Toxins as PD cause/Manganese
The first person to link manganese (Mn) toxicity to the onset of Parkinson’s Disease symptoms was Couper (1837). .
He described the effects of exposure to manganese oxide on workers at the chemical factory of Charles Tennant and Co.(staggering, drooling, impassive expression and low audibility}.
These observations were confirmed by subsequent researchers, who added that, in contrast to other PD cases, manganese toxicity was marked by a lack of a resting tremor and a poor repose to L-dopa therapy.  The condition has also been named manganism and has been extensively evaluated by Guilarte (2010).  It is believed that manganese induces Parkinsonism by inhibiting the production of tyrosine hydroxylation, which is an essential metabolic step in the formation of dopamine.
Santamaria et al  reviwed the neurological risks associated with welding and concluded;-
Existing exposure data indicate that, in general, Mn exposures in welders are less than those associated with the reports of clinical neurotoxicity (e.g., "manganism") in miners and smelter workers. It was also found that although manganism was observed in highly exposed workers, the scant exposure-response data available for welders do not support a conclusion that welding is associated with clinical neurotoxicity.
Butterworth  decribes a form of Parkinsonism arising from cirrhosis of the liver.
Acquired hepatolenticular degeneration, also known as "Parkinsonism in cirrhosis" is characterized by extrapyramidal symptoms including hypokinesia, dystonia and rigidity that are rapidly progressive and may be independent of the severity of cognitive dysfunction..... The cause of Parkinsonism in cirrhosis has been attributed to manganese deposition in basal ganglia structures, leading to the dysfunction of the dopaminergic neurotransmitter system.
Several reports from Eastern Europe have recorded MnPD arising from the intravenous injection of a homemade psychostimulant drug called “ephedrone” or “Russian cocktail,” a drug in which ephedrine is oxidized using potassium permanganate and acetic acid
MnPD has not been observed among ephedrone users in North America. Here, however, chromate is used as the oxidizing agent rather than potassium permanganate.
Patients with chronic liver disease excrete manganese into their bile and this too can lead to MnPD. Welders are prone to MnPD from the inhalation of manganese fumes and, atypically, show a positive response to L-dopa therapy.
There is scope for more research into the natural occurrence of manganese compounds in the environment and its production as a by-product of industrial processes.
Yoshikawa,K; Matsumoto, M.;Hamanaka,M. and Nakagawa, M. J. Full Text
Neurol. Neurosurg. Psychiatry No.(74) 1312-1314
A case of manganese-induced Parkinsonism in hereditary haemorrhagic telangiectasia. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1738686/pdf/v074p01312.pdf
National Parkinson Foundation,Full Text Environmental Risks for PD: Manganese, Welding, Mining, and Parkinsonism
Manganese toxicity in Parkinson’s
Foote, Meyers, Mielke and Flowers.
Manganese Poisoning, Manganism, Parkinsonism, Wilson's Disease, and Parkinson's Disease
http://www.manganese-wilsons-parkinsons-disease.com/ Okun, Dr. Michael
- Cadmium - Copper - Dieldrin - Manganese - Maneb - Mercury - MPTP - n-Hexane - Paraquat - Rotenone - Toluene - Trichloroethylene - Ziram
- Couper, J.(1837) Br Ann Med Pharmacol 1:41–42.On the effects of black oxide of manganese when inhaled in the lungs
- Guilart, Tomás R. (2010) Environmental Health Perspectives 118 (8). Manganese and Parkinson’s Disease¨A Critical Review and New Findings.http://ehp03.niehs.nih.gov/article/fetchArticle.action?articleURI=info%3Adoi%2F10.1289%2Fehp.0901748
- Santamaria, A.B.; Cushing, C.A.; Antonini, J.M.; Finley, B.L. and Mowat, F.S. (2007) Abstract J. Toxicol. Environ. Health B. Crit. Rev. 10 (6) 417- 465. State-of-the-science review: Does manganese exposure during welding pose a neurological risk? http://www.ncbi.nlm.nih.gov/sites/entrez?cmd=Retrieve&db=pubmed&dopt=AbstractPlus&list_uids=17710609
- Butterworth, R.F. (2012) Abstract Metab. Brain Diss. Parkinsonism in cirrhosis: pathogenesis and current therapeutic options. http://www.ncbi.nlm.nih.gov/pubmed/23086199
- Sanotsky, Y.; Lesyk, R.; Fedoryshyn, L.; Komnatska, I.; Matviyenko, Y. And Fahn, S. (2007) Mov. Dusord. 22 (9) 1337-1343. Manganic encephalopathy due to "ephedrone" abuse. http://www.ncbi.nlm.nih.gov/pubmed/17566121
- Stepens, A.; Logina, I.; Liguts, V.; Aldins, P.; Eksteina, I.; Platkājis, A.; Mārtinsone, I.; Tērauds, E.; Rozentāle, B. And Donaghy, M. (2008). N. Engl. J. Med 358 (10) 1009-1017. http://www.ncbi.nlm.nih.gov/pubmed/18322282 A Parkinsonian syndrome in methcathinone users and the role of manganese.