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Biomedical subjects

H Checkoway

Publications and source records attributed to H Checkoway.

101 records · Page 6Linked to original sources
PubMed1983

Lymphocytic leukemia and exposures to benzene and other solvents in the rubber industry.

Previous epidemiological studies on one cohort of rubber industry workers indicated that observed mortality excesses from lymphocytic leukemia were related to solvent exposures. The results of a detailed examination of the solvent exposure histories of 15 cases of lymphocytic leukemia from this cohort and 30 matched industry controls are presented. Extensive review of historical solvent use, raw materials specifications and job description records were used to reconstruct exposures to specific agents. Cases were 4.5 times as likely as controls to have had direct exposures to both benzene and other solvents. Analysis by manufacturing production source of solvent revealed that cases spent greater proportions of their work experience in jobs with potential exposures to coal tar-based benzene and xylene. No differences were seen for petroleum-derived solvents.

Adult↗
PubMed1982

A hematology survey of workers at a styrene-butadiene synthetic rubber manufacturing plant.

A previous epidemiologic study of the U.S. rubber industry indicated that there has been an excess of leukemia and lymphoma mortality among hourly workers at one styrene-butadiene rubber manufacturing plant. This investigation was a combined industrial hygiene and hematology cross-sectional survey at the same plant. The objectives of the survey were to quantify exposure levels for styrene, butadiene, benzene and toluene, and to relate these levels to hematologic variation. Personal air samples and blood specimens were obtained from 157 production workers. All exposure levels for the four chemicals assayed were well below recommended standards. The higher mean styrene (13.67 ppm) and butadiene (20.03 ppm) concentrations were found in the Tank Farm area; in all other departments the mean levels for the four chemicals were less than 2 ppm. The Tank Farm workers had slightly lower levels of circulating erythrocytes, hemoglobin, platelets and neutrophils, and slightly higher mean corpuscular red cell volumes and neutrophil band counts than the other workers. Overall, in this population there was no pronounced evidence of hematologic abnormality, as determined from examination of peripheral blood.

Adult↗
PubMed1981

A case-control study of bladder cancer in the United States rubber and tyre industry.

A case-control study of bladder cancer was conducted in five United States rubber and tyre companies to determine if there were high-risk jobs and work areas within the industry. The study included 220 male cases of bladder cancer, of whom 107 were identified from hospital record reviews and 113 from death certificates. Each case was matched individually with two industry controls by sex, race, year of birth, and company. One control was matched additionally by year of hire and duration of employment. Comparisons of cases and controls not matched by year of hire and age of hire showed no differences for those variables, which suggests that age and calendar period of first exposure to the industry were not risk determinants. When the work histories of both cases and controls were contrasted it was found that cases were more likely than controls to have worked in milling (odds ratio (OR) = 1.91) and calender operation (OR = 2.21) jobs. The relative risk estimates for milling and calender operation both exhibited linear trends of increase with duration of exposure. Milling and calender operation jobs entail potential exposures to volatilised reaction products from heated rubber stock. A better understanding of aetiological associations with job type will require more detailed characterisation of the work environment with regard to the sources and levels of aromatic amines and other suspected bladder carcinogens.

Adult↗
PubMed1977

Bias due to misclassification in the estimation of relative risk.

Lack of bias in the estimation of relative effect in epidemiologic studies depends on the internal validity of the study. This paper conveys in graphic and tabular form the direction and magnitude of bias due to misclassification of study subjects. A series of computer-generated graphs shows that the departure of the estimate of effect (relative risk or odds ratio) from its true value is a function of sensitivity and specificity (measures of classification validity), disease frequency, and exposure frequency. The discussion of bias emphasizes misclassification of the "outcome" variable; i.e., disease occurrence in a cohort study and exposure rate in a case-control study. Examples are used to illustrate that the magnitude of the bias can be large under circumstances which occur readily in epidemiologic research. When misclassification is equal for the two compared groups, the estimate is biased toward the null value, and in some instances beyond; when differential misclassification occurs (as in selective recall in case-control studies) the bias can be in either direction, and may be great. Formulas are derived to estimate the underlying true value of the relative risk or odds ratio using the investigator's observations together with the estimated sensitivity and specificity of the classification procedure.

