The NIEHS has supported a number of studies to better understand the potential health effects associated with exposure to manganese, an abundant metal that is found in air, water, soil, and food. These studies show that long-term occupational exposure to manganese results in irreversible damage to areas of the brain that control body movements. These findings have resulted in federal standards that limit the amount of manganese in drinking water, and new approaches for the prevention and treatment of neurological damage caused by manganese exposure.
Because manganese is a natural component of all living things, food is the primary source of manganese for most people. Manganese is also found in small quantities in drinking water. Since manganese is an essential trace element, small amounts are necessary for good health. However, studies conducted on Chilean manganese miners in the early 1900s showed that the miners had developed serious neurological and psychiatric problems, including movement difficulties characteristic of Parkinson’s Disease (PD).
In 1999, the NIEHS funded a study on the health consequences of occupational exposure to manganese. The results showed that miners and steel workers exposed to high levels of manganese in occupational settings developed problems with balance, movement, and fine motor coordination characteristic of PD, and were at much greater risk of developing PD itself.
During the past five years, NIEHS-funded researchers at Columbia University have studied the effects of manganese exposure on 10-year-old children in Bangladesh, where groundwater levels of the toxic metal are relatively high. Their results showed that children who received the highest doses of manganese in their drinking water had significantly lower scores on tests of intellectual function.
People may also be exposed to manganese if they live in high traffic areas where manganese is used as a gasoline additive. Results from a recent study revealed that people who inhaled manganese from automobile emissions, and had high levels of the compound in their blood, showed signs of neurological problems that were similar to those reported in occupationally exposed individuals.
Other studies conducted by NIEHS-supported scientists are designed to identify the underlying causes of manganese’s effects on brain function. Their research shows that manganese exposure produces the same pattern of brain cell death as that seen in PD patients. The loss of these cells results in reduction of a critical neurotransmitter called dopamine, the chemical messenger responsible for coordinated muscle movement. These insights into the impact of manganese exposure on critical brain functions will eventually pave the way for new strategies designed to protect these dopamine-producing neurons from manganese-induced damage.