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PubMed2004

Photo-assisted oxidation of chlorophenols in aqueous solutions using hydrogen peroxide and titanium dioxide.

In the present work, the efficiency of phenol and chlorophenol degradation under irradiation using hydrogen peroxide as oxidant and titanium dioxide powder as photo-catalyst was investigated. In the absence of titanium oxide, increased concentrations of hydrogen peroxide resulted in higher conversions. Generally, phenol was the most readily oxidized compound, whereas in excess of hydrogen peroxide, the more chlorine atoms were present in the ring, the less degradable the chlorophenol was, in terms of initial rate of oxidation. In the case of 4-chlorophenol, the catalytic photo-oxidation efficiency with hydrogen peroxide and titanium oxide was dependent on the catalyst concentration exhibiting a maximum at 0.025-0.05 g L(-1) titanium oxide. The combined use of titanium oxide and hydrogen peroxide resulted in higher degree of oxidation compared to results obtained when using hydrogen peroxide. Finally, the presence of Fe(III) proved to be beneficial for the photo-catalytic oxidation only in the presence of hydrogen peroxide.

Chlorophenols↗
PubMed1984

Comparative formation of chlorophenol metabolites from hexachlorocyclohexane in mouse and rat in vivo and in vitro.

Comparative formation of chlorophenol metabolites were evaluated in hexachlorocyclohexane (HCH) fed mouse and rat livers by h.p.l.c. No significant species differences were noted in the formation of chlorophenol metabolites studied both in vivo and in vitro. The results indicate that the marked species difference that is observed in tumor induction between mice and rats by HCH may not be due to the different rate of formation of chlorophenol metabolites.

Animals↗
PubMed1998

Second follow-up of a Dutch cohort occupationally exposed to phenoxy herbicides, chlorophenols, and contaminants.

A retrospective cohort study of workers exposed to phenoxy herbicides, chlorophenols, and contaminants (2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and other polychlorinated dioxins and furans) has been conducted in a chemical factory in the Netherlands. Male workers exposed to phenoxy herbicides or chlorophenols showed increased relative risks (adjusted for age, calendar period at end of follow-up, and time since first exposure/employment) for total mortality (relative risk (RR)=1.8, 95% confidence interval (CI) 1.2-2.5), cancer mortality (RR=4.1, 95% CI 1.8-9.0), respiratory cancer (RR=7.5, 95% CI 1.0-56.1), non-Hodgkin's lymphoma (RR=1.7, 95% CI 0.2-16.5), and ischemic heart diseases (RR=1.8, 95% CI 0.9-3.6) compared with an internal referent group of nonexposed workers. By using TCDD levels (predicted at the time of maximum exposure), based on extrapolated TCDD levels that were measured in a subset of the cohort, estimated relative risks for workers with medium and high TCDD levels were comparable with risks derived from the simple and earlier applied dichotomous exposure classification. In general, relative risks were highest in the highest category, indicating exposure-related increases in risk with TCDD level. In conclusion, results of this cohort study support the evidence of a high cancer risk in workers exposed to phenoxy herbicides, chlorophenols, and contaminants.

Adult↗
PubMed1999

Reductive dehalogenation and conversion of 2-chlorophenol to 3-chlorobenzoate in a methanogenic sediment community: implications for predicting the environmental fate of chlorinated pollutants.

Biotransformation of 2-chlorophenol by a methanogenic sediment community resulted in the transient accumulation of phenol and benzoate. 3-Chlorobenzoate was a more persistent product of 2-chlorophenol metabolism. The anaerobic biotransformation of phenol to benzoate presumably occurred via para-carboxylation and dehydroxylation reactions, which may also explain the observed conversion of 2-chlorophenol to 3-chlorobenzoate.

Anaerobiosis↗
PubMed1996

Purification and characterization of chlorophenol 4-monooxygenase from Burkholderia cepacia AC1100.

