14 September 2011

Mobile phones and radiation

By Dr Kho Yau Hee

Most of us will have difficulty going through the day without our mobile phones. How could we, after all, since the device has become so much a part of our lives. It practically changed the way we interact, socialize and, yes, even the way we do business. 

While it may be one of the best things ever invented after sliced bread, a recent a World Health Organisation (WHO) panel recently declared that mobile phones may cause cancer, placing the hand-held device into the same category as some pesticides that are harmful to human health.

The finding by the International Agency for Research on Cancer (IARC) adds to concerns among a small but growing group of experts about the effects of low level radiation emitted by mobile phones. Classifying the appliance as “possibly carcinogenic” was based largely on epidemiological data that show an increased risk, among heavy mobile phone users, to a rare type of brain tumour called a glioma. While this may raise concern, it must be appreciated that the radiation discharged is not the same as radioactivity emanating from Japan’s damaged nuclear reactors following a recent earthquake.

Radiation from mobile phones is non-ionising. When ionisation of an atom occurs, electrons are removed from it, resulting in charged ions that may damage the DNA in cells, which in turn may lead to cancer. Mobile phone radiation does not carry enough energy to ionise an atom but merely excites the atom and causes it to vibrate. This in turn produces a heating effect. Microwave oven works in the same manner: when electromagnetic radiation from the oven bombards your cup of coffee, the energy from the radiation causes water molecules to vibrate. This increases the temperature of the water, thus warming up the coffee.

The level of radiation from mobile phones is, of course, much less than that emitted by a microwave oven which typically operates at 1000 watts. The power transmitted by a mobile phone is about 0.5 watts and only about 50% of this is projected towards your head. In most cases the antenna is rarely 100% efficient. So, of the 0.5 watts that the mobile phone transmits, your head is exposed to only about 0.125 watts (0.5 watts transmitted x 0.5 directed towards your head x 0.5 antenna efficiency).

Let’s compare this with the amount of power we are exposed to from direct sunlight. The Sun is a reasonable basis for comparison because sunlight reaches us through cosmic radiation which heats up any surface area subjected to it.

Depending on the region and time of day, the Sun on average has a radiation intensity of about 1372 watts per square metre. The bigger an area, the more power it is subjected to. Let’s assume that your head is exposed to direct sunlight. We then model your head as a circle with a radius of 10 cm. That gives a cross section area of 0.0314 sq m (circular area is calculated as πr2 with π given as 3.14 and r2 as 0.01). The amount of power your head is exposed to will be about 43 watts (1372 x 0.0314). That is about 344 times more than the power from mobile phone use.
It is therefore more critical, in my opinion, to avoid direct Sun exposure, specifically ultra violet light, as it is known to cause skin cancer especially among those with fair skin.

The health issue related to electromagnetic radiation from mobile phones and other wireless devices such as Wi-Fi, radio and TV has been a controversial subject. Many experts have divided opinions on the issue. The Institution of Engineering and Technology has been investigating this issue since 1992, but scientific evidence to date does not indicate that exposure to low-level electromagnetic radiation is harmful.

Despite the WHO declaration there is no conclusive evidence linking brain tumour to mobile phone radiation. On the other hand, it is also impossible to declare with certainty that the radiation emitted by mobile phones is safe. There is certainly nothing to lose by practicing some safety measures such as reducing the time spent talking on the phone, avoid sleeping with the unit under your pillow and/or refrain from using it when the signal strength is low.

Dr Kho Yau Hee is a lecturer with the School of Engineering, Computing and Science at Swinburne University of Technology Sarawak Campus. He can be contacted at ykho@swinburne.edu.my