Paris: If you are an urban knowledge worker, keen to take advantage of the conveniences of information technology, your exposure to the invisible cloud of energy called the electromagnetic field—EMF, or electrosmog—may be considerably higher than that of your low-tech, old-media peers.

It’s 1a.m. Is your neighbour’s refrigerator behind the wall you sleep against? Is your mobile phone alarm set for 6a.m., positioned strategically within arm’s reach on

Under a cloud: If you work in close proximity with many electrical devices, your exposure to electromagnetic fields will be high.

If any of this rings true, you’re slumbering in a thick blanket of electrosmog.

Power lines, electric generators and motors, electric appliances, electronic devices and wireless communication systems all generate electric and magnetic fields, which together constitute EMF—fields of energy created by any electrical system.

At the office, you might sit within a metre of several power adapters, each kicking out EMF of varying strength. Then there’s the wireless office network, the microwave oven in the canteen, scores of mobile phones and the 11kV power main running under the sidewalk next to the building—all of which contribute to an invisible, but readily measurable balance of electromagnetic haze.

If you work in a hospital, you have the added EMF bonus from magnetic resonance imaging machines (remove those credit cards, please—an MRI scanner will erase the magnetic data in a heartbeat if you’re within a few metres, even on the floor below), X-ray machines (which generate non-ionizing EMF as well as X-rays) and hundreds of other high-power medical appliances.

Few people believe low-level electric fields are dangerous. They are easy to shield against, in any case—any conducting material, such as a metal screen or a human being, will do the trick. But the magnetic component in EMF, linked more frequently to health problems, is far more difficult to mitigate. The only sure protection against magnetic field is distance. Materials that are high in nickel, such as good quality stainless, can divert magnetic field, but do not eliminate it.

EMF comes in two basic flavours: microwave frequency and power frequency. Both are non-radioactive and often measured in milliGauss (mG). Simple Gaussmeters are available over the Internet for less than $100 (Rs3,980).

Power frequency

Modern electricity grids use alternating current, which oscillates back and forth along the power line. This oscillation generates magnetic power frequency at 50 or 60Hz, depending on the country. Typical sources include appliances, power lines, and the power adapters used with computers, printers and modems.

Ironically, most electronic devices use direct current, not AC. Because grid power is AC, you need a power adaptor—the heavy square plug weighing down your laptop bag.

Sitting 50cm away from an AC/DC adaptor for a laser printer exposes a user to 1 to 6mG of EMF. By comparison, the Swedish government recommends child care centres keep ambient EMF levels to 2mG or below.

Some electronic devices—certain DSL modems, for example—use AC power, although the voltage from the socket must still be lowered, usually to 12 volts, from 110 or 220 volts. AC/DC power adaptors emit a lot of EMF—as much as 16mG at 50cm.

Microwave frequency

Microwaves are at frequencies falling between 300MHz and 30GHz on the electromagnetic spectrum. On earth, almost all microwave radiation is man-made.

Microwave sources include mobile phones and transmission masts, Wi-Fi systems and cordless phones. Microwave ovens generate power frequency, but little microwave. They are heavily shielded to stop leakage and shut off automatically if the door is opened.

Mobile phones use microwave energy at a slightly lower frequency of 800-900MHz. Can something that cooks your dinner heat your brain as well? Yes, although the output from mobile phones varies depending on the model and its distance from the nearest relay station.

Most mobile phone makers publish the amount of radiation particular models pump into the brains of the users, using a standard called the specific absorption rate.

There is far less consensus on the need for people to protect themselves from microwave Wi-Fi signals, which are transmitted at very low power—usually less than 0.1 watt. But as Wi-Fi systems proliferate, so too will electrosmog. One way to reduce your exposure is to turn off your Wi-Fi device when you’re not using it.