美國英語聽力80篇2 Lesson30

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Pesticides

A new American study shows that chemicals used to kill insects in the home may increase the risk of developing Parkinson's disease.
Earlier studies have shown that people who work around pesticides are at greater risk of developing the disease.
But scientists say the latest study is the first to link the'disease to the use of pesticides in the home.
Parkinson's is a disease of the central nervous system.
It causes the loss of a chemical in the brain called dopamine.
As the disease progresses, it causes the muscles to become hard and difficult to move.
It also causes the arms and legs to shake.
Scientists at Stanford University in California studied about 500 people from northern California who have Parkinson's disease.
The people were asked detailed questions about past use of pesticides and other chemicals in their homes or outdoor gardens.
This information from the Parkinson's patients was compared with information from more than 500 people who did not have the disease.
Researchers found that the people who were exposed to pesticides
were more than two times as likely to develop Parkinson's disease as those who were not exposed to the chemicals.
Scientists say exposure to pesticides in the home was linked to the highest risk of developing the disease.
People who used pesticides in their outdoor gardens were not found to be at greater risk for Parkinson's.
It is not clear why pesticides may increase the risk of Parkinson's disease.
Scientists say some chemical compounds may target and kill cells in some parts of the brain.
Damage to nerve cells in a part of the brain called the substantia nigra leads to signs of Parkinson's disease.
Lorene Nelson is the leading researcher of the Study.
She presented the findings earlier this month at the yearly meeting of the American Academy of Neurobiology in San Diego,California.
She says chemicals in the environment may cause the death of some brain cells.
But she says it is too early to suggest that people change their use of pesticides.
Ms Nelson says more studies are needed before scientists can know for sure what causes Parkinson's disease.