After Brain Study, New Questions About Mobile Phones

This is the VOA Special English Health Report.
How important is your mobile phone, better known to Americans as a cell phone?
MAN: "I use my phone all the time. I'm always on my phone."
WOMAN: "It's kind of pretty much important to me because it's like my life saver."
WOMAN: "I need my cell phone."
So far, no studies have proven beyond question that the radio signals from cell phones cause brain cancer or other health problems. But a new study by government scientists in the United States has some people wondering what to think.
The scientists found that holding a cell phone to your ear for at least fifty minutes increases brain cell activity. Even the scientists themselves are not sure about the meaning of their findings.
Dr. Nora Volkow led the study. She heads the National Institute on Drug Abuse, part of the National Institutes of Health. Dr. Volkow says she would not be concerned that fifty minutes of cell phone exposure would harm anyone. But she says the research does show the need to study whether or there are long-lasting effects of repeated exposure over several years.
A man speaking on his cell phone in San Francisco
Her team studied forty-seven healthy volunteers between January and December of two thousand nine. The volunteers had cell phones placed against both ears while the scientists made images of their brain activity.
As part of the test, one phone was activated² but muted for fifty minutes. The other phone was off. After that, the people were tested with both phones turned off. Dr. Volkow says the brain scans showed increased activity in brain cells closest to the activated phone.
NORA VOLKOW: "This right area of the brain that was very close to the antenna³ shows the largest increase in metabolism⁴ as compared when the telephones were off. Even though the radio frequencies that are emitted from current cell phone technologies are very weak, they are able to activate¹ the human brain to have an effect.''
The scans showed how the brain cells used sugar to produce energy, a normal activity. The activity was seven percent higher in areas of the brain closest to the cell phone antenna.
The study appeared in the Journal of the American Medical Association.
Experts say people who are concerned about mobile phones can take steps like using a hands-free device.
Dr. Giuseppe Esposito is a nuclear medicine expert at Georgetown University Medical Center in Washington. He says after many years of studies, better kinds of research are still needed to settle questions about cell phone safety. These studies would take years.
GIUSEPPE ESPOSITO: "We need what are called epidemiological studies where you will follow a population using cell phones -- high users or light users -- and then see what happens over the years."
And that's the VOA Special English Health Report. For more health news, go to voaspecialenglish.com. You can also post comments on our website or on Facebook at VOA Learning English. I'm Steve Ember.
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Contributing: Jessica Berman and Vidushi Sinha

1 activate   

vt.使活动起来，使开始起作用

参考例句：

• We must activate the youth to study.我们要激励青年去学习。
• These push buttons can activate the elevator.这些按钮能启动电梯。

2 activated   

adj. 激活的 动词activate的过去式和过去分词

参考例句：

• The canister is filled with activated charcoal.蒸气回收罐中充满了活性炭。

3 antenna   

n.触角，触须；天线

参考例句：

• The workman fixed the antenna to the roof of the house.工人把天线固定在房顶上。
• In our village, there is an antenna on every roof for receiving TV signals.在我们村里，每家房顶上都有天线接收电视信号。

4 metabolism   

n.新陈代谢

参考例句：

• After years of dieting,Carol's metabolism was completely out of whack.经过数年的节食，卡罗尔的新陈代谢完全紊乱了。
• All living matter undergoes a process of metabolism.生物都有新陈代谢。