Concentration-time Values Research Articles

Modifications to sorption and sinking capability of microplastics after chlorination

Abstract Chlorination disinfection in water treatments may be highly destructive to microplastics (MPs). Herein, low- and high-dose (concentration–time values at 75 and 9,600 mg min L−1, respectively) chlorination processes were used to simulate short-term chlorination in drinking water treatment plants and long-term residual chlorine reaction in drinking water supply systems, respectively. Both chlorination processes induced modifications to polyethylene (PE), polyethylene terephthalate (PET), polystyrene (PS), and polyvinyl chloride (PVC) MPs, varying in polymer types and sizes. Oxidized and chlorinated bonds were detected, and destructed surfaces with increased specific surface area and reduced hydrophobicity were observed. As a result, the sorption capacity of all MPs was weakened, e.g., low-dose chlorination (pH 7) depressed the sorption of ciprofloxacin by 6.5 μm PE (Kf from 0.140 to 0.128 L g−1). The sinking behavior of PET, PS, and PVC MPs was enhanced, e.g., the sinking ratio of 200 μm PET increased by ∼30% after low-dose chlorination (pH 7). By contrast, PE tended to float after high-dose chlorination. Furthermore, chlorination of MPs generated various products, which were the degraded fragments from the MP skeleton. In general, chlorination disinfection reduces the potential of MPs as transport vectors of organic contaminants.

Comparison between the penetration characteristics of methyl bromide and ethanedinitrile through the bark of pine (Pinus radiata D.Don) logs.

Ethanedinitrile (EDN) is a fumigant being commercialized worldwide as an alternative phytosanitary treatment to methyl bromide (MB) for forest products. The penetration characteristics of MB and EDN were measured through the bark of wooden blocks (100 × 100 × 50 mm) cut from the upper (average bark thickness 5 ± 2 mm) and lower (average bark thickness 25 ± 5 mm) trunk of recently felled pine (Pinus radiata D.Don) trees. Doses of 48 g m-3 MB and 50 g m-3 EDN were applied to chambers at 10 and 20°C for 10h. Penetration of MB was influenced by the interaction between fumigation time and temperature, with concentrations increasing at a higher rate at 20°C compared with at 10°C. After 10h, an average concentration of 8.05 ± 0.89 g m-3 had penetrated the bark of log sections at 20°C, whereas 5.20 ± 0.89 g m-3 was measured at 10°C. By contrast, the factors examined in this study did not significantly impact the penetration of EDN. Concentration × time (CT) values for MB under the bark were 35.20 ± 2.30 g h m-3 at 10°C and 55.85 ± 9.58 g h m-3 at 20°C; whereas for EDN, CT values were 19.50 ± 6.80 g h m-3 at 10°C and 19.08 ± 4.10g h m-3 at 20°C. MB can achieve a higher concentration under the bark of log sections during simulated fumigations, but all of the factors examined affected the ability of MB to penetrate the bark of wooden blocks. By comparison, the penetration of EDN through the bark is more consistent than MB under laboratory conditions. © 2022 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

A systematic review on chlorine tolerance among bacteria and standardization of their assessment protocol in wastewater.

Though chlorine is a cost-effective disinfectant for water and wastewaters, the bacteria surviving after chlorination pose serious public health and environmental problems. This review critically assesses the mechanism of chlorine disinfection as described by various researchers; factors affecting chlorination efficacy; and the re-growth potential of microbial contaminations in treated wastewater post chlorination to arrive at meaningful doses for ensuring health safety. Literature analysis shows procedural inconsistencies in the assessment of chlorine tolerant bacteria, making it extremely difficult to compare the tolerance characteristics of different reported tolerant bacteria. A comparison of logarithmic reduction after chlorination and the concentration-time values for prominent pathogens led to the generation of a standard protocol for the assessment of chlorine tolerance. The factors that need to be critically monitored include applied chlorine doses, contact time, determination of chlorine demands of the medium, and the consideration of bacterial counts immediately after chlorination and in post chlorinated samples (regrowth). The protocol devised here appropriately assesses the chlorine-tolerant bacteria and urges the scientific community to report the regrowth characteristics as well. This would increase the confidence in data interpretation that can provide a better understanding of chlorine tolerance in bacteria and aid in formulating strategies for effective chlorination.

