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PubMed2005

Biodegradation of trace gases in simulated landfill soil cover systems.

The attenuation of methane and seven volatile organic compounds (VOCs) was investigated in a dynamic methane and oxygen counter gradient system simulating a landfill soil cover. The VOCs investigated were: Tetrachloromethane (TeCM), trichloromethane (TCM), dichloromethane (DCM), trichloroethylene (TCE), vinyl chloride (VC), benzene, and toluene. Soil was sampled at Skellingsted landfill, Denmark. The soil columns showed a high capacity for methane oxidation, with oxidation rates up to 184 g/m2/d corresponding to a 77% reduction of inlet methane. Maximal methane oxidation occurred at 15-20 cm depth, in the upper part of the column where there were overlapping gradients of methane and oxygen. All the chlorinated hydrocarbons were degraded in the active soil columns with removal efficiencies higher than 57%. Soil gas concentration profiles indicated that the removal of the fully chlorinated compound TeCM was because of anaerobic degradation, whereas the degradation of lower chlorinated compounds like VC and DCM was located in the upper oxic part of the column. Benzene and toluene were also removed in the active column. This study demonstrates the complexity of landfill soil cover systems and shows that both anaerobic and aerobic bacteria may play an important role in reducing the emission of trace components into the atmosphere.

Air Pollutants↗
PubMed2007

Tn5530 from Burkholderia cepacia strain 2a encodes a chloride channel protein essential for the catabolism of 2,4-dichlorophenoxyacetic acid.

Chloride channel proteins (ClC) are found in living systems where they transport chloride ions across cell membranes. Recently, the structure/function of two prokaryotic ClC has been determined but little is known about the role of these proteins in the microbial metabolism of chlorinated compounds. Here we show that transposon Tn5530 from Burkholderia cepacia strain 2a encodes a ClC protein (BcClC) which is responsible for expelling Cl(-) ions generated during the catabolism of 2,4-dichlorophenoxyacetic acid (a chlorinated herbicide). We found that BcClC has the ability to transport Cl(-) ions across reconstituted proteoliposome membranes. We created two mutants in which the intrachannel glutamate residue of the protein, known to be responsible for opening and closing the channel (i.e. gating), was changed in order to create constitutively open and closed forms. We observed that cells carrying the closed-channel protein accumulated Cl(-) ions intracellularly leading to a decrease in intracellular pH, cell stasis and death. Further, we established that BcClC has the same gating mechanism as that reported for the ClC protein from Salmonella typhimurium. Our results show that the physiological role of ClC is to maintain cellular homeostasis which can be impaired by the catabolism of chlorinated compounds.

2,4-Dichlorophenoxyacetic Acid↗
PubMed2006

Characterization of ceria-zirconia mixed oxides as catalysts for the combustion of volatile organic compounds using inverse gas chromatography.

Inverse gas chromatography (IGC) has been used in this work for characterizing the adsorption of different volatile organic compounds (VOCs) (1,2-dichloroethane (DCE), trichloroethylene (TCE), and n-hexane) over ceria-zirconia mixed oxides (Ce(x)Zr(1-x)O2, with x = 0, 0.15, 0.5, 0.68, 0.8 and 1). These materials have shown to be very active catalysts for the deep oxidation of the studied VOCs in previous papers. The enthalpies of adsorption (-deltaH(ads)), adsorption isotherms (corresponding to the Henry region), and dispersive (gamma(s)(D)) and specific (I(sp)) components of the surface energy for the adsorption of the investigated compounds are determined using IGC at infinite dilution. These chromatographic data and other surface parameters (surface area, oxygen storage capacity, surface acidity, and reducibility) are correlated with the activity and selectivity of these catalysts. As a result, for n-hexane, the catalytic activity is mainly correlated with the adsorption capacity of the solids, whereas the activity for chlorinated compounds oxidation (as well as the selectivity to oxidation products) depends on both oxygen storage capacity and specific interaction of the chlorinated compound with the surface.

Adsorption↗
PubMed2004

Reductive dechlorination of carbon tetrachloride in aqueous solutions containing ferrous and copper ions.

