PT - JOURNAL ARTICLE AU - Rosemarie M Bowler AU - Harry A Roels AU - Sanae Nakagawa AU - Marija Drezgic AU - Emily Diamond AU - Robert Park AU - William Koller AU - Russell P Bowler AU - Donna Mergler AU - Maryse Bouchard AU - Donald Smith AU - Roberto Gwiazda AU - Richard L Doty TI - Dose–effect relationships between manganese exposure and neurological, neuropsychological and pulmonary function in confined space bridge welders AID - 10.1136/oem.2006.028761 DP - 2007 Mar 01 TA - Occupational and Environmental Medicine PG - 167--177 VI - 64 IP - 3 4099 - http://oem.bmj.com/content/64/3/167.short 4100 - http://oem.bmj.com/content/64/3/167.full SO - Occup Environ Med2007 Mar 01; 64 AB - 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/m3 (55% >0.20 mg/m3). 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.