April 1998

Invisible killer?

Electromagnetic waves may induce cancer

By Wayne Leung

The jury is still out, but some research shows that people who frequently eat food prepared in microwave ovens may have a higher chance of suffering from cancer. Radiation given off by computer and television monitors may also be harmful, according to some research.

Similar radiation, known as electromagnetic waves, is also emitted by mobile phones.

Mr. Leung Kon-chong is an assistant professor in the Radioisotope Unit of Hong Kong University.

Photo by Joanna Lam

He said, “There is a heating effect when electromagnetic waves are ambient. If humans absorb electromagnetic waves, there is also heating effect. But how this effect affects people’s health depends on the density of the wave.

“The heating effect can influence human metabolism, making the cells more active,” said he.

There is also a biochemical effect such as those on the transmission of impulses along nerve fibres.

Said Mr. Leung: “When there are strong electromagnetic waves, the external magnetic field can influence people’s nervous systems. People then become nervous. They also affect body secretions.

Photo by Joanna Lam

“If the condition is serious, people will die,” Mr. Leung added.

According to Mr. Leung, cases and research show that electromagnetic waves affect people’s health.

For example, a Canadian study re-vealed that close proximity with high voltage cables that emit electromagnetic waves increased the chances of getting cancer.

“Embryo develop-ment is also affected if pregnant women stay in front of the computer screens frequently,” said Mr. Leung.

However, no conclusion can be drawn from these individual cases. Even the International Health Organization does not say that there is a close relationship.

On the other hand, Mr. Leung said scientists tend to believe that the relationship between electromagnetic waves and cancer is indirect.

But some people hold a different view.

Said Ms Annie Suen, marketing communications manager of Whirlpool (Hong Kong) Limited: “I don’t think there is a definite linkage between cancer and using microwave oven.

“I heard of some tests and research done by other companies. The results show that there is only limited or even no harmful effect produced by electromagnetic waves,” said Ms Suen.

“In fact, the frequency of microwaves sent by microwave ovens is lower then that by television and radio,” she said.

Ms Lee Bik-ki is a 19-year-old student studying computer science at the City University of Hong Kong. She uses a computer almost every night to do her homework.

“I read in the newspaper that the radiation from the screens of computers is harmful and I believe it. So I bought a filter and put it in front of the screen. It may not be much help, but it is all I can do,” said Ms Lee.

Ms Wong Yu, a 30-year-old clerk, said that she waits for a while before eating food reheated in a microwave oven.

“But I do this just to cool down the food a little bit. I don’t believe that eating the food immediately would cause cancer,” she said.

Ms Suen said users should allow the food to stand for some time after using the microwave.

“However, we recommend users to do so simply because it helps to improve the cooking,” said Ms Suen. “The food would be more evenly heated if some standing time is allowed.”

The International Protection Association of Radiation has a committee called International Nonionizing Radiation Committee.

This committee sets certain protection levels of electromagnetic waves that people can tolerate.

According to the exposure limits set by the Committee in 1988, mobile phones with a wave frequency of 900 or 1,800 MHz should have a maximum electric field of 90,000 V/m and a magnetic field of 243 A/m

Devices emitting waves with frequencies between 2,000 and 300,000 MHz should have a maximum electric field of 137 V/m and a magnetic field of 0.36 A/m.

Waves from microwave ovens have a frequency of 3,000 MHz.

Television and computer monitors give off radiation of higher frequency.

Mr. Leung said people need not take any special action if they use the appliances properly. Said he: “The producers have matched the level indicated by the protection levels before the appliances are sold to customers.”

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