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Biomedical subjects

W J Nicholson

Publications and source records attributed to W J Nicholson.

At least 37 records · Page 2Linked to original sources
PubMed1990

Severe aortic regurgitation as a late complication of temporal arteritis.

Two patients with a remote history of pathologically documented giant cell arteritis developed severe regurgitation. The first patient developed severe aortic regurgitation five years after the pathologic documentation of giant cell arteritis of the temporal arteries. Giant cell arteritis involvement of the aortic root was confirmed. The second patient developed aortic regurgitation seven years after pathologic documentation of giant cell arteries of the temporal arteries. Although pathologic confirmation of the aortic root process was not obtained, this case strengthens the clinical association between giant cell arteritis of the temporal arteries and subsequent aortic root dilatation and severe aortic regurgitation. Observation for signs of de novo severe aortic regurgitation is indicated in follow-up of patients with temporal arteritis.

Aged↗
PubMed1989

Quantitative assessment of lives lost due to delay in the regulation of occupational exposure to benzene.

Benzene exposure can cause leukemia, aplastic anemia, and possibly lymphoma. In 1978, on the basis of strong but incomplete data then available on the risk of benzene-induced leukemia, the U.S. Occupational Safety and Health Administration (OSHA) reduced the permissible occupational exposure standard for benzene from 10 ppm to 1 ppm. Shortly thereafter, the Fifth Circuit Court of Appeals stayed this ruling, and in 1980, the Supreme Court overturned the regulation, citing insufficient evidence of benefit. Thus, from 1978 until the standard was again lowered to 1 ppm in 1987, American workers were exposed to benzene at levels in excess of 1 ppm. An estimated 9600 were exposed to levels between 1 and 10 ppm, and an additional 370 were exposed at levels above 10 ppm. To assess the risk resulting from this delay in regulation, we have conducted an epidemiologic risk analysis. We merged data on numbers of persons (238,000) exposed to benzene in seven occupational categories with dose-response data from three epidemiologic studies. The range of risk in these studies indicates that 44 to 152 excess leukemia deaths will ultimately result from exposure to benzene at 10 ppm over a working lifetime (45 years) and that lower or briefer exposures will result in proportionately fewer deaths. On this basis, we calculated that between 30 and 490 excess leukemia deaths will ultimately result from occupational exposures to benzene greater than 1 ppm that occurred between 1978 and 1987. Deaths from aplastic anemia and lymphoma will likely add to this toll. These data confirm the risk of regulatory delay. They suggest that the courts, in reviewing public health regulations, must beware of facile cost-benefit arguments and be willing to accept strong evidence of health risk even when such evidence is incomplete.

Benzene↗
PubMed1989

Airborne mineral fibre levels in the non-occupational environment.

Numerous sources of asbestos exist that may contribute to non-occupational exposures, among the important ones being building surfacing materials that have been damaged or allowed to deteriorate. Even more important is the potential exposure from improperly controlled maintenance activities in buildings. Evidence exists suggesting that vehicle braking makes a significant contribution to ambient asbestos levels, but more data are required to establish its extent. Many asbestos materials are present in homes, and fibres may be released during home renovations or repairs. Little information exists on the levels of other mineral fibres in the non-occupational environment or on the relative contributions from potential sources.

Air Pollutants↗
PubMed1988

Multipurpose A2 catheter approach to left heart catheterization in severe aortic stenosis.

An approach has been presented for the performance of right and left heart catheterization, left ventriculography, supravalvular aortography, and coronary arteriography utilizing a #8 French, A2 multipurpose catheter. Using the manipulations described herein, the left ventricle was entered in 96% of the patients. The multipurpose catheter is an excellent catheter for left ventriculography, negating the need for catheter exchange once the left ventricle has been entered. Likewise, this catheter provides excellent supravalvular aortography and selective coronary arteriography supplemented as needed with preformed coronary arteriographic catheters. This method provides a very safe, efficient approach to the performance of complete heart catheterization in patients with clinically significant aortic stenosis.

Aortic Valve Stenosis↗
PubMed1988

IARC evaluations in the light of limitations of human epidemiologic data.

Considerable human data are available that would causally associate human cancer with occupational exposures through the identification of substantial workplace risks. Much additional data are available, indicating lesser risks, that have not achieved widespread acceptance because of the limitations of epidemiologic techniques. Limitations of epidemiologic techniques also limit the associations that can be made, using general population data, between cancer mortality and occupation. These same uncertainties, however, also affect assertions of absence of effect. Apparently "negative" results must be evaluated with the same critical view as are most "positive" results.

Adult↗
PubMed1985

Selection factors in cohort studies.

Cohort studies play an important role in the quantitation of cancer risk among occupationally exposed individuals. Properly conducted cohort studies can develop important data on the age, time, and exposure dependence of cancer risk. Such information allows identification of possible selection effects which may be present and allows generalization of risk estimates to other exposure circumstances.

Adult↗
PubMed1984

Distribution of blood lead, blood cadmium, urinary cadmium, and urinary arsenic levels in employees of a copper smelter.

