Search PubMed⌕ Search

Biomedical subjects

R M Park

Publications and source records attributed to R M Park.

At least 19 recordsLinked to original sources
PubMed1996

The healthy worker survivor effect and mortality at two automotive engine manufacturing plants.

Attributes such as time since hire or length of followup may be important in occupational mortality due to the "healthy worker survivor effect." In a regression analysis of mortality odds ratios at two automotive engine plants, strong effects of overall employment duration (latency weighted) were observed in addition to effects for (similarly weighted) cumulative exposures. The duration effects were negative for several cancer and noncancer outcomes, and confounded exposure effects. The lung cancer odds ratio declined to 0.68 (95% CI = 0.51, 0.90) at the mean duration of employment. With control for employment duration, adjusted lung cancer odds ratios for work as millwrights increased from 3.0 to 3.8, and for work in cylinder head production, from 3.3 to 3.9. Several causes of death with strong duration effects were smoking-related, suggesting diminished smoking risk factors with increasing employment duration. Similarly, trends for cirrhosis of the liver mortality suggested the alcohol risk factor is smaller in long-duration workers. If personal risk factors are an important component of the healthy worker survivor effect, they could be powerful negative confounders of exposure-response for related outcomes. Including a term for employment duration in regression models appears to partially correct for healthy worker survivor bias.

Aged↗
PubMed1996

A survey of mortality at two automotive engine manufacturing plants.

Mortality at two engine plants was analyzed using proportional mortality and logistic regression models of mortality odds ratios to expand previous observations of increased cancers of the stomach, pancreas, and bladder, and cirrhosis of the liver among workers exposed to machining fluids. Causes of death and work histories were available for 1,870 decendents. There was a significant excess of deaths coded as diabetes for white men in both plants (PMR = 25/16.7 = 1.5, 95% CI = 1.02, 2.20), and a deficit of respiratory diseases. Black men had fewer than expected diabetes deaths and more emphysema deaths. Elevated PMRs for cancers of the stomach, pancreas, prostate, bladder, and kidney were not statistically significant in plantwide populations. However, stomach cancer mortality increased with duration in camshaft and crankshaft production at Plant 1 (OR = 5.1, 95% CI = 1.6, 17; at mean duration of exposed cases), and among tool room workers (OR = 6.3, 95% CI = 1.3, 31), but these results were based on five cases. Nitrosamines were probably present in camshaft and crankshaft grinding at Plant 1. Pancreas cancer risk increased among workers at both plants ever employed in inspection (OR = 2.5, 16), in machining with straight oil (OR = 3.6, 95% CI = 1.04, 12), or in skilled trades (OR = 2.9, 95% CI = 1.1, 7.5). Lung cancer increased in cylinder head machining (OR = 3.9, 95% CI = 1.4, 11), millwright work (OR = 3.8, 95% CI = 1.6, 9.0), and in Plant 2 generally (OR = 1.45, 95% CI = 0.97, 2.2). Potential lung carcinogens included heat treatment emissions, chlorinated oils, and coal tar fumes (millwrights). Bladder cancer increased with duration among workers grinding in straight oil MF (OR = 3.0, 95% CI = 1.15, 7.8) and in machining/heat-treat operations (OR = 2.9, 95% CI = 1.14, 7.2).

Automobiles↗
PubMed1996

Occupational disease surveillance using disability insurance at an automotive stamping and assembly complex.

