Control of the freshwater fouling bivalveCorbicula fluminea by halogenation

Mortality levels for adult and juvenile Asiatic clam,Corbicula fluminea, were determined after exposure to halogens (chlorine, bromine) in 28 to 32-day laboratory and field (industrial water supply) tests. Low levels of mortality (<53%) were generated in laboratory studies on exposure to constant doses of total residual chlorine (TRC) when mean test temperatures were <16C. Mortality levels were elevated (>53%) when test specimens were exposed to comparable TRC levels (0.2 to 1.0 mg/L) at temperatures in excess of 18C. Mortalities generated among adults by an initial 14-day low dose (0.25 mg/L TRC) followed by an 18-day high dose (0.50 to 1.00 mg/L TRC; >80% mortality) were comparable to those from a constant high dose (0.50 to 1.00 mg/L; 60 to 95% mortality). Adults and juveniles were comparably sensitive to halogen concentrations adequate for control. There is no substantial difference in the effectiveness of either chlorine or bromine in controlling adult and juvenile stages ofC. fluminea. Field studies conducted in the spring and fall produced markedly dissimilar results. Mortality levels during the spring field study exceeded 90% after 28 days of exposure to 0.25 mg/L TRC, while ambient temperatures rose from 20 to 25C. Mortality levels not exceeding 23% were observed among test organisms after 28 days of exposure to elevated TRC levels (<0.50 mg/L), while ambient temperatures were declining from 20 to 12C during October and November 1985.     

Contaminated sediments from tributaries of the Great Lakes: Chemical characterization and carcinogenic effects in medaka (Oryzias latipes)

Sediments from four inshore industrial sites and a reference site in the Great Lakes were extracted with organic solvents to produce a crude extract, which was separated on alumina into two fractions: predominantly polycyclic aromatic hydrocarbons; and predominantly nitrogencontaining polycyclic aromatic compounds. Crude extracts were redissolved in acetone and analyzed by gas chromatography and gas chromatography-mass spectrometry. The acetone-redissolved crude extracts from the four industrialized sites contained 5.6–313.3 g total polycyclic aromatic compounds/g sediment and 3.0–36.4 g other compounds/g sediment. In addition to the typical EPA priority pollutants, a substantial amount (228.7 g/g sediment) of alkyl-polycyclic-aromatic compounds was detected in sediments from one of the industrialized sites. Extracts from the reference site contained 1.55 g total polycyclic aromatic compounds/ g sediment. Medaka (Oryzias latipes) were exposed to multiple pulse doses of acetone-redissolved extracts and fractions. Medaka were also exposed to a known carcinogen, methylazoxymethanol acetate, to verify that chemicals produced tumors in the test fish. Acetone-redissolved extracts and fractions from contaminated sediments were toxic to medaka. Fin erosion and non-neoplastic liver abnormalities were more prevalent in medaka after exposure to acetoneredissolved extracts and fractions from contaminated sediments. Neoplasms previously associated with chemical exposure in wild fishes were induced in medaka exposed to acetone-redissolved extracts and fractions from two of the contaminated sites, but not from the reference site or controls. These findings further support the hypothesis that chemical contaminants in sediments are involved in epizootics of neoplasms in wild fishes at contaminated sites.     

