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People know that there's something going on. They know they get headaches, they feel the side of their head heat up, and they're getting devices that reduce radiation output or hold the phone away from their head.
It's our constant companion in the modern world; it's all around us, all the time, but we're hardly aware of it.
It's electromagnetic radiation and, in the form of radio waves or microwaves, it emanates from radio transmitters, mobile phones, mobile phone base stations, microwave ovens and radar antennae. Your TV set accelerates electrons to make the picture on the screen and produces low-energy X-rays. Electric current in wiring also produces magnetic and electric fields.
How dangerous is all this? Not very, or we'd all be dead – EMR exposure is practically universal in cities. Industry and most scientists say there is nothing to worry about, but a few concerned voices are being raised.
Before sampling this sometimes heated debate, let's look at the basic facts.
The electromagnetic spectrum is a concept scientists use to classify different types of radiation, from power line fields to visible light to X-rays. Power line radiation (or strictly speaking, its electromagnetic field) has a low frequency and long wavelength. At the other end of the spectrum, X-rays have a very high frequency and short wavelength.
High-frequency radiation such as that emitted by ultra-violet rays and X-rays have a unique and nasty characteristic. They can break molecular bonds and damage DNA. Radiation that does this is called ionising radiation.
Microwave radiation doesn't ionise, but it can heat objects in its path. It and high-frequency radio emissions – such as those from mobile phones – are acknowledged to have thermal effects if they are broadcast in sufficient strength. The low-frequency electromagnetic fields around power lines are not thought to have any measurable thermal effect.
Radiation from all sources obeys the inverse square law. That is, the further you are from the source the less intense your exposure to the radiation. In fact, it drops off with the square of your distance from the source. If you are twice as far from a fire you feel one-quarter of the radiant heat, but if you move four times as far away you feel only one-sixteenth of the heat.
Power lines have been accused of promoting cancer – in particular, leukemia – through their electric and magnetic fields. Power lines generate both electric and magnetic fields. The electric field is proportional to the voltage in the line. The magnetic field is proportional to the current flow in the line. If the line is carrying alternating current then the magnetic field also alternates.
"It's not been established that there are any long-term health risks associated with power lines. Because no risks have been established, it's impossible to determine any exposure guidelines," says Graeme Elliott of the Australian Radiation Protection And Nuclear Safety Agency.
ARPANSA says there are no effects associated with weak electric fields. In experiments, weak magnetic fields have demonstrated effects such as altered hormone and enzyme levels. The health implications of these changes, if any, are not known.
A Harvard University study suggested that electric fields, although blocked by the body's spherical cells, were able to penetrate other, differently shaped cells, such as the long tails of nerve cells. The health effects of this, if any, are also unknown.
A US study at the Fred Hutchinson Cancer Research Centre in Seattle suggested low-level electromagnetic fields reduced production of melatonin in women. Melatonin is a hormone that helps regulate the body's internal clock. The health implications of decreased melatonin levels are not known and, in any case, the body produces less melatonin as it ages, with 80-year-olds producing 80 per cent less than young people.
Appliances in the home also generate electric and magnetic fields. You can reduce your exposure to these by turning off any device you are not using. Your hair dryer and clock radio generate electromagnetic fields.
Using an electric blanket while you are in bed will expose you to its fields – if this concerns you, setting the blanket to heat the bed before you get in is a better option.
''Children should under no circumstances be put to bed on a turned-on electric blanket," says Senator Lyn Allison from the Democrats, who considers electromagnetic radiation to be a public health issue. "Hair dryers, too, are a significant source of EMR. Any source close to the brain is an issue."
Mobile phones emanate electromagnetic radiation. The frequencies and wavelengths used by mobiles are similar to those used by microwave ovens, although mobile phones are much less powerful.
"People know that there's something going on, in spite of the whole [telecommunications] industry denying that there's a problem. They know they get headaches, they feel the side of their head heat up, and they'e voting with their feet and getting devices that reduce radiation output or hold the phone away from their head," says Allison.
There are thought to be two possible physical effects of mobile phone use. One is the thermal effect, in which signals from the phone handset heat the head in a similar way to a microwave oven cooking food. The heating effect of a phone is very small, less than one degree Celsius.
Another theory, suggested by a 1996 Washington University study, is that emissions from mobile phone handsets can damage DNA. The study found DNA damage in the brains of rats exposed to low doses of microwave radiation.
An experiment at the Royal Adelaide Hospital in 1997 suggested that exposure to mobile phone frequencies led to increased rates of lymphoma in mice. A follow-up study began in February. An experiment conducted by Alan Preece at Bristol Royal Infirmary in Britain suggests that mobile phone use might affect memory. Preece worked with volunteers who had transmitters attached to their heads. Half the volunteers were subjected to transmission similar in wavelength and power to a mobile phone's. Preece found they performed worse in memory and cognitive function tests than the volunteers who were not exposed.
Stephen Cornay, a former British Telecom engineer who retired after suffering memory problems, is suing his employer, claiming his problems were caused by constant use of a mobile phone in his job.
A German study reported that human volunteers using a GSM mobile phone for 35 minutes showed a 5-10mm Hg rise in blood pressure. A rise in blood pressure by this amount has no known health consequences.
The Australian Mobile Communications Association, a telecommunications industry lobby group, says there is no substantiated evidence that using mobile phones or living near mobile phone base stations can cause adverse health effects.
The association points out that different scientific studies frequently contradict each other. No clear pattern is emerging, it says.
"I get a headache from using my mobile phone sometimes, but it's more to do with what's said over the phone," says Peter Russell, AMCA spokesman. He also says that although mobile phones are new, research into other types of radio transmitter has been going on for nearly 50 years.
One British researcher, Helen Dolk, found a greater incidence of leukemia among people living near a TV transmission tower in Sutton Coldfield, in England. But when she studied 20 other British towers and communities living nearby her team found no correlation.
Graeme Elliott is sceptical but open-minded.
"At the moment, in my view the research hasn't confirmed that there are any effects," he says.
"Based on the current research it's not indicated that there is a definite risk, but there's other research being done. We need to wait and see."