Concentration time values in two-arm snatch weightlifting, 109-kg junior class (under 20)

Elite sport is a social phenomenon strongly anchored in the reality of today’s world. In an increasingly advanced technological society, no one is surprised by the use of the fastest means of multimedia communication. Implementing this technology in the field of top-level sport offers multiple possibilities for an objective behavioural analysis of athletes during competition. This study, the first to address juniors aged 17-20 years, is part of a broader research aimed at investigating athletes (of both genders and different classes) with regard to certain moments that involve the analysis of concentration times characterising weightlifting styles. The current study focuses on the recording and analysis of concentration times from the moment the feet are just under the bar until the bar is lifted off. Objectives: 1. To examine the possibilities of using the computerised imaging technique in snatch weightlifting; 2. To identify concentration times in snatch weightlifting by recordings and measurements performed with AviSynth equipment. The main research method used is computerised technology connected to video technology. The research presents the recording and analysis of concentration times for snatch weightlifters in value group A, 109-kg Junior Class. It includes 11 male athletes aged 17-20 from various countries. Thus, Bulgaria participated with two athletes, and Albania, Armenia, Azerbaijan, Belarus, Georgia, Poland, Russia, Spain and Turkey, with one athlete each. The result analysis highlights aspects regarding concentration times in the snatch event: average concentration times for the three attempts and for each attempt, the relationship between lifted weight and concentration time.

Reduction of Human Norovirus GI, GII, and Surrogates by Peracetic Acid and Monochloramine in Municipal Secondary Wastewater Effluent.

The objective of this study was to characterize human norovirus (hNoV) GI and GII reductions during disinfection by peracetic acid (PAA) and monochloramine in secondary wastewater (WW) and phosphate buffer (PB) as assessed by reverse transcription-qPCR (RT-qPCR). Infectivity and RT-qPCR reductions are also presented for surrogate viruses murine norovirus (MNV) and bacteriophage MS2 under identical experimental conditions to aid in interpretation of hNoV molecular data. In WW, RT-qPCR reductions were less than 0.5 log10 for all viruses at concentration-time (CT) values up to 450 mg-min/L except for hNoV GI, where 1 log10 reduction was observed at CT values of less than 50 mg-min/L for monochloramine and 200 mg-min/L for PAA. In PB, hNoV GI and MNV exhibited comparable resistance to PAA and monochloramine with CT values for 2 log10 RT-qPCR reduction between 300 and 360 mg-min/L. Less than 1 log10 reduction was observed for MS2 and hNoV GII in PB at CT values for both disinfectants up to 450 mg-min/L. Our results indicate that hNoVs exhibit genogroup dependent resistance and that disinfection practices targeting hNoV GII will result in equivalent or greater reductions for hNoV GI. These data provide valuable comparisons between hNoV and surrogate molecular signals that can begin the process of informing regulators and engineers on WW treatment plant design and operational practices necessary to inactivate hNoVs.

Comparative Inactivation of Murine Norovirus and MS2 Bacteriophage by Peracetic Acid and Monochloramine in Municipal Secondary Wastewater Effluent.

Chlorination has long been used for disinfection of municipal wastewater (MWW) effluent while the use peracetic acid (PAA) has been proposed more recently in the United States. Previous work has demonstrated the bactericidal effectiveness of PAA and monochloramine in wastewater, but limited information is available for viruses, especially ones of mammalian origin (e.g., norovirus). Therefore, a comparative assessment was performed of the virucidal efficacy of PAA and monochloramine against murine norovirus (MNV) and MS2 bacteriophage in secondary effluent MWW and phosphate buffer (PB). A suite of inactivation kinetic models was fit to the viral inactivation data. Predicted concentration-time (CT) values for 1-log10 MS2 reduction by PAA and monochloramine in MWW were 1254 and 1228 mg-min/L, respectively. The 1-, 2-, and 3-log10 model predicted CT values for MNV viral reduction in MWW were 32, 47, and 69 mg-min/L for PAA and 6, 13, and 28 mg-min/L for monochloramine, respectively. Wastewater treatment plant disinfection practices informed by MS2 inactivation data will likely be protective for public health but may overestimate CT values for reduction of MNV. Additionally, equivalent CT values in PB resulted in greater viral reduction which indicate that viral inactivation data in laboratory grade water may not be generalizable to MWW applications.

