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A prominent American cancer doctor has warned his colleagues to limit their use of cellphones because he believes they might pose a cancer risk, while other experts disagree.

Dr. Ronald B. Herberman of the University of Pittsburgh Cancer Institute wrote a memo to the hospital's 3,000 faculty and staff urging them to take precautions when using their mobile phones, The Associated Press reported.

He said that although current medical data does not indicate a clear link between cellphones and cancer, he believes people should not wait for current and future studies to be concluded.

Herberman said future research could yet prove a link between the electromagnetic radiation produced by cellphones and an increased risk of cancer.

"Really at the heart of my concern is that we shouldn't wait for a definitive study to come out, but err on the side of being safe rather than sorry later," Herberman told AP.

In his memo, Herberman said children should only use cellphones in emergency situations because their brains are still developing.

He also advised that adults hold cellphones away from their heads, or use speakerphone or a wireless headset.

Herberman also warned against using cellphones in public places, such as buses, where elcromagnetic waves can reach other people.

'No clear evidence'

Dr. Daniel Krewsky, a lead author on a World Health Organization study on the link between cancer and cellphone use, said current research does not indicate a significant risk.

"There has been an extensive body of scientific literature that's accumulated over the last two decades on the potential health affects of exposure to radiofrequency fields from wireless telecommunications devices," he told Â鶹ӰÊÓnet.

"Literally, there are thousands of individual research studies. And collectively, they do not provide any clear evidence of an association between cellphone use and adverse outcomes, at this point in time."

Krewsky, who does not use an earpiece when using his cellphone, added that the research hints at "subtle effects" that need to be explored further.

"But the weight of evidence is not compelling for a link between cellphone use and cancer risk," he said.

Health Canada also says there is no scientific evidence yet to show a link between cellphone use and the development of cancer.

"So far, there is currently no convincing evidence, from animal or human studies, that the energy from cell phones is enough to cause serious health effects, such as cancer, epileptic seizures or sleep disorders," states Health Canada's report entitled Safety and Safe Use of Cellular Phones.

However, Toronto Public Health recently issued a warning that because the long-term risks of cellphone use are unknown, parents should limit their children's exposure to them. The warning recommended that children under the age of eight use land lines as much as possible and limit the duration and frequency of cellphone chats.

Ontario Premier Dalton McGuinty also recently advised parents to monitor their children's cellphone use for health reasons.

According to the AP article, Devra Lee Davis, the director of the university's centre for environmental oncology, encouraged Herberman to write the memo.

"The question is do you want to play Russian roulette with your brain?" she said to AP while speaking on her cellphone. "I don't know that cellphones are dangerous. But I don't know that they are safe."

Herberman makes reference a 13-nation research project that is studying the effects of cellphone use on brain tumour development. The published research has so far not proven any link, but is still ongoing.