New Methods Used in Pharmacokinetics and Therapeutic Monitoring of the First and Newer Generations of Antiepileptic Drugs (AEDs)

The review presents data from the last few years on bioanalytical methods used in therapeutic drug monitoring (TDM) of the 1st-3rd generation and the newest antiepileptic drug (AEDs) cenobamate in patients with various forms of seizures. Chemical classification, structure, mechanism of action, pharmacokinetic data and therapeutic ranges for total and free fractions and interactions were collected. The primary data on bioanalytical methods for AEDs determination included biological matrices, sample preparation, dried blood spot (DBS) analysis, column resolution, detection method, validation parameters, and clinical utility. In conclusion, the most frequently described method used in AED analysis is the LC-based technique (HPLC, UHPLC, USLC) combined with highly sensitive mass detection or fluorescence detection. However, less sensitive UV is also used. Capillary electrophoresis and gas chromatography have been rarely applied. Besides the precipitation of proteins or LLE, an automatic SPE is often a sample preparation method. Derivatization was also indicated to improve sensitivity and automate the analysis. The usefulness of the methods for TDM was also highlighted.

Suppression of the photoparoxysmal response in photosensitive epilepsy with cenobamate (YKP3089)

OBJECTIVE

To evaluate the effect of cenobamate in patients with photoparoxysmal-EEG response (PPR) to intermittent photic stimulation (IPS) as proof of principle of efficacy in patients with epilepsy.

METHODS

In this multicenter, single-blind study, adults with photosensitive epilepsy, with/without concomitant antiepileptic drug therapy, underwent IPS under 3 eye conditions after a single dose of placebo (day -1, day 2) or cenobamate (day 1; 100, 250, or 400 mg). Complete suppression was a standardized photosensitivity range reduction to 0 over ≥1 time points for all eye conditions. Partial suppression was a ≥3-point reduction over ≥3 testing times vs the same time points on day -1 in ≥1 eye condition. Pharmacokinetics and safety were assessed.

RESULTS

Of 6 evaluable patients, 5 reentered to receive higher doses. Cenobamate 100 mg produced partial suppression in 1 of 3 patients; 250 mg produced complete suppression in 1 of 4 and partial suppression in 4 of 4 patients; and 400 mg produced complete suppression in 1 of 4 and partial suppression in 2 of 4 patients. PPR was consistently reduced on days 1 and 2 (>24 hours after cenobamate) vs day -1 (placebo) with the 250- and 400-mg doses. Area under the plasma concentration-time curve (before dose to last measurable concentration) values between 201 and 400 μg/h/mL resulted in partial suppression in 4 of 6 (66%) patients. Most common adverse events were dizziness and somnolence.

CONCLUSIONS

This proof-of-principle study demonstrated that cenobamate is a potentially effective product for epilepsy.

CLINICALTRIALSGOV IDENTIFIER

NCT00616148.

CLASSIFICATION OF EVIDENCE

This study provides Class III evidence that, for patients with photosensitive epilepsy, cenobamate suppresses IPS-induced PPR.

Fate of the organophosphorus pesticide profenofos in cotton fiber

Pesticides carried by cotton fiber are potential risk for production workers and consumers. Dissipation behaviour of a commonly used cotton pesticide profenofos in cotton fiber during growing period and scouring treatment was investigated. The results showed that profenofos in the fiber from the pre-opened and post-opened bolls both decreased to undetectable amounts 21 days after pesticide application. However, a minority of profenofos was converted to a strongly irritant compound, 4-bromo-2-chlorophenol and retained a non-negligible amount in cotton fiber even after 28 days. Profenofos and its degradation product could be completely removed during the conventional cotton scouring process. The degradation half-time of profenofos in scouring bath was only 3.0 min, and the degradation product was also 4-bromo-2-chlorophenol. Cotton products made of profenofos-carrying fiber are safe; however, the scouring waste should be detoxicated before discharge due to the accumulation of 4-bromo-2-chlorophenol in the scouring bath. These results could be useful for evaluating the risk of cotton fiber from the profenofos applied fields.

Metabolism and Residues of 2,4-Dichlorophenoxyacetic Acid in DAS-40278-9 Maize (Zea mays) Transformed with Aryloxyalkanoate Dioxygenase-1 Gene

DAS-40278-9 maize, which is developed by Dow AgroSciences, has been genetically modified to express the aryloxyalkanoate dioxygenase-1 (AAD-1) protein and is tolerant to phenoxy auxin herbicides, such as 2,4-dichlorophenoxyacetic acid (2,4-D). To understand the metabolic route and residue distribution of 2,4-D in DAS-40278-9 maize, a metabolism study was conducted with ¹⁴C-radiolabeled 2,4-D applied at the maximum seasonal rate. Plants were grown in boxes outdoors. Forage and mature grain, cobs, and stover were collected for analysis. The metabolism study showed that 2,4-D was metabolized to 2,4-dichlorophenol (2,4-DCP), which was then rapidly conjugated with glucose. Field-scale residue studies with 2,4-D applied at the maximum seasonal rate were conducted at 25 sites in the U.S. and Canada to measure the residues of 2,4-D and free and conjugated 2,4-DCP in mature forage, grain, and stover. Residues of 2,4-D were not detectable in the majority of the grain samples and averaged <1.0 and <1.5 μg/g in forage and stover, respectively. Free plus conjugated 2,4-DCP was not observed in grain and averaged <1.0 μg/g in forage and stover.

Metabolic fate of 2,4-dichlorophenol and related plant residues in rats

This study compared the metabolic fate of [(14)C]-DCP, [(14)C]-residues from radish plants, and purified [(14)C]-DCP-(acetyl)glucose following oral administration in rats. A rapid excretion of radioactivity in urine occurred for [(14)C]-DCP, [(14)C]-DCP-(acetyl)glucose, and soluble residues, 69, 85, and 69% within 48 h, respectively. Radio-HPLC profiles of 0-24 h urine from rats fed [(14)C]-DCP and [(14)C]-DCP-(acetyl)glucose were close and qualitatively similar to those obtained from plant residues. No trace of native plant residues was detected under the study conditions. The structures of the two major peaks were identified by MS as the glucuronide and the sulfate conjugates of DCP. The characterization of a dehydrated glucuronide conjugate by MS and NMR of DCP was unusual. In contrast to soluble residues, bound residues were mainly excreted in feces, 90% within 48 h, whereas total residues were eliminated in both urine and feces. For total residues, the radioactivity in feces was higher than expected from the percentage of soluble and bound residues in radish plants. This result highlighted that less absorption took place when residues were present in the plant matrix as compared to plant-free residues and DCP.

