San-Francisco/Oakland Bay Bridge welder study

Background: The sense of smell can be damaged by airborne xenobiotics, including aerosolized heavy metals, reflecting the direct exposure of its receptors to the outside environment. Objectives: To determine whether professional welders working in confined spaces exhibit olfactory dysfunction. To determine whether such dysfunction, if present, is related to indices of metal exposure associated with welding, as well as measures of neurologic and neuropsychological function. Methods: The University of Pennsylvania Smell Identification Test (UPSIT) and a battery of neurologic and neuropsychological tests were administered to 43 welders who worked for 1 to 2 years on the San Francisco/Oakland Bay Bridge. Blood levels of Mn, Fe, Cu, and Pb were obtained. Results: Relative to matched controls, the welders had significantly lower UPSIT scores, with a mean (SEM) of 29.51 (0.90) for welders and 36.55 (0.88) for controls. Eighty-eight percent scored below their individually matched controls. As in idiopathic Parkinson disease, the welders' olfactory test scores were unrelated to a broad spectrum of neurologic and neuropsychological test measures, as determined by principal components analysis. Although blood levels of Mn were associated with the time spent working on the bridge, workers with the highest Mn blood levels exhibited better olfactory function than those with the lowest Mn blood levels. The basis of this paradox, which has been observed previously, is unknown. Conclusions: Professional welders may be at risk for loss of smell function, although such loss seems to be unrelated to neurologic and neuropsychological test performance.