|Back To Previous Page|
|Print This Page|
Contradictory Studies Heat Up Radiation Question
A new long-term animal study of cell-phone radiation suggests that emissions don't cause cancer. However, studies by a second team hint that cell phones may damage people in other ways.
As cellular phones' popularity has soared, so have concerns about health effects from an electromagnetic-radiation source held so near the brain. Although the small amount of energy from a cell phone has been reported to generate stress responses in animals' cells and affect people's reflexes, scientists are still at a loss to say whether such radiation poses significant health risks.
To collect more information, researchers at Washington University School of Medicine in St. Louis exposed rats to the two frequencies of radiation emitted most commonly by cellular phones, says study leader Joseph L. Roti Roti. For 2 years, the scientists placed 480 rats in chambers adjacent to radio antennas. For 5 hours each day, a third of the animals was exposed to the frequency produced by a digital cell phone and another third, to the frequency of an analogue cell phone. The remaining rats received no radiation.
At the end of the experiment, the team examined the animals for tumors in the brain and 30 other tissues. The researchers found no significant difference in tumor incidence among the groups. The team presented the findings this week in Quebec City at a meeting of the Bioelectromagnetics Society.
"As far as I can tell . . . the greatest hazard with cell phones is driving a car while talking on one," says Roti Roti, whose study was partially funded by telecommunications-industry giant Motorola.
Other scientists aren't as convinced. The type of emissions the team tested isn't the most common or the most penetrating, comments W. Ross Adey of Loma Linda University in California. Though Roti Roti tested the variety of signal that is used in the United States, says Adey, most of the world uses another signal type, which can travel further into tissue.
Adey also notes that other long-term animal studies have shown mixed results.
Other findings presented at the bioelectromagnetics meeting link cell phones' radiation to molecular changes in cells. A team from Finland examined the activity of about 4,500 genes in human cells cultured in the laboratory and exposed to cell-phone radiation for 48 hours. The researchers, led by Dariusz Leszczynski of the Radiation and Nuclear Safety Authority in Helsinki, found that in cells exposed to radiation, more than 20 genes were either more or less active than usual. They also noted changes in the amounts of proteins produced by these genes.
Preliminary results suggest that some of the genes control cell proliferation and response to stress. "It's difficult to speculate on potential health effects at this stage," says Leszczynski.
At the meeting, he also revealed results of an experiment exploring how cellular phones might increase blood-vessel permeability in the brain, as suggested by previous rodent studies. The effect would permit molecules normally excluded from the brain to seep in.
In the experiment, which used cultured human blood-vessel cells, Leszczynski found that the active form of a protein known as heat shock protein 27 increases in abundance when cells are exposed to cell-phone radiation. This activity leads to an accumulation of stress fibers, which are part of a cell's internal scaffolding. The extra fibers may distort the cells that make up blood-vessel walls and thereby increase permeability, Leszczynski says.
Leszczynski's work is "absolutely fascinating," comments Alan Preece of the University of Bristol in England. "If repeated in the intact body, it has horrific implications." Preece chaired a conference session on electromagnetic radiation and cognition.