Response of Fouling Brown Mussel, Perna perna (L.), to Chlorine

Perna perna (L.), the edible brown mussel, is very widely distributed in the tropical and subtropical regions and is commonly found in rocky shores. Apart from being a candidate for commercial cultivation, P. perna is also a common pest organism in cooling water systems of coastal power stations. Therefore, a lethal and sublethal response of this mussel to commonly used antifouling biocides is of considerable interest to the industry. Mortality pattern (LT₅₀ and LT₁₀₀) and physiological activities (oxygen consumption, filtration rate, foot activity index, and byssus thread production) of different size groups (9–34 mm shell lengths) of P. perna were studied in the laboratory under different residual chlorine concentrations (0.25, 0.50, 0.75, and 1.00 mg/L for sublethal responses and 1, 2, 3, and 5 mg/L for mortality). Results showed that exposure time for 100% mortality of mussels significantly decreased with increasing residual chlorine concentration. For example, mussels of 9 mm size group exposed to 1 mg/L chlorine residual took 384 h (16 days) to reach 100% mortality, whereas those exposed to 5 mg/L chlorine took 84 h (4 days). The effect of mussel size on mortality was significant between 1 mg/L and 5 mg/L residual chlorine, with larger mussels showing greater resistance than smaller ones. For example, at 2 mg/L residual chlorine, 9 mm and 34 mm size group mussels took 228 h (10 days) and 304 h (13 days), respectively, to achieve 100% mortality. All size groups of P. perna showed progressive reduction in physiological activities, when chlorine residuals were gradually increased from 0 to 1 mg/L. Reduction in physiological activities was strongly correlated with the residual level. A comparison of present data with data available for other common fouling organisms suggests that P. perna is relatively less tolerant to chlorine than Perna viridis (L.) and Brachidontes striatulus (Hanley), which also cause fouling problems in tropical coastal waters. Received: 2 May 2002/Accepted: 5 September 2002     

Avoidance behavior of juvenile striped bass,Morone saxatilis,subjected to simultaneous chlorine and elevated temperature conditions

The avoidance responses of juvenile striped bass (Morone saxatilis) were evaluated by exposing test organisms to simultaneous elevated temperature (0, 2, 4, and 6?C) and total residual chlorine (TRC) (0.00, 0.05, 0.10 and 0.15 mg/L) conditions at four acclimation temperatures ranging from 15–30?C. An unbalanced 3-factor factorial design was used to develop response surface avoidance models at all acclimation temperatures. The percent avoidance models at 15?C showed that the interaction term (TRC×δT) was the most important term influencing avoidance; TRC was the most important factor at 20?C; the models at 25 and 30?C showed that δT was the most important factor. The results of tests conducted at 15?C suggest that preference for a higher temperature overrides a chlorine avoidance response to 0.15 mg/L TRC. Avoidance responses of striped bass tested at acclimation temperatures of 20, 25, and 30?C showed that preference for a higher temperature (6?C δT) did not override a chlorine avoidance response. A significant difference (p<0.01) existed between avoidance models at all acclimation temperatures; greatest avoidance generally occurred for all combinations of test conditions at 30?C.     

Seasonal temperature and power plant chlorination effects on estuarine invertebrates

The influence of seasonal temperatures (15–22°C) on chlorine (0.00, 0.15 and 0.30 mg/L total residual chlorine), T (2, 6 and 10°C), and exposure duration (0.08, 2.0 and 4.0 hr) interaction studies simulating power plant entrainment and effluent discharge conditions was evaluated for opossum shrimp,Neomysis americana and amphipods,Gammarus sp. Seasonal temperature was an important factor affecting the toxicity of the three treatment variables with both of these organisms. Mortality responses were greater at the higher acclimation temperatures.     

