Study finds overexposure to element may spell trouble for those at risk

Manganese is an essential element we all need to survive. However, too much of it can be toxic and may speed up the development of Parkinson's disease, new research shows.

A study, published in this month's issue of Neurotoxicology and Teratology, found that while manganese exposure does not cause Parkinson's, higher than normal levels of it may cause symptoms of the disease to show up much earlier in susceptible patients.

Recent proposals to add manganese to gasoline prompted the researchers to tackle the topic, says study author Donald Smith, an associate professor of environmental toxicology at the University of California in Santa Cruz.

Such a move would increase the levels of manganese exposure in the environment, Smith says, adding "it's important to pay attention to how environment plays a role in diseases like Parkinson's."

Parkinson's is a chronic neurological disease that can cause tremors on one side of the body, slowness of movement, stiffness in the limbs and gait and balance problems.
　　For this study, Smith and his colleagues examined four groups of rats. One group had a condition similar to what humans who have not yet developed symptoms of Parkinson's have. Another group was exposed to higher levels of manganese, and a third group had both the pre-Parkinson condition and the manganese exposure. The final group had neither.

The rats were exposed to levels of manganese that are higher than what is currently found in the environment. But the exposure was less than what those who work with manganese -- welders, miners and others -- get on a daily basis, says Smith.

The rat group with pre-Parkinson's that was exposed to manganese did significantly worse on several tests than any of the other groups, says Smith. This, he says, "suggests an interaction between the two, and that there is a significantly greater risk of acquiring impairments if those with pre-Parkinson's are also exposed to high levels of manganese."

Interestingly, Parkinson's and an overexposure to manganese seem to affect different parts of the brain, says Smith, and this creates an additive effect, making the damage to one area worse than it otherwise might be.

Dr. Sandra Shuman, an associate professor of neurology at the Temple University School of Medicine in Philadelphia, says the study is interesting but she has some questions about the findings. For example, the Parkinson-like condition was induced in the rats, and Shuman believes the way it was induced might have caused some symptoms on its own.

But, she says, the study seems to suggest there are those who "might never develop Parkinson's if they are not exposed to the toxicity of manganese."

The idea that it might be added to gasoline is worrisome, she adds, because it would mean much more airborne manganese exposure. There is already existing data showing that miners in South America develop Parkinson-like symptoms very early in life, she adds.

(From HealthScout)