Fe(II) associated with iron-containing minerals has been shown to be a potential reductant in natural subsurface environments. While it is known that the surface-bound iron species has the capacity to dechlorinate various chlorinated compounds, the role of transition metals to act as catalysts with these iron species is of importance. We previously observed that the reduction of Cu(II) by Fe(II) associated with goethite enhanced the dechlorination efficiency of chlorinated compound. In this study, the reductive dechlorination of carbon tetrachloride (CCl4) by dissolved Fe(II) in the presence of Cu(II) ions was investigated to understand the synergistic effect of Fe(II) and Cu(II) on the dechlorination processes in homogeneous aqueous solutions. The dechlorination efficiency of CCl4 by Fe(II) increased with increasing Cu(II) concentrations over the range of 0.2-0.5 mM and then decreased at high Cu(II) concentrations. The efficiency and rate of CCl4 dechlorination also increased with increasing dissolved Fe(II) concentration in the presence of 0.5 mM Cu(II) at neutral pH. When the Fe(II)/Cu(II) ratio varied between 1 and 10, the pseudo-first-order rate constant (k(obs)) increased 250-fold from 0.007 h(-1) at 0.5 mM Fe(II) to 1.754 h(-1) at 5 mM Fe(II). X-ray powder diffraction and scanning electron microscopy analyses showed that Cu(II) can react with Fe(II) to produce different morphologies of ferric oxides and subsequently accelerate the dechlorination rate of CCl4 at a high Fe(II) concentration. Amorphous ferrihydrite was observed when the stoichiometric Fe(II)/Cu(II) ratio was 1, while green rust, goethite, and magnetite were formed when the molar ratios of Fe(II)/Cu(II) reached 4-6. In addition, the dechlorination of CCl4 by dissolved Fe(II) is pH dependent. CCl4 can be dechlorinated by Fe(II) over a wide range of pH values in the Cu(II)-amended solutions, and the k(obs) increased from 0.0057 h(-1) at pH 4.3 to 0.856 h(-1) at pH 8.5, which was 9-25 times greater than that in the absence of Cu(II) at pH 7-8.5. The high reactivity of dissolved Fe(II) on the dechlorination of CCl4 in the presence of Cu(II) under anoxic conditions may enhance our understanding of the role of Fe(II) and the long-term reactivity of the zerovalent iron system in the dechlorination processes for chlorinated organic contaminants.

Carbon Tetrachloride↗
PubMed1991

Residue levels of chlorinated hydrocarbon compounds in water and sediment samples from Nile branches in the Delta, Egypt.

Water and sediment samples were collected from eight different locations along the River Nile and its branches. Residues of hexachlorocyclohexane (HCH's), hexachlorobenzene (HCB), DDT's, cyclodienes and polychlorinated biphenyls (PCB's) were analyzed by GLC. Data on Grand Total (GT) concentration values pointed out that Rosetta Branch was more polluted with all components than Demietta Branch. Kafr El-Ziate was the most polluted location showing 1355.8 ng/L for water and 7396.9 ng/g for sediments, while Delta Barrage was the least polluted site. The concentrations of gamma-HCH were higher than the other isomers (alpha- and beta-HCH) in all studied sites. The results showed that HCB was the smallest pollutant at all locations on comparison with other chlorinated hydrocarbons. El-Mansoura, Rosetta and Kafr El-Ziate sites contained the highest concentrations of DDT's in both water and sediment samples. P,P'-DDE was dominate in all locations of water samples, but P,P'-DDT was in sediment samples. Also, the results showed the prominent presence of cyclodienes when compared with the other OC's compounds in sediment samples, especially Aldrin. Kafr El-Ziate was the most polluted location by PCB's, particularly the Ar1242. However, there were increasing levels of chlorinated hydrocarbons in the sediment samples parallel to percentage extractable organic matter (% EOM). Sediment/water ratios were calculated for all locations.

DDT↗
PubMed1991

In vivo and in vitro toxicity of fractionated fish lipids, with particular regard to their content of chlorinated organic compounds.

