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W K Morgan

Publications and source records attributed to W K Morgan.

At least 19 recordsLinked to original sources
PubMed2001

Radiographic abnormalities in long-tenure Vermont granite workers and the permissible exposure limit for crystalline silica.

This study was undertaken to assess the prevalence of radiographic abnormalities consistent with silicosis in a group of 600 retired granite workers who were receiving pensions. Files of regional clinics and hospitals were searched for chest radiographs taken on these men, and 470 x-ray films suitable for interpretation were located. After exclusions (women, and men who had worked in the granite industry elsewhere), 408 x-ray films were independently read by three experienced readers using the 1980 International Labour Office scheme. Dust exposures were estimated for workers hired after 1940, when the dust-control standard of 10 million particles per cubic foot (mppcf) (equivalent to 0.1 mg/m3) was put in place and monitored by the Vermont Division of Industrial Hygiene. Dust levels were initially high but were gradually reduced from 1940 to 1954, after which average quartz exposures stabilized to a mean of approximately 0.05 to 0.06 mg/m3; however, about 10% to 15% of samples after 1954 exceeded 0.1 mg/m3. Of the 408 x-ray films, 58 were taken on workers hired before dust controls were instituted in 1940, and 25.9% showed abnormalities (a profusion score of 1/0 or greater). A total of 350 x-ray films were taken on workers hired in 1940 or after, and the prevalence in this group was 5.7%. The radiographic changes in workers hired after 1940 are likely due to excessive exposures during the first 15 years of dust control. We conclude that if the exposure standard of 0.1 mg/m3 is rigorously observed in the workplace, radiographic abnormalities caused by quartz dust in long-term workers will be rare.

Aged↗
PubMed2000

Silica, silicosis, and lung cancer: a response to a recent working group report.

The relationship between crystalline silica and lung cancer has been the subject of many recent publications, conferences, and regulatory considerations. An influential, international body has determined that there was sufficient evidence to conclude that quartz and cristobalite are carcinogenic in humans. The present authors believe that the results of these studies are inconsistent and, when positive, only weakly positive. Other, methodologically strong, negative studies have not been considered, and several studies viewed as providing evidence supporting the carcinogenicity of silica have significant methodological weaknesses. Silica is not directly genotoxic and is a pulmonary carcinogen only in the rat, a species that seems to be inappropriate for assessing particulate carcinogenesis in humans. Data on humans demonstrate a lack of association between lung cancer and exposure to crystalline silica. Exposure-response relationships have generally not been found. Studies in which silicotic patients were not identified from compensation registries and in which enumeration was complete did not support a causal association between silicosis and lung cancer, which further argues against the carcinogenicity of crystalline silica.

Animals↗
PubMed2000

Rise and fall of the FEV(1).

BACKGROUND: Most studies of the rate of decline in ventilatory capacity in normal subjects take into account a relatively restricted number of factors, such as age, smoking, and dust exposure. There is increasing evidence to suggest that such a limited approach is inadequate. OBJECTIVE: To carry out a prospective study of those factors influencing the rate of decline of the ventilatory capacity in a cohort of automobile workers. DESIGN: Prospective cohort study. SETTING: Southern Ontario, Canada. PARTICIPANTS: A cohort of 181 workers employed in assembling and spray painting the chassis of new cars, a minority of whom used paints containing isocyanates. MEASUREMENTS: All participants underwent annual anthropometric measurements. Spirometry was carried out at yearly intervals, and a questionnaire relating to respiratory symptoms and smoking habits was completed annually by all participants. Daily monitoring of the isocyanate levels was carried out. RESULTS: There was no indication of any effect from isocyanate exposure. The annual decline in the FEV(1) was similar to that found in other studies, with the respective annual decrements for smokers, ex-smokers, and nonsmokers being 0.055 L, 0.046 L, and 0.035 L, respectively. The decline of the FEV(1) in those > 35 years old and < 35 years old differed appreciably. The decrements in the FEV(1) in subjects < 35 years old were influenced as much by excessive weight gain as by cigarette smoking. Loss of weight in those significantly overweight was frequently associated with improved lung function. CONCLUSIONS: While age and smoking play an important role in determining the rate of decline in the ventilatory capacity, it is clear that body weight plays a significant role and needs to be taken into account in all epidemiologic studies of the ventilatory capacity.