Burkholderia (formerly Pseudomonas) cepacia AC1100 mineralizes the herbicide 2,4,5-trichlorophenoxyacetate (2,4,5-T), and the first intermediate of 2,4,5-T degradation is 2,4,5-trichlorophenol. Chlorophenol 4-monooxygenase activity responsible for 2,4,5-trichlorophenol degradation was detected in the cell extract. The enzyme consisted of two components separated during purification, and both were purified to more than 95% homogeneity. The reconstituted enzyme catalyzed the hydroxylation of several tested chlorophenols with the coconsumption of NADH and oxygen. In addition to chlorophenols, the enzyme also hydroxylated some chloro-p-hydroquinones with the coconsumption of NADH and oxygen. Apparently, the single enzyme was responsible for converting 2,4,5-trichlorophenol to 2,5-dichloro-p-hydroquinone and then to 5-chlorohydroxyquinol (5-chloro-1,2,4-trihydroxybenzene). Component A had a molecular weight of 22,000 and contained flavin adenine dinucleotide. Component A alone catalyzed NADH-dependent cytochrome c reduction, indicating that it had reductase activity. Component B had a molecular weight of 58,000, and no catalytic activity has yet been shown by itself.

Burkholderia cepacia↗
PubMed1982

Health effects of chlorophenol wood preservatives on sawmill workers.

At the request of the International Woodworkers of America, Local 1-85, woodworkers in two Port Alberni, British Columbia, sawmills were surveyed for health complaints possibly associated with chlorophenol exposure. On the basis of their exposure to anti-sapstain, workers were divided into low/moderate and high exposure groups. Health status was determined through a questionnaire that included lists of symptoms associated with exposure to chlorophenates and their contaminants. Extensive differences were found between exposure groups, especially in terms of the prevalence and extensiveness of symptoms related to dermatological, upper and general respiratory, and neurological structures and functions. Significant elevations of a wide range of other symptom complaints directly related to chemical exposure were also found. While improved spray control operations and the use of personal protective equipment will decrease injury among workers, they cannot be expected to decrease the hazards of chlorophenol exposure to an acceptable level. The only effective means of eliminating worker and public health risks attendant with these chemical exposures is to implement an alternative means of anti-sapstain treatment and to seek an end to the use of chlorophenol for this purpose.

Adult↗
PubMed1998

Inhibition of camel lens zeta-crystallin/NADPH: quinone oxidoreductase activity by chlorophenols.

Chlorophenols comprise a major class of environmental contaminants. They are extensively used as insecticides, fungicides, mold inhibitors, antiseptics and disinfectants. We found some of these compounds to be strong inhibitors of zeta-crystallin. This oxidoreductase enzyme was isolated from camel lens and its enzymatic activity was inhibited by the chlorophenols tested in a time-independent but concentration-dependent manner. 2,4,5-Trichlorophenol was the most potent inhibitor (IC50 = 3 microM; Ki = 3.2 microM) whereas 4-chlorophenol was the least potent (IC50 = 4.1 mM). There appeared to be a relationship between the degree of chlorination of the phenols and inhibition of zeta-crystallin activity. The position of the chlorine substituent on the phenol may also influence the potency of these compounds.

Animals↗
PubMed2003

Kinetics of biodegradation during remediation of consecutive accidental spills of chlorophenols in a sandy aquifer.

Kinetics of biodegradation of chlorophenols were studied in six sandy aquifer columns (0.06 m I.D.; 1.00 m L). Remediation of chlorophenols was enhanced by using a "closed-loop" configuration system, where local groundwater was recirculated through the polluted site in a controlled manner. Consecutive accidental spills of phenol, 2-monochlorophenol (2-MCP) and 2,4,6-trichlorophenol (2,4,6-TCP) as single pollutants were removed following first order kinetics. The removal of chlorophenols increased by one order of magnitude following consecutive accidental spills demonstrating adaptation of the resident micro flora. The biodegradation rate constants in this study were in the same range and agreed with those reported in the literature for biodegradation in aerobic aquifers. Following the fate of the resident micro flora (enhanced by adding NH4Cl and KH2PO4 at a ratio C/N/P equal to 120:10:1), biomass growth was observed in the sandy aquifer columns and particle size analyses of the aqueous phase recirculated through the polluted site experimentally proved aggregation of cells. Aggregation of cells has been hypothesized as one of the causes for low biodegradation rates found in the field compared to those calculated using biodegradation rate constants determined in batch culture.