Six different lipid matrices (the intact lipid (IL), four lipid fractions with different polarity, and the free fatty acids (FFAs) obtained by hydrolysis of the triacylglycerol (TAG) containing fraction) were obtained from salmon (Salmo salar) and eel (Anguilla anguilla), each collected at a contaminated and a comparatively uncontaminated catch site along the coast of Scandinavia. The lipid matrices were studied in toxicological test systems representing various biological functions of different organ systems from several species and trophic levels. The results were evaluated with particular respect to the concentrations of extractable organically bound chlorine (EOC1) in the matrices tested. In some test systems, the specimens with a higher EOC1 concentration appeared to be more toxic. For example, the TAG containing fraction (F2) from Idefjord eel, having a higher EOC1 content than F2 from Oslofjord eel, reduced the number and hatchability of eggs laid by zebrafish. Both IL and F2 of Idefjord eel increased mortality and reduced the oxygen/nitrogen-ratio in blue mussels. Non-polar compounds (F1) from Bothnian Sea salmon induced 7-ethoxyresurofin O-deethylase (EROD) activity in rainbow trout hepatocytes, whereas F1 from Senja salmon did not. F1 from Bothnian Sea salmon also reduced the number of T-cells in foetal mouse thymus analagen in vitro compared with the cell number in anlagen exposed to F1 from Senja salmon. A positive correlation between EOC1 concentration and test response was found for EROD activity in rainbow trout hepatocytes and for ATP-leakage in Erlich ascites tumour cells when testing the phospolipid containing fraction (F4). However, in most test systems the fish oils, irrespective of EOC1 content, were of low toxicity, and the observed effects need to be verified in future studies.

Animals↗
PubMed1993

Contamination of human ovarian follicular fluid and serum by chlorinated organic compounds in three Canadian cities.

OBJECTIVES: To determine the extent of contamination of ovarian follicular fluid and serum samples in women undergoing in-vitro fertilization and to study the effect of the contaminants on reproductive outcome. DESIGN: Inception cohort study. PATIENTS: Seventy-four women undergoing in-vitro fertilization at three regional clinics in Halifax, Hamilton, Ont., and Vancouver. MAIN OUTCOME MEASURES: Follicular fluid and serum levels of contaminants, cleavage rates and time to cleavage of first egg. RESULTS: Five chlorinated organic chemicals were frequently found in the two types of samples: alpha-chlordane (ALCH), dichlorochlorophenylethylene (DDE), heptachloroepoxide-oxychlordane (OXCH), hexachlorobenzene (HCB) and polychlorinated biphenyl (PCB). The levels were generally low. Regional differences between the three clinics were present. Samples from the Halifax clinic had the lowest frequency and level of contamination. The source of drinking water (well, bottled or municipal) was an important confounder. The concentrations of the five contaminants did not affect the cleavage rate or the time to cleavage of the first egg. CONCLUSION: Trace amounts of toxic and persistent chlorinated organic chemicals found in the follicular fluid of Canadian women undergoing in-vitro fertilization did not seem to have any adverse biologic effect on the rate of fertilization and the time to cleavage. Reasons for regional differences in the concentrations of contaminants require further study.

British Columbia↗
PubMed1996

Biodegradation of chlorinated phenolic compounds.

Chlorophenolic compounds are generated from a number of industrial manufacturing processes including pulp and paper manufacture. These compounds are found to be toxic and recalcitrant and hence their discharge into the environment must be regulated. Slow and partial degradation of chlorophenols under aerobic and anaerobic natural environment has been observed. Aerobic biodegradation of chlorophenols proceeds through the formation of catechols while under anaerobic conditions, reductive dehalogenation is the preferred metabolic pathway. Number and position of chlorine substituents on the phenolic ring has influence on the rate and extent of biodegradation of chlorophenols. In engineered systems, acclimatization of biomass to chlorophenols markedly enhances the biodegradation ability by reducing the initial lag phase and by countering inhibition. Partial removal of chlorophenols between 40-60% is usually observed in aerobic and anaerobic processes. Removal can be enhanced by a combination of aerobic and anaerobic operations.

Journal Article↗
PubMed2004

Characterization of Co, Fe and Mn-exchanged zeolites by inverse gas chromatography.

The adsorption of several alkanes, cyclic hydrocarbons, aromatic hydrocarbons and chlorinated compounds on NaX, CaA, and exchanged Co, Mn and Fe zeolites as adsorbents was investigated. Zeolite composition and structure was determined by ICP-mass spectroscopy, XRD, and nitrogen adsorption. Adsorption parameters (enthalpy of adsorption and free energy of adsorption) as well as dispersive surface energy interaction and specific interaction parameters were determined for each solute-adsorbent system by inverse gas chromatography (IGC). The original zeolites NaX and CaA show the higher values of enthalpy of adsorption but specific interactions depend on the metal exchanged. Zeolites Mn-NaX and Co-NaX exhibit the strongest interactions with benzene, whereas zeolite Co-CaA shows the strongest interactions with chlorinated compounds. The trivalent cation (Fe3+) does not affect the either the adsorption efficiency or specific interaction.