Teratogenesis,toxicity, and bioconcentration in frogs exposed to dieldrin

Teratogenesis, acute and chronic toxicity, growth and bioconcentration were investigated in various life stages (embryos, tadpoles, juveniles, adults) of the frogsXenopus laevis (African clawed frog),Rana catesbeiana (bullfrog) andRana pipiens (leopard frog) exposed to aqueous dieldrin in static-renewal and flow-through systems in a study on the development of wildlife-based water quality criteria.R. catesbeiana was the most sensitive tadpole in acute tests;X. laevis was the most sensitive in embryo-larval and chronic tadpole tests. Tadpole 96-h LC50s ranged from 40.4 to 49.5 g/L dieldrin forX. laevis, from 8.7 to 30.3 g/L forR. catesbeiana and was 71.3 g/L forR. pipiens. The 24-day LC50 forX. laevis tadpoles was 5.5 g/L dieldrin; the 28-day LC50 forR. pipiens tadpoles was 8.3 g/L. AdultR. pipiens had a 28-day LC50 of 53.4 g/L dieldrin. Gross spinal deformities in embryo-larval tests were observed at dieldrin concentrations as low as 1.3 g/L after 10-days exposure toX. laevis and at 25.4 g/L for a 21-day exposure toR. catesbeiana. MeanX. laevis 14 to 21-day LOAEL (Lowest Observed Adverse Effect Level) and NOAEL (No Observed Adverse Effect Level) values for embryo-larval tests (25.5 and 11.0 g/L dieldrin, respectively) were virtually the same as the 21-day single test values obtained forR. catesbeiana (25.1 and 11.0 g/L dieldrin). Mean 14 to 24-dayX. laevis LOAEL and NOAEL values for tadpole chronic tests (1.6 and <1.4 g/L dieldrin, respectively) were lower than the 28-day single test values obtained forR. pipiens (4.1 and 1.9 g/L, respectively).Tissue dieldrin levels at the LC50, LOAEL and NOAEL in the tadpole acute tests were fairly similar betweenX. laevis (11, 24 and 7 g/g, respectively) andR. catesbeiana (means of 8.6, 12.0 and 1.2 g/g, respectively). In the tadpole chronic tests, dieldrin tissue concentrations were even closer for these parameters forX. laevis (1.8, 1.5 and 0.8 g/g, respectively) andR. pipiens (1.7, 0.6 and 0.4 g/g, respectively). Mean steady-state bioconcentration factors (BCF) for tadpoles (whole body) ranged from 430 forX. laevis, and from 540 to 1,130 forR. pipiens. Mean steadystate BCFs for adultR. pipiens skin, muscle and liver ranged from 40 to 310. The relative similarity of response to dieldrin betweenX. laevis and the two ranid species in this study demonstrates its usefulness in assessing potential environmental hazards. The current dieldrin water quality criterion of 0.0019 g/L appears protective of frogs.     

Effectiveness of emergency water treatment practices in refugee camps in South Sudan

Objective

To investigate the concentration of residual chlorine in drinking water supplies in refugee camps, South Sudan, March–April 2013.

Methods

For each of three refugee camps, we measured physical and chemical characteristics of water supplies at four points after distribution: (i) directly from tapstands; (ii) after collection; (iii) after transport to households; and (iv) after several hours of household storage. The following parameters were measured: free and total residual chlorine, temperature, turbidity, pH, electrical conductivity and oxidation reduction potential. We documented water handling practices with spot checks and respondent self-reports. We analysed factors affecting residual chlorine concentrations using mathematical and linear regression models.

Findings

For initial free residual chlorine concentrations in the 0.5–1.5 mg/L range, a decay rate of ~5x10^-3 L/mg/min was found across all camps. Regression models showed that the decay of residual chlorine was related to initial chlorine levels, electrical conductivity and air temperature. Covering water storage containers, but not other water handling practices, improved the residual chlorine levels.

Conclusion

The concentrations of residual chlorine that we measured in water supplies in refugee camps in South Sudan were too low. We tentatively recommend that the free residual chlorine guideline be increased to 1.0 mg/L in all situations, irrespective of diarrhoeal disease outbreaks and the pH or turbidity of water supplies. According to our findings, this would ensure a free residual chlorine level of 0.2 mg/L for at least 10 hours after distribution. However, it is unknown whether our findings are generalizable to other camps and further studies are therefore required.     

Identification of the Herbicide Surflan and Its Active Ingredient Oryzalin, a Dinitrosulfonamide, as Xenoestrogens

Numerous environmental contaminants have been identified as endocrine disruptors (EDs) — substances that alter endocrine homeostasis by interfering with the biological action, production, or pharmacokinetics of endogenous hormones. Xenoestrogens are those EDs whose biological activity is similar to endogenous estrogen. This report presents data that identified Surflan, a proprietary herbicide emulsion, and its active ingredient oryzalin as xenoestrogens. In vitro, Surflan and oryzalin activated an estrogen-inducible reporter gene, and oryzalin competitively displaced 17-estradiol from the estrogen receptor. In vivo, Surflan and oryzalin induced expression of estrogen-regulated high-molecular-weight choriogenin genes in medaka (Oryzias latipes). These results are consistent with the characteristics of previously identified xenoestrogens and indicate that Surflan and oryzalin have the potential to adversely affect numerous estrogen-regulated biological processes.     

