Occupational categories at risk for Parkinson's disease.

BACKGROUND: The etiology of Parkinson's disease (PD) is considered to have a strong environmental component, but relatively few studies have investigated the potential association between occupation and the disease. METHODS: In a population-based case-control study, we collected comprehensive occupational histories from all study participants, 144 case and 464 control subjects. RESULTS: Chi-square analysis revealed that working in an agricultural occupation increased estimated PD risk (OR = 1.74; 95% CI = 0.85, 3.60). In contrast, a history of ever working in a service occupation was negatively associated with PD risk (OR = 0.69; 95% CI = 0.47, 1.00). Risk estimates were close to one for specific service occupations. Adjusted odds ratios for all non-service occupational and industrial categories were similar, and working in a service occupation was the only significant inverse predictor of PD risk. CONCLUSIONS: Future investigations focusing on lifestyle factors and environmental exposures within the agricultural and service occupational categories are warranted.

A family history of Parkinson's disease and its effect on other PD risk factors.

Parkinson's disease (PD) is likely a result of both inherited and exogenous factors. In a study of 144 PD cases and 464 controls, we used PD family history as a surrogate for inherited PD susceptibility. Cases were more likely to report a first- or second-degree relative with PD: 16.0 vs. 4.3%; odds ratio (OR) = 4. 2; 95% confidence interval (CI) = 2.3-7.6. A PD family history was a greater risk factor for PD in subjects under age 70 (OR = 8.8; 95% CI = 3.4-22.8) compared with those over 70 (OR = 2.8; 95% CI = 1.3-6. 1) and in men (OR = 8.1; 95% CI = 3.4-19.2) compared with women (OR = 2.6; 95% CI = 1.1-6.0). We also tested whether a PD family history modified the effects of other PD risk factors. In subjects with a PD family history, occupational exposure to copper, lead or iron increased the risk for PD (OR = 3.0; 95% CI = 0.7-13.3), but this was not the case for those without a family history (OR = 1.1; 95% CI = 0.7-1.6). Ever smoking cigarettes was inversely associated with PD in those without a PD family history (OR = 0.6; 95% CI = 0.4-0.9), but was positively associated with PD in those with a PD family history (OR = 1.7; 95% CI = 0.5-5.9). In summary, our results suggest that a PD family history, and perhaps, therefore, an inherited susceptibility, confers a greater risk for PD in men and individuals under 70 years of age and may modify the effects of environmental risk factors for PD.

Occupational exposure to manganese, copper, lead, iron, mercury and zinc and the risk of Parkinson's disease.

A population-based case-control study was conducted in the Henry Ford Health System (HFHS) in metropolitan Detroit to assess occupational exposures to manganese, copper, lead, iron, mercury and zinc as risk factors for Parkinson's disease (PD). Non-demented men and women 50 years of age who were receiving primary medical care at HFHS were recruited, and concurrently enrolled cases (n = 144) and controls (n = 464) were frequency-matched for sex, race and age (+/- 5 years). A risk factor questionnaire, administered by trained interviewers, inquired about every job held by each subject for 6 months from age 18 onward, including a detailed assessment of actual job tasks, tools and environment. An experienced industrial hygienist, blinded to subjects' case-control status, used these data to rate every job as exposed or not exposed to one or more of the metals of interest. Adjusting for sex, race, age and smoking status, 20 years of occupational exposure to any metal was not associated with PD. However, more than 20 years exposure to manganese (Odds Ratio [OR] = 10.61, 95% Confidence Interval [CI] = 1.06, 105.83) or copper (OR = 2.49, 95% CI = 1.06,5.89) was associated with PD. Occupational exposure for > 20 years to combinations of lead-copper (OR = 5.24, 95% CI = 1.59, 17.21), lead-iron (OR = 2.83, 95% CI = 1.07,7.50), and iron-copper (OR = 3.69, 95% CI = 1.40,9.71) was also associated with the disease. No association of occupational exposure to iron, mercury or zinc with PD was found. A lack of statistical power precluded analyses of metal combinations for those with a low prevalence of exposure (i.e., manganese, mercury and zinc). Our findings suggest that chronic occupational exposure to manganese or copper, individually, or to dual combinations of lead, iron and copper, is associated with PD.

Intra- and inter-rater agreement in the assessment of occupational exposure to metals.