Adsorption↗
PubMed2004

Dehalogenation of chlorinated aromatic compounds using a hybrid bioinorganic catalyst on cells of Desulfovibrio desulfuricans.

A novel bioinorganic catalyst was obtained via reduction of Pd(II) to Pd0 on to the surface of cells of Desulfovibrio desulfuricans at the expense of H2. Palladised biomass, supplied with formate or H2 as an electron donor, catalysed the dehalogenation of 2-chlorophenol and polychlorinated biphenyls. In the example of 2,3,4,5-tetrachlorobiphenyl, the bioinorganic catalyst promoted a rate of chloride release of 9.33 +/- 0.17 nmol min(-1) mg (-1) and only approximately 5% of this value was obtained using chemically reduced or commercially available Pd0. In the case of 2,2',4,4',6,6'-hexachlorobiphenyl the rate was more than four orders of magnitude faster than the degradation reported using a sulfidogenic culture. Negligible chloride release occurred from any of the chloroaromatic compounds using biomass alone, or from palladised biomass challenged with hexane carrier solvent only. Analysis of the spent solution showed that in addition to catalysis of reductive dehalogenation the new material was able to remove very effectively the organic residua, with neither any PCB nor any breakdown products identifiable by GC/MS.

Biodegradation, Environmental↗
PubMed2000

ATR-FTIR sensor development for continuous on-line monitoring of chlorinated aliphatic hydrocarbons in a fixed-bed bioreactor.

This article describes the continuous on-line monitoring of a dechlorination process by a novel attenuated total reflection-Fourier transform infrared (ATR-FTIR) sensor. This optical sensor was developed to measure noninvasively part-per-million (ppm) concentrations of trichloroethylene (TCE), tetrachloroethylene (PCE), and carbon tetrachloride (CT) in the aqueous effluent of a fixed-bed dechlorinating bioreactor, without any prior sample preparation. The sensor was based on an ATR internal reflection element (IRE) coated with an extracting hydrophobic polymer, which prevented water molecules from interacting with the infrared (IR) radiation. The selective diffusion of chlorinated compound molecules from aqueous solution into the polymer made possible their detection by the IR beam. With the exclusion of water the detection limits were lowered, and measurements in the low ppm level became possible. The best extracting polymer was polyisobutylene (PIB) in the form of a 5.8-microm thick film, which afforded a detection limit of 2, 3, and 2. 5 mg/L (ppm) for TCE, PCE, and CT, respectively. Values of the enrichment factors between the polymer coating and the water matrix of these chloro-organics were determined experimentally and were compared individually with predictions obtained from the slopes of absorbance/concentration curves for the three analytes. Before coupling the ATR-FTIR sensor to the dechlorinating bioreactor, preliminary spectra of the chlorinated compounds were acquired on a laboratory scale configuration in stop-flow and flow-through closed-loop modes. In this way, it was possible to study the behavior and direct response of the optical sensor to any arbitrary concentration change of the analytes. Subsequently, the bioreactor was monitored with the infrared sensor coupled permanently to it. The sensor tracked the progression of the analytes' spectra over time without perturbing the dechlorinating process. To calibrate the ATR-FTIR sensor, a total of 13 standard mixtures of TCE, PCE and CT at concentrations ranging from 0 to 60 ppm were selected according to a closed symmetrical experimental design derived from a 3(2) full-factorial design. The above range of concentrations chosen for calibration reflected typical values during normal bioreactor operation. Several partial least squares (PLS) calibration models were generated to resolve overlapping absorption bands. The standard error of prediction (SEP) ranged between 0.6 and 1 ppm, with a relative standard error of prediction (RSEP) between 3 and 6% for the three analytes. The accuracy of this ATR-FTIR sensor was checked against gas chromatography (GC) measurements of the chlorocompounds in the bioreactor effluents. The results demonstrate the efficiency of this new sensor for routine continuous on-line monitoring of the dechlorinating bioreactor. This strategy is promising for bioprocess control and optimization.

