Motorola and Sony Ericsson, the world’s No. 3 and 6 mobile phone makers, said they needed further scientific evidence that radio waves harm body cells and damage DNA.
The results of the European Union-funded study, which was made available on a Web site this week by the coordinating German institute Verum, first needed to be published in a scientific magazine, said Sony Ericsson, Japanese- Swedish venture.
"Then, the published results have to be balanced with the total picture of research. There are other studies published that failed to show any link between radio signals and DNA damages," the company said in an e-mailed response to questions.
A Motorola spokesman in Washington said his company was also "awaiting evaluation by the scientific community".
Verum said it was in talks with several magazines and a publication decision was expected within months.
The four-year research project measured a significant increase in single and double-strand DNA breaks in human and animal cells after being exposed to electromagnetic fields that are typical for mobile phones.
The damage could not always be repaired by the cell. DNA carries the genetic material of an organism and its different cells. "There was remaining damage for future generation of cells," project leader Franz Adlkofer told Reuters.
He said the laboratory study did not prove that mobile phones are a risk to health but concluded that more research is needed to see if effects can also be found outside a lab.
PREVIOUS STUDIES
Previous independent studies into the health effects of mobile phone radiation have found it may have some effect on the human body, such as heating up the brain and causing headaches and nausea, but no study that could be independently repeated has proved that radiation had permanent harmful effects.
About 650 million mobile phones are expected to be sold to consumers this year, and over 1.5 billion people around the world use one.
Motorola said two other major research projects were underway, one from the Internationa? Agency for Research on Cancer (IARC), a specialized cancer research agency of the World Health Organisation (WHO), and a separate WHO study.
The first study assesses whether electromagnetic fields from cell phones are a cause of cancer in humans, after IARC found in June 2001 that this was a "possibility". The other study looks into other health effects of radiation.
Results of the studies were expected this year, but are now expected late 2005 at the earliest for IARC, and a year later for the WHO research project.
Sony Ericsson said it sponsors research, but mainly those projects recommended by the WHO.
The so-called Reflex study conducted by 12 research groups in seven European countries was two-thirds funded by the European Union.