The following list presents neurotoxins in approximate order of decreasing risk, where risk is the likelihood of being poisoned times the resulting damage in case of being poisoned. However, risk varies depending on geographical location, economic status, and ethnicity. Also, males tend to be more sensitive to neurotoxins than females. [1] 

• Poisonous metals
  • Aluminum damages the blood-brain barrier, impairs learning, and reduces motor coordination; it has a causal role in autism spectrum disorder, brain aging, and Alzheimer's disease. Exposure is mostly the result of sociopolitical factors. [2,3,4,5,6]
    
  • Mercury contributes to autistic behaviors. It can result in impaired neurological development in infants and children, can cause central nervous system damage, depression, behavioral disturbances, deafness, and constriction of the visual field. The most common source of mercury poisoning is seafood. The losses due to mercury and aluminum are additive.  [7,8,9,10,11,12,13]
  • Manganese. Chronic exposure has been shown to produce a parkinsonism-like illness. Children may develop increased hyperactive and oppositional behavior. Well-water is a primary source of exposure.  [14] Another source is the synthetic analogue of khat, methcathinone.  Street names include “Jeff,” “Mulka,” “Murtsovka,” “Cat,” “M-Cat,” and “Ephedrone.” [15]
  • Cadmium plays a causal role in autism spectrum disorder. [3]
  • So does Lead. [3]
  • Arsenic occurs in common foods such as apple juice, grape juice, and rice. [16]
    
  • Depleted uranium is a known neurotoxin; its primary environmental source is the U.S. military. [17,18]
    
  • Zinc-induced copper deficiency. Zinc itself isn't toxic, but it does flush copper, and the resulting deficiency can result in loss of the myelin sheath surrounding nerve axons, causing widespread neuropathies. Vitamin B12 deficiency causes similar problems. [15]
• Poisonous chemicals
• Ethel alcohol. Long-term use causes brain damage. [19]
• Methanol and formaldehyde. The liver metabolizes methyl alcohol to formaldehyde, which is a carcinogenic toxin. The human body has a limited ability to process formaldehyde. Airborne formaldehyde causes allergies and asthma. [20]
• Fluoride is a neurotoxin that is especially harmful to children. [21]
  
• Chlorpyrifos is a neurotoxin that used as a commercial pesticide. There is no known safe exposure level. Children are especially vulnerable. The question of whether to ban it has been in the courts and EPA reviews for many years. [22,23,24]
  
• Tetrachloroethylene is a solvent used in dry cleaning. Chronic exposure may cause impaired cognitive and motor performance. [25]
  
• Aspirin causes hearing loss. It also decreases word discrimination and temporal integration ability. [26]
• MSG may contribute to fibromyalgia. [27,28]
• Biological toxins. Sources include C. botulinum, C. tetani, puffer fish, poisonous snakes, curare, and the deathstalker scorpion. [2]

References

1.    Kern J, Geier D, Homme K, et al. Developmental Neurotoxicants and the Vulnerable Male Brain: A Systematic Review of Suspected Neurotoxicants That Disproportionally Affect Males. Acta neurobiologiae experimentalis. Review, published 2017 [abstract, full text].

2.    WikiProjects Medicine / Toxicology, Molecular and Cell Biology, Chemistry, Pharmacology. Toxin. Wikipedia.org. Exposition, updated 2020 May 29 [full text].

3.    Yasuda H,Tsutsui T. Assessment of Infantile Mineral Imbalances in Autism Spectrum Disorders (ASDs). International journal of environmental research and public health. Review, online 2013 November 10 [full text].

4.    Bondy S. Prolonged Exposure to Low Levels of Aluminum Leads to Changes Associated With Brain Aging and Neurodegeneration. Toxicology. Review, online 2013 November 1 [absract].

5.    Walton J. Chronic Aluminum Intake Causes Alzheimer's Disease: Applying Sir Austin Bradford Hill's Causality Criteria. Journal of Alzheimer's disease. Causality analysis, published 2014 May 19 [abstract].

6.    Exley C. Why Industry Propaganda and Political Interference Cannot Disguise the Inevitable Role Played by Human Exposure to Aluminum in Neurodegenerative Diseases, Including Alzheimer’s Disease. Frontiers in Neurology. Exposition, online 2014 October 27 [full text].