Atrazine uptake,photosynthetic inhibition,and short-term recovery for the submersed vascular plant,Potamogeton perfoliatus L.

The processes of atrazine (2-chloro-4-[ethylamino]-6-[isopropylamino-]-s-tri-azine) uptake and release in the submersed vascular plant,Potamogeton perfoliatus L., were rapid, approaching equilibrium with the surrounding environment within one hr. The ratio of internal atrazine concentration to external concentration was approximately 10 at the point of maximum photosynthetic inhibition and rapidly increased at lower external atrazine concentrations. The I₅₀ (the concentration inhibiting photosynthesis by 50%) for atrazine in solution was 80 g/L with the maximum observed photosynthetic reduction (87%) at a solution concentration of 650 g/L. Initial photosynthetic recovery ofP. perfoliatus following exposure to atrazine was rapid with oxygen evolution from treated plants (5, 25, and 100 g/L) being statistically indistinguishable from control plants after two hr of atrazine-free wash. However, there was an indication of residual photosynthetic depression in dosed plants, even after a 77 hr recovery period. In Chesapeake Bay, potential long-term exposure of submersed plants to concentrations of atrazine greater than 10 g/L is doubtful so that reduction ofP. perfoliatus photosynthesis under such conditions would be minimal and reversible.     

Acute toxicity of industrial surfactants toMysidopsis bahia

Three-to eight-day oldMysidopsis bahia were used to evaluate the acute toxicities of 17 industrial surfactants having a wide range of physiochemical characteristics. LC50s based on nominal concentrations covered approximately three orders of magnitude (<1 to >4,000 mg/L). The base structure of the surfactants (i.e., aromatic or aliphatic, branched or linear) was not a factor controlling toxicity. Low solubility surfactants with low ethylene oxide (EO) molar ratios were the most toxic surfactants tested. Ethylene oxide chain length was the best predictor of toxicity, and would be a good parameter to use to screen for surfactant toxicity in hazard assessment. Substitution of terminal OH with SO₃ or PO₄ reduced toxicity of a selected group of surfactants. Sensitivity ofM. bahia up to 26 days old was not significantly different from that of 3-to 8-day old animals. Use of one surfactant as a reference toxicant demonstrated that sensitivity ofM. bahia was consistent throughout the various tests.     

Characterization of cytochrome P4501A induction in medaka (Oryzias latipes) by samples generated from the extraction and processing of coal

The objective of this study was to characterize cytochrome P4501A induction in medaka liver as a biomarker for detecting polyaromatic hydrocarbon (PAH)-type compounds in samples of processed coal or petroleum. Ethoxyresorufin-O-deethylase (EROD) activity in individual medaka livers was used to assess induction of P4501A following the addition of various samples to aquaria water. Samples included a known P4501A inducer, -naphthoflavone, and various processed coal samples, as well as a petroleum-pitch. The sensitivity of detecting significant EROD induction by adding samples to aquaria water was 0.1 mg/L for most samples; however, a coal-tar pitch significantly increased EROD activity at 0.01 mg/L. Different samples induced EROD activity to different extents. All samples elicited a concentration-dependent increase in EROD activity, with maximum EROD induction 2 days after a single administration of xenobiotics to aquaria water. Western blot studies established that induction of EROD activity by all xenobiotics tested was associated with corresponding increased amounts of immunoreactive P4501A. EROD induction was not influenced by gender, by single or multiple xenobiotic exposures, nor by feeding or fasting animals during the course of xenobiotic exposure. The ability of xenobiotics to induce EROD activity in medaka liver did not always correlate with their genotoxic potential determined by bacterial mutagenesis assays. Induction of P4501A in medaka liver appears to provide a convenient, economical, reliable and sensitive indicator for the presence of PAH-type compounds in coal- or petroleum-derived samples.Abbreviations BNF -naphthoflavone - CTP coal tar pitch - DMSO dimethylsulfoxide - EROD ethoxyresorufin-O-deethylase - H400 test sample hydrogenated at 400°C - H450 test sample hydrogenated at 450°C - SDS PAGE sodium dodecyl sulphate polyacrylamide gel electrophoresis - PP petroleum pitch - DMEM Dulbecco's Modified Eagles Medium     

