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Biomedical subjects

M G Morgan

Publications and source records attributed to M G Morgan.

At least 19 recordsLinked to original sources
PubMed2000

Fungal surveillance of an open haematology ward.

Air sampling and surveillance cultures for fungi were performed in a Scottish general haematology ward over a five-month period in 1997. The mean total fungal count from the air sampling appeared to be correlated with the number of patients colonized by Aspergillus. The most commonly isolated species were Aspergillus versicolor, A. fumigatus and A. niger. Rooms with portable air filtration units had significantly lower total fungal counts than the others. Swabs were taken from 70 patients (mean age 62 years); 114 of the 563 cultures (20.2%) were positive. The most commonly isolated species were A. fumigatus, Candida albicans, C. glabrata and C. parapsilosis. Samples taken from the tongue and perineum showed colonization more often than those taken from the nostrils. Almost half the patients (48.6%) were colonized on, or within seven days of, admission; 11.4% became colonized whilst on the unit. One patient developed fatal aspergillosis. We conclude that colonization or high air-borne spore concentrations are not necessarily predictive of fungal infection but may prompt early treatment or more aggressive prophylaxis of potentially fatal invasive infections.

Adolescent↗
PubMed2000

Categorizing risks for risk ranking.

Any practical process of risk ranking must group hazards into a manageable number of categories. Defining such categories requires value choices that can have important implications for the rankings that result. Most risk-management organizations will find it useful to begin defining categories in terms of environmental loadings or initiating events. However, the resulting categories typically need to be modified in light of other considerations. Risk-ranking projects can benefit from considering several alternative categorization strategies and drawing upon elements of each in developing their final categorization of risks. In principle, conducting multiple ranking exercises by using different categorizations could be interesting and useful. In practice, agencies are unlikely to have either the resources or patience to do this, but other groups in society might. Done well, such additional independent rankings could add valuable inputs to democratic risk-management decision making.

Air Pollution, Indoor↗
PubMed1998

The efficacy of different methods for informing the public about the range dependency of magnetic fields from high voltage power lines.

The AC electric and magnetic fields associated with high voltage power lines have become a concern as a possible health risk. In most cases the strength of these fields decreases as the inverse square of the distance from the line. In earlier work, we found that laypeople do not understand how rapidly field strength decreases with distance. Most believe that any high voltage power line they can see is exposing them to strong fields. This paper confirms the earlier finding and explores a number of strategies which might be used in risk communications to correct this misperception. We found it relatively easy to provide subjects with a better understanding of the range-dependency of magnetic field strength. Moreover, the quality of this acquisition was apparently independent of the manner in which they were instructed. Such successful instruction is markedly different from the well-established difficulty of teaching people about many qualitative domains, such as physics or ideas in probability. Clearly, while some erroneous beliefs are highly resistant to change, others can be altered quite readily. We suspect that an important distinction between knowledge about the range-dependency of power-frequency magnetic fields and less tractable topics involves the presence or absence of prior folk-theories or "mental models" of the domain.

Adolescent↗
PubMed1998

Influence of biological and analytical variation on urine measurements for monitoring exposure to cadmium.

OBJECTIVE: To define the mean intraindividual biological variation in urinary concentrations of cadmium and retinol binding protein (RBP) in untimed, random urine samples and the influence of creatinine or specific gravity correction on reducing this variation. The relation between biological variation and analytical variation in defining uncertainty in a single measurement and significant differences between successive measurements was explored. METHODS: Repeat measurement study in subjects with either high historical exposure to cadmium but without current exposure, or unexposed volunteers. Standard statistical tools used in clinical laboratory medicine were applied to define intraindividual biological and analytical variation. RESULTS AND CONCLUSION: Both creatinine and specific gravity correction of urinary cadmium measurements in random urine samples seem to reduce the intraindividual variability compared with uncorrected values. With a standard definition, acceptable long term analytical precision for measurements of cadmium and RBP combined with creatinine analyses should be < 9% and < 15% respectively. The mean intraindividual biological variation of cadmium and RBP, expressed as creatinine corrected, was 18% and 40% respectively in the subjects exposed to cadmium. With the analytical precision used, significant differences (p < 0.05) between consecutive measurements for creatinine corrected urinary cadmium and RBP would need to show changes of > 54% and > 110% respectively. The relation between significant differences in consecutive results and differences in the analytical precision of the method used to measure the samples is described.

Analysis of Variance↗
PubMed1997

Effects function simulation of residential appliance field exposures.

