What do lead, chloroform, coffee and cellphones have in common? The World Health Organisation (WHO) believes they may all cause cancer.
The organisation has thrown its weight behind the argument cellphone use may cause cancer, after reviewing all available scientific evidence on the matter.
A working group of 31 scientists from 14 countries at the WHO's International Agency for Research on Cancer (IARC) said the review suggested cellphone use should be classified as "possibly carcinogenic" to humans.
Group chairman Dr Jonathan Samet said some evidence suggested a link between an increased risk for glioma, a type of brain cancer, and radio-frequency electromagnetic fields from cellphones.
The classification, which puts cellphone use in the same broad IARC cancer-risk category as lead, chloroform and coffee, could spur the United Nations health body to look again at its guidelines on cellphones.
However, more lengthy and detailed research was needed before a more definitive answer on any link could be given, Dr Samet said.
"The working group members were also struck by the need for further research to fill in the gaps. More people are using mobile phones ... nearly five billion people worldwide. As the numbers continue to grow, people will be exposed for longer and longer," he said.
Associate Prof Brian Cox, director of the University of Otago Hugh Adams Cancer Epidemiology Unit, told the Otago Daily Times the classification was "understandable", given it was a "low-level" grade which said cellphone use only "possibly" caused cancer.
"It's a couple of steps away from being conclusive. They are being cautious. It's a matter of how one wishes to interpret the statement `possibly causes cancer'," Prof Cox said.
He believed cellphone users should "not get too excited about it at this point of time" and the low-level classification was "reassuring, really".
"I'm certainly not convinced that cellphone use causes cancer," he said.
NZ National Radiation Laboratory senior adviser Martin Gledhill said it should be noted the data on which the conclusion was based mostly involved older phones.
"Newer technologies [3G/XT/CDMA] produce much lower exposures than these phones," he said.
If people were concerned about exposure they could use phones in places with good signal strength, which allowed phones to transmit at reduced power; minimise the length of time spent on calls; or use landline, not cordless, phones, or a car kit with an external antenna.
Also, hands-free kits have been found to reduce exposure to the head by up to 98%.
