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Mercury-induced motor and sensory neurotoxicity: systematic review of workers currently exposed to mercury vapor.

ABSTRACT: The neurotoxicity of elemental mercury (Hg0) is well-recognized, but it is uncertain whether and for how long neurotoxicity persists; among studies that evaluated previously exposed workers, only one examined workers during and also years after exposure ceased. The aim of this review is to document the type, frequency, and dose-relatedness of objective neurological effects in currently exposed mercury workers and thereby provide first approximations of the effects one would have expected in previously exposed workers evaluated during exposure. We systematically reviewed studies of neurotoxicity in currently exposed mercury workers identified by searching MEDLINE (1950-2015), government reports, textbook chapters, and references cited therein; dental cohorts were not included. Outcomes on physical examination (PE), neurobehavioral (NB) tests, and electrophysiological studies were extracted and evaluated for consistency and dose-relatedness. Forty-five eligible studies were identified, comprising over 3000 workers chronically exposed to a range of Hg0 concentrations (0.002-1.7?mg/m3). Effects that demonstrated consistency across studies and increased frequency across urine mercury levels (<50; 50-99; 100-199; ?200??g/L) included tremor, impaired coordination, and abnormal reflexes on PE, and reduced performance on NB tests of tremor, manual dexterity and motor speed. The data suggest response thresholds of UHg ?275??g/L for PE findings and ?20??g/L for NB outcomes. These results indicate that PE is of particular value for assessing workers with UHg >200??g/L, while NB testing is more appropriate for those with lower UHg levels. They also provide benchmarks to which findings in workers with historical exposure can be compared.

SUBMITTER: Fields CA

PROVIDER: S-EPMC5931703 | biostudies-literature | 2017 Nov

REPOSITORIES: biostudies-literature

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Mercury-induced motor and sensory neurotoxicity: systematic review of workers currently exposed to mercury vapor.

Fields Cheryl A CA Borak Jonathan J Louis Elan D ED

Critical reviews in toxicology 20170718 10

The neurotoxicity of elemental mercury (Hg<sup>0</sup>) is well-recognized, but it is uncertain whether and for how long neurotoxicity persists; among studies that evaluated previously exposed workers, only one examined workers during and also years after exposure ceased. The aim of this review is to document the type, frequency, and dose-relatedness of objective neurological effects in currently exposed mercury workers and thereby provide first approximations of the effects one would have expec ...[more]

PMID: 28718354

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Project description:Background: The clinical outcome of patients suffering from stroke is dependent on multiple factors. The features of the lesion itself play an important role but clinical recovery is remarkably influenced by the plasticity mechanisms triggered by the stroke and occurring at a distance from the lesion. The latter translate into functional and structural changes of which cortical thickness might be easy to quantify one of the main players. However, studies on the changes of cortical thickness in brain areas beyond stroke lesion and their relationship to sensory-motor recovery are sparse. Objectives: To evaluate the effects of cerebral stroke on cortical thickness (CT) beyond the stroke lesion and its association with sensory-motor recovery. Materials and Methods: Five electronic databases (PubMed, Embase, Web of Science, Scopus and the Cochrane Library) were searched. Methodological quality of the included studies was assessed with the Newcastle-Ottawa Scale for non-randomized controlled trials and the Risk of Bias Cochrane tool for randomized controlled trials. Results: The search strategy retrieved 821 records, 12 studies were included and risk of bias assessed. In most of the included studies, cortical thinning was seen at the ipsilesional motor area (M1). Cortical thinning can occur beyond the stroke lesion, typically in regions anatomically connected because of anterograde degeneration. Nonetheless, studies also reported cortical thickening of regions of the unaffected hemisphere, likely related to compensatory plasticity. Some studies revealed a significant correlation between changes in cortical thickness of M1 or somatosensory (S1) cortical areas and motor function recovery. Discussion and Conclusions: Following a stroke, changes in cortical thickness occur both in regions directly connected to the stroke lesion and in contralateral hemisphere areas as well as in the cerebellum. The underlying mechanisms leading to these changes in cortical thickness are still to be fully understood and further research in the field is needed. Systematic Review Registration: https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42020200539; PROSPERO 2020, identifier: CRD42020200539.

Dataset Information

Mercury-induced motor and sensory neurotoxicity: systematic review of workers currently exposed to mercury vapor.

Publications

Mercury-induced motor and sensory neurotoxicity: systematic review of workers currently exposed to mercury vapor.

Similar Datasets

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