Efficient removal of fluoride from water using a paramagnetic adsorbent: FeAlOxHy combined with superconducting magnetic separation

ABSTRACTThe present study investigated fluoride removal by high-gradient superconducting magnetic separation (HGSMS) and paramagnetic adsorbents. FeAlOxHy adsorbents with different Fe/Al molar ratios were synthesized and characterized. The adsorption capacities of FeAlOxHy increased with increasing Al content. The FeAlOxHy were effectively separated in HGSMS, and approximately 87% of the fluoride was removed. Higher magnetic intensity, lower flow rate and finer steel wool are among the advantages of FeAlOxHy separated in HGSMS. The maximum desorption efficiency of fluoride adsorbed by FeAlOxHy was measured as 92.06%. A fluoride concentration time value of 40 was obtained using FeAlOxHy followed by the HGSMS process.

Effects of biochar on the emissions, soil distribution, and nematode control of 1,3-dichloropropene

ABSTRACTEmissions of volatile soil fumigant 1,3-dichloropropene (1,3-D) from soil to air are a significant concern in relation to air quality, and cost-effective strategies to reduce such emissions are urgently required by growers to help them comply with increasingly stringent regulations. In this work, application of a rice husk-derived biochar to the surface of a sandy loam soil chamber reduced soil–air emissions of 1,3-D from 42% in a control (no biochar) to 8% due to adsorption onto the biochar. This adsorbed 1,3-D showed a potential for re-volatilization into air and solubilization into the soil–liquid phase. Biochar at the soil surface also reduced soil–gas concentrations in the upper soil; based on the determination of concentration–time values, this may limit 1,3-D-induced nematode control in the upper soil. In batch studies, the mixing of biochar into the soil severely limited nematode control; 1,3-D application rates around four times greater than the maximum permissible limit would be required to give nematode control under such conditions. Therefore, the use of biochar as a surface amendment, while showing an emission reduction benefit, may limit pest control during subsequent fumigations if, as seems probable, it is plowed into the soil.

Application of ozone gas for decontamination of nucleoside anticancer drugs.

BackgroundExposure to anticancer drugs is hazardous and may lead to chromosomal abnormalities and spontaneous abortion in healthcare workers. Guidelines recommend surface decontamination and cleaning in order to minimize the occupational exposure to anticancer drugs, although no single process has been found to deactivate all currently available hazardous drugs. Ozone gas is oxidative and a decontaminant for bacteria; its characteristic as a gas has advantages in that it does not need to be wiped off or neutralized after use.MethodsThe nucleoside anticancer drugs, cytarabine and fluorouracil, were exposed to ozone gas on plates under controlled humidity. The levels of exposed ozone were evaluated using the concentration-time (CT) value, which is the mathematical product of ozone concentration and exposure time. The effects of exposure to ozone on levels of the anticancer drugs were determined by high-performance liquid chromatography (HPLC).ResultsThe levels of cytarabine decreased with increasing CT value and were not detected beyond 40,000 CT. The decomposition levels of the anticancer drug by ozone were CT-dependent irrespective of the maximum concentration of ozone. Higher humidity in the range from 70 to 90 % accelerated the decomposition of cytarabine and fluorouracil, and neither of the drugs were detected at 90 % humidity after exposure to ozone gas.ConclusionsOzone gas decomposed these nucleoside anticancer drugs. This is the first report of the applicability of ozone gas as a decontaminator for anticancer drugs.

Vancomycin pharmacokinetic and pharmacodynamic models for critically ill patients with post-sternotomy mediastinitis.