Aging↗
PubMed1997

Zamboni disease.

Explore the source record for details and available documents.

Hockey↗
PubMed1997

Health effects of diesel emissions.

We have reviewed the literature relating to the health effects of diesel emissions with particular reference to acute and chronic morbidity and to carcinogenicity. It is apparent that exposure to diesel fumes in sufficient concentrations may lead to eye and nasal irritation but there is no evidence of any permanent effect. A transient decline of ventilatory capacity has been noted following such exposures. There is also some evidence that the chronic inhalation of diesel fumes leads to the development of cough and sputum, that is chronic bronchitis, however, it is usually impossible to show a cause and effect relationship because of the concomitant and confounding exposures to mine dust and cigarette smoke. Although there have been a number of papers suggesting that diesel fumes may act as an carcinogen, the weight of the evidence is against this hypothesis. Finally, the role of small particles, less than 10 microns, which are frequently present in diesel emissions requires further study since there is some limited evidence that they may be partly responsible for some of the exacerbations of asthma.

Adult↗
PubMed1997

On evidence, embellishment and efficacy.

Evidence-based medicine (EBM) - to use a vogue word - is the contemporary mantra of many academic physicians. Unfortunately, the evidence they consider, although superficially convincing, is often slanted, occasionally deliberately, but more often as a result of carelessness and defects in study design. These biases and confounding factors are often hidden and arcane and seriously impair objective assessment. Such defects can only be detected when all investigators agree to go along with Bradford Hill's dictum, namely 'It is the essence of science to disclose both the data upon which a conclusion is based and the methods by which the conclusion is obtained'; a cardinal rule more often honoured in the breach than the observance.

Bias↗
PubMed1996

Effects of prolonged low exposure to methyl isocyanate.

An assessment of human pulmonary effects from long-term, low-level exposure to methyl isocyanate (MIC) has been undertaken. Serial pulmonary function data, cigarette smoking histories, and other information were available for over 400 workers from a large chemical facility. In addition, industrial-hygiene measurements had been made and were used to classify jobs according to level of MIC exposure. In some instances, work records were incomplete and workers' predominant job and extent of inferred exposures were therefore based on the ratings of their supervisors and coworkers. The availability of these data allowed us to evaluate the frequency of pulmonary impairment in workers according to the assumed four levels of MIC exposure. No specific or consistent pulmonary impairment was evident. Long-term, low-level exposure to MIC at the levels existing at this particular facility could not be shown to be producing detectable effects on lung function.

Air Pollutants, Occupational↗
PubMed1996

The pneumoconioses.

The stringent industrial hygiene regulations that have been introduced in North America, Europe, and Australasia have led to a decline in the incidence and prevalence of silicosis, coal workers' pneumoconiosis, and asbestosis. Although new cases of asbestosis are not occurring, an appreciable number of mesotheliomata are still being diagnosed, and there has yet been little, if any, decline in the latter tumor. These new cases are nearly entirely due to exposure to amphiboles in the 1940s and 1950s. It is expected that by about the year 2000 the incidence of mesothelioma will begin to decrease in the United States and Canada. Meanwhile there is an undue preoccupation with more and more sensitive methods of detecting asbestosis, silicosis, and coal workers' pneumoconiosis, eg, magnetic resonance imaging, bronchoalveolar lavage, and so forth. Much effort is being made in trying to detect disease in groups of workers with extremely low exposures and no symptoms. Smaller and smaller effects are being detected, with the ultimate aim appearing to be detecting nothing at all. Efforts should be made at surveying other populations exposed to agents that have recently been introduced and that could conceivably have long-term effects.

Asbestos, Amphibole↗