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Biomedical subjects

J C McDonald

Publications and source records attributed to J C McDonald.

At least 19 recordsLinked to original sources
PubMed2006

Sixty years on: the price of assembling military gas masks in 1940.

BACKGROUND: Between 1940 and 1944 military gas masks with filter pads containing 20% crocidolite were assembled in a Nottingham factory. METHODS: Records supplied by the late Professor Stephen Jones were of 1154 persons, mainly women, who had worked in the factory during this period; they included many deaths from mesothelioma. A systematic effort was therefore made to establish causes of death for the whole cohort. RESULTS: Of 640 employees with full name and sex recorded, 567 (89%) were traced. Of these, 491 had died, including 65 from mesothelioma, though only 54 were certified as such. After exclusion of these 54, standardised mortality ratios were significantly raised for respiratory cancer (SMR 2.5) and carcinomatosis (SMR 3.2). The pattern of mortality in the remaining 514 employees without full identification was similar, but a low tracing rate (40%) did not justify their further analysis. The first death from mesothelioma was in 1963 (22 years after first exposure) and the last in 1994, whereas a further 5.0 cases would have been expected between 1996 and 2003 (p = 0.0065). CONCLUSION: These findings in a cohort followed over 60 years after brief exposure to crocidolite confirm a high and specific risk of mesothelioma (28% peritoneal) and perhaps of lung cancer some 20-50 years later. The statistically significant absence of further mesothelioma cases during the past eight years suggests that crocidolite, though durable, is slowly removed.

Asbestos, Crocidolite↗
PubMed2006

Incidence by occupation and industry of work-related skin diseases in the United Kingdom, 1996-2001.

BACKGROUND: Work-related skin disease is common but few cases are documented in statutory reports or disability systems. Voluntary reporting by specialist physicians provides more complete information. AIMS: To summarize incidence rates of work-related skin diseases reported by consultant dermatologists and occupational physicians, with emphasis on contact and allergic dermatitis by occupation and industry. METHODS: Cases reported in 1996-2001 to the EPIDERM and OPRA national surveillance schemes were analysed by causal agent, occupation and industry, with incidence rates calculated against appropriate denominators. RESULTS: Average annual incidence rates based on data from dermatologists were 97 per million overall, 74 for contact dermatitis and 14 for neoplasia. The corresponding rates for occupational physicians were 623 overall, 510 and 2, respectively. For infective disease, the rates for occupational physicians were 28 compared to 2 for dermatologists. Contact dermatitis was most frequently attributed to rubber chemicals, soaps and cleaners, wet work, nickel and acrylics; most cases of contact urticaria were attributed to rubber chemicals or foods and flour. The pattern of incidence rates by occupation and industry was complex, but correlated with the probable type of exposure. Rates of contact dermatitis were highest among skilled workers in the petrochemical and rubber and plastic manufacturing industries, with machine operators and technical workers in metal and automotive industries also at increased risk. High proportions of cases attributed to rubber chemicals were in nurses and technicians in the health and social services. CONCLUSIONS: These findings identify jobs and types of work where contact with causal agents is common and potentially preventable.

Adult↗
PubMed2006

The radiological properties of a novel lung tissue substitute.

Lung phantoms have been manufactured using commercially available, polyurethane foam products. Some of these materials are no longer available; therefore, a new lung tissue substitute was developed. The elemental composition and radiological properties of the new lung tissue substitute are described in this paper. Because the lung tissue substitute will be used to manufacture phantom lungs that will be used to evaluate chest counting systems, it is necessary to know the radiological properties of the material. These properties must be compared with reference materials and materials that have been used for lung phantoms in the past. The radiological properties of interest include the electron density, mean excitation energy, electron stopping power and photon mass attenuation coefficients. In all these properties, the calculated values for the new lung tissue substitute closely matched the calculated values of ICRU Publication 44 lung tissue. Good agreement was also found when the new lung tissue substitute was compared with the Griffith lung tissue substitute described by the ICRU. The new material was determined to be an excellent lung tissue substitute.

Biomimetic Materials↗
PubMed2005

Incidence by occupation and industry of acute work related respiratory diseases in the UK, 1992-2001.