Kinetic studies on the adsorption of phenol, 4-chlorophenol, and 2,4-dichlorophenol from water using activated carbons

This study uses rate parameters in pseudo-first-order (PFO) and pseudo-second-order (PSO) equations (k(1) and k(2)q(e), respectively) to judge the extent for approaching equilibrium in an adsorption process. Out of fifty-six systems collected from the literature, the adsorption processes with a k(2)q(e) value between 0.1 and 0.8 min(-1) account for as much as 70% of the total. These are classified as fast processes. This work compares the validity of PFO and PSO equations for the adsorption of phenol, 4-chlorophenol (4-CP), and 2,4-dichlorophenol (2,4-DCP) on activated carbons prepared from pistachio shells at different NaOH/char ratios. The activated carbons, recognized as microporous materials, had a surface area ranging from 939 to 1936 m(2)/g. Findings show that the adsorption of phenol, 4-CP, and 2,4-DCP on activated carbons had a k(2)q(e) value of 0.15-0.58 min(-1), reflecting the fast process. Evaluating the operating time by rate parameters revealed that k(2)q(e) was 1.6-1.8 times larger than k(1). These findings demonstrate the significance of using an appropriate kinetic equation for adsorption process design.

Bioaccumulation, bioavailability and environmental fate of chlorophenol impurities, polychlorinated hydroxydiphenylethers and their methoxy analogues

The bioaccumulation potential and environmental fate of polychlorinated hydroxydiphenyl ethers (HO-PCDEs; polychlorinated phenoxyphenols, PCPP), the major impurities of chlorophenol formulations and their methoxy analogues (MeO-PCDEs; polychlorinated methoxyanisoles, PCPAs) were investigated. Oligochaete worms (Lumbriculus variegatus) exposed to sediment spiked with a model substance of one HO-hexaCDE (4'-HO-PCDE 161) or its methoxy analogue (4'-MeO-PCDE 161) clearly accumulated the test compounds revealing the potential for environmental risk of HO-PCDEs and MeO-PCDEs. The HO-PCDE tested has earlier been reported as an abundant component in a Finnish chlorophenol formulation (Ky-5) and its methoxy analogue is recognized as an abundant MeO-PCDE in sawmill soil contaminated by the formulation. The occurrence of 4'-HO-PCDE 161 and its methoxy analogue among other HO-PCDEs and MeO-PCDEs in lake mussels (Anodonta piscinalis) incubated in a river contaminated via the manufacture of Ky-5 showed that these compounds are bioavailable and transported in the aquatic environment. Mussel comparison with sediment data pointed to a higher accumulation potential for MeO-PCDEs than for HO-PCDEs. The finding of HO-PCDEs in groundwater samples collected from a groundwater reservoir, which had been contaminated by chlorophenols, points to potential of HO-PCDEs for transport with water in soil.

Sequestration of a fluorinated analog of 2,4-dichlorophenol and metabolic products by L. minor as evidenced by 19F NMR

Fate of halogenated phenols in plants was investigated using nuclear magnetic resonance (NMR) to identify and quantify contaminants and their metabolites. Metabolites of 4-chloro-2-fluorophenol (4-Cl-2-FP), as well as the parent compound, were detected in acetonitrile extracts using 19F NMR after various exposure periods. Several fluorinated metabolites with chemical shifts approximately 3.5 ppm from the parent compound were present in plant extracts. Metabolites isolated in extracts were tentatively identified as fluorinated-chlorophenol conjugates through examination of signal-splitting patterns and relative chemical shifts. Signal intensity was used to quantify contaminant and metabolite accumulation within plant tissues. The quantity of 4-Cl-2-F metabolites increased with time and mass balance closures of 90-110% were achieved. In addition, solid phase 19F NMR was used to identify 4-Cl-2-FP which was chemically bound to plant material. This work used 19F NMR for developing a time series description of contaminant accumulation and transformation in aquatic plant systems.

Modelling 2,4-dichlorophenol bioavailability and bioaccumulation by the freshwater fingernail clam Sphaerium corneum using artificial particles and humic acids

The complex and variable composition of natural sediments makes it very difficult to predict the bioavailability and bioaccumulation of sediment-bound contaminants. Several approaches have been proposed to overcome this problem, including an experimental model using artificial particles with or without humic acids as a source of organic matter. For this work, we have applied this experimental model, and also a sample of a natural sediment, to investigate the uptake and bioaccumulation of 2,4-dichlorophenol (2,4-DCP) by Sphaerium corneum. Additionally, the particle-water partition coefficients (K(d)) were calculated. The results showed that the bioaccumulation of 2,4-DCP by clams did not depend solely on the levels of chemical dissolved, but also on the amount sorbed onto the particles and the characteristics and the strength of that binding. This study confirms the value of using artificial particles as a suitable experimental model for assessing the fate of sediment-bound contaminants.

Activity of Desulfitobacterium sp. strain Viet1 demonstrates bioavailability of 2,4-dichlorophenol previously sequestered by the aquatic plant Lemna minor

Aquatic plants take up and sequester organic contaminants such as chlorophenols through incorporation in cell wall materials and storage in vacuoles. The ultimate fate of plant-sequestered chlorophenols, however, remains unclear. This research investigated 2,4-dichlorophenol (2,4-DCP) sequestration by the aquatic plant Lemna minor and evaluated contaminant release and bioavailability after plant death and cellular disruption. 14C-labeled 2,4-DCP was used to establish that contaminant removed from the aqueous phase was retained internal to L. minor. An assay with Desulfitobacterium sp. strain Viet1 was used to assess the readily bioavailable fraction of plant-sequestered 2,4-DCP and plant metabolites of 2,4-DCP. In plant-free systems, strain Viet1 dechlorinated 2,4-DCP to stoichiometric amounts of 4-chlorophenol (4-CP) as a stable and quantifiable end product. Anaerobic microcosms containing inactivated L. minor, which had accumulated 3.8 micromol of 2,4-DCP equivalents/g of plant material (fresh weight) during a preceding aerobic exposure, were inoculated with strain Viet1. After 118 d of incubation with strain Viet1, 43.5% (+/-1.4%) of the contaminant was recovered as 4-CP, indicating a large portion of plant-sequestered 2,4-DCP was bioavailable for dechlorination by strain Viet1. In contrast, 4-CP formation was not observed in autoclaved microcosms, and only 26.1% (+/-1.0%) of plant-sequestered 2,4-DCP was recovered in the aqueous phase. These findings demonstrate contaminant cycling between plants and microorganisms, and emphasize that understanding the mechanisms and pathways of contaminant sequestration by plants is critical for predicting long-term contaminant fate.

Bioconcentration of atrazine and chlorophenols into roots and shoots of rice seedlings

Accumulation of o-chlorophenol (CP), 2,4-dichlorophenol (DCP), and atrazine (ATR), as single and mixed contaminants, from hydroponic solutions into roots and shoots of rice seedlings was studied following 48-h exposure of the plant roots. As single contaminants at low levels, the observed bioconcentration factors (BCFs) of CP and DCP with roots approximated the equilibrium values according to the partition-limited model. The BCF of atrazine with roots was about half the partition limit for unknown reasons. The BCFs of CP and ATR with shoots also approximated the partition limits, while the BCF for more lipophilic DCP with shoots was about half the estimated limit, due to insufficient water transport into plants for DCP. As mixed contaminants at low levels, the BCFs with both roots and shoots were comparable with those for the single contaminants; at high levels, the BCFs generally decreased because of the enhanced mixed-contaminant phytotoxicity, as manifested by the greatly reduced plant transpiration rate.