Sickness and accident-insurance (sick leave) claims at an automotive stamping and assembly complex were analyzed using Poisson regression over a 4-year period to identify occupational health problems. The incidence of lower-respiratory disability (excluding asthma) was higher in painting operations (rate ratio [RR] = 2.9, 95% confidence interval [CI] = 1.2 to 6.8), and final assembly and processing areas (RR = 2.7, 95% CI = 1.0 to 7.4) at the assembly plant, and in metal assembly (welding) areas (RR = 2.8, 95% CI = 1.4 to 5.7) at the stamping plant. Disability rates for upper-extremity musculoskeletal disorders were statistically significantly higher (RR = 3.1 to 3.8) in major assembly plant production areas, as were back disability rates (RR = 1.5). During the first 6 months of new work assignments in painting or final assembly, respiratory problem rates were four times higher than in other areas. Upper-extremity musculoskeletal rate ratios ranged from 4.4 to 5.7 for new assignments in body, hard trim, and chassis areas. Higher rates in new assignments appeared to result from assignment changes precipitated by developing health problems, or from routine assignments to new tasks, some of which conferred high risk and were tolerated for less than 6 months. Musculoskeletal disability was consistent with known ergonomic hazards and paralleled that reported on the Occupational Safety and Health Administration log. Work-related musculoskeletal and other problems can be readily identified from disability insurance claims without dependence on plant medical visits or workers' compensation records. Disability insurance appears to absorb considerable work-related medical and absence costs.

Accidents, Occupational↗
PubMed1992

Cumulative trauma disorders of the hand and wrist in the auto industry.

Surveillance for cumulative trauma disorders (CTDs) of the hand and wrist was carried out in five US automotive plants from 1985 to 1986, using Occupational Safety and Health Administration (OSHA) Form 200 injury and illness logs and medical insurance claims. Results using both record sources indicated that hand and wrist disorders may be more common in foundries than in other types of automotive plants. Similarly, in assembly plants, employees in certain departments appeared to be at higher risk for CTDs. Although our results are based on small numbers of cases, they suggest plants and departments that might be targeted for more detailed investigation.

Automobiles↗
PubMed1992

Use of medical insurance claims for surveillance of occupational disease. An analysis of cumulative trauma in the auto industry.

Medical insurance claims, linked with work histories for a large automotive manufacturer over a 3-year period, identified large numbers of cases of potentially work-related diseases, including 30,600 episodes of probable cumulative trauma disorders (CTD). CTD incidence rates were calculated within five plants, and high-risk areas identified, however, unknown differences in medical insurance coverage by exposure group limited interpretation. Case-control analyses, with controls also identified by insurance claims, addressed coverage and produced age-adjusted and sex-adjusted estimates of risks. All five plants had departments with statistically significant, elevated risks for one or more of the diagnoses carpal tunnel syndrome, CTD of other upper extremities, rotator cuff syndrome, CTD of the neck and of the lower back. Medical insurance claim data linked with work history provide the basis for practical and comprehensive surveillance for CTD and potentially a variety of other occupational diseases.

Accidents, Occupational↗
PubMed1991

A technique for the preparation of cross-sectional TEM samples of ZnSe/GaAs heterostructures which eliminates process-induced defects.

Cross-sectional transmission electron microscopy (TEM) sample preparation of ZnSe/GaAs epitaxial films is investigated. Conventional argon ion milling is shown to produce a high density (approximately 5-8 x 10(11)/cm2) of small (diameter approximately 60-80 A) extended defects (stacking faults, microtwins, double positioning twins, etc.). In addition, transmission electron diffraction results indicate a thin ZnO layer can also occasionally form upon ion milling or electron-beam irradiation although the exact conditions for ZnO formation are not well understood. Conventional TEM (amplitude contrast) and high-resolution TEM (phase contrast) imaging in combination with transmission electron diffraction studies were performed to determine the optimum method of removing the ion milling related damage and ZnO layers during sample preparation. HF/HCl, NaOH/H2O, H2SO4/H2O2/H2O and Br2/CH3OH etching mixtures as well as low voltage argon or iodine ion milling were studied. A low energy (2 keV) iodine or argon ion milling step was shown to remove the ZnO layer and reduced the density of the extended defects associated with Ar+ ion milling, but was unsuccessful in removing all of the defects. Auger electron spectroscopy results indicate residual iodine was either left on the surface or implanted beneath the surface during iodine ion milling. Etching the XTEM samples in HF/HCl was shown to be effective in removing the ZnO layer but had little or no effect on the ion milling induced defects. Etching the samples in a 0.5% Br2/CH3OH solution resulted in complete elimination of the ion milling induced extended defects including the residual defects associated with iodine ion milling. In addition the Br2/CH3OH etch produced the best surface morphology. Thus a brief (1-2 seconds) Br2/CH3OH etch after conventional preparation (argon ion milling) of cross-sectional ZnSe/GaAs TEM samples appears to be an inexpensive and superior alternative to iodine ion milling.