AIMS: To summarise incidence rates and epidemiological characteristics of new cases of work related respiratory disease reported by specialist physicians in thoracic and occupational medicine, with particular reference to occupation, industry, and causal agents for asthma, inhalation accidents, and allergic alveolitis. METHODS: Cases reported 1992-2001 to the SWORD and OPRA national surveillance schemes, in which almost all UK chest and occupational physicians participate, were analysed by age, sex, cause, occupation, and industry, with incidence rates calculated against appropriate denominators. RESULTS: Excluding diseases of long latency, infrequently seen by occupational physicians, the distribution of diagnoses in the two specialties was similar, but with rates generally much higher in occupational than chest physicians. Occupational asthma was responsible for about 25% of cases overall, affecting mainly craft related occupations and machinists, and most often attributed to isocyanates, metals, grains, wood dusts, solders, and welding fume. These same occupations were those at highest risk from inhalation injuries, most frequently caused by irritant gases, vapours, and fume. Among medical technicians and nurses, however, glutaraldehyde and latex were the main causes of occupational asthma. Allergic alveolitis was seldom reported, with almost all cases in agriculture, forestry, and fishing. CONCLUSION: During the 10 year period studied, there were few changes in level of reported incidence, apart from some decline in occupational asthma and inhalation injuries. These results and their implications should be distinguished from much higher estimates of asthma made worse by work derived from population surveys, based on prevalence rather than incidence, and self-reported symptoms rather than diagnoses made by specialist physicians. Even so, the reported incidence of new cases of acute respiratory illness caused by work remains substantial.

Accidents, Occupational↗
PubMed2005

Asbestos, asbestosis, and lung cancer: a critical assessment of the epidemiological evidence.

The question of whether lung cancer can be attributed to asbestos exposure in the absence of asbestosis remains controversial. Nine key epidemiological papers are reviewed in a point/counterpoint format, giving the main strengths and limitations of the evidence presented. Of the nine papers, two concluded that asbestosis was necessary and seven that it was not. However, the study design, nature and circumstances of exposure and method of analysis of the studies differed considerably, and none was considered definitive. It is concluded that, because of the relative insensitivity of chest radiography and the uncertain specificity of findings from histological examinations or computed tomography, it is unlikely that epidemiology alone can put either the strict scientific or practical medicolegal questions beyond doubt. It is probable that the issue may depend critically on asbestos fibre type, an aspect not so far addressed.

Asbestos↗
PubMed2004

Dose limits for man do not adequately protect the ecosystem.

As has been noted by both of our participants, it is interesting to see that their views approached agreement during the course of the debate. This is not altogether unexpected since the topic is on that has many facets. It is fair to say that protecting man is an appropriate starting point for the protection of other more, or less, radiosensitive life forms sharing the planet with us. That there may be special situations requiring attention has been recognized by both of our participants. That the ICRP recognizes the need for further work on this topic is encouraging for ourselves as well as the 'bugs and bunnies'.

Conservation of Natural Resources↗
PubMed2004

Mortality in a cohort of vermiculite miners exposed to fibrous amphibole in Libby, Montana.

BACKGROUND: Fibrous tremolite is a widespread amphibole asbestiform mineral, airborne fibres of which constitute an environmental hazard in Libby, Montana, northern California, and elsewhere. AIMS: To determine excess risk from lung cancer, mesothelioma, and all-cause mortality in a cohort of men exposed to tremolite, but no other form of asbestos. METHODS: Mortality by certified cause and various measures of exposure to tremolite and related amphibole fibres was assessed in a cohort of 406 vermiculite mineworkers in Libby, Montana, employed before 1963 and followed until 1999. RESULTS: Total deaths were: lung cancer 44 (SMR 2.40), non-malignant respiratory disease (NMRD) 51 (SMR 3.09), all causes 285 (SMR 1.27); included among the total were 12 deaths ascribed to mesothelioma (4.21% of all deaths). Adjusted linear increments in relative risks (per 100 f/ml.y), estimated by Poisson regression, were: lung cancer (0.36, 95% CI 0.03 to 1.20), NMRD (0.38, 95% CI 0.12 to 0.96), and all deaths (0.14, 95% CI 0.05 to 0.26). CONCLUSIONS: The all-cause linear model would imply a 14% increase in mortality for mine workers exposed occupationally to 100 f/ml.y or about 3.2% for a general population exposed for 50 years to an ambient concentration of 0.1 f/ml. Amphibole fibres, tremolite in particular, are likely to be disproportionately responsible for cancer mortality in persons exposed to commercial chrysotile, but to what extent cannot be readily assessed.

Aluminum Silicates↗
PubMed2003

Semper Paratus.

Explore the source record for details and available documents.

Disaster Planning↗
PubMed2003

Back to basics?

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Conflict of Interest↗
PubMed2003

On the interpretation and use of neutron calibration coefficients.

Calibration laboratories provide measurement services that include determining the calibration coefficients for neutron survey meters and personal dosemeters. While there are numerous documents dealing with the procedures for calibration of neutron measuring devices, the purpose of this paper is to clarify the use of the particular dose equivalent conversion coefficients used at the National Institute of Standards and Technology and the Pacific Northwest National Laboratory for these calibrations.

Calibration↗
PubMed2002

Microdosimetric properties of ionizing electrons in water: a test of the PENELOPE code system.