Bioconcentration factor of relatively low concentrations of chlorophenols in Japanese medaka

Bioconcentration factors (BCF) for pentachlorophenol (PCP) and 2,4-dichlorophenol (2,4-DCP) in Japanese medaka (Oryzias latipes) were determined at five different concentrations of the chemicals, between 0.1 and 10 microg/l (PCP), 0.3 and 30 microg/l (2,4-DCP), in the ambient water. Medaka were exposed to each chemicals in a continuous-flow system during the embryonic development period and 60 days after hatching from eggs collected in the laboratory. Both the exposure time and the aqueous concentrations are much more realistic and closer to natural aquatic environments than those used in conventional BCF studies. The BCF values of PCP were from (4.9+/-2.8)x10(3) at the aqueous concentration of 0.074+/-0.028 microg/l to (2.1+/-1.4)x10(3) at 9.70+/-0.56 microg/l. The BCF value of 2,4-DCP were from (3.4+/-3.0)x10(2) at 0.235+/-0.060 microg/l to 92+/-27 at 27.3+/-1.6 microg/l. Generally, BCF values increased as the aqueous concentrations of PCP or 2,4-DCP decreased. This finding suggests that a relatively low and realistic aqueous concentration of these compounds is necessary to more accurately determine their BCF values in natural aquatic environments. Conventional BCF experiments at higher aqueous concentrations may underestimate the BCF values.

Final report on the safety assessment of 6-Amino-m-Cresol, 6-Amino-o-Cresol, 4-Amino-m-Cresol, 5-Amino-4-Chloro-o-Cresol, 5-Amino-6-Chloro-o-Cresol, and 4-Chloro-2-Aminophenol

Each of these ingredients function as hair colorants. 5-Amino-4-Chloro-o-Cresol and 5-Amino-6-Chloro-o-Cresol are identified as oxidative hair dyes, that is, they are combined with an oxidizing agent before being applied to the hair. 6-Amino-m-Cresol, 6-Amino-o-Cresol, 4-Amino-m-Cresol, and 5-Amino-4-Chloro-o-Cresol are used in oxidative hair dyes, but it is not known if they are also used in nonoxidative (semipermanent) hair dyes. No toxicologically significant impurities are present with these two ingredients. To supplement the safety test data on these ingredients, available data on related ingredients (4-amino-2-hydroxytoluene and p-,m-, and o-aminophenol) previously found safe as used by the Cosmetic Ingredient Review (CIR) Expert Panel were summarized. 5-Amino-4-Chloro-o-Cresol and 5-Amino-6-Chloro-o-Cresol do not absorb significant ultraviolet radiation in the UVB region and none in the UVA region, although 4-Amino-m-Cresol had a symmetrical UV absorption peak at 300 nm. Percutaneous penetration of 5-Amino-4-Chloro-o-Cresol and 5-Amino-6-Chloro-o-Cresol alone was significant, but when combined with oxidative developer, skin absorption was extremely low. Both of these dyes are excreted rapidly via the urine. Repeated exposure of animal skin to 5-Amino-4-Chloro-o-Cresol and 5-Amino-6-Chloro-o-Cresol failed to produce any cumulative irritation and single exposures up to 10%were not irritating to animal skin. 5-Amino-4-Chloro-o-Cresol and 5-Amino-6-Chloro-o-Cresol combined with oxidizer were not sensitizers in guinea pig maximization tests. Ocular irritation resulted from exposure of animals to undiluted 5-Amino-4-Chloro-o-Cresol, but not to a 5%solution. Only minor irritation was observed with 5%5-Amino-6-Chloro-o-Cresol. Subchronic toxicity testing in animals using 5-Amino-4-Chloro-o-Cresol, 5-Amino-6-Chloro-o-Cresol, and 4-Amino-m-Cresol did not yield any adverse reactions. 6-Amino-m-Cresol and 4-Amino-m-Cresol were generally not mutagenic in in vitro and in vivo tests. Exposure to 5-Amino-4-Chloro-o-Cresol, 5-Amino-6-Chloro-o-Cresol, 6-Amino-m-Cresol and 4-Amino-m-Cresol from cosmetics were several orders of magnitude below developmental toxicity no-observed-adverse effect levels (NOAELs). Although irritation data on several ingredients are absent, products containing these ingredients must include a caution statement and patch test instructions for determining whether the product causes skin irritation. The Expert Panel expects that following this procedure would identify individuals who would have an adverse reaction and allow them to avoid significant exposures. These compounds, when tested alone, are moderate skin sensitizers, but when combined with the developer, these ingredients are not sensitizers in animal tests. This information, coupled with the available animal test data, supports the safety of these ingredients in oxidative hair dyes. In the absence of systemic toxicity data, however, the available data are insufficient to support the safety of 6-Amino-o-Cresol and 4-Chloro-2-Aminophenol in semipermanent hair dyes. The types of data required for these two ingredients for this use include (1) physical and chemical properties, including the octanol/water partition coefficient; (2) impurities data, especially regarding the presence of m-cresol, other organic molecules, and heavy metals; (3) data demonstrating that the metabolism is similar to that of 4-amino-2-hydroxytoluene and/or p-,m-, and o-aminophenol, or 28-day dermal toxicity with histopathology, dermal reproductive toxicity data, and an in vitro genotoxicity study for 6-Amino-o-Cresol and one genotoxicity study in a mammalian system; if positive, a 2-year dermal carcinogenicity study using National Toxicology Program methods may be needed.

Kinetics of biotransformation of 2,4-dichlorophenol using UASB-reactor

Chlorophenol compounds are environmental pollutants that are both anthropogenic and xenobiotics. Some of these chemicals are carcinogens and are both toxic to a number biochemical processes. Biotransformation of 2,4-dichlorophenol (2,4-DCP) was studied in the presence of glucose on an upflow anaerobic sludge blanket reactor (UASB) using mixed culture. A continuously operated UASB reactor was employed using mixed synthetic wastewater. Results obtained from the 1.8 L volume capacity UASB reactor were subjected to kinetic evaluation constants. Results indicate that the degradation of 2,4-DCP in the presence of glucose was strongly influenced by the concentration of the compound. High degradation levels were observed when the concentration of 2,4-DCP was in the range of 50-150 mg L(-1). Concentrations of 2,4-DCP above 160 mg L(-1) were toxic to microbes even in the presence of glucose. The maximum degradation of 2,4-DCP was found to be 70.4% when initial concentration of 2,4-DCP was 124 mg L(-1) and glucose concentration of 500 mg L(-1) at hydraulic retention time of 13.2 hr. The biodegradation followed first order reaction kinetics with a rate constant (K) of 0.67, Vmax of 0.244 kg m(-3) day(-1), Ks of 0.117 kg m(-3) day(-1) and correlation coefficient of 0.766.