BACKGROUND: Among the methods of retrospective occupational exposure assessment, expert review is considered the most accurate. Although expert review provides a more objective measure of exposure, depending on the exposure of interest it may still result in a significant degree of misclassification. METHODS: To evaluate the reliability in occupational metal exposure assessment by expert review, we analysed job history data from a case-control study of a neurological disease. First, one industrial hygienist (IH) did an initial exposure assessment of the metals copper, iron and lead, blinded to case-control status, for 608 subjects who had 3033 total jobs. We then compared exposure assessments from the original review with a second blinded review of 60 job histories (306 jobs) by the same IH (intra-rater) and of 64 job histories (361 jobs) by a different IH (inter-rater). RESULTS: The per cent agreements for the intra-IH comparisons were 89.6 for copper, 87.9 for iron and 94.6 for lead, whereas the inter-IH per cent agreements were 86.4 for copper, 81.1 for iron and 76.2 for lead. Based on the assumption that reliability is related to validity, we calculated an estimate of misclassification of metal exposure by one IH. Our exposure misclassification estimates show a sizable attenuation of the odds ratio, with the expected bias similar for copper and iron when using either intra- or inter-reliability results to estimate misclassification. CONCLUSION: Our results suggest that variation in the expert assessment of metal exposure is due mainly to the difficulties involved in transforming an occupational history into an estimate of exposure.

Occupational exposures to metals as risk factors for Parkinson's disease.

In a population-based case-control study, we investigated the potential role of occupational exposure to iron, copper, manganese, mercury, zinc, and lead as risk factors for Parkinson's disease (PD). Concurrently recruited, nondemented patients (n = 144) with idiopathic PD and controls (n = 464) consisting of men and women > or =50 years of age, frequency-matched for age (within 5 years), race, and sex were enrolled. All had primary medical care at Henry Ford Health System in urban/suburban metropolitan Detroit. Subjects were given an extensive risk-factor questionnaire detailing actual worksite conditions of all jobs held for more than 6 months from age 18 onward. An industrial hygienist, blinded to the case-control status of subjects, rated occupational exposure to each of the metals of interest. When adjusted for sex, race, age, and smoking status, we found in those with more than 20 years' exposure a significantly increased association with PD for copper (OR = 2.49, 95% CI = 1.06, 5.89) and manganese (OR = 10.61, 95% CI = 1.06, 105.83). For more than 20 years' exposure to combinations of lead-copper (OR = 5.24, 95% CI = 1.59, 17.21), lead-iron (OR = 2.83, 95% CI = 1.07, 7.50), and iron-copper (OR = 3.69, 95% CI = 1.40, 9.71), there was a greater association with PD than with any of these metals alone. These findings suggest that chronic exposure to these metals is associated with PD, and that they may act alone or together over time to help produce the disease.

Comparability of different methods of retrospective exposure assessment of metals in manufacturing industries.

Many occupational case-control studies have relied on either self-report or exposure assessment based on job titles linked to a job exposure matrix (JEM) as opposed to the generally considered more accurate, but labor intensive, method of expert review of job histories. Our study examined the comparability of these different methods in assessing occupational exposure to the metals copper (Cu), lead (Pb), and iron (Fe) in manufacturing industries. Subjects were older people from a case-control study of a neurologic disease, and consisted of 188 individuals (72% male, 85% white) who had worked an average of 22.4 years in the manufacturing industry. An industrial hygienist review (IHR) of occupational history data from a comprehensive questionnaire was used as the reference method. The percent agreement (%A), sensitivity (SE), and specificity (SP) for direct self-report of metal exposures were: Cu, %A = 94.6, SE = 83.6, SP = 96.1; Pb, %A = 91.9, SE = 72.5, SP = 93.5; and Fe, %A = 82.7, SE = 64.5, SP = 88.1. Using the National Institute for Occupational Safety and Health (NIOSH) JEM, we analyzed the jobs of 115 of the 188 study subjects who had all their jobs listed in the JEM. Exposure assessment based on the NIOSH JEM compared with the IHR resulted in greater misclassification relative to direct self-report: Cu, %A = 81.5, SE = 21.2, SP = 89.2; Pb, %A = 86.0, SE = 0.0, SP = 92.6; and Fe, %A = 69.2, SE = 15.5, SP = 86.4. For all three study metals, combining the information from both direct self-report and the JEM did not improve upon the results compared with direct self-report alone. Due to the complex nature of metal exposure assessment, we suggest using an expert review of job histories whenever possible to minimize potential misclassification.

Industrial hygiene and safety controls at a 1.5 MeV electron beam accelerator facility.

This paper discusses radiological safety measures built in to a 1.5 MeV electron beam accelerator at the General Motors Research Laboratories. The accelerator is used to study the interaction of electrons with plastic materials. The safety features described represent the type of precautions taken over and above legal requirements and include the results of experience gained in other installations.