Accidents↗
PubMed2003

[Research advances in biodegradation of chlorophenols in environment].

This paper examines the biodegradation of chlorophenols by microbes and deals with the chlorophenols-degrading microbes and the usage of biotechnology with special emphasis on degradation mechanisms. Dechlorination is the first critical step in the bacterial degradation of many chloroniated pollutans. Under aerobic condition, the degradation of mono- and dichlorophenols is shown to be initiated by oxygenation into chlorocatechols, and dechlorination occurs only after ring cleavage of the chlorocatechols. The degradation of polychlorinated phenols starts by hydrolytic para-hydroxylation, yielding chlorinated para-hydroquinone. The anaerobic biodegradation of chlorophenols occurs by reductive dechlorination, a process by which chlorines are replaced with hydrogen.

Biodegradation, Environmental↗
PubMed2004

Catalytic dechlorination of o-chlorophenol by nanoscale Pd/Fe.

Transformation of chlorophenols by nanoscale bimetallic particles represents one of the latest innovative technologies for environmental remediation. Nanoscale Pd/Fe bimetallic particles were synthesized in the laboratory for treatment of o-chlorophenol. Most of the nanoscale particles are in the size range of 20-100 nm. BET specific surface area of the nanoscale Pd/Fe particles is 12.4 m2/g. In comparison, a commercially available Fe powder( < 100 mesh) has a specific surface area of just 0.49 m2/g. Batch experiments demonstrated that the nanoscale Pd/Fe bimetallic particles can effectively dechlorinate o-chlorophenol. Dechlorination efficiency is affected by the mass fraction of Pd in the bimetal, nanoscale Pd/Fe mass concentration and mixing intensity.

Catalysis↗
PubMed1983

Selected ion mass spectrometric identification of chlorophenol residues in human urine.

A method is presented for the detection and confirmation of trace chlorophenol residues in environmental and biological samples by mass spectrometry with selected ion monitoring (SIM). Propionate and acetate ester derivatives of phenol, cresols, mono-, di-, tri-, and tetrachlorophenols, pentachlorophenol, as well as the internal standard 4,6-dibromo-o-cresol, were prepared directly in aqueous solution, using the appropriate anhydride reagent. The acetate or propionate esters were quantitatively extracted and then separated by gas-liquid chromatography using either an SP-1240DA or OV-101 packed column. Electron impact SIM was carried out by simultaneously monitoring up to 4 diagnostic fragment ions of each chlorinated phenol. The use of SIM eliminated background interference encountered using flame ionization or electron capture detectors, and allowed identification of chlorophenol residues in extracts of urine samples collected from individuals without known exposure to chlorophenols. Phenol concentrations as low as 1.0 pmol/mL urine gave peaks that were readily discernible by SIM.

Acetates↗
PubMed2006

High-affinity blockade of voltage-operated skeletal muscle sodium channels by 2,6-dimethyl-4-chlorophenol.