A cross-sectional medical examination of a copper smelter work force included determination of blood lead (Pb-B), zinc protoporphyrin (ZPP), blood cadmium (Cd-B), urinary cadmium (Cd-U), and urinary arsenic (As-U), since it was known that such metal impurities were present in the copper concentrate. A total of 776 copper smelter employees (680 active and 96 retirees and ex-employees) were examined. Another 144 men, never employed in the smelter, but who had worked in copper mines (and sometimes in gold mines) were also examined. Mean Pb-B, ZPP, Cd-B, and As-U were significantly higher in active copper smelter employees than in retirees or miners, indicating exposure and absorption in the copper smelter. Significant correlations between Pb-B and Cd-B, and Cd-U and As-U were present, confirming the common source of absorption. Although there was evidence for an increased lead absorption, this was very moderate, with practically no Pb-B levels in excess of 60 micrograms/dl. A marked effect of smoking on blood cadmium levels was present; nevertheless, for all smoking categories Cd-B levels were significantly higher in active employees, indicating the independent contribution of exposure to cadmium in the smelter. Cd-U did not exceed 10 micrograms/g creatinine, the generally accepted "critical" level for the kidney, but was higher than 2 micrograms/g creatinine, a level very rarely exceeded in the general population, in a sizable proportion of those examined. The highest Cd-U levels were found in retired copper smelter employees; age might have been a contributing factor, besides a longer duration of exposure in the smelter.

Absorption↗
PubMed1984

Occupational hazards in the VC-PVC industry.

Overall, the results of the analysis of 12 studies of VC production and polymerization workers demonstrate an enormously elevated risk of liver malignancies, the possibility of a twofold increased risk of brain and central nervous system tumors and perhaps, also, of malignancies of the lymphatic and hematopoietic system. However, the role of other agents cannot be excluded in the etiology of nonhepatic malignancies. Bronchogenic carcinoma does not appear to be increased from exposures to VC monomer, although a relationship to PVC dust was suggested in one study. These conclusions must be considered in light of limited data on workers followed more than 25 years from onset of exposure. Considering the numbers of observed and expected deaths in all studies, it would appear that the excess of malignancies at nonhepatic sites is less than the excess of liver tumors. Data presented elsewhere in this volume (Nicholson and Henneberger, 1983) suggest that exposure reductions in 1974 may have virtually eliminated the VC-associated risk of liver cancer if the current U.S. standard is met. To the extent that VC exposure is associated with other cancers, a similar risk reduction would be expected. Raynaud's phenomenon, acroosteolysis, scleroderma-like skin lesions, hepato- and splenomegaly with noncirrhotic hepatic fibrosis, and severe portal hypertension have been associated with past heavy exposures to VC. Evidence exists that the liver disease and portal hypertension may progress following cessation of exposure. However, all of the above syndromes were found largely in heavily exposed individuals. Their occurrence would be much less likely in workers exposed only to concentrations currently allowed. Pulmonary deficits, X-ray abnormalities, and, perhaps, lung cancer have been associated with VC/PVC exposure. Because of the possible contribution of PVC dust to these findings, engineering controls during polymer drying, bagging and usage are warranted.

Chemical Industry↗
PubMed1984

Trends in cancer mortality among workers in the synthetic polymers industry.

A high risk of death from liver HSA has been documented from past exposures to VC. Similar to other carcinogens, the risk of VC-induced liver HSA appears to increase as the second or third power of time from onset of exposure. It is possible to project future mortality using this power relationship, estimates of VC exposure, and observed mortality to 1980. These projections suggest that 200-600 deaths may occur in the United States and 550-2,800 in Western Europe from liver HSA. These projections also suggest that a 1 ppm standard in the VC industry will go far to protecting workers from future malignant disease.

Chemical Industry↗
PubMed1983

Urinary mutagen levels in smokers.

Urinary mutagen levels were measured over an 8-week period in a group of 13 smokers. Individual urinary mutagen levels were observed to be relatively constant and while there was a general correlation between mutagen excretion levels and cigarette consumption, individuals' excretion levels could not be predicted on the basis of either the numbers of cigarettes smoked or the tar content of the cigarettes.

Dose-Response Relationship, Drug↗
PubMed1982

Occupational exposure to asbestos: population at risk and projected mortality--1980-2030.

Estimates have been made of the numbers of cancers that are projected to result from past exposures to asbestos in a number of occupations and industries. From 1940 through 1979, 27,500,000 individuals had potential asbestos exposure at work. Of these, 18,800,000 had exposure in excess of that equivalent to two months employment in primary manufacturing or as an insulator (greater than 2-3 f-yr/ml). 21,000,000 of the 27,500,000 and 14,100,000 of the 18,800,000 are estimated to have been alive on January 1, 1980. It is further estimated that approximately 8,200 asbestos-related cancer deaths are now occurring annually. This will rise to about 9,700 annually by the year 2000. Thereafter, the mortality rate from past exposure will decrease, but still remain substantial for another three decades.

Adolescent↗
PubMed1980

Radiological evidence of asbestos disease among ship repair workers.

Asbestos materials are now infrequently used in new ship construction. However, significant amounts were used in vessels constructed before 1975. As a consequence, for the next 30 or more years, the potential for asbestos exposure in the repair of such vessels will remain. We studied 286 workers who were 30 or more years from onset of employment in ship repair work. Eighty-six percent had radiological evidence of asbestosis, and five instances of previously undiagnosed lung cancer were found. This suggests that unless industrial hygiene precautions are taken in the future repair of vessels that have been built with asbestos, we will add additional decades to the legacy we already face as the result of uncontrolled shipyard exposures of the past.

Adult↗
PubMed1980

Lung cancer prevalence among shipyard workers.

The prevalence of lung cancer has been ascertained during a survey of 286 shipyard workers all 20 to 45 years from onset of asbestos exposure in shipyard work. Two men had had previous thoracic surgery for lung cancer. In addition, bronchogenic carcinoma was found in five men. One was among the 35 men less than 30 years in the yard; three were in the 191 who had begun work 30 to 39 years before, and one was in the group of 60 men who were 40+ years from onset. The potential usefulness of large-scale surveillance programs for the early detection of lung cancer among current and former shipyard workers is discussed.

Aged↗