Biodegradation, Environmental↗
PubMed1997

Concentrations of chlorinated organic compounds in biota and bed sediment in streams of the San Joaquin Valley, California.

Samples of resident biota and bed sediments were collected in 1992 from 18 sites on or near the floor of the San Joaquin Valley, California, for analysis of 33 organochlorine compounds. The sites were divided into five groups on the basis of physiographic region and land use. Ten compounds were detected in tissue, and 15 compounds were detected in bed sediment. The most frequently detected compound in both media was p,p'-DDE. Concentrations of SigmaDDT (sum of o,p'- and p, p' forms of DDD, DDE, and DDT) were statistically different among groups of sites for both tissue and sediment (Kruskal-Wallis, p < 0.05). Concentrations in both media were highest in streams draining the west side of the valley. Concentrations of SigmaDDT in tissue were significantly correlated with specific conductance, pH, and total alkalinity (p < 0.05), which are indicators of the proportion of irrigation return flows in stream discharge. Concentrations in sediment on a dry-weight basis were not correlated with these water-quality parameters, but total organic carbon (TOC) normalized concentrations were significantly correlated with specific conductance and pH (p < 0.05). Regressions of the concentration of SigmaDDT in tissue, as a function of SigmaDDT in bed sediment, were significant and explained up to 76% of the variance in the data. The concentration of SigmaDDT in sediment may be related to mechanisms of soil transport to surface water with bioavailability of compounds related to the concentration of TOC in sediment. The results of this study did not indicate any clear advantage to using either bed sediment or tissues in studies of organochlorine chemicals in the environment. Some guidelines for protection of fish and wildlife were exceeded. Concentrations of organochlorine chemicals in biota, and perhaps sediment, have declined from concentrations measured in the 1970s and 1980s, but remain high compared to other regions of the United States.

Animals↗
PubMed2005

[Evaluation of occupational risk factors and laboratory workers' health in biochemical and clinical laboratories of hospitals of Kaunas city].

UNLABELLED: Impact of occupational risk factors on the health of hospital laboratories workers is not entirely assessed in Lithuania. Objectives of the study were to evaluate the main health disorders of laboratory workers and to define the relationship between the health complaints and working conditions in biochemical and clinical laboratories. MATERIAL AND METHODS: A cross-sectional epidemiological study was conducted in 2002. The questionnaire with questions on the most frequent health disorders and main occupational hazards, lifestyle factors, etc., was distributed among workers of biochemical and clinical laboratories in 6 hospitals of Kaunas city. Odds ratios with significance level p< or =0.05 were calculated. RESULTS: 112 laboratory workers completed the questionnaire. Laboratory assistants were exposed to higher number of workplace hazards rather than other workers. All health complaints were also more prevalent among laboratory assistants. Weakness, sleepiness at work, headache and sleep disturbances were the most prominent complaints among them to compare with other occupations. Skin irritation due to chemicals (chlorine compounds and hydrogen peroxide mainly) was more frequent among laboratory assistants as well. The most frequent localization of irritation was in hands. Complaints due to eyestrain were found in almost one third of responders. Neck pain, back pain, waist pain and joint pain due to long lasting fixed position was rather frequent among laboratory workers. Inconvenient work posture increased risk for waist pain (OR=1.65; p>0.05), neck pain (OR=2.32; p>0.05) and sleep disorders (OR=4.32; p<0.05). There was no significant relationship between health disorders and work experience. Mental stress is common in job of laboratory workers. CONCLUSIONS: More than one third of workers work in inconvenient posture, most of them spent in this position more than a half of work time. Inconvenient work position significantly increases risk for hand numbness sleep disorders and joint pain. Skin irritation and rash, especially in hands, caused by chlorine compounds, soap and water is quite common among laboratory workers, mainly assistants. Mental stress is common in job of laboratory workers. No statistically significant relationship between health complains and work duration was found.

Adult↗
PubMed2003

Sulphate-reducing bacteria, palladium and the reductive dehalogenation of chlorinated aromatic compounds.

