Search PubMed⌕ Search

Biomedical subjects

G M Marsh

Publications and source records attributed to G M Marsh.

71 records · Page 4Linked to original sources
PubMed1983

Critical review of epidemiologic studies related to ingested asbestos.

Thirteen epidemiologic studies of ingested asbestos conducted in five areas of the United States and Canada were reviewed and evaluated for the definitiveness and applicability regarding the development of ambient water quality standards. One or more studies found male or female associations between asbestos in water supplies and cancer mortality (or incidence) due to neoplasms of the esophagus, stomach, small intestine, colon, rectum, gallbladder, pancreas, peritoneum, lungs, pleura, prostate, kidneys, brain, and thyroid, and also due to leukemia. Several methodologic weaknesses and limitations were found in each study, leading to the determination that no individual study or aggregation of studies exist that would establish risk levels from ingested asbestos. A binomial probability analysis of the eight independent studies suggested that, while the level of male-female agreement was generally low, the number of observed positive associations in males and females for neoplasms of the esophagus, stomach, pancreas, and prostate was unlikely to have been generated by chance factors alone, and thus, may have a biological basis related to ingested asbestos. Cancers of the small intestine and leukemia were implicated to a lesser degree in this analysis. The patterns of integrated findings for most gastrointestinal cancers were somewhat consistent with patterns observed among asbestos-exposed occupational groups, whereas the patterns found for pancreatic cancer, kidney cancer, and leukemia were not consistent.(ABSTRACT TRUNCATED AT 250 WORDS)

Asbestos↗
PubMed1982

Cancer among workers exposed to arsenic and other substances in a copper smelter.

A study of the mortality experience of 2802 men who worked one year or more during the period 1940-4964 at a copper smelter in Tacoma, Washington, where arsenic exposure occurred showed a twofold excess in respiratory cancer deaths. Using a time-weighted measure of exposure, a life table method for accumulating dose, and a 10-year lag period, the excess ranged from 1.5 in the lowest exposure category to 2.5 in the highest exposure category. Neither duration of exposure nor time since first exposure contributed strongly to the respiratory cancer excess. The twofold excess in respiratory cancer deaths held for workers with relatively short exposures (less than 10 years) and with a relatively short latency period (less than 20 years) as well as for those with longer exposure and latent periods. This appeared to be because the respiratory cancer excess tended to disappear with time for workers who terminated employment alive, and because workers in high-exposure jobs tended to terminate more quickly than workers in low-exposure jobs. A somewhat unorthodox analytic method showed a weak relationship between the respiratory cancer excess and exposure duration when exposure intensity was held constant. Here, arsenic exposure intensity made an independent contribution to the respiratory cancer excess.

Adult↗
PubMed1982

Computerized approach to verifying study population data in occupational epidemiology.

IN a previous paper a method was presented for verifying the completeness of occupational study populations independently of company-held records. The basis for the verification scheme was the Employers Quarterly Report on Earnings (Internal Revenue Service Form 941) that is submitted to the IRS each quarter of every year for all employees on a company payroll. In employing the verification scheme two approaches can be taken in determining how many and which quarterly reports are selected: (1) If the work force is large and/or many years are surveyed, a probability sample of years and quarters within years can be selected, allowing inferences to be made with respect to the entire study population. (2) If the number of survey years and/or the size of the work force is sufficiently small, copies of all quarterly returns for each survey year can be requested thus allowing a comprehensive check for completeness to be conducted. Te verification method described in the previous paper concentrated primarily on the first-mentioned approach. The second approach is herein being dealt with as well as a computerized method for verifying the completeness of study populations. In addition a new computerized method is described that utilizes the quarterly reports as an unbiased data base for checking the accuracy of certain work history data as developed from company records. An application of the computerized methods is given using data from a recent historical-prospective study of chemical production workers.

Computers↗
PubMed1982

Proportional mortality patterns among chemical plant workers exposed to formaldehyde.

To examine the possible health risks associated with occupational exposure to formaldehyde a proportional mortality analysis was conducted on deaths occurring between 1950 and 1976 among 136 men who had been employed a month or more in one of five formaldehyde-related areas of a large chemical producing plant located in Springfield, Massachusetts, USA. Overall, no statistically significant excesses or deficits in proportional mortality were observed among the formaldehyde-exposed group based on comparisons with both United States men and men from the local county area. In addition, no important differences in mortality were observed among this group when comparisons were made with 456 male decedents from the same plant who had not had a month or more of formaldehyde exposure. Within the calendar period examined, no deaths from sinonasal cancer were observed among the chemical workers studied nor was mention made on any death certificate of sinonasal cancer as a contributory cause of death. No important excesses, trends, or patterns in cancer mortality were observed among white male formadelhyde-exposed workers when consideration was given to age and time period of death, type and duration of formaldehyde exposure, and the lapse period from the onset of the first formaldehyde-related job assignment. Although certain limitations of this study do not allow definite conclusions to be drawn, the results indicate no trends or patterns in proportional mortality that could be directly linked to exposures to formaldehyde.

