Search

OBJECTIVE: The exposure-response relationship for manganese (Mn)-induced adverse nervous system effects is not well described. Symptoms and neuropsychological deficits associated with early manganism were previously reported for welders constructing bridge piers during 2003 to 2004. A reanalysis using improved exposure, work history information, and diverse exposure metrics is presented here. METHODS: Ten neuropsychological performance measures were examined, including working memory index (WMI), verbal intelligence quotient, design fluency, Stroop color word test, Rey-Osterrieth Complex Figure, and Auditory Consonant Trigram tests. Mn blood levels and air sampling data in the form of both personal and area samples were available. The exposure metrics used were cumulative exposure to Mn, body burden assuming simple first-order kinetics for Mn elimination, and cumulative burden (effective dose). Benchmark doses were calculated. RESULTS: Burden with a half-life of about 150 days was the best predictor of blood Mn. WMI performance declined by 3.6 (normal = 100, SD = 15) for each 1.0 mg/m3 x mo exposure (P = 0.02, one tailed). At the group mean exposure metric (burden; half-life = 275 days), WMI performance was at the lowest 17th percentile of normal, and at the maximum observed metric, performance was at the lowest 2.5 percentiles. Four other outcomes also exhibited statistically significant associations (verbal intelligence quotient, verbal comprehension index, design fluency, Stroop color word test); no dose-rate effect was observed for three of the five outcomes. CONCLUSIONS: A risk assessment performed for the five stronger effects, choosing various percentiles of normal performance to represent impairment, identified benchmark doses for a 2-year exposure leading to 5% excess impairment prevalence in the range of 0.03 to 0.15 mg/m3, or 30 to 150 microg/m3, total Mn in air, levels that are far below those permitted by current occupational standards. More than one-third of workers would be impaired after working 2 years at 0.2 mg/m3 Mn (the current threshold limit value). [ABSTRACT FROM AUTHOR]

OBJECTIVE:: Cancer mortality and morbidity are described for the first time in all Korean workers exposed to ionizing radiation. METHODS:: Based on hospital admissions, Standardized Rate Ratios (SRR) and Standardized Mortality Ratios (SMR) were modeled with Poisson regression. RESULTS:: Cancer admissions during 2000 to 2005 were low compared with autoworkers with the exception of nuclear power workers (SRR = 1.13, 95% CI = 0.94-1.36). Thyroid cancer was statistically significantly elevated in women radiation workers in medical (SRR = 2.90, 95% CI = 1.05-7.94) and research institutions (SRR = 3.91, 95% CI = 1.36-11.0) and industry (SRR = 5.07, 95% CI = 1.56-15.6), and in all nuclear power workers (SRR = 2.59, 95% CI = 1.33-5.13), and there was a significant association with dose (ERR = 20.4 per Sv, 90% CI = -8 to 60, one-tailed P = 0.049). The 935 deaths revealed a healthy worker effect for all causes (SMR = 0.58, 95% CI = 0.54-0.62) and all-cancer (SMR = 0.73, 95% CI = 0.64-0.82). Lung cancer (SMR = 0.77, 95% CI = 0.55-1.05) and leukemia (SMR = 0.59, 95% CI = 0.28-1.06) mortalities were also less than expected. Compared with autoworkers, radiation workers displayed decreased all-cause mortality except for nuclear power workers (statistically not significant). CONCLUSIONS:: ERRs as high as 300 per Sv appear to be ruled-out in this population with regulated exposure to ionizing radiation while ERRs as high as 100 per Sv are not. [ABSTRACT FROM AUTHOR]

Objectives: The butter flavoring additive, diacetyl (DA), can cause bronchiolitis obliterans (BO) by inhalation. A risk assessment was performed using data from a microwave popcorn manufacturing plant., Methods: Current employees' medical history and pulmonary function tests together with air sampling over a 2.7-year period were used to analyze forced expiratory volume in 1 second (FEV1) and FEV1/forced vital capacity (FVC). The exposure responses for declining pulmonary function and for possible early onset of BO were estimated using multiple regression methods. Several exposure metrics were investigated; benchmark dose and excess lifetime risk of impairment were calculated., Results: Forty-six percent of the population had less than 6 months exposure to DA. Percent-of-predicted FEV1 declined with cumulative exposure (0.40 per ppm-yr, P < 10) as did percent FEV1/FVC (0.13 per ppm-yr, P = 0.0004). Lifetime respiratory impairment prevalence of one per thousand resulted from 0.005 ppm DA and one per thousand lifetime incidence of impairment was predicted for 0.002 ppm DA., Conclusion: DA exposures, often exceeding 1 ppm in the past, place workers at high risk of pulmonary impairment.

Mortality was analyzed for an automotive engine foundry and machining complex, with process exposures derived from department assignments. Logistic regression models of mortality odds ratios (ORs) were calculated for 2546 deaths, and numbers of work-related deaths were estimated. Lung cancer mortality in the foundry was increased where cleaning and finishing of castings was performed (OR, 1.7; 95% CI, 1.15 to 2.4 [at mean exposure duration of exposed cases]) and in care-making after 1967 (OR, 1.5; 95% CI, 1.11 to 2.0). Black workers had excess lung cancer mortality in machining heat-treat operations (OR, 2.5, 95% CI, 1.4 to 4.3) and excess nonmalignant respiratory disease mortality in molding (OR, 2.5; 95% CI, 1.16 to 5.5) and core-making (OR, 2.7; 95% CI, 1.25 to 5.8). Stomach cancer mortality was elevated among workers with metalworking fluid exposures in precision grinding (OR, 2.4; 95% CI, 1.14 to 5.1). Heart disease mortality was increased among all workers in molding (OR, 1.6; 95% CI, 1.09 to 2.3), as was stroke mortality among workers exposed to metalworking fluids (OR, 1.8; 95% CI, 1.22 to 2.7). Malignant and nonmalignant liver disease mortality was elevated in assembly/testing and precision grinding. In this modern foundry, 11% of deaths were estimated to be work-related despite it's being largely in regulatory compliance over its 40-year existence. Machining plant exposures accounted for 3% or more of deaths there.

To evaluate medical insurance claims for chronic disease investigation, claims from eight automotive machining plants (1984 to 1993) were linked with work histories (1967 to 1993), and associations with respiratory, cardiac, and cancer conditions were investigated, in a case-control design analyzed with logistic regression. The primary focus was tool grinding, but other important processes examined were metal-working, welding, forging, heat treat, engine testing, and diverse-skilled trades work. Considerable variability in claim-derived incidence rates across plants was not explained by age or known exposure differences. Asthma incidence increased in tool grinding (at mean cumulative duration: odds ratio [OR], 3.0; 95% confidence interval [CI], 0.90 to 10.0), as did non-ischemic heart disease (cardiomyopathy, cor pulmonale, rheumatic heart disease, or hypertension; OR, 3.1; 95% CI, 1.26 to 7.6). These trends appeared in models with deficits (OR < 1.0) for those ever exposed to tool grinding because of exposure-response miss-specification, demographic confounding, or removal of high-risk workers from the exposed group. The apparent cancer rates identified from claims greatly exceeded the expected rates from a cancer registry, suggesting that diagnostic, "rule-out," and surveillance functions were contributing. This study supports the epidemiologic use of medical insurance records in surveillance and, possibly, etiologic investigation and identifies issues requiring special attention or resolution.

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.

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.