Analysis of available literature for the purposes of the evaluation of Neurotoxicity Potential - Metallic Manganese
Manganese is an essential trace element with multiple essential physiologic functions. Despite its essential nature, chronic exposure of humans to high levels of manganese may lead to its accumulation in the basal ganglia, resulting in a parkinsonian-like syndrome.
The publication of the ECHA Assessment of Regulatory Needs Report and the European Commission’s Restriction Road Map Report, triggered the largest Literature review on the neurotoxicity potential of metallic manganese since 2010.
The review focused on chronic exposure to manganese, which can accumulate in the brain and lead to neurological effects resembling Parkinson’s disease. The literature search using PubMed was conductedand the studies obtained were screened initially using titles and abstracts followed by full text review. Studies were included if they reported original data, were peer reviewed and published in English, had a non-exposed control group, had a duration of ³ 21 days, included oral or inhalation exposure to metallic manganese, and reported one or more neurotoxicity endpoints including neurobehavior, neurochemistry or neuropathology.
The recent review of the neurotoxicity potential of metallic manganese found that, despite its essential role in human health, the data available is too limited. Only three inhalation studiesthat met the inclusioncriteriawere analysed. Two conducted by Normandin et al. (2004) and St-Pierre et al. (2001),and a third unpublished report (Envigo, 2016).
Normandin et al. (2004) and St-Pierre et al. (2001),exposied rats to manganese dust for 13 weeks. Theyfound increased manganese levels in some brain regions but mixed results regarding motor activity. The third study by Envigo (2016) followed a similar exposure period, examining neurologic effects such as motor activity and brain weight. No significant treatment-related neurologic changes were observed in this study.
The experts concluded that, based on the above data, metallic manganese cannot be classified for Specific Target Organ Toxicity.
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