Adult↗
PubMed1982

Mortality among workers in a nickel refinery and alloy manufacturing plant in West Virginia.

Workers from a nickel refinery at Huntington, W. Va., which received a nickel matte from smelters in Ontario, Canada, during 1922-47 were studied for excesses in sinonasal and lung cancers. Other workers who were in a nickel alloy production plant operated in conjunction with the refinery but who did not work in the refinery were also studied. Evidence is presented on the existence of a nasal cancer hazard and possibly a lung cancer hazard among workers employed in the nickel refinery. Two of these workers developed a sinonasal cancer. Evidence of a respiratory cancer hazard in other parts of the plant before or after 1947 is weak, and the observed results could be due to chance variations from the mortality experience of the standard reference populations. Among nonrefinery workers hired while the nickel refinery was in operation, 2 employees had a probable sinonasal cancer. The first employee worked in a high-temperature conversion process where nickel carbonate was decomposed to nickel oxide, and the second employee is believed to have done maintenance work in the plant where this process was used. For both cohorts combined there were slight overall excesses in lung, stomach, and prostate cancers with some evidence of a dose-response relationship for these cancers.

Air Pollutants, Occupational↗
PubMed1981

Endothelial morphology in long-term keratoconus corneal transplants.

Endothelial morphology was studied in 55 long-term keratoconus grafts. Photographs were taken with a Zeiss non-contact endothelial lens and analyzed with a Zeiss MOP-3 digital analyzer. Donor ages were known in 39 cases. Statistical analysis was carried out correlating endothelial cell count with several parameters, including recipient age and cell form as expressed by the coefficient of variation. Cell counts varied from 502 to 1708 cells/mm2. No correlation between cell counts and donor age was found. Recipient age had an unexpected significance as a predictor of endothelial cell survival in that cell counts decreased as recipient age increased despite donor age. As the grafts aged, more cell pleomorphism was found as expressed by the coefficient of variation.

Adolescent↗
PubMed1981

The psychiatric physical examination - Part II: findings in 75 unselected psychiatric patients.

The psychiatric physical examination described in the previous paper was done on 75 new psychiatric inpatients. The examiners were one psychiatrist and two psychiatrist-internists. Results confirmed the high frequency of known and unsuspected medical illnesses previously reported in the literature. Additionally, the specific "psychiatric physical examination" confirmed the known psychiatric diagnoses in 76% of the patients and led to consideration of a second or other psychiatric diagnoses in 43% of the patients.

Adolescent↗
PubMed1981

Use of THA in treatment of Alzheimer-like dementia: pilot study in twelve patients.

THA, a centrally acting anticholinesterase, was given intravenously in varying doses to 12 unselected cases of Alzheimer-like senile dementia. Significant improvement in memory testing occurred in 6 of 12 subjects; 9 of 12 improved in clinical staging. Analysis of results with respect to staging of dementia revealed that the degree of improvement was inversely related to the severity of dementia. Statistical analysis of these data by the Friedman test is detailed.

Acridines↗
PubMed1980

Mortality studies of smelter workers.

In view of the historic importance of smelter workers in the field of occupational medicine, it is surprising that until very recently little data was available on the mortality experience of these workers. The problem in most studies lies in identifying the smelter workers, because smelting, strictly speaking, refers to the melting of ores for the purposes of recovering metals, whereas smelters sometimes perform the operations of roasting, calcining, sintering, converting, and refining. These distinctions are not made in most mortality studies. Most mortality studies of smelter workers conducted to date have shown some excess in lung cancer. For lead, copper, cadmium, and nickel smelters a different etiologic agent has been proposed for each. These different explanations arise partly from different initial perspectives in conducting the studies. In this paper, data are presented on a current historical-prospective study of males who worked a year or more during the period January 1, 1940 to December 31, 1964 at a copper smelter in Tacoma, Washington. This smelter (and refinery) handled a copper ore with a relatively high arsenic content and produced arsenic trioxide as a by-product. Overall 97.2% of the original study population was traced through 1976. Of the 1,061 who were found to have died, death certificates were obtained for 1,018, or 96%. For all causes of death, the mortality rates in this cohort, expressed as a Standardized Mortality Ratio (SMR), were 3.5% higher than that expected based on the United States white male mortality experience. A total of 104 respiratory system cancers were observed compared to 54.6 expected (SMR = 190.5, p less than .05). Respiratory cancer rates were found to be elevated in both smokers and nonsmokers. Overall, a gradual rise in SMR's for respiratory cancer was observed with increasing duration of exposure but not with an increasing interval from onset of exposure. This observation is consistent with the notion that the effects of arsenic on cancer incidence disappear with time. This phenomenon has also been observed for cigarette smokers and chromate workers. Additional analyses are planned for the Tacoma cohort, which will examine mortality according to process as well as by exposure to arsenic and other contaminants. The importance of studies of workers at other kinds of smelters and refineries is stressed.

Aged↗
PubMed1980

Mortality of workers in the man-made mineral fibre industry.

