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Biomedical subjects

H Checkoway

Publications and source records attributed to H Checkoway.

At least 91 records · Page 5Linked to original sources
PubMed1993

Mortality among workers in the diatomaceous earth industry.

A cohort mortality study was conducted among workers from two plants in the diatomaceous earth mining and processing industry in California. Diatomaceous earth consists of the skeletal remains of diatoms. Exposure to amorphous (non-crystalline) and crystalline silica in the form of quartz results from open pit mining and exposure to crystalline silica (principally cristobalite) occurs in the processing of the material. Lung cancer and non-malignant respiratory diseases have been the health outcomes of greatest concern. The main study cohort included 2570 white men (533 Hispanic and 2017 non-Hispanic workers) who were employed for at least 12 months cumulative service in the industry and who had worked for at least one day during the follow up period, 1942-87. Vital status was ascertained for 91% of the cohort and death certificate information was retrieved for 591 of 628 (94%) identified deaths. The all causes combined standardised mortality ratio (SMR) was slightly increased (SMR = 1.12; 628 observed) compared with rates among US white males. The principal contributors to this excess were increased risks from lung cancer (SMR = 1.43; 59 observed) and non-malignant respiratory disease (NMRD) excluding infectious diseases and pneumonia (SMR = 2.59; 56 observed). The excess of lung cancer persisted when local county rates were used for comparison (SMR = 1.59). Internal rate comparisons by Poisson regression analysis were conducted to assess potential dose-response relations for lung cancer and NMRDs. Mortality trends were examined in relation to duration of employment in dust exposed jobs and with respect to an index of cumulative exposure to crystalline silica. The crystalline silica index was a semiquantitative measure that combined information on duration of exposure, differences in exposure intensity between jobs and calendar periods, the crystalline content of the various product mixes, and the use of respiratory protection devices. Increasing gradients of risk were detected for lung cancer and NMRD with both exposure indices. The relative risk trends for lung cancer and NMRD with crystalline silica exposure lagged 15 years were respectively: 1.00, 1.19, 1.37, and 2.74, and 1.00, 1.13, 1.58, and 2.71. Based on a review of available but limited data on cigarette smoking in the cohort and from application of indirect methods for assessing confounding variables, it seems unlikely that smoking habits could account for all of the association between exposure to dust and lung cancer. The intense and poorly controlled dust exposures encountered before the 1950s were probably the most aetiologically significant contributors to risks from lung cancer and NMRDs. The absence of an excess of lung cancer among workers hired since 1960, and the finding of no deaths attributed to pneumoconiosis as an underlying cause of death among workers hired since 1950 indicate that exposure reductions in the industry during the past 40 years have been successful in reducing excess risks to workers. Further mortality follow up of the cohort and the analysis of radiographic data will be needed to determine conclusively the long term patterns of disease risks in this industry.

Adolescent↗
PubMed1993

Correlation between respiratory symptoms and pulmonary function in asbestos-exposed workers.

Studies of respiratory questionnaire efficacy have emphasized reliability of responses; few have validated symptom response with objective measures of pulmonary function. To determine whether respiratory symptoms are associated with diminished pulmonary function, symptoms reported on the American Thoracic Society (ATS-DLD-78A) questionnaire were correlated cross-sectionally with measured spirometric volumes in 816 asbestos-exposed workers. Cough, phlegm, wheeze, and dyspnea were inversely related to pulmonary function. Cough, phlegm, and chronic bronchitis were associated with a 2 to 8% reduction (p < 0.001) in predicted values for forced vital capacity (FVC) and forced expiratory volume (FEV1); wheeze and dyspnea were clinically more significant, with an 11 to 17% reduction (p < 0.001). Wheeze, dyspnea, and roentgenographic fibrosis were all significant independent predictors of risk for restrictive impairment. These results support the validity of the ATS questionnaire as an epidemiologic tool and emphasize the importance of clinical history in assessing respiratory status.

Aged↗
PubMed1993

Adverse reproductive outcomes and occupational exposures among nurses: an investigation of multiple hazardous exposures.

1. The increasing numbers of pregnant women and women of childbearing age who are employed and exposed to hazardous substances pose occupational health concerns. 2. The findings of this study indicate the importance of not minimizing concern about exposure to radiation. Radiation monitoring should be implemented to a greater extent, and methods to measure low dose chronic radiation exposure should be developed. 3. Synergy between the adverse reproductive effects from multiple workplace factors among nurses, including but not limited to radiation, video display terminal use, and chemotherapeutic agents, warrants further evaluation.

