Manganese exposure tied to Parkinson's symptoms

NEW YORK (Reuters Health) - People exposed to the metal manganese through industrial pollution may be at increased risk of Parkinson-like problems like tremors and impaired movement, a study suggests.

Manganese is used in steel production and as a coating on welding rods, among other industrial applications. The body needs tiny amounts of manganese, and it's found as a trace mineral in foods such as whole grains, fruits and vegetables.

However, overexposure to manganese is known to damage nerve cells, potentially causing Parkinson-like problems known as manganism -- including tremors, slowed movement and unsteady gait.

Whether environmental exposure to manganese from industrial pollution might raise people's risk of Parkinson-like symptoms is unclear.

In the new study, Italian researchers assessed Parkinson symptoms among more than 900,000 residents of the northern Italy province of Brescia. They found higher rates of so-called "Parkinsonian disturbances" in 37 communities near plants producing iron-manganese alloys for steel-making.

The rate in those communities was 492 cases per 100,000 residents, versus 321 per 100,000 in the other 169 municipalities studied, the researchers report in the American Journal of Industrial Medicine.

What's more, the study found a link between Parkinson-like symptoms and the amount of manganese in dust samples collected from residents' window sills.

Manganism is caused by heavy occupational exposure that causes sudden damage to specific brain areas, note the researchers, led by Dr. Roberto G. Lucchini of the University of Brescia.

In contrast, they explain, long-term exposure to low levels of manganese may affect the brain differently -- potentially acting as an "environmental trigger" that contributes to Parkinson-like symptoms in some people.

"Although our results are not conclusive," Lucchini's team writes, "they support the hypothesis that prolonged exposure to low levels of manganese beginning from very early stages of life (and possibly pre-natal) can increase the risk of Parkinsonian disorders."

They conclude that further research is needed to see whether some people are genetically more vulnerable to this risk, and to better define safe levels of environmental manganese exposure.

SOURCE: American Journal of Industrial Medicine, November 2007.