A cohort, consisting of 7049 males who worked for one year or more as production or maintenance workers during the period 1945-1963 in one of eight US plants producing man-made mineral fibres, was followed for deaths through 1973. Standardized mortality ratios were elevated for major causes of death for men with 20 years or more since first exposure and were high when compared with those of men with less than 20 years since first exposure. None of the excesses was statistically significant. Since many causes of death were involved, the excesses observed are probably unrelated to exposure to man-made mineral fibres. Data for the three mineral wool plants included in the study could not be interpreted due to the possible use of asbestos in one or more of these plants. For the five fibrous glass plants, there was no evidence of an excess in malignant or nonmalignant respiratory disease related to exposure to respirable fibrous glass. Estimated historical respirable fibre concentrations to which workers from fibrous-glass plants were exposed were very low, less than 1/100th of the standard proposed by the US National Institute for Occupational Safety and Health.

Air Pollutants↗
PubMed1979

A method for verifying the completeness of cohorts used in occupational mortality studies.

The completeness of cohorts identified for historical prospective studies of occupational diseases is subject to many sources of error, including clerical oversight or negligence and poor company record-deeping practices. It is impossible to verify the completeness of occupational cohorts based solely on plant records, since the company files themselves may not be 100% complete. This article presents a method of verification based on IRS records which is completely independent of company-held records. The sensitivity and effectiveness of the method are demonstrated through the application of the verification scheme to an ongoing study of man-made mineral fiber workers in the United States. In six participating plants, 1990 (21.4% of the original cohort) additional records were uncovered following an initial verification and a second complete survey of plant files. It is believed that, without independent verification, errors of this magnitude may be present in many historical prospective studies of this type. An independent verification should be incorporated into all occupational study designs which utilize historical plant records as the primary data base.

Epidemiologic Methods↗
PubMedDate not supplied

An investigation of secondary exposure misclassification effects of lifelong occupational history in exposure estimation.

The effects of exposure misclassification on the interpretation of results of occupational epidemiological studies has been widely investigated and reported. Usually, only the direct effects of misclassification have been considered or simple estimates of misclassification rates have been assigned to various types of exposure estimation processes. Lifelong job profile data obtained from a previously published case-control study provided complete or nearly complete job histories of 511 decedents. An analysis of these work histories and the comparison of exposures related to longest-held job to estimated total lifetime exposures suggest that single job-based exposure estimates may lead to significant exposure misclassification rates. In addition, the appearance of shorter duration jobs in a study population occurring predominantly early in the work history may exacerbate problems associated with exposure misclassification. While few specific suggestions emerge from this analysis, the inclusion of extensive recording of the work history of study subjects emerges as a reasonable basis for the investigation and potential reduction of secondary misclassification of exposures in occupational epidemiological studies.

Aged↗
PubMedDate not supplied

A case-control study of lung cancer mortality in four rural Arizona smelter towns.

To investigate factors related to lung cancer mortality in four Arizona copper-smelter towns, the authors identified 142 lung cancer cases and 2 matched controls per case from decedent residents during 1979-1990. The authors obtained detailed information on lifetime residential, occupational, and smoking histories via structured telephone interviews with knowledgeable informants. The authors linked estimated historical environmental exposures to smelter emissions (based on atmospheric diffusion modeling of measured sulfur dioxide concentrations) with residential histories to derive individual profiles of residential exposure. The results of this study provided little evidence of a positive association between lung cancer and residential exposure to smelter emissions. Conditional logistic regression analysis revealed a statistically significant positive association between lung cancer and reported employment in copper mines and/or smelters, although specific factors associated with the apparently increased risk among these workers could not be identified in this community-based study.

Adult↗
PubMedDate not supplied

Basic occupational epidemiologic measures.

This chapter focuses on the "response" side of the exposure-response relationship and summarizes some of the measures of effect that are commonly used in occupational epidemiologic research. The author covers some basic statistical standardization procedures that are used to help compare these measures among groups that differ with respect to age or other factors.

Case-Control Studies↗
PubMedDate not supplied

Applications and limitations of air dispersion modeling in environmental epidemiology.

In epidemiological investigations, when the estimation of integrated exposures over long time intervals covering years or decades is required, the quantitative assignment of exposure levels by simplistic models may prove to be inadequate for most applications. This difficulty may be partially addressed by modifying the mathematical models used for the prediction of dispersions of emissions from pollution sources. A theoretical model based on the atmospheric dispersion of contaminants is proposed. While the development of the theoretical model is straightforward, the data requirements in the application of the model may impose some limitations. The methods developed to resolve or alleviate these limitations suggest that many currently used environmental exposure assignment techniques may be too crude to be of value; even the more sophisticated method proposed can only be used with some reservations. Although several difficulties associated with environmental exposure estimation remain unresolved, the careful and rigorous analysis of the available data and the application of the method suggested here can reduce the exposure misclassification errors to acceptable levels. The quantitative estimations of the limitations are based on estimation procedures and aerometric data used in a hilly terrain, and thus should represent testing of the method under an extreme condition.

Air Pollution↗