Vancomycin is commonly used to treat serious methicillin-resistant staphylococcal infections, especially post-sternotomy mediastinitis (PSM). However, information on pharmacokinetics and pharmacodynamics in intensive care unit (ICU) patients remains scarce. We conducted vancomycin pharmacokinetic-pharmacodynamic modeling for ICU patients with PSM. This cohort study included 30 consecutive patients who received multiple vancomycin doses during primary closed drainage of PSM with Redon catheters, targeting serum drug trough concentrations of 25-35mg/L, and generating 359 serum vancomycin concentration-time values for analysis. Population pharmacodynamics served to describe the withdrawal of Redon catheters, i.e., the probability of in-ICU cure. Vancomycin pharmacokinetics corresponded to a two-compartment open model with first-order elimination kinetics. Mean [between-subject variability] population estimates were 1.91 (men)/1.25 (women) [0.28] L/h for vancomycin elimination, with intercompartmental clearance of 5.71 [1.01]L/h, and respective central and peripheral distribution volumes of 21.9 and 68 [0.53]L. Vancomycin clearance increased with body weight and declined with severity at ICU admission and serum creatinine (SCr), thereby allowing the prediction of the vancomycin plateau. Intercompartmental clearance decreased with diabetes mellitus (-70%). The probability of withdrawing all Redon catheters (patient cured) was dependent only on the area under the concentration-time curve to minimum inhibitory concentration (AUC/MIC) exposures ratio in plasma. Neither preoperative factors, antistaphylococcal co-treatments, nor the initial number of Redon catheters significantly influenced this probability. The AUC/MIC exposures ratio had no significant effect on SCr levels. These modeling analysis results identified five clinically relevant covariates that influenced vancomycin pharmacokinetics and might achieve better individualization of vancomycin dosing for methicillin-resistant staphylococcal PSM in ICU patients.

항생제 내성균 및 유전자제거를 위한 염소 CT 값 비교

The purpose of this study is to compare CT (disinfectant concentration * time) values in removing the antibiotic resistance bacteria, antibiotic resistance gene and transfer of antibiotic resistance genes. Different concentration of chlorine(C) and contact time(T) according to the removal of antibiotic resistance was calculated for each. As a result, for the 90% removal of antibiotic resistant bacteria, around 176~353 mg min/L CT values are needed. For the removal of the antibiotic resistance gene, 195~372 mg min/L CT values are required. For the 90% reduction of antibiotic resistance gene transfer by chlorine disinfection, 187~489 mg min/L CT values are needed. Based on our results, higher CT value was required for removing antibiotic resistant genes rather than antibiotic resistance bacteria.

Ozone application in water sources: effects of operational parameters and water quality variables on ozone residual profiles and decay rates

Systematic ozonation tests were conducted by means of a mobile pilot plant. Water source 1 was a low turbidity stream with very low solids content and very low turbidity, apparent color and alkalinity. Water source 2 was reservoir water with higher turbidity, solids content and alkalinity than source 1. The ozone plant was a counter-current contactor composed of four columns in series. Variations in contact time, in the feed gas concentration (in terms of percent by weight of ozone) and in splitting of the total applied ozone dosage between columns 1 and 2 were tested. Concentration - time (CT) products were calculated and decay coefficients K were estimated from experimental data. The relative importance of water quality and certain operational parameters with regard to CT products and ozone decay was assessed. Total CT values seemed to increase with: (a) total applied ozone dosage, (b) percent by weight of ozone in the feed gas to the bubble contactor, (c) increasing contact time and (d) higher water quality, with regard to turbidity, apparent color, total organic carbon and particle counts. As the total applied ozone dosage was increased, the more important the contact time and ozone dosage configuration became for the total CT value. The apparent first order ozone decay rate constant (K) decreased with increasing total applied ozone dosage. The contact time appeared to exert a much stronger influence on total CT values than on K values, particularly so as the total applied ozone dosage was increased.

Ozone technology in the post-harvest storage environment- a comparison of efficacy of high doses of ozone to insects treated under laboratory conditions and field conditions