Adolescent↗
PubMed1992

Cancer identification using a tumor registry versus death certificates in occupational cohort studies in the United States.

Studies of cancer incidences among occupational cohorts are rarely performed in the United States because of incomplete registration and a limited time period available for follow-up. This study used data from concurrent studies of cancer mortality and incidence among a cohort of 4,528 fire fighters and police officers employed by the cities of Seattle and Tacoma, Washington, between 1944 and 1979 to examine the relative advantages of tumor registry and death certificate information. As expected, an increased ability to study relatively common cancers with low fatality rates was demonstrated using incidence data. The most dramatic example was seen for bladder cancer. Twenty-four bladder cancers had been diagnosed among the study cohort between 1974 and 1989, whereas only two deaths were attributed to this malignancy. The standardized incidence ratio for bladder cancer was 1.05 (95% confidence interval 0.67-1.55), whereas the corresponding standardized mortality ratio was 0.46 (95% confidence interval 0.05-1.65). The observed relative risk estimates for rapidly fatal cancers were similar using the two sources of information, and no increase in precision was observed. Of 142 persons in the registry area who died of cancer during the study period, 20 (14%) had a different site listed on the death certificate than was identified by the registry. Approximately 7% of the potential person-years of follow-up were lost due to migration out of the registry area; loss to follow-up was greater among older and short-term workers, but did not exceed 13% of the person-years. Population-based tumor registries can be a useful resource in the investigation of occupational cancer in the United States, especially for the study of cancers with high survival rates.

Adult↗
PubMed1992

Time-weighted averages, peaks, and other indices of exposure in occupational epidemiology.

Dose surrogates commonly used in occupational epidemiology are exposure intensity, exposure duration, and cumulative exposure. The appropriateness of any of these measures as dose indicators depends on the nature of the induction process for the disease under consideration. Peak exposure intensity is often associated with acute health outcomes, whereas cumulative exposure is generally more relevant for diseases with long induction times, i.e., "chronic" diseases. However, there may be situations where peak exposure is etiologically relevant in chronic disease induction, such as might occur with nonlinear rates of damage during brief intervals of very high exposure. An approach is described for evaluating the effect of peak exposures in which peaks may be defined on a relative basis for each worker, or with respect to an absolute value, such as the permissible occupational exposure limit. The analytic strategy is illustrated with data from a case-control study of silicosis in relation to quantitative estimates of silica exposure. In this example, relative peak exposures and average non-peak exposures appear to be better predictors of silicosis risk than cumulative exposure.

Adult↗
PubMed1992

Peripheral blood cell activities of monoamine oxidase B and superoxide dismutase in Parkinson's disease.

Monoamine oxidase type B (MAO-B) and superoxide dismutase (SOD) are two enzyme systems that are potentially relevant to an oxidative stress model of Parkinson's disease (PD) causation. Activities of MAO-B in platelets (nmol/10(8) cells/hr) and total SOD in lymphocytes (U/mg protein) were assayed among 28 cases of idiopathic PD and 22 controls. As anticipated, MAO-B was lowest in PD cases on selegiline (L-deprenyl) therapy (mean 1.10). There was a slight deficit of MAO-B among male cases not taking selegiline compared to controls (3.78 vs. 4.15), but the opposite trend was observed for females (6.18 vs. 4.16). SOD was slightly higher in cases (7.40), than controls (6.81). Excess SOD among PD cases was seen irrespective of gender, age, or selegiline treatment, although none of the differences was statistically significant. Future research on SOD should take advantage of the availability of assays specific for the cytosolic and mitochondrial forms of the enzyme.

Adult↗
PubMed1992

Peripheral markers of neurochemical function among workers exposed to styrene.

A cross sectional study of biological markers of neurochemical function in peripheral blood cells, and self reported nervous system symptoms, was conducted among 60 workers exposed to styrene in three reinforced plastics plants and 18 reference workers not exposed to styrene or other solvents. Concentrations of styrene in the air at the plants ranged from less than 1 to 160 ppm. Biomarkers of neurochemical function measured were: sigma receptor binding in lymphocytes, monoamine oxidase type B (MAO-B) activity in platelets, and serotonin uptake by platelets. Blood styrene concentration was used as the exposure index to take account of the use of protective equipment and dermal uptake. Four blood styrene exposure groups were defined as: non-exposed (reference) and exposed to less than 0.05, 0.05-0.19, and greater than or equal to 0.20 micrograms/ml. The prevalences of headache, dizziness, light headedness, fatigue, irritability, memory loss, and feeling "drunk" at work increased with increasing blood styrene concentration. No effect on sigma receptor binding was seen. A slight positive correlation was found for uptake of serotonin, which has been used as an exposure related effect indicator in previous studies of workers exposed to solvents. The MAO-B activity decreased with increasing blood styrene concentration; the mean (SE) MAO-B values for the four groups were 34.2 (3.0), 28.1 (5.3), 20.1 (4.8), and 16.9 (7.7) pmol/10(7) cells/min. The MAO-B activity also correlated negatively with the number of reported nervous system symptoms, whereas no associations were seen between prevalence of symptoms and either serotonin uptake or sigma receptor binding. The findings for MAO-B activity are consistent with previously reported experimental data, and suggest that MAO-B may be a useful marker of styrene neurotoxicity.