BACKGROUND AND OBJECTIVE: The aromatic alcohol most closely resembling the aromatic tail of lidocaine is 2,6-dimethylphenol. This agent is as potent as lidocaine in blocking voltage-operated sodium channels. The aim of this study was to show the effect of halogenation in the para-position on the potency of this compound to block voltage-operated sodium channels. METHODS: Insertion of the halogen chloride into the para-position of the molecule 2,6-dimethylphenol yielded 2,6-dimethyl-4-chlorophenol. Block of sodium currents by this compound was studied using heterologously expressed voltage-operated rat neuronal (rat IIa) sodium channels. RESULTS: 2,6-dimethyl-4-chlorophenol reversibly suppressed depolarization-induced whole-cell sodium inward currents. The ECR50 for block of resting channels at a hyperpolarized holding potential (-150 mV) was 127 micromol, the Hill coefficient nH 1.7. Membrane depolarization inducing either fast or slow-inactivation strongly increased the blocking potency. This is an important feature of a local-anaesthetic-like action. The estimated half-maximum effect concentration for the fast-inactivated channel state ECI50 was 28 micromol, the Hill coefficient nH 3.8. When 20-30% of channels were slow-inactivated using long (2.5 s) prepulses, followed by a 10 ms repolarization period to allow recovery from fast inactivation, the IC50 at -100 mV holding potential was reduced to 53 micromol. CONCLUSION: These results, which show that 2,6-dimethyl-4-chlorophenol blocks voltage-operated sodium channels in a lidocaine-like manner while having a several fold higher potency than the non-halogenated parent compound, highlight a potentially meaningful principle of increasing the sodium channel blocking potency of phenol derivatives.

Algorithms↗
PubMed1997

Degradation of Chlorophenols by Alcaligenes eutrophus JMP134(pJP4) in Bleached Kraft Mill Effluent.

The ability of Alcaligenes eutrophus JMP134(pJP4) to degrade 2,4-dichlorophenoxyacetic acid, 2,4,6-trichlorophenol, and other chlorophenols in a bleached kraft mill effluent was studied. The efficiency of degradation and the survival of strain JMP134 and indigenous microorganisms in short-term batch or long-term semicontinuous incubations performed in microcosms were assessed. After 6 days of incubation, 2,4-dichlorophenoxyacetate (400 ppm) or 2,4,6-trichlorophenol (40 to 100 ppm) were extensively degraded (70 to 100%). In short-term batch incubations, indigenous microorganisms were unable to degrade such of compounds. Degradation of 2,4,6-trichlorophenol by strain JMP134 was significantly lower at 200 to 400 ppm of compound. This strain was also able to degrade 2,4-dichlorophenoxyacetate, 2,4,6-trichlorophenol, 4-chlorophenol, and 2,4,5-trichlorophenol when bleached Kraft mill effluent was amended with mixtures of these compounds. On the other hand, the chlorophenol concentration and the indigenous microorganisms inhibited the growth and survival of the strain in short-term incubations. In long-term (>1-month) incubations, strain JMP134 was unable to maintain a large, stable population, although extensive 2,4,6-trichlorophenol degradation was still observed. The latter is probably due to acclimation of the indigenous microorganisms to degrade 2,4,6-trichlorophenol. Acclimation was observed only in long-term, semicontinuous microcosms.

Journal Article↗
PubMed1976

Use of chlorophenols as fungicides in sawmills.

Several commercial formulations of chlorophenols used as fungicides in sawmills were found to contain impurities, some of which are known to be much more toxic than the main products. The most frequent impurities were chlorinated phenoxyphenols, chlorinated diphenyl ethers, chlorinated dibenzofurans, and chlorinated dibenzodioxins. Samples of wood dust from several positions in two Swedish sawmills were analyzed. The results suggest that the impurities in the chlorophenol formulations are enriched in the work environment in relation to the chlorophenols themselves, probably because of the low volatility and high chemical stability of the impurities. The effect of various methods of fungicide application on the work environment is discussed.

Fungicides, Industrial↗
PubMed1998

Degradation of various chlorophenols under alkaline conditions by gram-negative bacteria closely related to Ochrobactrum anthropi.

From concrete debris of a demolished herbicide production plant several Gram-negative bacterial strains were isolated, which exhibit metabolic capabilities for the degradation of 2,4-dichlorophenol (DCP)l), 4-chloro-2-methylphenol (MCP) and 4-chlorophenol (4-CP), while 2-chlorophenol (2-CP) was degraded at a slower rate. Degradative activity was inducible and was impeded by adding of 100 mg/l of chloramphenicol to growing cultures. The strains displayed alkaliphilic properties with optimum DCP/MCP degradation at pH values around 8.5-9.5; activity was observed up to pH values of 11. Degradation was most likely complete according to chlorine balances; formation of intermediary products was observed with MCP some time. Specific activity of up to 380 mumol/h.g dry mass was found within the concentration range of 10-20 mg/l DCP; higher concentrations retarded the activity with complete inhibition at 200-400 mg/l. Some of the strains carry plasmids whose presence was not unambiguously correlated to the degradative properties. Ribotyping revealed a high degree of relationship between the strains. Preliminary taxonomic investigations showed close relationship to Ochrobactrum anthropi.