Efficacy experiments were conducted to determine the ozone concentration (C) and treatment time (T) needed to effectively kill adult stages of red flour beetle (i>Tribolium castaneum) and maize weevil ( Sitophilus zeamais ). Under laboratory conditions, insects were exposed to concentrations of ozone ranging from 50 to 1800 ppm for 30 and 60 min. After treatment, insect mortality was scored, and if 100% mortality was not reached, more treatment-time was added in 30 min intervals at 1800 ppm. For both species, 100% mortality was reached after treatment at 1800 ppm for 120 min, which equates to a concentration*time (CT) product of 216,000 ppm.min. A similar CT product was attained under field conditions with a prototype auger designed to treat moving streams of grain with ozone during transfer. In field tests, 100% mortality was achieved for both insect species after a treatment of 47,000 ppm ozone for 6 min (CT = 282,000 ppm.min). The results indicate that CT values obtained in laboratory experiments correlated wll with those from field experiments. Based on these results, we now can calculate ozone concentration and auger length needed to treat grain in a fast-moving stream. Keywords : Ozone, Maize weevil, Sitophilus zeamais , Red flour beetle, Tribolium castaneum

Transport and Fate of Methyl Iodide and Its Pest Control in Soils

For fumigants, information on transport and fate as well as pest control is needed to develop management practices with the fewest negative environmental effects while offering sufficient pest control efficacy. For this purpose, a 2-D soil chamber with a surface-mounted flux chamber was designed to determine volatilization, real-time soil gas-phase concentration, degradation, and organism survivability after methyl iodide (MeI) fumigation. Three types of pests were used to give a broad spectrum of pest control information. An infected sandy loam soil with a volumetric water content of 10.6% was packed carefully into the 2-D chamber to a bulk density of 1.34 g cm(-3). After MeI fumigation at a rate of 56.4 kg ha(-1) for 24 h, about 28.9% of MeI was emitted into air, 6.8% remained in the soil, and 43.6% degraded in the soil (based on the residual iodide concentration). The uncertainty in the measured MeI degradation using iodide concentration was thought to mainly contribute to the unrecovered MeI (about 20%). The citrus nematodes [Tylenchulus semipenetrans] were effectively eliminated even at low concentration-time (CT) values (<30 microg h mL(-1)), but all Fusarium oxysporum survived. The response of barnyardgrass seeds [Echinochloa crus-galli] spatially varied with the CT values in the chamber. To fully control barnyardgrass seeds, CT of greater than 300 microg h mL(-1) was required. Using this experimental approach, different fumigant emission reduction strategies can be tested, and mathematical models can be verified to determine which strategies produce the least emission to the atmosphere while maintaining sufficient pest control efficacy.

Bioequivalence of Two Commercial Preparations of trimethoprim/sulfamethoxazole: A randomized, single-dose, single-blind, crossover trial

Background: Trimethoprinilsulfamethoxazole (TMP/SMX) is a combination of 2 antimicrobial agents that act synergistically, sequentially blocking 2 chemical reactions essential to bacterial survival. TMP/SMX is effective against organisms that are resistant to its separate components. Objective: The objective of this study was to comparethe bioavailability of 2 commercial preparations of T:MP/SMX 40/200 mg per 5-ml, oral suspension, used in Mexico for the treatment of bacterial infection. Methods: This study used a single-dose, randomized,single-blind, 2 × 2 crossover (2 dosing periods × 2 treatments) design to compare the 2 preparations. Healthy male volunteers aged 18 to 55 years received the trial and reference preparations in randomized sequence, under fasting conditions, with a 7-day washout period between dosing periods. Each preparation was administered as a single-dose 10-ml, oral suspension delivering 80 tng of TMP and 400 mg of SMX (equivalent to 2 doses of TMP/SMX 40/200 rig per 5 ml.). Pharmacokinetic (PK) parameters of C max AUC 0-t, and AUC 0-1 were determined for each component of each preparation. Schuirmann's unilateral double t test was performed. Null hypotheses indicating bioinequivalence ( P > 0.05) were rejected. Bioequivalence was determined if the quotient of the parameters of C max, AUC 0-t, and AUC 0-∞ were between 80% and 125%, at a power of 80% (α > 0.08). Results: Twenty-three of the 24 enrolled subjectscompleted the study. The subjects were all Hispanic, the mean (SD) age was 25 (6) years, and the mean (SD) body mass index was 22.54 (2.59) kg/m 2. Plasma concentration-time values of TMP and SMX were similar with both preparations. The null hypotheses of Schuirtnann's unilateral double t test were rejected, and results of the analyses of the PK parameters obtained 95% CIs within the predetermined range of bioequivalence (80%–125°10). The trial and reference preparations were statistically interchangeable and appeared to be bioequivalent. Conclusions: Based on similar PK profiles and statisticalanalyses, the trial and reference preparations were statistically interchangeable and appeared to be bioequivalent in this population of 23 healthy male volunteers in Mexico.