The surfaces of cells of Desulfovibrio desulfuricans, Desulfovibrio vulgaris and a new strain, Desulfovibrio sp. 'Oz-7' were used to manufacture a novel bioinorganic catalyst via the reduction of Pd(II) to Pd(0) at the cell surface using hydrogen as the electron donor. The ability of the palladium coated (palladised) cells to reductively dehalogenate chlorophenol and polychlorinated biphenyl species was demonstrated. Dried, palladised cells of D. desulfuricans, D. vulgaris and Desulfovibrio sp. 'Oz-7' were more effective bioinorganic catalysts than Pd(II) reduced chemically under H2 or commercially available finely divided Pd(0). Differences were observed in the catalytic activity of the preparations when compared with each other. Negligible chloride release occurred from chlorophenol and polychlorinated biphenyls using biomass alone.

Bacteria↗
PubMed1984

Permeation of chlorinated aromatic compounds through Viton and nitrile glove materials.

The ASTM cell was utilized to study permeation of chloro-, o-dichloro-, and m-dichloro-benzenes and o- and p-chlorotoluenes through Viton (unsupported) and nitrile (supported and unsupported) glove materials using isopropanol as collecting solvent, and FID/gas chromatography for quantitation. Adequate mixing in the collection chamber was accomplished by externally agitating the ASTM cell at the required speed in a moving-tray water bath at 25 degrees C. The Viton glove did not show permeation even after 4 hours. The nitrile gloves showed breakthrough times of less than 1 hour. The steady state molar flux rates for unsupported or supported nitrile gloves, or for the different challenge solvents were not statistically different. Thus, breakthrough times were better indicators of permeation than steady state molar flux rates. A "mixed" permeation mechanism was proposed, depending on swelling of the glove material.

Chlorobenzenes↗
PubMed2003

Cometabolic degradation of chlorinated aromatic compounds.

The degradation of chlorobenzene was investigated with the specially chosen strain Methylocystis sp. GB 14 DSM 12955, using 23 ml headspace vials and in a soil column filled with quaternary aquifer material from a depth of 20 m. A long-term experiment was carried out in this column, situated in a mobile test unit at a contaminated location in Bitterfeld (Germany). Groundwater polluted by chlorobenzene was continuously fed through the column, through which a mixture comprising 4% CH(4) and 96% air was bubbled. Chlorobenzene was oxidized by up to 80% under pure culture conditions in the model experiments and was completely degraded under the mixed culture conditions of the column experiments. Over a period of 4 months, the stability of the biological system was monitored regularly by analyzing the sMMO activity as well as by classical microbiological and molecular biological methods.

Biodegradation, Environmental↗
PubMed2003

Tolerability and efficacy of N-chlorotaurine in comparison with chloramine T for the treatment of chronic leg ulcers with a purulent coating: a randomized phase II study.

BACKGROUND: The well-known active chlorine compound chloramine T (CAT) with broad-spectrum antimicrobial activity is in common therapeutic use for leg ulcers with purulent coatings; however, this treatment is painful. The tolerability of the less aggressive N-chlorotaurine (NCT), an endogenous compound also produced in vivo by stimulated human granulocytes, could be superior. OBJECTIVES: To assess the tolerability and efficacy of NCT in the cleaning of purulent coatings in chronic leg ulcers in comparison with CAT. METHODS: In a double-blind, randomized phase IIb clinical study 40 patients were treated for a median of 7 days (range 3-14) with a 1% aqueous solution of either NCT (20 subjects) or CAT (20 subjects) by twice-daily application of dressings soaked in the test solutions. Criteria for evaluation of tolerability were intensity and duration of pain caused by the ulcer therapy and scores of tissue toxicity (necrosis, granulation tissue and re-epithelialization). Therapeutic efficacy was graded as scores of intensity of purulent coating of the ulcers. RESULTS: The concentration tolerated in vitro by human epidermoid carcinoma cells was at least 10-fold higher for NCT (0.01%) compared with CAT (0.0001-0.001%). There was significantly less pain caused by NCT compared with CAT (P < 0.05) on days 1 and 4 and a trend for a shorter duration of pain (P = 0.093). The scores of intensity of coating improved without difference in both treatment groups, whereas granulation and re-epithelialization appeared earlier in the NCT group (P < 0.05). Non-quantitative microbiological cultures from ulcer smears revealed persistence of colonization by bacterial species in approximately half of both treatment groups. CONCLUSIONS: Both active chlorine compounds were helpful in reducing purulent coatings. Because of its lower toxicity and better tolerability, NCT is of advantage in the treatment of leg ulcers.

Administration, Topical↗