With millions of new devices - cellphones, cordless phones and Wi-Fi networks - that emit electromagnetic fields becoming indispensable in homes and workplaces, should we be worried about the hidden health effects?

Yes, according to the BioInitiative Working Group, a collection of researchers from around the world who have written a report based on thousands of studies that look for links between EMF emissions and diseases like leukaemia and brain cancer.

No, according to a committee that advises the Government about the issue and which last week discussed the working group report. Committee chairman Jim Turnbull, group manager at the National Radiation Laboratory, part of the Ministry of Health, says the lab's radiation and radio frequency (RF) exposure guidelines follow the lead of the World Health Organisation (WHO) and won't be changing.

In 1996, the WHO began the EMF Project to keep an eye on evidence of health problems relating to radiation in the 0-300GHz range. The project's leader, Dr Emilie van Deventer, says the working group's report has been noted but won't result in any alteration of the WHO's fact sheets on EMF exposure.

Of cordless phones and Wi-Fi networks, the WHO says: "Considering the very low exposure levels and research results collected to date, there is no convincing scientific evidence that the weak RF signals from base stations and wireless networks cause adverse health effects." Dr David Carpenter, of the University of Albany in New York state, a co-editor of the report, begs to differ.

Carpenter says the report's contributors show strong enough links between heavy, long-term cellphone use and brain tumours, for instance, for a "business as usual" response from decision-makers to be unacceptable.

He says there tends to be a lag of many years between exposure to radiation and tumour growth but the number of cases already apparent suggest a much bigger problem to come.

"One would expect this to be only the tip of the iceberg because of the long latency of those diseases," Carpenter says.

Added to that is the increasing use of cellphones, especially by young people.

If that sounds alarming, it's not forceful enough for American Arthur Firstenberg, author of the 1996 book Microwaving Our Planet: The Environmental Impact of the Wireless Revolution.

Firstenberg has been preoccupied by the issue since the 1980s when, as a medical student, he became convinced that radiation from operating theatre equipment was making him ill. He says he's not a voice in the wilderness.