The neurotransmitter dopamine plays many roles in the brain. For example, when you experience pleasure from reward, dopamine is activated. But if the levels of dopamine become too low or too high, then different disorders can arise. One such disorder is Parkinson's disease, in which the levels of dopamine drop significantly, leading to problems with movement. This drop in dopamine levels results from destruction of cells in the brain that produce dopamine. As the National Institute of Neurological Disorders and Stroke (NINDS) explained, Parkinson's disease patients lose 60 to 80 percent of the cells in the substantia nigra that produce dopamine. Without adequate dopamine in the substantia nigra to send messages to the corpus striatum, the Parkinson's disease patient's brain cannot produce regular movement. As a result, patients experience tremors, rigidity and slowed movements.
But what causes the destruction of these dopamine-producing cells? Several theories exist, but scientists have not pinpointed exact causes. One area that scientists have investigated in the cause of Parkinson's disease is environmental factors. For example, exposures to certain toxins may have an impact on when the disease occurs, noted the NINDS. In a study published in the American Journal of Epidemiology, exposure to certain metals may increase the risk of Parkinson's disease.
Reuters Health reported that the researchers used information from five million Medicare beneficiaries and information from the Environmental Protection Agency on emissions of manganese, copper and lead. In the data included in the study, all of the people used did not move between counties between the years 1995 and 2003. The researchers found that 489 out of every 100,000 people had Parkinson's disease in counties that had high manganese levels; in comparison, 274 out of every 100,000 people had Parkinson's disease in counties that did not have much emission of metals, notes Reuters Health. While the researchers also found higher levels of Parkinson's disease in areas that had larger emissions of copper, they note that the slight increase may be the result of chance.
What is manganese? A type of mineral, manganese is used in metal production. As the University of California for the U.S. Department of Energy described, when manganese is used with steel, it “improves rolling and forging qualities, strength, toughness, stiffness, wear resistance, hardness and hardenability.” If a person comes into contact with toxic levels of manganese, it can lead to neurological issues. The Linus Pauling Institute at Oregon State University explained that inhaled manganese can result in permanent damage with Parkinson's disease-like symptoms, and ingested manganese may also lead to similar symptoms. As the authors of the Parkinson's disease study note, further studies are needed to confirm the link between manganese and Parkinson's disease, and if they do, it can affect metal emissions.