Identification of Yellow-Pigmented Bacteria Isolated from Hospital Tap Water in Japan and Their Chlorine Resistance

Twenty-five yellow chromogenic strains isolated from hospital tap water samples collected nationwide were identified by partial 16S rDNA sequencing. In addition, the chlorine resistance of the isolates was experimentally investigated. The results showed that of the strains tested, 12 strains (48.0%) were Sphingomonas ursincola/natatoria, which was most frequently identified, followed by 2 strains (8.0%) of Mycobacterium frederiksbergense and 1 strain (4.0%) each of Sphingomonas adhaesiva, Sphingopyxis witflariensis and Porphyrobacter donghaensis. The other strains were not identified clearly but they belonged to the order of Alphaproteobacteria. On the other hand, the identification results by sequencing and biochemical property testing were not consistent in any of the strains, showing that it was difficult to accurately identify the yellow chromogenic bacteria in tap water based on only their biochemical properties. When the 25 isolates were exposed to 0.1 mg/l residual free chlorine for 1 minute, 22 isolates (88.0%) survived. When the CT (Concentration Time) value killing 99.99% of the bacteria was investigated in 6 of these survivors, M. frederiksbergense (Y-1 strain) was most resistant to chlorine with the CT value of 32 mg x min/l, followed by S. ursincola/natatoria (Y-7 strain) with the CT value of 3.3 mg x min/l. The CT values of Y-5 (Sphingomonas sp.), Y-27 (S. ursincola/natatoria) and Y-21 (Asticacaulis sp.) were within the range of 0.9-0.1 mg x min /l. Of the 6 strains, S. adhaesiva (Y-10) showed the weakest resistance with the CT value of 0.03 mg x min/l. It was clarified that most yellow chromogenic bacteria isolated from hospital tap water were Sphingomonas spp., and these bacteria were experimentally resistant to chlorine.

Concentration-time exposure index for modeling soil fumigation under various management scenarios.

Best management decisions in soil fumigation require informed management selections of soil type, field geometry, application dosage, and depth to maximize fumigant distribution for efficacy and minimize off-site transport for environmental safety. An efficacy- or exposure-based concentration-time exposure index (CTEI) was used to serve as a continuous quantitative efficacy assessment for soil fumigation by subsurface drip irrigation using numerical model simulations. The CTEI was defined as the ratio between the soil volume where concentration-time (CT) exceeded a threshold value for a particular pest-fumigant combination and the total soil volume required for fumigation treatment. Applications of CTEI as a simple efficacy index were demonstrated by simulating combinations of three soil types (loam, sandy loam, sand); three field configurations consisting of 102- and 203-cm-wide bed systems and a flat surface system; three application depths (15, 30, 45 cm); and two application rates (82 and 327 kg ha(-1)) for 1,3-dichloropropene against citrus nematode (Tylenchulus semipenetrans) using a threshold air-phase CT value of 12 microg h cm(-3) obtained from a separate field study. For soil fumigation by subsurface drip irrigation, the order of importance in optimizing CTEI was soil type, depth of application and depth of treatment, dosage, and field configuration. Model simulation using CTEI as a numeric efficacy index can be an effective alternative to assist in the planning of field trials for making final management decisions concerning soil fumigation or other pesticide applications.

Concentration–Time Exposure Index for Modeling Soil Fumigation under Various Management Scenarios