Anti-Bacterial Agents↗
PubMed2000

New carrier electrolytes for the separation of chlorophenols by capillary electrophoresis.

Optimum conditions for the separation of positional isomers of chlorophenols by capillary zone electrophoresis (CZE) were established. The behavior of five volatile electrolytes (L-cysteic acid, 3-amino-1-propanesulfonic acid, aminomethanesulfonic acid, diethylmalonic acid, and ammonium acetate) was compared. The best performance based on low electrophoretic current and high separation efficiency was obtained for diethylmalonic acid as working electrolyte. The influence of pH on the separation, using both uncoated fused-silica capillaries and modified capillaries (NaAMPS from EKT) with anionic coating, was discussed. Moreover, the effect of electrolyte concentration and applied voltage using fused-silica capillaries was studied. The optimum CZE conditions that allowed the separation of 16 chlorophenols were 20 kV, 30 mM diethylmaIonic acid, pH 7.25, and uncoated fused-silica capillary. Figures of merit such as run-to-run and day-to-day precision, linearity, and limits of detection were calculated.

Chlorophenols↗
PubMed2001

Control of chemical risks during the treatment of soil contaminated with chlorophenol, creosote and copper-chrome-arsenic-wood preservatives.

BACKGROUND: Exposure to chemicals in polluted soil was studied during the remediation of four polluted sites. They are sawmill areas contaminated with chlorophenols and polychlorinated dibenzo-p-dioxins and furanes (PCDD/F), wood impregnating plants contaminated with polycyclic aromatic hydrocarbons (PAH) from creosote oil, old gas works area contaminated with PAH, and a wood impregnation plant contaminated with copper-chromium-arsenic (CCA) preservative. METHODS: The exposure levels were determined by both air and biological monitoring. RESULTS: Air monitoring showed that the exposure levels were generally well below the current occupational exposure limits. The calculations indicated, however, that the lowest acceptable daily intake value recommended for PCDD/F by the U.S. Environmental Protection Agency was exceeded. Chlorophenol exposure was generally low. Exposure to volatile PAH was 0.038-0.884 mg/m(3) and that to particulate PAH was 0.004-0.183 mg/m(3). The biomonitoring results (urinary 1-pyrenol) suggested that some exposure occurs, probably through the contamination of hands or skin absorption. At the sites contaminated with CCA salts, no exposure limits were exceeded. CONCLUSIONS: The results generally suggest that the exposure of cleanup workers is generally below the current occupational exposure limits but that short-term high exposure cannot be excluded. There was also some indication of poor skin protection, which should be improved when soil contaminated with PAH and creosote oil is handled.

Arsenic↗
PubMed1990

The use of Brauman's least squares approach for the quantification of deuterated chlorophenols.

The least squares method for the solution of ion overlap problems in quantitative mass spectrometry first introduced by Brauman was used to quantify isotopic mixtures of chlorophenol derivatives. The samples analyzed consisted of the chlorophenols resulting from the cytochrome P-450 mediated oxidation of isotopic mixtures of chlorobenzenes, and were analyzed on a VG-7070 double-focusing mass spectrometer. The application of this method is described and its advantages are highlighted. In some instances the use of the least squares methods resulted in smaller standard deviations of the means of replicate analyses. Significant features of the technique include its simplicity of use, the universality of its application to all cases of ion overlap and its inherent ability to detect erroneous data, e.g. that due to the presence of impurities or mass spectral parameter variation.

Chlorophenols↗