Arsenic↗
PubMed1991

A comparison of PMRs and SMRs as estimators of occupational mortality.

Standardized mortality ratios (SMRs) for occupational diseases are confounded by health differences between industrial and general populations. In 109 industrial cohorts largely free of work-related mortality, these selection effects were sizable for both malignant and nonmalignant outcomes. All-cancer SMRs were considerably less than 1.0 for many cohorts, and lung cancer was subject to almost as much selection-derived confounding as nonmalignant disease. Standardized proportional mortality ratios (PMRs) (approximated by relative SMRs (RSMRs] were less confounded than SMRs in estimating occupational risk. PMRs appeared to overestimate cancer mortality on average by 6%, while SMRs underestimated by 13%. PMRs underestimated nonmalignant respiratory disease by 16 percent but SMRs underestimated by 39 percent. The sources of confounding, in addition to selection on health status at hire, most likely include social class. SMRs, in the absence of internal population comparisons, would fail to detect both malignant and nonmalignant work-related mortality in many industrial cohorts.

Bias↗
PubMed1990

Brain cancer mortality at a manufacturer of aerospace electromechanical systems.

Standardized proportional mortality ratios and mortality odds ratios were calculated for 583 deaths between 1950 and 1986 among employees who had worked for at least 10 years at a facility manufacturing missile and aircraft guidance systems. There was a statistically significant excess of brain cancer proportional mortality (PMR = 16/3.8 = 4.2, p = .0001). Among hourly employees, 12 brain cancer deaths occurred for 2.7 expected (PMR = 4.4, p = .00005). The PMR for brain cancer increased from 1.8 (p = .45) among hourly workers with less than 20 years to 8.7 (p = .000003) in those with more than 20 years employment. Work in "clean rooms," where gyroscopes were assembled, was associated with the brain cancer excess but did not fully account for it. Among 105 deceased hourly women, all three brain cancer deaths occurred among gyro assemblers working in clean rooms, and the risk increased with duration in clean rooms. Although the proportion of brain cancer deaths among hourly men with clean-room experience was similar to that for women, only three of the seven male brain cancer deaths occurred in this group. The suspect agents include gyro fluids and chlorofluorocarbon solvents.

Air Pollutants, Occupational↗
PubMed1988

Causes of death among workers in a bearing manufacturing plant.

Recent studies identify digestive cancer excesses among workers exposed to cutting fluids, abrasive dusts, and oil smoke. Standardized proportional mortality and mortality odds ratio studies were carried out for a ball bearing plant. Cause of death and work histories were obtained for 702 of 768 hourly employees with ten or more years' service who died between 1969 and 1982. Union and company records were used to define exposure measures. The major findings were significant excesses in proportional mortality ratios (PMR) from stomach cancer (PMR = 2.0) and rectal cancer (PMR = 3.1) among white men. After control for age at death, there was a significant association between stomach cancer and precision grinding exposures, consisting primarily of direct contact with water-based cutting fluids (usually emulsified oils) and their aerosols. Some straight oils and synthetic cutting fluids were used as well. The pattern of stomach cancer is consistent with previous findings and suggests an association with the soluble oil cutting fluids.

Aged↗
PubMed1987

Use of the logistic regression model for the analysis of proportionate mortality data.

A new statistical analysis strategy for proportionate mortality data is proposed. It is assumed that the occupational exposure, if it has an effect on mortality, increases the rate of death for some subset of causes by a multiplicative factor while not affecting the rates for the remaining causes of death. The unconditional logistic regression model is shown to provide a structure for the data analysis, with one of the predictors being the logit of the probability in the reference population that death was due to the affected causes. Using this model, one can estimate the effect of exposure while simultaneously controlling for a number of potential confounding and selection variables. Also, this model avoids the problems of comparing standardized proportionate mortality ratios, which are indirectly standardized measures. The model is demonstrated on a set of proportionate mortality data for factory workers from the northeastern United States.

Epidemiologic Methods↗