By
Aloysius Choong
03/06/2002
URL:
http://asia.cnet.com/digitalliving/tips/0,3800004921,39046296,00.htm
With the increasing popularity of mobile phones around the world, it is no wonder that people have started questioning the safety of these devices. Here, we explain what you need to know about phone radio waves. Bear in mind that researchers everywhere are themselves still trying to understand the full effects of cell phone use.
Mobile phones are two-way radios that transmit and receive information via radio waves, also known as radio frequency (RF) energy. Whenever the user makes a phone call, his voice is encoded into radio waves and transmitted through the antenna to a nearby base station. These radio waves are at the heart of the controversy over cell phone safety.
Radio waves are just one of the many forms of electromagnetic energy that form the electromagnetic spectrum. Other types, including gamma rays, x-rays and light, also belong to this spectrum. They differ from radio waves in terms of wavelength and frequency.
Gamma rays and x-rays, which contain very high levels of electromagnetic energy, are called ionizing radiation. According to the United States Food and Drug Administration (FDA), such energy can ionize and damage biological tissues by causing electrons to be stripped away from their normal locations in atoms and molecules.
On the other hand, cell phone radio waves, visible light and ultraviolet are non-ionizing radiation, and generally considered safe. However, high-energy radio microwaves can damage tissue through heating, while intense ultraviolet can cause blindness and superficial skin burns. These exceptions have festered continued doubt about the safety of mobile phones.
SAR measurement setup (picture from Ericsson) |
Measuring radio waves
Specific Absorption Rate (SAR) measures the RF energy absorbed by a certain amount of body tissue through using a particular mobile. It is usually expressed in units of watts per kilogram (W/kg).
There are currently two main standards for the measurement of SAR values, each with its own safety guidelines and set of adherents.
The standard adopted in Singapore and much of Europe was developed by the International Commission on Non-Ionizing Radiation Protection (ICNIRP), and has been endorsed by the World Health Organization (WHO). The SAR limit specified by the ICNIRP is 2.0W/kg, averaged over 10g of tissue.
Ericsson T68 up close (picture from Ericsson) |
The Institute of Electrical and Electronics Engineers (
IEEE) has also defined a standard, adopted by the US and other countries. It uses a limit of 1.6W/kg, averaged over 1g of tissue.
Either way, SAR tests are conducted by pouring simulated human tissue into a mould of a human head. The mobile phone under test is placed outside the mould and configured to operate on full power. A robot arm then inserts a probe into the "tissue" to find the area of the highest RF field, commonly known as the "hot spot". The probe measures a value, mathematically processed, whereupon the SAR value is derived.
To find the SAR values of the latest phones, you can check out the CNETAsia
radiation chart.
Potential health hazards?
A British study announced that radiation from mobile phones may speed up users' response times, possibly resulting in detrimental effects on the brain.
In another study, two Swedish professors discovered a chilling finding: people who had used analog mobile phones for up to 10 years had a 26 percent higher risk of brain cancer compared to a control sample.
However, there have been studies that offer different conclusions. In December 2001, US researchers found that people who used mobile phones regularly for five years or more did not appear to have a greater risk of developing brain cancer.
The following year, a Danish study mirrored the above findings. It found that mobile phones, even when used regularly for as long as 18 years, did not seem to increase the risk of developing brain cancer, leukemia or cancer of the pancreas.
According to a recent new study conducted by Hungarian researchers, men who consistently carry a mobile may have their sperm count reduced by up to 30 percent. Although there're similar studies in the past, this is the first to suggest that radiation by the handset, even when it's not in use, may impact male fertility.
Amid all these conflicting reports, more researchers are heeding the WHO's call made earlier this month to conduct further mobile phone tests.
"Based on current epidemiological evidence, there is no evidence of a strong association between RF (radio frequency) exposure and cancer," said Elisabeth Cardis, chief of radiation and cancer at WHO's International Agency for Research in Cancer. "One can't rule out that there is a risk, but if there is a risk to mobile phone users it would be very small. More research is needed," she said.
Meanwhile, according to Stephen Chong, Singapore's Health Sciences Authority director of Center for Radiation Protection, the handsfree kit is the "only effective device" recommended by WHO in reducing mobile phone users' exposure to radiation.
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