Dose–effect relationships between manganese exposure and neurological, neuropsychological and pulmonary function in confined space bridge welders. Issue 3 (3rd October 2006)

• Record Type: Journal Article
• Authors: Bowler, Rosemarie M; Roels, Harry A; Nakagawa, Sanae; Drezgic, Marija; Diamond, Emily; Park, Robert; Koller, William; Bowler, Russell P; Mergler, Donna; Bouchard, Maryse; Smith, Donald; Gwiazda, Roberto; Doty, Richard L
• Is Part Of: Occupational and environmental medicine. Volume 64:Issue 3(2007)
• Page Start: 167
• Page End: 177
• Publication Date: 2006-10-03
• Subjects: Cal-OSHA, California Division of Occupational Safety and Health -- CATSYS, computer assisted tremor analysis system -- CEI, Cumulative Exposure Index -- FCAW, Flux Cored Arc Welding -- FVC, forced vital capacity -- FEV1, forced expiratory volume at 1 s -- IPD, idiopathic Parkinson's disease -- Mn-air, manganese air levels -- MnB, whole blood manganese -- MRI, magnetic resonance imaging -- SCL-90-R, Symptom Checklist 90-Revised -- SMAW, Shielded Metal Arc Welding -- UPDRS, Unified Parkinson Disease Rating Scale -- UPSIT, University of Pennsylvania Smell Identification Test -- WAIS-III, Wechsler Adult Intelligence Scale -- WMS III, Wechsler Memory Scale; Medicine, Industrial -- Periodicals; Environmental health -- Periodicals; 616.980305
• DOI: 10.1136/oem.2006.028761
• Languages: English
• ISSNs: 1351-0711

Abstract

Abstract : Background: Although adverse neuropsychological and neurological health effects are well known among workers with high manganese (Mn) exposures in mining, ore-processing and ferroalloy production, the risks among welders with lower exposures are less well understood. Methods: Confined space welding in construction of a new span of the San Francisco–Oakland Bay Bridge without adequate protection was studied using a multidisciplinary method to identify the dose–effect relationship between adverse health effects and Mn in air or whole blood. Bridge welders (n = 43) with little or no personal protection equipment and exposed to a welding fume containing Mn, were administered neurological, neuropsychological, neurophysiological and pulmonary tests. Outcome variables were analysed in relation to whole blood Mn (MnB) and a Cumulative Exposure Index (CEI) based on Mn-air, duration and type of welding. Welders performed a mean of 16.5 months of welding on the bridge, were on average 43.8 years of age and had on average 12.6 years of education. Results: The mean time weighted average of Mn-air ranged from 0.11–0.46 mg/m 3 (55% >0.20 mg/m 3 ). MnB >10 µg/l was found in 43% of the workers, but the concentrations of Mn in urine, lead in blood and copper and iron in plasma were normal. Forced expiratory volume at 1s: forced vital capacity ratios (FEV1 /FVC) were found to be abnormal in 33.3% of the welders after about 1.5 years of welding at the bridge. Mean scores of bradykinesia and Unified Parkinson Disease Rating Scale exceeded 4 and 6, respectively. Computer assisted tremor analysis system hand tremor and body sway tests, and University of Pennsylvania Smell Identification Test showed impairment in 38.5/61.5, 51.4 and 88% of the welders, respectively. Significant inverse dose–effect relationships with CEI and/or MnB were found for IQ (p⩽0.05), executive function (p⩽0.03), sustaining concentration and sequencing (p⩽0.04), verbal learning (p⩽0.01), working (p⩽0.04) and immediate memory (p⩽0.02), even when adjusted for demographics and years of welding before Bay Bridge. Symptoms reported by the welders while working were: tremors (41.9%); numbness (60.5%); excessive fatigue (65.1%); sleep disturbance (79.1%); sexual dysfunction (58.1%); toxic hallucinations (18.6%); depression (53.5%); and anxiety (39.5%). Dose–effect associations between CEI and sexual function (p<0.05), fatigue (p<0.05), depression (p<0.01) and headache (p<0.05) were statistically significant. Conclusions: Confined space welding was shown to be associated with neurological, neuropsychological and pulmonary adverse health effects. A careful enquiry of occupational histories is recommended for all welders presenting with neurological or pulmonary complaints, and a more stringent prevention strategy should be considered for Mn exposure due to inhalation of welding fume.