Environmental exposure to manganese in air: Associations with tremor and motor function

Abstract

Background Manganese (Mn) inhalation has been associated with neuropsychological and neurological sequelae in exposed workers. Few environmental epidemiologic studies have examined the potentially neurotoxic effects of Mn exposure in ambient air on motor function and hand tremor in adult community residents. Mn exposed residents were recruited in two Ohio towns: Marietta, a town near a ferro-manganese smelter, and East Liverpool, a town adjacent to a facility processing, crushing, screening, and packaging Mn products. Methods Chronic (≥10 years) exposure to ambient air Mn in adult residents and effects on neuropsychological and neurological outcomes were investigated. Participants from Marietta (n = 100) and East Liverpool (n = 86) were combined for analyses. AERMOD dispersion modeling of fixed-site outdoor air monitoring data estimated Mn inhalation over a ten year period. Adult Mn-exposed residents’ psychomotor ability was assessed using Finger Tapping, Hand Dynamometer, Grooved Pegboard, and the Computerized Adaptive Testing System (CATSYS) Tremor system. Bayesian structural equation modeling was used to assess associations between air-Mn and motor function and tremor. Results Air-Mn exposure was significantly correlated in bivariate analyses with the tremor test (CATSYS) for intensity, center frequency and harmonic index. The Bayesian path analysis model showed associations of air-Mn with the CATSYS non-dominant center frequency and harmonic index; while the Bayesian structural equation model revealed associations between air-Mn and lower Finger Tapping scores. Household income was significantly associated with motor dysfunction but not with tremor. Conclusion Tremor and motor function were associated with higher exposure to airborne Mn.

Validity of self-reported concentration and memory problems: Relationship with neuropsychological assessment and depression

“…This study is part of a larger cross-sectional study assessing the neurotoxic effects of air-Mn in residents living near a ferromanganese smelter in Marietta, Ohio, and an open-air Mn storage and packaging facility in East Liverpool, Ohio ( Bowler, Adams, et al, 2016 ; Bowler, Beseler, et al, 2016 ; Bowler et al, 2012 ; Kim et al, 2011 ). Both Marietta and East Liverpool have been reported by the U.S. Environmental Protection Agency (EPA) to have some of the highest measured environmental concentrations of respirable air-Mn in the U.S. ( U.S. EPA, 2011 U.S. EPA, 2012 ).…”

Medication use associated with exposure to manganese in two Ohio towns

“…A cross-sectional study design was used in this health study conducted in three Ohio towns (Bowler, Kornblith, et al 2015), two with reported high levels of Mn/A (Marietta and East Liverpool) and one town which is demographically similar, but unexposed to Mn/A (Mount Vernon). East Liverpool was reported by the U.S. Environmental Protection Agency (EPA) to have the highest measured concentrations of respirable Mn/A in the U.S. (U.S.…”

“…This methodology is further described in previous manuscripts (Bowler, Kornblith, et al 2015; Kim et al 2015). …”

“…Additionally, residents who have been exposed to environmental Mn near industrial sources, such as smelters, have developed health consequences similar to those described in occupational settings (Feldman 1999). Residential and occupational studies have identified deficits in motor, tremor, and cognitive functions with inhalation exposure to Mn in the air (Mergler et al 1999; Rodríguez-Agudelo et al 2006; Solís-Vivanco et al 2009; Kim et al 2011; Bowler, Kornblith, et al 2015). General environmental ambient air-Mn (Mn/A) exposures are typically significantly lower than in occupational study settings (Colledge et al 2015).…”

“…In recent decades, adult environmental studies of Mn exposure have reported physical (Santos-Burgoa et al 2001; Haynes et al 2010; Kim et al 2015) and mental health problems identified through cognitive (Bowler, Kornblith, et al 2015), mood (Bowler et al 2012), motor, and neurological (Rodríguez-Agudelo et al 2006; Kim et al 2011; Bowler, Beseler, et al 2015) testing of study subjects, but medical record reviews for exposed residents are rare in the literature. When medical records and clinical testing are unavailable, examination of residents’ current prescribed medication use (Dayal et al 1994; Zmirou et al 1994; Bowler et al 2002) has been used as a proxy of health effects associated with Mn or other neurotoxic chemical exposures.…”