Many animal experiments may be of little benefit to treating human disease, according to experts. Much of the research is poorly conducted and not thoroughly evaluated, say scientists at the London School Of Hygiene And Tropical Medicine.

They are now urging a systematic review of all existing animal research before new experiments are carried out. The findings, published in the British Medical Journal, have boosted animal rights groups.

However, on the same day that the BMJ paper is published, the Royal Society has produced a guide which says humanity has benefited immensely from scientific research involving animals. The society, which is the UK's national academy of science, says virtually every medical achievement in the past century has been reliant on the use of animals in some way.

"We are only asking that the same standards as are applied in human research are applied to animal research," said Professor Ian Roberts, one of the authors of the report. "We would not tolerate haphazard, potentially biased reviews of human research so why should we tolerate this for animal research? New research, whether in animals or humans, should only be carried out after a proper systematic review of the existing research. What's more, comparing results from systematic reviews of animal and human research will allow us to assess the contribution of animal research to improving human health."

He stressed that animal studies have indicated when it is not appropriate to move to human trials as much as when it is. The MRC's policy is that animals must only be used where it is strictly necessary and we are committed to developing alternatives to animal research. He pointed out that the vast majority of the animal research work funded by the MRC is not for trials of new drugs but for studies of disease processes and how the body works. "Where we do fund clinical trials of potential new treatments, we expect animal studies to be completed before human studies begin," he said. "Furthermore, researchers are expected to demonstrate what potential positive or negative effects have been found in animals."

Animal rights groups say the BMJ paper is a major breakthrough in the scientific community's willingness to debate the issue of animal experiments and whether they work. National Anti-vivisection Society chief executive Jan Creamer said: "Currently, we only see the results of animal experiments years after they have occurred - when the researcher publishes the work. This can be between three and 10 years after the event. So the debate about whether animals should have been used takes place too late. We want to shift this to the position where there is full public scrutiny before a licence is granted."

Worldwide efforts are needed to reduce the environmental damage caused by computer equipment, according to a United Nations research group.

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. 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. 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.

Hazardous Waste in PCs:

1: Lead in cathode ray tube and solder

2: Arsenic in older cathode ray tubes

3: Antimony trioxide as flame retardant

4: Polybrominated flame retardants in plastic casings, cables and circuit boards

5: Selenium in circuit boards as power supply rectifier

6: Cadmium in circuit boards and semiconductors

7: Chromium in steel as corrosion protection

8: Cobalt in steel for structure and magnetivity

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 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.

A taskforce made up of leading international think tanks has been launched to tackle climate change.

Former Cabinet minister Stephen Byers chaired the group's opening meeting in Windsor, Berkshire in March. Mr Byers warned climate change is the "overriding environmental challenge" of our age. The taskforce - which includes the UK Institute for Public Policy Research - will make recommendations to world governments in 2005.

A statement released before the inaugural conference said the participants were taking "a responsibility to future generations to hand to them a planet that is habitable and rich in life." Mr Byers said: "Climate change caused by greenhouse gas emissions from human activities threatens that objective".

Climate change could drive a million of the world's species to extinction as soon as 2050, according to a study published in January. The study - published in the journal Nature - suggested a quarter of animals and plants living on land in six world regions could be forced into oblivion.

Only cutting greenhouse gases and storing the main one, carbon dioxide, could save many species from vanishing, it warned. The United Nations says climate change poses a threat to billions of people who rely on the planet's ecosystem for their survival.