Best management decisions in soil fumigation require informed management selections of soil type, field geometry, application dosage, and depth to maximize fumigant distribution for efficacy and minimize off-site transport for environmental safety. An efficacy- or exposure-based concentration–time exposure index (CTEI) was used to serve as a continuous quantitative efficacy assessment for soil fumigation by subsurface drip irrigation using numerical model simulations. The CTEI was defined as the ratio between the soil volume where concentration–time (CT) exceeded a threshold value for a particular pest–fumigant combination and the total soil volume required for fumigation treatment. Applications of CTEI as a simple efficacy index were demonstrated by simulating combinations of three soil types (loam, sandy loam, sand); three field configurations consisting of 102- and 203-cm-wide bed systems and a flat surface system; three application depths (15, 30, 45 cm); and two application rates (82 and 327 kg ha−1) for 1,3-dichloropropene against citrus nematode (Tylenchulus semipenetrans) using a threshold air-phase CT value of 12 μg h cm−3 obtained from a separate field study. For soil fumigation by subsurface drip irrigation, the order of importance in optimizing CTEI was soil type, depth of application and depth of treatment, dosage, and field configuration. Model simulation using CTEI as a numeric efficacy index can be an effective alternative to assist in the planning of field trials for making final management decisions concerning soil fumigation or other pesticide applications.

Pharmacokinetics and residues in milk of oxytetra‐cyclines administered parenterally to dairy goats

To determine for two commercial preparations of oxytetracycline (OTC) the pharmacokinetic behaviour, the presence of detectable milk residues and the penetration in milk of OTC administered by intravenous (IV) (conventional formulation [CF]) and intramuscular (IM) routes (CF and long-acting [LA] formulations) in goats producing milk. The effects of these formulations on plasma activity values of creatine kinase (CK) and lactate dehydrogenase (LDH) were also determined as indicators of tissue damage. Five healthy lactating goats producing 1.5+/-0.5 L/d milk and weighing 56.0+/-4.8 kg were used. Single doses of OTC chlorhydrate (CF) were administered (20 mg OTC/kg) by IV (Trial 1 IV) and IM (Trial 1 IM) routes and OTC dehydrate (LA) by the IM route. The same goats were first given IV CF, then IM CF followed by IM LA with 3 weeks between each treatment. Blood and milk samples were taken. The quantification of OTC was performed by HPLC and the plasma activities of CK and LDH enzymes were determined by spectrophotometry. The presence of OTC residues in milk was determined by a commercial reagent. The plasma pharmacokinetic parameters were calculated using a two-compartment model. Estimates of kinetic variables following IV administration were: Vss= 400.0+/-120.0 mL/kg and CL= 110.0+/-14.0 (mL/h)/kg. The t(fi) for IV= 3.0+/-0.3 h; IM, CF = 10.5+/-2.1 h and IM, LA = 15.1+/-3.1 h. The concentration of OTC in milk at 48 h was: IV= 0.6+/-0.4; IM CF= 1.1+/-0.2 and at 72 h (IM LA)= 0.6+/-0.1 microg/mL and the penetration in milk of OTC was: IV= 70.0+/-18.0; IM CF= 79.0+/-14.0 and IM LA= 66.0+/-6.0%. The areas under the curve of CK and LDH activities in plasma were calculated by the trapezoidal method. Values of CK and LDH IM, LA were greater (P < 0.05) than those observed for IM, CF at 2 and 3 days after administration of the antibiotic. Finally, the bioavailability of OTC CF = 92.0+/-22.0 and LA= 78.0+/-23.0% was suitable for its usage by the IM route in lactating goats. Plasma concentration-time values of OTC administered parenterally in production dairy goats showed similar bioavailability for the two pharmaceutical preaprations. The presence of detectable residues in milk indicates that milk should not be used for human consumption for 2 and 3 days after administration of conventional and long-acting formulations, respectively. The increments in CK and LDH activities after the IM administration of LA are consistent with the presence of tissue damage provoked by the pharmaceutical preparations at the injection site.

Performance and Analysis of Tracer Tests to Determine Compliance of a Disinfection Scheme With the SWTR

The Surface Water Treatment Rule (SWTR) contains tables of disinfectant CT(concentration × time) values that have been demonstrated to achieve the required degree of inactivation of viruses and Giardia cysts. If the CT product for a water treatment plant meets or exceeds those in the SWTR tables, it is assumed this inactivation has been achieved. The objective of the study was to compare two methods for calculating C and T. Tracer tests were conducted to characterize the behavior of flow through the process units of water treatment plants. Effective CT values, which were calculated based on the residence time distribution and the kinetics of chlorine decay, were compared with the most conservative CT values recommended in the US Environmental Protection Agency guidance manual.