Classification↗
PubMedDate not supplied

Latency analysis in occupational epidemiology.

Allowance for prolonged disease induction and latency times is an important consideration in occupational epidemiology studies of cancer and other delayed effects of exposure. Two useful approaches for assessing prolonged induction and latency periods are (1) exposure lagging and (2) considering exposures only within moving time windows. The exposure weighting scheme proposed by Jahr2 to assess exposure burdens is another method that accounts for induction and latency, although not explicitly. These three approaches, which are shown to be special cases of exposure weighting, are illustrated with an analysis of lung cancer mortality among a cohort of workers from an asbestos textile plant.

Adult↗
PubMedDate not supplied

Neurophysiological function in farm workers exposed to organophosphate pesticides.

To investigate neurophysiological effects of low-level exposure to foliar organophosphate residues during one season among agricultural workers, the authors performed a cross-sectional study of 67 Hispanic farm workers and 68 age-, gender-, ethnicity-, and education-matched reference subjects. The neurophysiological examination included sensory and motor nerve conduction and neuromuscular junction testing. Erythrocyte cholinesterase activity was measured at the time of examination. No statistically significant neurophysiological differences between the exposed and reference groups were observed. Farm workers and reference subjects had similar sensory nerve latency and amplitude (sural), motor nerve conduction velocity (ulnar), and neuromuscular junction function (ulnar). No relationship between duration of exposure during the season and electrophysiological measures of nerve function was found. Exposure of farm workers to the low levels of organophosphate pesticides during one season experienced by farm workers in this study was not associated with impaired peripheral neurophysiological function.

Adolescent↗
PubMedDate not supplied

Mesothelioma surveillance to locate sources of exposure to asbestos.

To determine whether there were previously unrecognized sources of asbestos exposure in British Columbia, incident mesothelioma cases (n = 51) and population-based controls (n = 154) were interviewed about their occupational histories and asbestos exposures. The following occupations were at elevated risk: sheet metal workers (OR = 9.6, 95% CI: 1.5-106), plumbers and pipefitters (OR = 8.3, 95% CI: 1.5-86), shipbuilding workers (OR = 5.0, 95% CI: 1.2-23), painters (OR = 4.5, 95% CI: 1.0-24), welders (OR = 3.9, 95% CI: 0.8-22), gardeners (OR = 3.9, 95% CI: 0.8-22), bricklayers (OR = 3.5, 95% CI: 0.9-14), miners (OR = 3.4, 95% CI: 0.9-13), machinists (OR = 3.2, 95% CI: 1.0-11), construction foremen (OR = 3.1, 95% CI: 0.9-11), and electricians (OR = 3.0, 95% CI: 0.8-12). In a reanalysis excluding subjects who worked in occupations or processes considered strongly a priori at risk, three groups remained of interest: non-asbestos miners (OR = 9.6, 95% CI: 1.8-53), bricklayers (OR = 5.4, 95% CI: 1.0-28), and construction labourers (OR = 2.8, 95% CI: 0.7-10.6).

Adult↗
PubMedDate not supplied

Genetic polymorphisms in Parkinson's disease.

The search for genetic polymorphisms relevant to Parkinson's disease etiology and pathogenesis has been motivated by recent thinking emphasizing the potential significance of gene-environment interactions. Especially influential to this research have been the MPTP model of PD induction, hypotheses concerning oxidative stressor reactions, and epidemiological observations of an inverse relation between cigarette smoking and PD risk. This brief review summarizes trends in genetic polymorphism research, with examples provided by investigations of cytochrome P450 enzymes, monoamine oxidase, superoxide dismutase, and mitochondrial genes.

Animals↗