Partial purification and characterisation of a 2,4,5-trichlorophenol detoxifying O-glucosyltransferase from wheat

An enzyme preparation with UDP-glucose-dependent O-glucosyltransferase (OGT; EC 2.4.1.-) activity toward 2,4,5-trichlorophenol has been purified 215-fold from wheat shoots. The OGT co-purified with the major extractable glucosylating activity toward the flavonol quercetin and was characterised as a monomeric 53 kDa protein. Among the xenobiotic phenols tested, the purified enzyme preparation showed at least a 10-fold preference for 2,4,5-trichlorophenol. When assayed with flavonoids, the OGT was active toward flavonols and coumestrol, showing a clear preference for 3-hydroxy flavone when incubated with a range of monohydroxylated flavonoids. It was concluded that the major 2,4,5-trichlorophenol-detoxifying OGT in wheat shoots is most probably a flavonol-3-O-glucosytransferase.

Toxicokinetics, toxicity and lethal body residues of two chlorophenols in the oligochaete worm, Lumbriculus variegatus, in different sediments

Bioavailability, toxicokinetics and toxicity (LC(50)) of water- and sediment-associated 2,4,5-trichlorophenol (2,4,5-TCP) and pentachlorophenol (PCP) were measured in Lumbriculus variegatus Müller in a set of experiments. The critical body residue approach was applied by measuring also the lethal body residues (LBR(50)). Freshwater and three different sediments with various sediment organic carbon (SOC) concentrations were used as exposure media. SOC decreased the bioavailability of both chlorophenols, and the uptake rates decreased by 81% and 91% for 2,4,5-TCP and PCP, respectively, in the sediment with a SOC of 6.9% compared to those in sediment with a SOC of 0.5%. SOC appeared to be an important factor controlling the bioavailability as after the carbon normalisation the difference between the sediments was much smaller. The 96-h LC(50) values for instance for PCP were 145.3 microg/l in freshwater, and 6.8 and 8.1 microg/g dry weight in sediments with SOC concentrations of 0.5% and 2.4%, respectively. The LBR(50) values, were practically the same in freshwater and sediments: between 1.0 and 1.6 and from 0.4 to 0.9 micromol/g wet weight for 2,4,5-TCP and PCP, respectively, demonstrating the usefulness of this method for accurate, and more comparable, measurement of toxicity of chemicals with the same mode of toxic action in varying conditions. L. variegatus expressed a dose-response sediment avoidance behaviour but the PCP tissue concentrations were not affected by this behaviour.

Phytoremediation of 2,4-dichlorophenol by Brassica napus hairy root cultures

We have obtained hairy root cultures of Brassica napus with high biomass and genetic stability which produce peroxidases, enzymes involved in biodegradation processes. In this work, these hairy root cultures were used to study the removal of 2,4-dichlorophenol (2,4-DCP), a common contaminant in industrial effluents that is highly toxic for human and aquatic life. The optimum conditions to obtain high efficiency in the removal process were established. Roots were able to remove 2,4-DCP from aqueous solutions containing 100-1000 mg/l, in the presence of H(2)O(2) concentrations ranging from 5 to 10 mM. After a short period of incubation (15 min), high removal efficiencies were achieved (91-94%) and maximal removal, of approx. 97-98%, was obtained with 1 h of reaction. High removal efficiencies (93-95%) were observed in a broad pH range (pH 3-9), reaching 98-99% in the range pH 4-8. Moreover, roots could be re-used, almost for six consecutive cycles, to remove 2,4-DCP. The oxidation catalysed by peroxidases would be the main mechanism involved in this process. The results suggest that these cultures could be useful tools for phytoremediation.

Adsorptive removal of 2-chlorophenol by low-cost coir pith carbon

Adsorption of 2-chlorophenol (2-CP) by coir pith carbon was carried out by varying the parameters such as agitation time, 2-CP concentration, adsorbent dose, pH and temperature. Adsorption equilibrium reached at 40, 60, 80 and 100 min for 2-CP concentration of 10, 20, 30 and 40 mg/l, respectively. Adsorption followed second-order kinetics. The adsorption equilibrium data obeyed Freundlich isotherm. Acidic pH was favorable for the adsorption of 2-CP. Desorption studies showed that chemisorption plays a major role in the adsorption process.

Photosynthesis-dependent removal of 2,4-dichlorophenol by Chlorella fusca var. vacuolata

Of 7 green algae, Chlorella fusca var. vacuolata removed about 23% of 2,4-dichlorophenol (DCP) at 10-80 microM after 4 d when grown photoautotrophically. Removal of DCP was growth-dependent and was suppressed dose-dependently by the photosynthesis inhibitor, 3-(3,4-dichlorophenyl)-1,1-dimethyl urea.

4-chlorophenol degradation by chloroperoxidase from Caldariomyces fumago: formation of insoluble products

This study investigated the degradation of 4-chlorophenol (4-CP) by Caldariomyces fumago chloroperoxidase (CPO). Enzymatic oxidations were studied in reaction mixtures at pH 3.0, 4.0, and 6.0 in the presence and absence of Cl- containing 3.5 IU of CPO and 4-CP and hydrogen peroxide concentrations within the range of 0.5-50 and 0.005-50 mM, respectively. Distinct patterns of products regarding color, concentration, and solubility were observed. Reaction mixtures at pH 6.0 containing 3.5 IU of CPO and 5.0 mM 4-CP and H2O2 (1:1 stoichiometry) showed the highest 4-CP removal of 95% and the highest formation of a dark precipitate.

Biodegradation and enzymatic responses in the marine diatom Skeletonema costatum upon exposure to 2,4-dichlorophenol

The biodegradation and responses of selected detoxification and antioxidant enzymes in the marine diatom, Skeletonema costatum, upon exposure to sublethal concentrations of 2,4-dichlorophenol (2,4-DCP) were investigated. Results show that 2,4-DCP was readily metabolised, but bioaccumulation and adsorption were negligible. Glutathione S-transferase, ascorbate peroxidase and superoxide dismutase activities were increased markedly after exposure to 2,4-DCP for 96 h, while no appreciable change in peroxidase activity was observed. The addition of exogeneous glutathione to diatom culture enhanced the degradation of 2,4-DCP, and promoted diatom growth. The inhibition of glutathione synthesis enhanced the toxicity of 2,4-DCP. These results suggest that glutathione conjugation was one of the principal mechanisms involved in the degradation of 2,4-DCP in this diatom.