Assessment of some aqueous residual chlorine measurements

Conclusions Sodium hypochlorite solutions, filter effluent, plant effluent, and tap water were analyzed by the amperometric titration (AT), residual chlorine electrode, (EL), and DPD ferrous titrimetric (DPD) methods and the results were compared for the range 0.2 to 2.0 ppm residual chlorine. Overall precision for measurements by all three methods and in three laboratories was 10% RSD for TARC and 20% for FARC. Amperometric titration was judged the method of choice because of precision of measurements, simplicity of operation, and capability for both TARC and FARC determinations.A rapid initial decay of TARC in stored water samples containing high initial levels of FARC was observed. Residual chlorine values obtained from such samples after storage could not be meaningfully correlated with other water parameters obtained during the monitoring study. Correlation was only meaningful for water samples which did not show a significant change in residual chlorine levels after storage.     

Survival and growth ofTanytarsus dissimilis (Chironomidae) exposed to copper,cadmium, zinc,and lead

Tanytarsus dissimilis (Johannsen) was exposed to four heavy metals. Static exposure began during embryogenesis and continued through hatching and larval development to the 2nd or 3rd instar. The LC50 concentrations for cadmium, copper, and zinc were 3.8, 16.3, and 36.8g/l, respectively. The LC50 for lead was 258g/1. Growth was not reduced at exposure concentrations less than the LC50.The LC50 concentrations obtained in this insect exposure are as much as 1,600 times lower than other insect exposures reported in the literature. This is probably due to a combination of exposure of this insect during important life cycle events and species-specificity.     

Reproductive Assessment of Japanese Medaka (<Emphasis Type="Italic">Oryzias latipes</Emphasis>) Following a Four-Week Fluoxetine (SSRI) Exposure

The occurrence of environmental pharmaceutical products has recently received considerable attention, but impacts on the aquatic environment are largely unknown. Fluoxetine is a widely prescribed antidepressant and acts physiologically as a selective serotonin reuptake inhibitor (SSRI). To determine its potential to disrupt teleost reproductive function, Japanese medaka (Oryzias latipes) were exposed to fluoxetine at aqueous nominal concentrations of 0, 0.1, 0.5, 1 and 5 g/L for 4 weeks. The last 14 days of this exposure included a reproductive assessment in which no significant changes were observed in egg production, rate of fertilization and spawning, or hatching success of fertilized eggs. A low incidence (1.97–2.53%; 4.02–5.16-fold greater than controls) of developmental abnormalities was observed in offspring from all fluoxetine treatments. Adult gonadal somatic index, hepatic vitellogenin, and ex vivo gonadal steroidogenesis were also unaffected. Circulating plasma estradiol levels in females were significantly increased by 0.1 and 0.5 g/L treatments. Our study provides novel information on fish biochemical, physiological, and reproduction responses to environmentally realistic fluoxetine concentrations.     

In vitro susceptibility of mycelial and yeast forms of Penicillium marneffei to amphotericin B,fluconazole, 5-fluorocytosine and itraconazole

