Alzheimer Disease and Environmental Exposure to Neurotoxic Factors: A Controversy

Abstract

Background: Common neurodegenerative diseases including Alzheimer disease are a major public health issue because of their high prevalence and etiopathogenic complexity. Ageing, combined with a genetic predisposition and modifiable risk factors including cardiovascular factors, has been shown to be the main risk factor of Alzheimer and related diseases. The international scientific community suspects that physicochemical environmental factors may be involved. The lack of consensus justifies a general review of current knowledge on the role of environmental neurotoxic factors in the occurrence of some neurodegenerative diseases, particularly Alzheimer disease. Methodology: A literature search was conducted on PubMed using the keywords dementia, dementia syndrome, Alzheimer disease, Alzheimer type dementia, exposure, neurotoxicity aluminium, mercury, pesticide. After reading all of the abstracts and ruling out irrelevant articles, only relevant articles in English or French were selected. We read more than 600 abstracts and based on these we selected and read 352 articles, 176 for each of the two authors. Finally, our bibliography includes 78 articles. Results: The neurotoxicity data from animal experiments are old, and in the professional environment there is no evidence regarding the gradient of environmental toxicity. Synergistic, multiple-factor neurotoxicity is complex and difficult to document epidemiologically as it is due to a cumulative toxic continuum rather than a dose/effect relationship. Within this recognized multi-causal model of neurodegenerative diseases, particularly Alzheimer disease, chronic exposure to neurotoxic products has a real pathogenic effect on the central nervous system though certain aspects of this effect are not entirely proven. Conclusion: The lack of overall agreement about precautions for heavy metals does not mean that latent and prolonged exposure to these products is safe, especially with regard to the potential risk of worsening neurodegenerative diseases.