, and it was applied to the analyses of spiked river water samples. The capillary packed with the SPE sorbents can be used for more than 400 runs without performance deterioration.

Chlorophenols↗
PubMed1993

Role of electron-donating cosubstrates in the anaerobic biotransformation of chlorophenoxyacetates to chlorophenols by a bacterial consortium enriched on phenoxyacetate.

A bacterial consortium that anaerobically mineralized phenoxyacetate, with transient production of phenol as an intermediate, was obtained from a methanogenic aquifer site near the Norman, OK municipal landfill. This consortium was able to convert the eight halogenated chlorophenoxyacetates tested to the corresponding chlorophenols. The chlorophenols were not subsequently metabolized. The addition of reduced substrates increased the rate of degradation of all chlorophenoxyacetates, with 78% of mono- and di-chlorinated substrates being transformed to chlorophenols in butyrate-amended cultures, compared to less than 37% transformed in unsupplemented cultures. Butyrate increased the transformation of 2,4,5-trichlorophenoxyacetate from 10% to 20%. An experiment evaluating the effects of several compounds on the side-chain cleavage reaction of 3-chlorophenoxyacetate showed that addition of compounds which readily act as hydrogen donors (butyrate, crotonate, ethanol, propionate, and hydrogen) resulted in 2 to 5 times the amount of 3-chlorophenoxyacetate transformed compared to controls with no amendment, formate had a slight stimulatory effect, and acetate and methanol had no effect. Butyrate addition also increased the rate of phenoxyacetate degradation, resulting in transient phenol accumulation not observed in butyrate-unamended controls. These results support the hypothesis that the side-chain cleavage of phenoxyacetate is a reductive process that is stimulated by the oxidation of reduced cosubstrates.

2,4,5-Trichlorophenoxyacetic Acid↗
PubMed2005

Degradation of chlorophenols using pentachlorophenol-degrading bacteria Sphingomonas chlorophenolica in a batch reactor.

Chlorophenols are common environmental contaminants that have been used as the major component in wide-spectrum biocides in industry and agriculture. Many chlorophenols tend to persist in the environment and may become public health hazards. This research studied the ability of the pentachlorophenol (PCP)-degrading bacterium Sphingomonas chlorophenolica to degrade and dechlorinate other chlorophenols. In addition, the characteristics of S. chlorophenolica were also investigated. When S. chlorophenolica cells were preincubated with PCP, the lag phase PCP degradation periods became shorter and the PCP concentrations that could be removed became higher. S. chlorophenolica was able to completely degrade 2,3,6-trichlorophenol (2,3,6-TCP), 2,4,6-trichlorophenol (2,4,6-TCP), 2,3,4,6-tetrachlorophenol (2,3,4,6-TeCP), and PCP within 38.1, 15.1, 11.8, and 11.8 h, and to release concentrations of 50.1, 60.9, 63.7, and 58.5 mg/L chloride at the same period of time. In the presence of supplementary carbon sources, the PCP removal efficiency increased with the presence of glucose or pyruvate. However, the removal efficiency of 75 mg/L 2,4-dichlorophenol did not increase with supplemental carbon sources.

Biodegradation, Environmental↗
PubMed1995

Polychlorodibenzo-p-dioxin and polychlorodibenzofuran concentrations in human fat samples in a village after pollution of drinking water with chlorophenols.

Polychorodibenzo-p-dioxin and polychlorodibenzofuran (PCDD/F) and polychlorobiphenyl (PCB) concentrations were analyzed in fat samples of seven people from a village where the population had been exposed to chlorophenols for over twenty years, and in seven matched controls. There was only a minor difference in both PCDD/F and PCB concentrations which seemed to reflect the general difference in background pollution between the locations. We found nothing which could be construed as evidence of elevated levels of PCDD/Fs due to the chlorophenol exposure. Hence any detrimental health effects must be considered as being due to chlorophenols rather than PCDD/F impurities.

Adipose Tissue↗