The mycelial (25°C) and yeast-like (37°C) forms of Penicillium marneffei clinical and type strains were investigated for their in vitro susceptibility to amphotericin B (AmB), 5-fluorocytosine (5-FC), fluconazole (FLU) and itraconazole (ITZ), using Bacto antibiotic medium 3, yeast-nitrogen, Sabouraud's dextrose (pH 5.7) and high resolution (pH 7.1) broth media (1ml/tube), respectively. Results indicated that the minimal inhibitory and minimal fungicidal concentrations (MICs and MFCs) for the mycelial cultures of P. marneffei to AmB were in the range 0.78–1.56 and 0.78–3.125 g/ml, respectively, as against 3.125–25 g (MICs) for the yeast form cultures. The MFCs to AmB for the yeast form were one dilution higher. The MICs to FLU were generally lower for the yeast form (6.25–25 g) than the mycelial form (25–50 g/ml), whereas MFCs for the mycelial cultures were > 100 g as compared to 6.25–100 g for their yeast form. The MICs for the mycelial form to 5-FC ranged from < 0.195–0.39 g. Higher MICs (6.25 g) were recorded for their yeast form. The MFCs to 5-FC for the yeast form were 25–100 g/ml. The MICs for the mycelial form to ITZ ranged from < 0.195 to 3.125 g/ml. Higher values (< 0.195–50 g) were recorded for their yeast-like form. The MFCs to ITZ for mycelial and yeast forms ranged from < 0.195–0.39 and 25–100 g/ml, respectively. Results indicate that P. marnefei's yeast form is more sensitive to FLU and ITZ (8 of 10 strains) while the mycelial form displayed greater susceptibility to AmB and 5-FC. The MICs for ITZ remained steady in SD medium, pH 5.7 to 7.1. However, some strains gave higher MIC values (0.39–1.56 g/ml) when tested in the HR.     

Organizational socialization of employees with disabilities: Critical issues and implications for workplace interventions

Organizational socialization is the process whereby newcomers to work organizations become insiders. The socialization process has been linked to various outcomes including newcomer job satisfaction, organizational commitment, job knowledge and performance, promotion and advancement rate, salary, and turnover. The purpose of the present paper is threefold: (1) to examine issues facing persons with disabilities during organizational socialization in order to help guide future research on this topic; (2) to provide an awareness of potential aditional barriers (unrealistic newcomer expectations, interaction avoidance, norm to be kind, low work group expectations) that face newcomers with disabilities as they begin jobs; and (3) to suggest some possible policies, programs, and interventions that might help persons with disabilities to overcome those barriers.     

Short-term exposure of zooplankton to the synthetic pyrethroid,fenvalerate, and its effects on rates of filtration and assimilation of the alga,Chlamydomonas reinhardii

In acute tests of toxicity, two cladocerans,Daphnia galeata mendotae andCeriodaphnia lacustris, and the calanoid,Diaptomus oregonensis, were more sensitive to fenvalerate thanDaphnia magna, the organism used in standard laboratory bioassays. The 48-hr EC₅₀s for each species/stage in order of increasing sensitivity were adultD. magna — 2.52 g/L;D. magna (48-hr old) — 0.83 g/L; adultD. galeata mendotae — 0.29 g/L; adultC. lacustris — 0.21 g/L;D. galeata mendotae (48-hr old) — 0.16 g/L; adultDiaptomus oregonensis — –0.12 g/L. No toxicity was observed when these organisms were exposed to a range of concentrations of the emulsifiable concentrate without fenvalerate (the EC blank).Rates of filtration of the¹⁴C-labelled alga,Chlamydomonas reinhardii byD. galeata mendotae, C. lacustris andD. oregonensis were decreased significantly at sublethal concentrations of fenvalerate after only 24-hr exposure.Ceriodaphnia lacustris showed the greatest sensitivity with rates of filtration significantly decreased at 0.01 g fenvalerate/ L. Concentrations of fenvalerate 0.05 g/L resulted in decreased rates of filtration byD. galeata mendotae. A concentration of 0.10 g fenvalerate/ L caused rates of filtration to increase inD. oregonensis. whereas 0.05 and 0.5 g/L resulted in a decrease in these rates.Rates of assimilation of algae byD. galeata mendotae, C. lacustris andD. oregonensis exposed to similar concentrations of fenvalerate were decreased at concentrations 0.05 g fenvalerate/L. Changes in rates of assimilation were not as sensitive a parameter of toxicity as changes in rates of filtration. The EC blank had no significant effects on rates of filtration or assimilation for all three species.     