Adult↗
PubMed1991

Capillary gas chromatographic method for mandelic and phenylglyoxylic acids in urine.

In support of an occupational investigation of styrene exposure, a capillary gas chromatographic method was developed for the quantitation of the styrene metabolites mandelic and phenylglyoxylic acids. The method was based on that of Guillemin and Bauer, in which phenylglyoxylic acid was converted to mandelic acid by reduction before instrumental analysis. The earlier method had to be modified for use with capillary columns; the resulting method was sensitive, selective and reproducible. The detection limit was approximately 0.001 mg/ml urine. Approximately less than 5% relative precision was achieved in the range of 0.05-2 mg/ml urine. Mandelic acid was resolved from other components of urine and from by-products of derivatization.

Air Pollutants, Occupational↗
PubMed1991

Occupational carpal tunnel syndrome in Washington State, 1984-1988.

BACKGROUND: There are no published population-based studies of occupational carpal tunnel syndrome (OCTS) using a strict case definition. Most studies are either industry specific or present patient self-report of symptoms. METHODS: We conducted a population-based incidence study of OCTS using the Washington State Workers' Compensation database. Incident OCTS claims were identified with paid bills for physician reported ICD codes 354.0 and 354.1. RESULTS: There were 7,926 incident OCTS claims identified for the years 1984-1988, which yields an industry-wide incidence rate of 1.74 claims/1,000 FTEs. The mean age (37.4 years) and female/male ratio (1.2:1) in this population differ from those reported in nonoccupational carpal tunnel studies (mean age, 51 years; female/male ratio, 3:1). The female-specific OCTS incidence rate increased significantly during the study period. The highest industry specific OCTS rates were found in the food processing, carpentry, egg production, wood products, and logging industries. CONCLUSION: Demographic differences and industry-specific rates consistent with workplace exposures suggest that OCTS is distinct from CTS occurring in nonoccupational settings. Workers' compensation data proved useful in identifying high risk industries.

Adult↗
PubMed1991

A pilot study of occupational and environmental risk factors for Parkinson's disease.

Increasingly, the etiology of Parkinson's disease (PD) has been linked to exposures to environmental toxicants. This epidemiologic pilot study used a self-administered questionnaire among 34 PD cases and 22 other neurology clinic control patients. All subjects were at least 40 years old. Risk factors investigated included occupation, well-water use, pesticide use, metal exposures, medical history, smoking, alcohol consumption, and drug use. Twenty-six percent of the male PD cases reported having been employed in farming versus eleven percent for male controls (OR = 3.1, 95% C.I. = 0.3 to 35). Sixteen percent of male cases versus none of the controls reported employment as welders. No clear trends involving exposure to either occupational or home pesticides emerged. In assessing occupational exposures to metals, aluminum and copper exposures tended to be more common among male cases than male controls. Additionally, as reported in other studies, smoking showed an inverse relationship with PD. Although the findings reported here are provocative, these results are statistically imprecise and must be interpreted cautiously because of the small number of subjects included in the study.

Adult↗
PubMed1991

Data pooling in occupational studies.

Summarizing epidemiologic data from multiple studies can be accomplished either by a meta-analysis of published findings or by pooling data and performing new analyses of enlarged data sets. Meta-analysis is relatively easy and inexpensive to perform but usually is restricted to examination of overall risks. Data pooling offers a more direct approach for subcohort analyses and for estimation of dose-response relationships. The advantages of pooling data from multiple studies of workers with similar exposures pertain primarily to enlarged study bases and a greater potential for evaluating statistically stable dose-response relationships than can be accomplished by meta-analysis. Valid methods for data pooling that are developed for cohort mortality studies of relatively large worker populations ultimately can be applied to studies of other health outcomes using different study designs.