The ability to simulate the tortuous path of very low-energy electrons in condensed matter is important for a variety of applications in radiobiology. Event-by-event Monte Carlo codes such as OREC, MOCA and PITS represent the preferred method of computing distributions of microdosimetric quantities. However, event-by-event Monte Carlo is computationally expensive, and the cross sections needed to transport simulations to this level of detail are usually only available for water. In the recently developed PENELOPE code system, 'hard' electron and positron interactions are simulated in a detailed way while soft' interactions are treated using multiple scattering theory. Using this mixed simulation algorithm, electrons and positrons can be transported down to energies as low as 100 eV. To our knowledge, PENELOPE is the first widely available, general purpose Monte Carlo code system capable of transporting electrons and positrons in arbitrary media down to such low energies. The ability to transport electrons and positrons to such low energies opens up the possibility of using a general purpose Monte Carlo code system for microdosimetry. This paper presents the results of a code intercomparison study designed to test the applicability of the PENELOPE code system for microdosimetry applications. For sites comparable in size to a mammalian cell or cell nucleus, single-event distributions, site-hit probabilities and the frequency-mean specific energy per event are in reasonable agreement with those predicted using event-by-event Monte Carlo. Site-hit probabilities and the mean specific energy per event can be estimated to within about 1-10% of those predicted using event-by-event Monte Carlo. However, for some combinations of site size and source-target geometry, site-hit probabilities and the mean specific energy per event may only agree to within 25-60%. The most problematic source-target geometry is one in which the emitted electrons are very close to the tally site (e.g., a point source on the surface of a cell). Although event-by-event Monte Carlo will continue to be the method of choice for microdosimetry, PENELOPE is a useful, computationally efficient tool for some classes of microdosimetry problem. PENELOPE may prove particularly useful for applications that involve radiation transport through materials other than water or for applications that are too computationally intensive for event-by-event Monte Carlo, such as in vivo microdosimetry of spatially complex distributions of radioisotopes inside the human body.

Dose-Response Relationship, Radiation↗
PubMed2002

Soluble HLA-II expression in African-Americans.

OBJECTIVE: In this study we evaluated the contribution of major histocompatibility complex (MHC) genes to soluble histocompatibility antigen class II (sHLA-II) secretion in African American patients with rheumatoid arthritis (RA). METHODS: A sensitive enzyme-linked immunoassay was used to quantitate sHLA-II in the serum of 7 patients with RA, as well as 28 of their kinships and 49 HLA typed normal African American individuals. RESULTS: Mean sHLA-II values were higher in patients with RA than those in healthy African American individuals (p < 0.05). There were variations in concentrations in individual patients but these were unrelated to any apparent clinical event. The proportion of unaffected family members with detectable levels of sHLA-II was not significantly different than those in normal controls. Neither specific HLA-haplotype, or HLA-allele(s) correlated with high or low sHLA-II secretion. CONCLUSIONS: Our data suggest that sHLA-II molecules are not regulated by MHC linked genes but may be regulated by non-MHC linked genes and racial background may reflect genetic heterogeneity of the expression of this soluble HLA material. These observations contrast with previous observations concerning soluble HLA class I (sHLA-I) molecules in a described population sample which were almost the precise reverse.

Arthritis, Rheumatoid↗
PubMed2002

Surveillance for work-related hearing loss in the UK: OSSA and OPRA 1997-2000.

Surveillance data on occupational audiological disorders have been collected by the Occupational Surveillance Scheme for Audiological Physicians (OSSA) since October 1997 and by the Occupational Physicians Reporting Activity (OPRA) from January 1996. During the 3 years ending in September 2000, a total of 1620 new cases were received from consultant audiological physicians; 988 new cases were estimated from reports by occupational physicians in the period from October 1997 to September 2000. The annual incidence of occupational noise-induced hearing loss (NIHL) was 1.94 and 1.23 per 100 000 workers for the OSSA and OPRA schemes, respectively. The median age at diagnosis with NIHL was 59 years in OSSA reports and 50 years in OPRA; nearly all cases were seen in men (95.6 and 92.5% male cases for OSSA and OPRA, respectively). High incidence rates based on OSSA reports were seen in foundry labourers (64.0 per 100 000 employed), coal gas and coke oven furnace workers (54.6), workers in transport and communication (43.1), metal workers (31.3), and members of the armed forces (28.3). Data from occupational physicians point to high rates in sawyers and woodworking machinists, metal furnace workers, coach and carriage builders, maintenance fitters, and engineering labourers. Among workers aged < or =45 years, those in manufacturing and the armed forces were prominent. The long latency of occupational hearing loss makes surveillance difficult, but consistent patterns in occupational risk suggest targets for preventive efforts.

Female↗