Lethal body residue of chlorophenols and mixtures of chlorophenols in benthic organisms

The lethal body residue (LBR) of a few chlorophenol congeners were measured in the oligochaete worm Lumbriculus variegatus, and the LBR of pentachlorophenol was measured also in a midge, Chironomus riparius larvae. LBR is defined as the concentration of the compound in the organism, on molar basis, to cause death, and the LBR(50) is defined as the calculated LBR value to cause a 50% mortality in population after a given time. Groups of 30 or 40 organisms were exposed to different chlorophenol concentrations in artificial soft fresh water to achieve differential mortality. Exposure times were either 24 h or 48 h. In addition to exposures with individual congeners, mixtures of chlorophenols were also tested. After each exposure, the surviving organisms were collected and the body burden of chlorophenols was measured by gas chromatography with electron capture detection. The measured body burden was related to the percent mortality in the group. The trichlorophenols and pentachlorophenol have a 48-h LBR(50) of 0.45-0.66 micromol/g wet weight in L. variegatus. The 48-h LBR(50) of pentachlorophenol for C. riparius was 0.15 micromol/g wet weight, indicating a slight difference in the sensitivity of these two species. The 48-h LBR(50) of 2,3,4,6-tetrachlorophenol is 0.91 micromol/g wet weight, and the value for 2,6-dichlorophenol is 1.2 micromol/g wet weight in L. variegatus. The 48-h LBR(50)s of the chlorophenol mixtures ranged from 0.50 to 0.83 micromol/g wet weight, demonstrating an additive toxicity.

Impact of protein binding on the availability and cytotoxic potency of organochlorine pesticides and chlorophenols in vitro

In vitro toxicity data are generally based on nominal concentrations and thus depend on both activity and availability of a compound. The aims of the present study were to examine the influence of protein binding on the cytotoxicity of selected organochlorine pesticides and chlorophenols in Balb/c 3T3 cell cultures and to determine parameters of protein binding which can be used to estimate protein bound fractions and to model distribution in vitro. EC(50)-values derived from concentration-effect relationships determined in the presence of various concentrations of bovine serum albumin (BSA) were linearly correlated to BSA concentration. Increasing the BSA concentration from about 1.2 to 40 mg/ml increased the EC(50)-values by factors between 3.4 and 34.4. Molar ratios of substance bound to albumin ranged from 0.11 to 2.42. Calculated fractions bound to albumin in the normal growth medium were 0.075-0.17 (p,p'-DDT, p,p'-DDE, dieldrin, lindane), 0.09-0.1 (4-mono- and 2,4-dichlorophenol), 0.68 (2,4,5-trichlorphenol) and almost 1.0 (pentachlorophenol). At 40 mg/ml BSA any compound was largely bound to albumin (fractions bound > or = 0.74). Distribution modelling revealed that the availability of the highly hydrophobic organochlorines additionally was significantly reduced by partitioning into lipids. The results clearly demonstrate that nominal and relative toxic potencies of organochlorine pesticides and chlorophenols determined in vitro are substantially influenced by effects of protein binding on availability.

Transformation of 2,4,6-trichlorophenol by free and immobilized fungal laccase

Laccase from the white rot fungus Coriolus versicolor was immobilized on Celite R-637 by covalent binding with glutaraldehyde. After a sharp primary decline in activity (up to 50%), the retained enzyme activity was stable over a storage period of 33 days at 4 degrees C. A comparative study of soluble and immobilized laccases revealed the increased resistance of immobilized enzyme to the unfavourable effects of alkaline pH, high temperature and the action of inhibitors. A combination of these properties of immobilized laccase resulted in the ability to oxidize 2,4,6-trichlorophenol (2,4,6-TCP) at 50 degrees C at pH 7.0. The reactions of soluble and immobilized laccase with 2,4,6-TCP were examined in the presence and absence of redox mediators. 3,5-Dichlorocatechol, 2,6-dichloro-1,4-benzoquinone and 2,6-dichloro-1,4-hydroquinone were found to be the primary products of 2,4,6-TCP oxidation by laccase; oligo- and polymeric compounds were also found.

Environmental fate and bioavailability of wood preservatives in freshwater sediments near an old sawmill site

Impacts of an old contaminated sawmill site located in Eastern Finland were studied, with emphasis on transportation and bioaccumulation of wood preservatives in the surrounding water system. To assess the transportation of chlorophenols and chromated copper arsenate (CCA) from the sawmill to the nearby lake, the concentrations of these compounds in selected sediment samples were analyzed. To assess the contribution of a pulp mill further upstream, the concentration of extractable organic halogens (EOX) was analyzed. Bioaccumulation of wood preservatives from sediments was examined using Lumbriculus variegatus as test organism. In sediments collected from the sawmill area, concentrations of chlorophenols, arsenic, chromium and copper were high. In the surrounding area the concentrations of these compounds were slightly elevated at some sampling points but were mostly within the natural range of variation. Thus, it can be concluded that transportation of wood preservatives from the sawmill area to its surroundings is fairly low. However, 60 microg/l of arsenic and 50 microg/l of copper were found in water taken from a brook that runs through a landfill area of the sawmill to the nearby river, and the concentration of arsenic in the surface sediment at one sampling point in the lake was slightly elevated. The total amount of organohalogens in sediment was higher in the river and the lake than in the sawmill area. Of all the wood preservatives studied, only arsenic was found to bioaccumulate in present conditions, reaching a tissue concentration of 362 microg/g dw in organisms exposed for 28 days to sediment from the brook. High concentration of arsenic in oligochaeta tissue was related to high concentration of arsenic in the pore water.

Toxicity of mono-, di- and tri-chlorophenols to lux marked terrestrial bacteria, Burkholderia species Rasc c2 and Pseudomonas fluorescens

Burkholderia species RASC and Pseudomonas fluorescens were marked with lux genes, encoding for bioluminescence and used to assess the toxicity of mono-, di- and tri-chlorophenols by determining the decline in bioluminescence following exposure to the compounds in aqueous solution. Toxicity was expressed as a 50% effective concentration value (EC50, equating to the concentration of compound which caused a 50% decline in bioluminescence. Comparing the toxicity values of the compounds showed that, in general, increasing the degree of chlorination, increased toxicity. By carrying out forward multiple linear regressions with log10 EC50 values and physio-chemical descriptors, it was shown that molecular parameters describing the hydrogen bonding nature of a chlorophenol provided a better fit than regressions between toxicity data and log10 Kow alone. Utilising these descriptor variables in equations, it was shown that the toxicity of chlorophenols to the lux marked bacteria could be predicted from the compounds physio-chemical characteristics. By correlating lux marked RASC c2 and P. fluorescens EC50 values with toxicity values using Pimephales promelas (fathead minnow), Tetrahymena pyriformis (ciliate) and marine bacterium Vibriofischeri, it was apparent that lux marked RASC c2 correlated well with the freshwater aquatic species (P. promelas and T. pyriformis). This implied that for predictions of toxicity of organic xenobiotic compounds to higher organisms, lux marked RASC c2 could be utilised as a rapid surrogate.

