Biomedical subjects
C D Watts
Publications and source records attributed to C D Watts.
Partitioning of marine antifoulants in the marine environment.
The partitioning behaviour of the organic biocides, Irgarol 1051 and diuron and two inorganic biocides (copper and zinc) was investigated using six sediments of differing physico-chemical properties collected from unimpacted sites along the south coast of England. The kinetics of sorption and equilibrium partitioning between the sediments and seawater were investigated over a period of 20 days. Resulting organic carbon/water partition coefficients (log Koc) were related to suspended sediment concentration and ranged from 2.28 to 5.20 for diuron; and from 2.41 to 4.89 for Irgarol 1051. Sediment/water partition coefficients (log Kp) for copper and zinc varied from 2.46 to 5.08 l/kg and from 2.49 to 4.97 l/kg, respectively. Kinetic data indicated that there were significant interactions between the dissolved and particulate phases at the start of the experiments, just after mixing. This is thought to be a result of redistribution of organic carbon between the two phases.
Long term variation in water colour from Yorkshire catchments.
Water colour is a problem in the upland water-gathering grounds of the UK. It has shown considerable variation over recent years and this needs to be put into the longer-term context. In order to do this, factors to convert water colour measured in absorbance units per metre (Au/m) to Hazen units are presented for ten sites in the Yorkshire region using data from August 1997 to June 1998. The conversion factors are site-specific and there is some evidence that they may show seasonal variation. There is also a short-term upward trend in the conversion factor for a number of catchments, which may be related to their recovery following the 1995 drought. Time series of water colour in Hazen from 1980 to 1998 are shown for selected sites. The seasonal variation in colour levels is disrupted at all sites during and following drought periods, notably 1990-1992 and 1995-1998 and, in the case of two sites with long-term colour measurements, the 1975-1976 drought. These periods are followed by enhanced levels of colour and, since the end of the 1995 drought, unprecedented high values have been recorded at some catchments.
Water quality of Scottish rivers: spatial and temporal trends.
The Harmonised Monitoring Scheme (HMS) was initiated in 1974 and represents the best-organised source of temporal and spatial data describing water quality for the major mainland rivers of Scotland, England and Wales. This paper presents the first detailed analysis of HMS data for Scotland, and identifies temporal changes in water quality from 1974 to 1995. From a concomitant analysis of catchment land cover characteristics, water quality indices have been linked with potential 'drivers' of change, influencing both point and diffuse sources. Nitrate concentrations between rivers are highly correlated with the amount of arable land, and relationships exist between grassland cover, orthphosphate-P and suspended solids concentrations. Similarly, urban catchments are highly correlated with ammonium-N, orthophosphate-P and suspended solids. Spatial and temporal trends in water quality for the rivers of Scotland are discussed.
The application of predictive models in the environmental risk assessment of ECONOR.
Environmental risk assessment of products requires information on the physico-chemical properties, persistence and ecotoxicity of the product, its constituents and possible metabolic and degradation products. Experimental investigations are usually required to generate this information and consequently risk assessment can be costly and time consuming. One possible approach to minimising the amount of experimental testing is to supplement experimental data with data predicted using models such as quantitative structure-activity relationships (QSARs). Using these models, information can be generated based primarily on the knowledge of the chemical structure of the substance(s) under investigation. In this study predictive models were used to assess the environmental risk of the veterinary medicine, ECONOR which contains the active ingredient valnemulin. Available experimental data on the properties, degradability and ecotoxicity of valnemulin was supplemented with predicted data. Where possible, experimental data was used to validate the predicted approaches and this indicated that the predictions were accurate. Information on usage, properties and degradability was input to fate models to predict environmental concentrations (PECs) of valnemulin in soil, pore water and groundwater. Comparison of PECs with experimental and predicted ecotoxicity data for valnemulin indicated that that even under 'worst case' scenarios the environmental risk posed by valnemulin was low.
Analytical performance testing of an atrazine immunoassay system.