Data Collection↗
PubMed1989

Injuries on the fireground: risk factors for traumatic injuries among professional fire fighters.

This case-control study within a metropolitan fire department evaluated the effect of self-contained breathing apparatus (SCBA) and other risk factors on three types of injury at the scene of a fire (smoke inhalation, burns, and falls). Data on 75 injured fire fighters and 144 controls came from telephone interviews and department records. The two sets of uninjured fire-fighter controls were matched to cases on incident (n = 72) or on job position and fire type and size (n = 72). Smoke inhalation cases were not significantly different from controls in SCBA use, cigarette smoking, previous fires in the shift, or injury history. Jobs with high risk of burns included nozzle operator, engine officer, and forcible-entry person in first-due companies (OR = 20.1). Other risk factors for burns were: basement origin of fire (OR = 10.2); prior fire-fighting training outside the present department (same fire: OR = 11.2; similar fire: OR = 3.9); and on-duty injury in the prior 12 months (same fire: OR = 4.3; similar fire: OR = 3.5). When other risk factors were considered, consistent SCBA use was associated with falls (same fire: OR = 11.8; similar fire: OR = 4.3) but not with burns. Risk of falls also was elevated among members of truck companies (OR = 17.7) and fire fighters without children (same fire: OR = 8.4; similar fire: OR = 7.4). On-duty injury in the past 12 months was associated with falls when one compared cases with similar-fire controls (OR = 5.5), but not with controls attending the same fire. Neither age nor experience was related to injury in this population.

Accidental Falls↗
PubMed1989

Design and conduct of occupational epidemiology studies: I. Design aspects of cohort studies.

Cohort and case-control studies are two standard approaches for investigating the etiology of occupational diseases. This paper, which is the first of a four-part series, contains a review of the design features of occupational cohort studies. Topics discussed include the basic features of prospective and historical cohort studies, options for defining the cohort, disease incidence ascertainment, and considerations involved in planning an occupational cohort study. Subsequent papers in this series will focus on data analysis of occupational cohort studies and the design and analysis of occupational case-control studies.

Cohort Studies↗
PubMed1989

Design and conduct of occupational epidemiology studies: II. Analysis of cohort data.

This paper reviews strategies and statistical methods for analyzing data from occupational cohort studies. Emphasis is placed on the common methods for grouped data analysis involving external and internal comparison populations. Analysis procedures reviewed are standardized mortality ratio, standardized rate ratio, and Mantel-Haenszel techniques for estimating relative risks. Methods for control of confounding, assessment of effect modification, and allowance for disease latency are discussed. These concepts and procedures are illustrated with data from an historical cohort mortality study of workers from an asbestos textile plant.

Biometry↗
PubMed1989

Design and conduct of occupational epidemiology studies: III. Design aspects of case-control studies.

Currently available approaches for the design of occupational case-control studies are reviewed. An accompanying paper reviews methods of analysis. We commence by drawing a distinction between cohort-based and registry-based studies. Methods for selecting cases and controls are then reviewed, including cumulative incidence and incidence density sampling, matching, sources of controls, and issues in control selection. Finally, the advantages and disadvantages of the case-control approach are summarized.

Cohort Studies↗
PubMed1989

Design and conduct of occupational epidemiology studies: IV. The analysis of case-control data.

This paper reviews the basic methods of analysis of data from case-control studies. The standard analytic methods are outlined first for a single stratum. The discussion is then extended to stratified analysis, multiple exposure levels, and analyses allowing for disease induction and latency periods. Finally, logistic regression is discussed as an extension of the more basic forms of analysis. The methods are illustrated with data from a study of lung cancer among asbestos textile plant workers.

Biometry↗
PubMed1988

Estimating the potential disease rate reduction under varying conditions of combined effects.

The disease rate difference between people exposed and not exposed to some factor is the familiar estimate of attributable risk. When there are two or more causal exposures which demonstrate joint effects and are independently distributed, partitioning a population's overall rate between factors requires estimates of the marginal distributions of exposures and the independent (unconditional) and combined rate ratios for each exposure factor. The net potential reduction in the overall disease rate resulting from elimination of one of the exposures depends on these parameters and on the model of combined effect assumed, additive, multiplicative or some departure therefrom. In this paper the authors illustrate the extent to which the assumed model of combined effect of exposures determines which parameters need to be specified to estimate disease rate reductions. The concepts presented are demonstrated algebraically and with simulated hypothetical data. An application of the method is given with data from a case-control study of smoking, asbestos exposure and lung cancer.

Data Interpretation, Statistical↗