The pattern of organochlorines in mussels Mytilus edulis L. from the south west Baltic Sea

The concentration of organochlorines (PCB, DDT and its metabolites, HCH isomers and HCB) were determined in mussel, Mytilus edulis from the south west Baltic Sea. The harbor Kiel Innenförde showed the highest contamination with PCB (487 g/kg dry weight), the Gelting bathing beach area the lowest contamination (38 g/kg). The highest contamination with DDT was measured in Lübeck bay, which may be explained by the long term application of DDT in the former German Democratic Republic.Penta- and hexa-chlorinated PCB were selectively accumulated in Mytilus edulis whereas highly lipophilic PCB with more than seven chlorine atoms were found in negligible concentrations. The accumulation of these compounds in mussels is determined by equilibrium partitioning with ambient water.     

Toxicity of seleno-L-methionine, seleno-DL-methionine, high selenium wheat, and selenized yeast to mallard ducklings

The toxicity of four chemical forms of selenium (seleno-L-methionine, seleno-DL-methionine, selenized yeast, and high selenium wheat) was compared in day-old mallard ducklings (Anas platyrhynchos). In the first experiment, in which the basal diet was 75% wheat, survival after 2 weeks was lower for ducklings fed 30 g/g selenium as seleno-L-methionine (36%) than for ducklings fed 30 g/g selenium as seleno-DL-methionine (100%) or 30 g/g selenium from high selenium yeast (88%). The concentration of selenium at 2 weeks in the livers of survivors was similar for ducklings fed 15 g/g selenium as seleno-DL-methionine (12 g/g, wet weight), seleno-L-methionine (11 g/g), and high selenium wheat (11 g/g), but was lower when the selenium came from selenized yeast (6.2 g/g). When fed 30 g/g selenium from the various sources, the selenium concentrations in liver were 20 g/g for seleno-DL-methionine, 19 g/g for seleno-L-methionine, and 9.9 g/g for selenized yeast. In a second experiment, in which the basal diet was a commercial duck feed, survival after 2 weeks was 100% in ducklings fed 30 g/g selenium as seleno-DL-methionine, seleno-L-methionine, or selenized yeast. Selenium concentrations in liver were similar for ducklings fed the 30-g/g selenium diets as the DL or L forms of selenomethionine (27 and 25 g/g), but lower for ducklings fed selenized yeast (13 g/g). The greater toxicity of the L form of selenomethionine was probably related to the palatability or nutritional nature of the wheat-based diet used in experiment 1, but the exact reason for the difference between the DL and L forms is unknown. Biologically incorporated selenium, derived from high selenium wheat, was no more toxic than selenium derived from the two purified forms of selenomethionine, and the selenium in selenized yeast was not as toxic as that in the two forms of selenomethionine.     

Inactivation of Nitrosomonas europaea and pathogenic Escherichia coli by chlorine and monochloramine

The purpose of this study was to measure the chlorine and monochloramine inactivation kinetics of Nitrosomonas europaea at 21°C in the presence and absence of particles. The inactivation kinetics rates were compared with those obtained with Escherichia coli O157:H7. The results show that, in pure water, the use of free chlorine produced 4 log₁₀ of N. europaea inactivation at a CT value of 0.8 mg.min l^-1, whereas monochloramine yielded 4 log₁₀ of inactivation at CT values of approximately 9.9–16.4 mg.min l^-1. With E. coli, chlorine produced approximately 4 log₁₀ of inactivation at a CT of 0.13 mg.min l^-1, whereas monochloramine resulted in 4 log₁₀ of inactivation at a CT of approximately 9.2 mg.min l^-1. These results suggest that N. europaea is more resistant to monochloramine and chlorine than E. coli. Corrosion debris, soil material and wastewater had no statistically significant (p < 0.05) impact on the inactivation of N. europaea by either chlorine or monochloramine. It seems likely that the CT values present in distribution systems would be sufficient to control suspended cells of these two organisms, especially under conditions of breakpoint chlorination, which could be used to control nitrification. Adequate disinfection should prevent the growth of these organisms in a distribution system.