A modeling approach to bioregeneration of granular activated carbon loaded with phenol and 2,4-dichlorophenol

A predictive isotherm model was developed to evaluate the extent of bioregeneration of granular activated carbon loaded with phenol and 2,4-dichlorophenol (2,4-DCP). Two basic substrates (116 mg/L of phenol and 100 g/L 2,4-DCP) as single solute were prepared. The mixture of them was provided to bisolute system for assessing the competitive adsorption. The effect of by-products, which were generated during biodegradation of substrate and measured as COD, on bioregeneration in the bisolute was investigated. Freundlich adsorption parameters (Kads and 1/n) of 2,4-DCP were obviously higher than those of phenol in both single and bisolute. By-products in the bulk solution brought an adverse effect on adsorption capacity of GAC in all cases. By taking into account the by-product effect on adsorption, the Freundlich isotherms were used to formulate a predictive model of bioregeneration. Simulated results showed good consistency of observed results. Practical relevant of the proposed model for assessing of bioregeneration in the wastewater treatment was discussed by applying model to the BAC-SBR in the steady-state operation.

Photochemical oxidation of p-chlorophenol by UV/H2O2 and photo-Fenton process. A comparative study

In this study, photochemical advanced oxidation processes (AOPs) utilizing the combinations of UV/H2O2 and the photo-Fenton reaction (UV + classical Fenton reaction) were investigated in lab-scale experiments for the degradation of p-chlorophenol. The study showed that the photo-Fenton process, (a mixture of hydrogen peroxide and ferrous or ferric ion), was the most effective treatment process under acidic conditions and produced a higher rate of degradation of p-chlorophenol at a very short radiation time. It accelerated the oxidation rate by 5-9 times the rate for the UV/H2O2 process. The reaction was found to follow the first order, the reaction was influenced by the pH, the input concentration of H2O2 and the amount of the iron catalyst and the type of iron salt. The experimental results showed that the optimum conditions were obtained at a pH value of 3, with 0.03 mol/l H2O2, and 1 mmol/l Fe(II) for the UV/H2O2/Fe(II) system and 0.01 mol/l H2O2 and, 0.4 mmol/l Fe(III) for the UV/H2O2/Fe(III) system. The reactions were accompanied by the generation of Cl- which reached its maximum value at a short reaction time when using the photo-Fenton process. Finally a rough comparison of the specific energy consumption shows that photo-Fenton process reduced the energy consumption by at least 73 to 83% compared with the UV/H2O2 process.

Can adsorption isotherms predict sediment bioavailability?

The adsorption and desorption of 2,4-dichlorophenol (DCP) and pentachlorophenol (PCP) were studied for a range of synthetic particles, a dimethylditallowammonium exchanged clay and a natural sediment. The synthetic particles were Dowex 1X8400, Toyopearl Phenyl 650M and Toyopearl SP 650M. The bioaccumulation of the DCP and PCP from these particles was then studied using the oligochaete, Lumbriculus variegatus. There is a correlation between contaminant-particle interactions, as determined from adsorption and desorption isotherms, and bioaccumulation. Bioaccumulation by L. variegatus was found to be highest from the systems where differences in the classification of adsorption and desorption isotherms were observed.

Ozonation of p-chlorophenol in aqueous solution

The ozonation of p-chlorophenol (CHP) in aqueous solution has been studied in the pH range 2.0-8.0, in the presence of tert-butyl alcohol, which prevents the activation of the radical mechanism of oxidation. Results indicate that the pH influences the system reactivity and that only a partial chlorine release is observed for lengthy ozonation too, after the complete substrate disappearance. For adopted experimental conditions the oxidation process develops under a quasi-diffusional regime of absorption with reaction, a transition domain between kinetic and diffusional regimes in which ozone and dissolved substances react exclusively in the liquid film. A proper mathematical model has been developed and used to simulate the system behaviour

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.

Effects of culture parameters on the degradation of 2,4-dichlorophenoxyacetic acid (2,4-D) and 2,4-dichlorophenol (2,4-DCP) by selected fungi. Groupe pour l'Etude du Devenir des Xénobiotiques dans l'Environnement (GEDEXE)

In order to enhance 2,4-D and 2,4-DCP degradation by four selected fungi (Cunninghamella elegans, C. echinulata, Rhizoctonia solani and Verticillium lecanii), three culture parameters (initial chemical concentration, amounts of glucose and nitrogen) were varied. The levels of both xenobiotics in the culture media were monitored by HPLC analysis after five days of cultivation. The best results were obtained at low initial concentration (20 mg.L-1 vs 100) and with low amounts of glucose (5 g.L-1 vs 10) and nitrogen (2.4 mM vs 24). When these two elements were lacking from the culture media, biodegradation was not suppressed, but took place to a lesser extent. Thus, initial chemical concentration and amounts of carbon and nitrogen, in the culture medium, were shown to strongly influence the extent of 2,4-D and 2,4-DCP removal by fungi.

[Study on the existence, distribution and bioaccumulation of chlorophenols in crucian carps]

Four representative chlorophenols (CPs) and their conjugates in fish tissues were determined by gas chromatography with electron capture detector(GC-ECD). Crucian carps were exposed to water contaminated with CPs or not contaminated water separately at room temperature(22 +/- 5 C) for 96 h. If the contaminated water samples are continuously replaced at 24 h interval, the concentration of CPs can be maintained constant throughout the experiment. The presence of fish will not have influence on the concentration of CPs. The experiment results showed that both free and conjugated CPs existed in fish tissues. The total amount of these chlorophenols in fish tissues is bile > liver and kidney > muscle. The proportion of conjugated CPs increases with the number of chlorine atoms in each compound, nevertheless, the proportion of conjugated CPs in PCP is less than that of TCP. Conjugated CPs in bile are composed of glucuronide and sulfate ester conjugates, and glucuronide conjugate is over 93%. The bio-accumulation of CPs in fish tissues is expressed by bio-concentration factors (BCF). The BCF abstained from free CPs and their sulfate ester conjugate in bile has no correlation with the partition coefficient of 1-octanol/water system(Kow). On the other hand, a good correlation is observed between BCF and Kow abstained from glucuronide conjugate and total amount of CPs(r > 0.96). The bioconcentration factors(BCF) of CPs in bile are 2.0 x 10(3)-6.3 x 10(3).

Effect of liquid inhibitors on PCDD/F formation. Prediction of particle-phase PCDD/F concentrations using PLS modelling with gas-phase chlorophenol concentrations as independent variables

Emissions of polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs) from municipal waste incineration are currently a subject of considerable public concern because of their extreme toxicity. PCDD/F formation in incineration processes is being studied widely, but little work has been done on their inhibition. We studied the effect of two liquid inhibitors, sodium ammonium hydrogen phosphate (NAHF) and urea (H2NCONH2), on PCDD/F formation in the combustion of liquid fuel doped with copper and chlorine using a pilot-scale plant. The inhibitors were injected into the flue gas stream at a temperature of 725 degrees C, whereupon both the chlorophenol and PCDD/F concentrations decreased. Particle-phase PCDD/F concentrations in particular decreased by up to 90% with NAHF and 70% with urea, but gas phase reduction took place only with urea. The results suggest that the formation of PCDD/Fs is hindered in the particle phase at the early stages of the PCDD/F formation chain, probably even before precursors such as chlorophenols have been formed. As a consequence, particle-phase PCDD/F concentrations can be predicted by a PLS (partial least-squares) approach with the gas-phase chlorophenol concentrations as independent variables. The structure and partial charges of Cu(+)-urea complex were calculated by the HF/3-21G basis set.

