Studies have differed on whether the use of mobile phones increases the risk of cancer as the handsets have become increasingly popular and efficient.
The governmental agency asked Dr. John D. Boice Jr. and Dr. Joseph K. McLaughlin of the International Epidemiology Institute in Rockville, Md., to evaluate published epidemiological research on the subject.
The review looked at nine studies since 1996 that included factors such as type of phone, duration and frequency of use and brain tumor location and found that more research was needed.
"No consistent evidence was observed for increased risk of brain cancer [or other form]," the scientists said in the review, released Wednesday.
The agency acknowledged public concern about the issue and said many studies were still being performed and continued follow-up was needed on any possible carcinogenic effect linked to mobile phone usage.
"You can never say that something is without risk, but at least we can say that there is no scientific evidence for a causal association between the use of cellular phones and cancer," said Lars-Erik Paulsson, a radiation expert with the agency.
Magnus Ingelman-Sundberg, a professor in molecular toxicology at Stockholm's Karolinska Institute, agreed that there was no clear risk that cell phone usage increases the risk of cancer.
"From a cell biological and molecular biological standpoint, it is not possible to explain how cancer could arise from the energy and the type of radiation that is transmitted by cell phones," said Ingelman-Sundberg, who was not connected to the study.
The review singled out research by Swedish oncologist Lennart Hardell, which said that long-term users of old-fashioned analog cell phones were at least 30 percent more likely than nonusers to develop brain tumors. Newer digital phones emit less radiation than older analog models of the sort studied.
Hardell has testified in connection with an $800 million lawsuit against Motorola Corp. and other major mobile-phone carriers that was brought by Christopher Newman, a Maryland doctor stricken with brain cancer.
Hardell, whose study was published recently in the European Journal of Cancer Prevention, studied 1,617 patients with brain tumors and compared them with a similar-sized group of people without tumors.
He did not return phone calls seeking further comment.
The review said Hardell's study and some U.S. research with similar findings were "non-informative, either because the follow-up was too short and numbers of cancers too small, or because of serious methodological limitations."
It contrasted those with three studies in the United States, and studies in Finland and Denmark, which Paulsson said used more reliable sampling methods and were based on medical reports rather than interviews with patients.
Those studies found "a consistent picture ... that appears to rule out, with a reasonable degree of certainty, a causal association between cellular telephones and cancer to date," the agency said.
Copyright 2002. Associated Press. All rights reserved. This material may not be published, broadcast, rewritten, or redistributed.