A rigorous performance evaluation of an enzyme immunoassay (EIA) kit for the determination of atrazine in water samples was undertaken. Eleven individual batches of samples containing standards and spiked drinking waters were analysed and precision, bias and limit of detection were measured using statistical analysis. The technique was shown to be capable of achieving performance criteria (a total standard deviation of less than 5% or 2.5 ng, whichever is the greater) demanded of modern analytical systems and achieved a limit of detection of 9.2 ng l-1. There was no statistically significant bias measured for drinking water samples. Interference tests showed that the atrazine immunoassay was not significantly affected in the pH range 4.0-8.0 or by drinking water matrix components (anions, cations and chlorination by-products), even at their maximum allowable concentrations. There was a small extent of cross-reaction with simazine and atrazine degradation products, but given the persistence of atrazine, through its resistance to hydrolysis, breakdown products are likely to be present at much lower concentrations than the parent compound in drinking water. Simazine may potentially be more problematic, so it would be prudent to monitor a proportion of samples for simazine to determine the extent to which this may be contributing to the 'atrazine' measured in drinking water samples using the EIA kit.
A survey of smoking and quitting patterns among black Americans.
A sample of adult Black policyholders of the nation's largest Black-owned life insurance company was surveyed in 1986 to add to limited data on smoking and quitting patterns among Black Americans, and to provide direction for cessation initiatives targeted to Black smokers. Forty per cent of 2,958 age-eligible policyholders for whom current addresses were available returned a completed questionnaire. Population estimates for smoking status agree closely with national estimates for Blacks age 21-60 years: 50 per cent never-smokers; 36 per cent current smokers; 14 per cent ex-smokers. Current and ex-smokers reported a modal low-rate/high nicotine menthol smoking pattern. Current smokers reported a mean of 3.8 serious quit attempts, a strong desire and intention to quit smoking, and limited past use of effective quit smoking treatments and self-help resources. Correlates of motivation to quit smoking were similar to those found among smokers in the general population, including smoking-related illnesses and medical advice to quit smoking, previous quit attempts, beliefs in smoking-related health harms/quitting benefits, and expected social support for quitting. Methodological limitations and implications for the design of needed Black-focused quit smoking initiatives are discussed.
Results of the 1984 to 1985 survey of graduate medical education programs.
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Nonvolatile organic compounds in treated waters.
Over the past decade much information has been published on the analysis of organics extracted from treated water. Certain of these organics have been shown to be by-products of the chlorination disinfection process and to possess harmful effects at high concentrations. This has resulted in increased interest in alternative disinfection processes, particularly ozonation. The data on organics had been largely obtained by using gas chromatography-mass spectrometry, which is only capable of analyzing, at best, 20% of the organics present in treated water. Research in key areas such as mutagenicity testing of water and characterization of chlorination and ozonation by-products has emphasized the need for techniques suitable for analysis of the remaining nonvolatile organics. Several methods for the isolation of nonvolatile organics have been evaluated and, of these, freeze-drying followed by methanol extraction appears the most suitable. Reverse-phase HPLC was used for separation of the methanol extract, but increased resolution for separation of the complex mixtures present is desirable. In this context, high resolution size exclusion chromatography shows promise. Characterization of separated nonvolatiles is possible by the application of state-of-the-art mass spectrometric techniques. Results obtained by these techniques have shown that the nonvolatile organic fraction of chlorinated drinking water consists of many discrete compounds. Among these, some of the chlorinated compounds are almost certainly by-products of disinfection. Studies of the by-products of ozonation of fulvic and humic acids isolated from river waters have indicated a similar proportion of nonvolatile organics. Further, ozonation can result in the release of compounds that are trapped in the macromolecules.
Health insurance coverage for underserved populations.
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Intussusception complicating pregnancy. Report of a case.
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Lincoln Hospital of Durham, North Carolina. A short history.
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Intestinal complications found from potassium chloride. Case report.
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