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.

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.

Changes in pH at the dentin surface in roots obturated with calcium hydroxide pastes

The purpose of this study was to determine the pH, after defined periods of time, in cavities prepared in the facial surface of the cervical, middle, and apical regions of roots obturated with calcium hydroxide pastes. Root canal instrumentation was performed on 40 recently extracted, single-rooted human teeth. Cavities 1.5 mm in diameter and 0.75 mm in depth were prepared in the cervical, middle, and apical regions of the facial surface of each root. Teeth were randomly divided into four groups. One group was left unobturated and served as a control. The three remaining groups were obturated with either aqueous calcium hydroxide, calcium hydroxide mixed with camphorated monochlorophenol. or Pulpdent pastes. Access cavities and apical foramina were closed with Cavit. Each tooth was stored individually in a vial containing unbuffered isotonic saline. pH at the surface was measured in the cervical, middle, and apical cavities at 0 and 3, 7, 14, 21, 28, 45, 60, 90, and 120 days. Results indicate that hydroxyl ions derived from calcium hydroxide pastes diffused through root dentin at all regions over the experimental period of 120 days. The pattern of pH change at the tooth surface was similar in all regions of the root, regardless of the type of calcium hydroxide paste used. This was a rapid rise in pH from a control value of pH 7.6, to greater than pH 9.5 by 3 days, followed by a small decline to pH 9.0 over the next 18 days, before finally rising and remaining at, or above pH 10.0 for the remainder of the experimental period. Pulpdent paste in the apical region was the only exception in this pattern, producing a pH rise nearly one full unit below the other pastes, pH 9.3. These results indicate that, for all pastes tested, a high pH is maintained at the root surface for at least 120 days.

[Distribution of chlorophenols in a water environment]

The purpose of this study was to establish the distribution of the selected chlorophenols of point (2,4-DCF, 2,6-DCF, 2,4,5-TCF and 2,3,6-TCF) and nonpoint origin (2,4,6-TCF,2,3,4,6-TeCF and PCF) under conditions simulating the environment of river and distilled water and laboratory water ecosystem. The distribution process developed in accordance with the kinetic equation of 1st order, the average degradation half-time at 20 degrees C amounted: model of river -23, 58-76, 92 days, and model of distilled water-36, 53-47, 25 days. The rate degradation in river and distilled water indicates that the river water microorganisms have no influence on the degradation of determined compounds. When the microflora had been adapted to the presence of chlorophenols the process of degradation was as rule more rapid both investigated temperatures (20 degrees C and 7 degrees C). This process was slowed down by temperature fall to about 7 degrees C. The mixture of chlorophenols at concentration of 10 and 50 micrograms/l when exposed for 20 days to water ecosystem under dynamic conditions, was found to be reduced up 13%. Chlorophenols were not absorbed by Elodea canadensis and Physa fortinalis and weakly by Lebistes reticulatus (cumulation coefficients -0.42-30.27). In the case residual DCP and TCP -weakly (4.71-46.23 micrograms/kg). The investigated concentrations of chlorophenols didn't exert positive effect on the aquatic biocenosis (except Lebistes reticulatus), settled in the ecosystem.

Degradation of trichlorophenols by Alcaligenes eutrophus JMP134

The degradation of chlorophenols by Alcaligenes eutrophus JMP134 (pJP4) was studied. The strain grew on 2,4,6-trichlorophenol or 2,4,6-tribromophenol as the sole carbon and energy source. Complete degradation of 2,4,6-trichlorophenol was confirmed by chloride release and gas chromatography analysis of supernatants from growth cultures. The 2,3,5-, 2,3,4-, 2,3,6- and 2,4,5-isomers of trichlorophenol did not support growth. However, up to 40% of 2,4,5-trichlorophenol was mineralized during growth of A. eutrophus on chemostats fed with either phenol (0.4 mM) or 2,4,6-trichlorophenol (0.4 mM) plus 2,4,5-trichlorophenol (0.1 mM). Growth on 2,4,6-trihalophenols was also observed in A. eutrophus JMP222, the strain lacking pJP4, suggesting that this new degradative ability reported for A. eutrophus is not related to pJP4 encoded catabolic functions.

[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.

Physiological properties and substrate specificity of a pentachlorophenol-degrading Pseudomonas species

A bacterial strain capable of utilizing pentachlorophenol (PCP) as sole source of carbon and energy for growth was isolated from enrichment cultures containing 100 mg/l PCP in a mineral salts medium inoculated with contaminated soil from a lumber treatment waste site. The isolate, designated strain SR3, was identified as a species of Pseudomonas by virtue of its physiological and biochemical characteristics. Mineralization of PCP by Pseudomonas sp. strain SR3 was demonstrated by loss of detectable PCP from growth medium, stoichiometry of chloride release (5 equivalents of chloride per mole of PCP), and formation of biomass consistent with the concentration of PCP mineralized. PCP-induced cells of strain SR3 showed elevated rates of oxygen consumption in the presence of PCP, and with different chlorinated phenols, with complete degradation of 2,3,5,6-, 2,3,6-, 2,4,6-, 2,4-, and 2,6-chloro-substituted phenols. Concentrations of PCP up to 175 mg/liter supported growth of this organism, but maximal rates of PCP removal were observed at a PCP concentration of 100 mg/liter. Based on its degradative properties, Pseudomonas sp. strain SR3 appears to have utility in bioremediation of soil and water contaminated with PCP.

2,4,6-Trichlorophenol (TCP) induces chromosome breakage and aneuploidy in vitro

2,4,6-Trichlorophenol (2,4,6-TCP), a non-mutagen to Salmonella, was reportedly negative in tests for chromosome breakage in vitro, but did produce numerical chromosome changes and micronuclei in V79 cells (Jansson and Jansson, 1992). This apparent specific ability to induce aneuploidy is of interest since aneuploidy testing is not part of routine genotoxicity test procedures. Here we show 2,4,6-TCP clearly induces structural chromosome aberrations in CHO cells and in V79 cells using a 3-h treatment and 20-h sampling time (17-h recovery). The isomers 2,4,5- and 2,3,6-TCP were also clastogenic in this protocol. There was no increase in aberrations when we used the protocol of Jansson and Jansson (1992), i.e., a 24-h treatment with sampling either immediately, or with a 24-h recovery period. However, positive results were obtained when a recovery time of 4-12 h was allowed after the 24-h treatment with 2,4,6-TCP. Previous negative aberration tests of 2,4,6-TCP (Galloway et al., 1987; Ishidate, 1988) are also likely due to inappropriate protocols. All these results were obtained without S9 metabolic activation. We also found positive results in CHO cells when 2,4,6-TCP was tested with S9. The present study demonstrates that 2,4,6-TCP induces both structural and numerical aberrations, and underscores the importance of protocol design, in particular the appropriate recovery time after treatment, for detecting clastogenic activity in vitro.

