A study says making the average PC requires 10 times the weight of the product in chemicals and fossil fuels.

Many of the chemicals are toxic, while the use of fossil fuels help contribute to global warming.

And the short lifetime of today's IT equipment leads to mountains of waste, the UN University report says.

That waste is then dumped in landfill sites or recycled, often in poorly managed facilities in developing countries, leading to significant health risks.

The authors say that both manufacturers and computer users across the world should be given greater incentives to upgrade or re-use computer hardware instead of discarding it.

In life and death

As computers become smaller and more energy-efficient, their environmental burden might be expected to decrease - but the study suggests that the opposite is happening.

It found that manufacturing a 24kg PC with monitor needs at least 240kg of fossil fuels to provide the energy, and 22kg of chemicals. Add to that, 1.5 tonnes of water, and your desktop system has used up the weight of a sports utility vehicle in materials before it even leaves the factory.

Compare this with cars or refrigerators, which use only between one and two times their weight in fossil fuels, and it is clear that making more than 130 million computers worldwide has a significant impact.

The study says people could be exposed to health risks at both ends of the short lifespan of computer equipment.

Chemicals such as brominated flame retardants and heavy metals including lead and cadmium pose potential risks to factory workers and users of water supplies near landfill sites where old computers are dumped.

Owning the problem

Little research on these impacts has been carried out, and there are several law suits pending from workers at semiconductor plants who claim their work is linked to birth defects and cancer.

The rector of the UN University in Tokyo, Hans van Ginkel, said: "This study clearly shows that our current understanding of the health and environmental impacts of computers is inadequate

"We can no longer ignore the potential for serious long-term problems."

The study welcomes new legislation coming into force this year in the European Union requiring the electronic industry to take responsibility for safe disposal of used equipment, but it says the environmental benefits will depend on how it is implemented.

Individuals can do a lot to cut down on computer waste, according to co-editor Eric Williams.

Broken sleep

"Every computer user has a role to play," he said.

"Users should think carefully about whether they really need to buy a new computer; if upgrading the existing machine could serve the same purpose. Promptly selling old machines to the used-product market is also important," he added.

And although modern computers use relatively little electricity while they are being operated, a huge amount of energy is wasted because equipment is left on permanently, often overnight.

Even energy-saving devices which automatically switch devices into standby mode can be deceptive, says the study, as they are frequently "woken up" by traffic from servers if they are connected to a network.