This paper demonstrates the application of effects function analysis to residential magnetic field exposure, focusing on appliance sources and mitigation choices. Residential field exposure time series were synthesized by using a sample of background household field measurements, a model of average daily appliance use, and a small sample of EMDEX data of field exposure from 12 household strength window, sudden field changes) were simulated by using the synthesized time series data for different exposure situations, such as high and low levels of appliance use, simple avoidance, and use of a set of hypothetical "low field" appliances (50% lower fields). In particular, field exposure from the use of bedside clocks and electric blankets was examined. Results demonstrate that the choice of effects function is critical for the ranks of field sources and exposure reduction choices. For the effects function of average field strength with or without a threshold, exposure from background fields dominated exposure from all appliances except for bedside clocks and electric blankets. In the case of the field strength window effects function, the dominant field sources changed with the width of the window. For the effects function based on rapid field changes, appliance use was the major source of exposure. Because of the small sample of our data set and other simplifications, specific results should be viewed as illustrative.

Computer Simulation↗
PubMed1995

A method for assessing alternative effects functions that uses simulation with EMDEX data.

A method for evaluating a variety of alternative biologically plausible effects functions through the use of simulation studies conducted on personal-monitor exposure data is described. Using magnetic field time series collected with EMDEX instruments, we demonstrate how the method can be used to explore 1) how the outputs from various effects functions simulations compare to the results obtained by assuming that effects are proportional to time average field strength; 2) how the results of epidemiological studies might be used to assess the relative likelihood that each of the alternative effects functions describes biological reality; and 3) how the results might be used to assess possible health risks. Although the available data are sufficient to demonstrate the general method, they are not yet sufficient to support actual discrimination among possible alternatives. The arguments on the use of the method are for illustrative purposes only.

Computer Simulation↗
PubMed1995

A method for evaluating transmission line magnetic field mitigation strategies that incorporates biological uncertainty.

A method to determine how much reduction in public exposure to power frequency magnetic fields can be obtained for different levels of investment is presented. Which if any "effects function" best describes the relationship between field exposure and biological effect is uncertain at this time. Also, in a particular context such as construction of new transmission lines there are a variety of different technologies which might be used to reduce exposure. We describe and demonstrate a method by which exposure reduction supply curves (i.e., the cost of purchasing different amounts of exposure reduction given various mitigation options) can be estimated parametrically for different exposure conditions and effects functions, and we display illustrative results.

Cost-Benefit Analysis↗
PubMed1994

Designing risk communications: completing and correcting mental models of hazardous processes, Part I.

Many risk communications are intended to help the lay public make complex decisions about risk. To guide risk communicators with this objective, a mental models approach to the design and characterization of risk communications is proposed. Building on text comprehension and mental models research, this approach offers an integrated set of methods to help the risk communication designer choose and analyze risk communication content, structure, and organization. An applied example shows that two radon brochures designed with this approach present roughly the same expert facts as a radon brochure widely distributed by the U.S. EPA but meet higher standards on other content, structure, and organization criteria.

Communication↗
PubMed1994

Evaluating risk communications: completing and correcting mental models of hazardous processes, Part II.

We propose a decision-analytic framework, called the mental models approach, for evaluating the impact of risk communications. It employs multiple evaluation methods, including think-aloud protocol analysis, problem solving, and a true-false test that allows respondents to express uncertainty about their answers. The approach is illustrated in empirical comparisons of three brochures about indoor radon.

Air Pollution, Indoor↗
PubMed1994

Perception of risks from electromagnetic fields: a psychometric evaluation of a risk-communication approach.

Potential health risks from exposure to power-frequency electromagnetic fields (EMF) have become an issue of significant public concern. This study evaluates a brochure designed to communicate EMF health risks from a scientific perspective. The study utilized a pretest-posttest design in which respondents judged various sources of EMF (and other) health and safety risks, both before reading the brochure and after. Respondents assessed risks on dimensions similar to those utilized in previous studies of risk perception. In addition, detailed ratings were made that probed respondents' beliefs about the possible causal effects of EMF exposure. The findings suggest that naive beliefs about the potential of EMF exposure to cause harm were highly influenced by specific content elements of the brochure. The implications for using risk-communication approaches based on communicating scientific uncertainty are discussed.

Attitude to Health↗
PubMed1993

Controversies in the laboratory diagnosis of community-acquired urinary tract infection.

Urine samples constitute the largest single category of specimens examined in most medical microbiology laboratories. The everyday nature and apparent simplicity of urinary tract infection belies the intense debate and controversy regarding the optimal methods of collection, transport and processing of urine specimens and reporting of results. There is considerable variation in the interpretation of quantitative culture results between laboratories and the etiology of abacterial cystitis remains unclear. Microscopy to detect pyuria provides information on an important indicator of inflammation and it has been proposed that detection of urinary antibody may provide similar information. Neither of these indices of host response is suitable for use in a screening test for urinary infection however, although they may usefully contribute to the interpretation of significance of culture results. The development of screening tests and automated systems continues, but at present microscopy and culture remain the most important techniques for laboratory diagnosis. However, these techniques have so far failed to provide an etiological diagnosis for abacterial cystitis and this remains a major area for research.

Adult↗