7.    Sakamoto M, Itai T,Murata K. [Effects of Prenatal Methylmercury Exposure: From Minamata Disease to Environmental Health Studies]. Nihon eiseigaku zasshi [Japanese journal of hygiene].  Exposition, published 2017 [abstract].

8.   Yılmaz F, Yılmaz H, Tutkun E, et al. Serum Biochemical Markers of Central Nerve System Damage in Children With Acute Elemental Mercury intoxicatıon. Clinical toxicology. Case control study, online 2014 January 9 [abstract].

9.    Rice K, Walker E, Miaozong Wu, et al. Environmental Mercury and Its Toxic Effects. Journal of preventive medicine and public health. Review, online 2014 March 31 [full text].

10.  Ryu J, Ha E-H, Kim B-N. Associations of Prenatal and Early Childhood Mercury Exposure With Autistic Behaviors at 5years of Age: The Mothers and Children's Environmental Health (MOCEH) Study. The Science of the total environment. Prospective study, online 2017 December 15 [abstract].

11.  Satoh H. Occupational and Environmental Toxicology of Mercury and Its Compounds. Industrial health. Exposition, 2000 April [abstract].

12.  Nakamura M, Hachiya N, Murata K-Y Methylmercury Exposure and Neurological Outcomes in Taiji Residents Accustomed to Consuming Whale Meat. Environment International. Case series, online 2014 March 31 [abstract].

13.  Peter N, Alexandrov P, Pogue A, et al. Synergism in Aluminum and Mercury . Neurotoxicity. Integrative food, nutrition and metabolism. In vitro study, online 2018 April 13 [full text].

14.  WikiProject Elements. Manganese. Wikipedia. Exposition, updated 2020 June 7 [full text].

15.  Tormoehlen L,Kumar N. "Methcathinone abuse and manganese neurotoxicity," in Neurotoxicology: five new things. "Neurology. Clinical practice". Review, 2012 December 2 [full text].

16.  Goodman B. Arsenic in Food: FAQ. WebMD. Exposition, online 2011 December 5 [full text].

17.  Jiang G, Aschner M. Neurotoxicity of Depleted Uranium: Reasons for Increased Concern. Biological trace element research. Review, published 2006 April [abstract].

18.  Williams J. U.S. Use of Uranium Weaponry. medium.com. Exposition, online 2017 April 23 [full text].

19.  WikiProjects Pharmacology, Chemicals, Medicine. Alcohol (drug). Wikipedia. Exposition, updated 2020 June 15 [full text].

20.  WikiProjects Chemicals / Core, Pharmacology, Occupational Safety and Health. Formaldehyde. Wikipedia. Exposition, updated 2020 June 9 [full text].

21.  Alban D. Fluoride As a Neurotoxin: 9 Ways It Harms Your Brain. Be Brain Fit. Exposition, online 2018 October 13 [full text].

22.  WikiProjects Chemicals, Occupational Safety and Health, Agriculture. Chlorpyrifos. Wikipedia. Exposition, updated 2020 June 13 [full text].

23.  (Anonymous). Chlorpyrifos. National Pesticide Information Center. Exposition, accessed 2020 June 15 [general fact sheet, technical fact sheet, references].

24.  (Anonymous) What You Need To Know About Chlorpyrifos. Earthjustice. Political document, accessed 2020 June 15 [full text].  

25.  (Anonymous). Tetrachloroethylene (Perchloroethylene). Enviroental Protection Agency. Hazard sheet, updated January 2000 [full text].

26.  Sheppard A, Hayes S, Chen G, Ralli M, Salvi R. Review of salicylate-induced hearing loss, neurotoxicity, tinnitus and neuropathophysiology. Acta otorhinolaryngologica Italica. Review, published 2014 April [full text].

27.  Smith J, Terpening C, Schmidt S, Gums J. Relief of Fibromyalgia Symptoms Following Discontinuation of Dietary Excitotoxins. The Annals of pharmacotherapy. Case series, published 2001 June [abstract].

28.  Holton F, Taren D, Thomson C, et al. The Effect of Dietary Glutamate on Fibromyalgia and Irritable Bowel Symptoms. Clinical and experimental rheumatology. Clinical trial, online 2012 December 14 [abstract].