You are going to read an extract from a New Scientist article written by Helen Phillips. For each question, choose the answer which you think fits best according to the text.

Exposure to low levels of the pesticide rotenone makes monkeys develop Parkinson’s disease, suggesting it has the same effect on people too.

“It provides proof of the concept that a lifetime of exposure to certain toxins can result in Parkinson’s disease,” says Timothy Greenamyre of Emory University in Atlanta, Georgia, whose team carried out the work.

The cause of Parkinson’s has long been elusive. Only a small fraction of cases are inherited. The best evidence that certain chemicals can cause the disease came when a substance called MPTP caused a cluster of cases among San Francisco drug users in the 1980s. But this could have been an exception.

Then four years ago Greenamyre’s work hit the headlines when his team reported that rats exposed to rotenone develop Parkinson’s (New Scientist, 11 November 2000, p 16). Rotenone is a natural insecticide still occasionally used by organic farmers and found in some garden products.

Now his team has shown that monkeys exposed to low levels of the pesticide for about 18 months develop Parkinson’s. “There is a selective neurodegeneration of the same systems that degenerate in Parkinson’s disease,” Greenamyre told the Society for Neuroscience meeting in

San Diego last week. “They have all the pathological hallmarks of the disease.” It is likely that stress, genetic predispositions and environmental toxins such as rotenone all play a role, says Michael Zigmond of the University of Pittsburgh. But he also has good news: he has shown that exercise has a protective effect. When his team injected the neurotoxin 6-hydroxydopamine into rats, only those forced to exercise did not develop Parkinson’s symptoms.

A small pilot trial involving 21 people with the disease has already begun in Pittsburgh, but Zigmond cautions that too much exercise might be damaging rather than helpful. […]

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