A placebo controlled double-blind evaluation of the pharmacodynamics of fengabine vs amitriptyline following single and multiple doses in elderly volunteers

1. The effects of fengabine were compared with those of amitriptyline in healthy elderly volunteers. Doses were administered double-blind and assessments were made before and after ingestion. 2. Psychomotor performance and cognitive ability were measured using tests of choice reaction time, tracking, critical flicker fusion threshold, memory scanning and word recognition. Subjective feelings were assessed using the Leeds sleep evaluation questionnaire (LSEQ) and line analogue rating scales (LARS). 3. Pharmacokinetic data suggest that fengabine may induce its own metabolism following repeated dosing. 4. The findings of this study show that fengabine 200 mg and 400 mg does not produce any noticeable behavioural toxicity in elderly volunteers, in contrast to amitriptyline which had a disruptive effect throughout.

Biodegradation kinetics of a mixture containing a primary substrate (phenol) and an inhibitory co-metabolite (4-chlorophenol)

Batch experiments on the simultaneous utilization of phenol (primary substrate) and 4-chlorophenol (cometabolic secondary substrate) demonstrated two critical substrate interactions. First, the cometabolic degradation of 4-chlorophenol was proportional to the rate of phenol oxidation, which provided the electrons for the initial monooxygenase reaction. Second, 4-chlorophenol inhibited the oxidation of the primary substrate, phenol. Modeling analyses of the degradation of phenol alone and of phenol and 4-chlorophenol together showed that the proportionality between phenol and 4-chlorophenol degradation rates averaged 0.1 mg 4-CP/mg phenol, which corresponds to 0.5% of the electrons generated by phenol oxidation being used as a cosubstrate for the monooxygenase reaction of 4-chlorophenol. In addition, modeling analyses suggest that 4-chlorophenol was a noncompetitive inhibitor of phenol oxidation for high phenol concentrations, but a competitive inhibitor for low phenol concentrations.

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.

Internal exposure to organic substances in a municipal waste incinerator

Fifty-three persons occupied in a municipal waste incinerator were examined with respect to their internal exposure to organic substances which may be produced during pyrolysis of organic matter. For this purpose the levels of benzene in blood, polychlorinated biphenyls (PCBs) and hexachlorobenzene (HCB) in plasma, and mono- (MCPs), di- (DCPs), tri- (TCPs), tetra- (TCEPs) and pentachlorophenol (PCP) and hydroxypyrene in urine were determined. For control purposes, 431 men and women were examined. Significantly higher values for the workers were found for the excretion of hydroxypyrene [median (m): 0.24 vs 0.11 microgram/l; non-smokers], 2,4/2,5-DCP (m: 10.5 vs 3.9 micrograms/l) and 2,4,5-TCP (m: 1.2 vs 0.8 micrograms/l) and for the HCB level in plasma (m: 4.4 vs 2.8 micrograms/l). For the concentrations of 4-MCP and 2,3,4,6/2,3,5,6-TECP, the controls had significantly higher concentrations in urine than did the workers in the incineration plant (m: 4-MCP 1.7 vs 1.2; 2,3,4,6/2,3,5,6-TECP: 1.2 vs 0.3 micrograms/l). No significant differences between workers and controls were detected with respect to benzene in blood (m: 0.20 vs 0.28 microgram/l; non-smokers), 2,4,6-TCP and PCPs in urine (m: 0.85 vs 0.60 and 2.2 vs 2.2 micrograms/l) or the levels of PCB congeners in plasma (m: sigma 138, 153, 180: 5.6 vs 4.1 micrograms/l). The elevated levels of hydroxypyrene, 2,4/2,5-DCP, 2,4,5-TCP and HCB in biological material may be related to the incineration of the waste. These elevations, however, are very small and are of interest more from the environmental than from the occupational point of view.

Reductive dechlorination of chlorophenols by a pentachlorophenol- acclimated methanogenic consortium

Anaerobic digester sludge fed 5,300 mg of acetate per liter, 3.4 microM pentachlorophenol, and nutrients for 10 days biotransformed pentachlorophenol by sequential ortho dechlorinations to produce 2,3,4,5-tetrachlorophenol and 3,4,5-trichlorophenol. Upon acclimation to 3.4 microM pentachlorophenol for 6 months, the methanogenic consortium removed chlorines from the ortho, meta, and para positions of pentachlorophenol and its reductive dechlorination products. Pentachlorophenol was degraded to produce 2,3,4,5-tetrachlorophenol, 2,3,4,6-tetrachlorophenol, and 2,3,5,6-tetrachlorophenol. Dechlorination of 2,3,4,5-tetrachlorophenol produced 3,4,5-trichlorophenol, which was subsequently degraded to produce 3,4-dichlorophenol and 3,5-dichlorophenol. 2,3,4,6-Tetrachlorophenol was dechlorinated at the ortho and meta positions to produce 2,4,6-trichlorophenol and 2,4,5-trichlorophenol. 2,3,5,6-Tetrachlorophenol yielded 2,3,5-trichlorophenol, followed by production of 3,5-dichlorophenol. 2,4,6-Trichlorophenol was degraded to form 2,4-dichlorophenol, and 2,4,5-trichlorophenol was dechlorinated at two positions to form 2,4-dichlorophenol and 3,4-dichlorophenol. Of the three dichlorophenols produced (2,4-dichlorophenol, 3,4-dichlorophenol, and 3,5-dichlorophenol), only 2,4-dichlorophenol was degraded significantly within 3 weeks, to produce 4-chlorophenol.

[Amounts of urinary metabolites of p-chloroaniline and their half lives in a patient with acute poisoning]

The aim of this study was to elucidate the time courses of amounts of urinary p-chloroaniline (p-CA) metabolites during acute poisoning and to establish a suitable method for biological monitoring of exposure to p-CA. Urinary p-CA metabolites which were previously identified in a patient with acute p-CA poisoning were determined quantitatively over time during admission of a patient by high-performance liquid chromatography (HPLC) and by the colorimetric method of diazo-positive metabolites (DPM). The data of urinary excretion of each p-CA metabolite were fitted to two-compartment model of pharmacokinetics. Major urinary metabolites of p-CA were conjugated p-CA and conjugated 2-amino-5-chlorophenol (2-A-5-CP), and the detected amounts of 2,4-dichloroaniline (2,4-DCA) and free p-CA were small. During the rapid phase for the disappearance of each metabolite, half lives of p-CA, 2-A-5-CP and 2,4-DCA were 2.4, 1.7 and 1.7 h, respectively, and during the slow phase, they were 4.5, 3.3 and 3.8 h, respectively. Urinary p-CA occupied about 62% of the total metabolites detected in the urine, 2-A-5-CP about 36%, and 2,4-DCA about 1%. 2-A-5-CP and p-CA were detected in the urine of the patient obtained on days 3 and 4, respectively, after the poisoning, but the amount of DPM after the second day of the poisoning was in the range of that of non-exposed persons.(ABSTRACT TRUNCATED AT 250 WORDS)