Anxiety affecting parkinsonian outcome and motor efficiency in adults of an Ohio community with environmental airborne manganese exposure

Manganese (Mn) is a nutrient and neurotoxicant sometimes associated with mood, motor and neurological effects. Reports of health effects from occupational exposure to Mn are well known, but the reported links to environmental airborne Mn (Mn-Air) are less conclusive. Marietta, OH (USA) is a previously identified community with elevated Mn-Air from industrial emissions. Households were randomly selected in Marietta and the comparison town (Mount Vernon, OH). The responders were used to recruit on a voluntary basis 30- to 75-year-old residents, i.e. 100 in Marietta and 90 in Mount Vernon. They were administered the Unified Parkinson's Disease Rating Scale (UPDRS), motor efficiency, and mood tests, along with a comprehensive questionnaire including demographics, health and work history. Blood Mn (MnB), serum ferritin, and hepatic enzymes were measured. Results were compared with those of 90 residents from a demographically similar comparison town, Mount Vernon, OH, where Mn-Air from industrial emissions was not of concern. Mn-Air exposure indices were modeled for Marietta residents. The Mn-exposed participants resided on average 4.75 miles (range 1-11) from the Mn point source. Their modeled residential Mn-Air estimate ranged from 0.04 to 0.96 μg/m(3) and was on average 0.18 μg/m(3). The group means of MnB were similar for the Mn-exposed (9.65 μg/L) and comparison (9.48 μg/L) participants. The Marietta group reported more generalized anxiety on the Symptom Checklist-90-Revised (SCL-90-R) than the comparison group (p=0.035). Generalized anxiety in Marietta was related to a cumulative exposure index (p=0.002), based on modeled Mn-Air concentration and length of residence. Higher generalized anxiety scores were related to poorer performance on UPDRS tests [adjusted relative risk (95%CI): 2.18 (1.46-3.25) for motor-related activities of daily living, 3.44 (1.48-7.98) for bradykinesia, and 1.63 (1.06-2.53) for motor/movement]. Group differences in SCL-90-R generalized anxiety between the two towns and the observed relationship between exposure indices and generalized anxiety suggest an association between environmental Mn exposure and anxiety states. Whether this association is due to direct neurotoxic effects of Mn-Air or concern about the health effects of air pollution remains an open question. The results highlight the importance of measuring anxiety in relation to neuropsychological and neurological endpoints, and should be validated in other studies of Mn-exposed communities.