Health & Fitness: Questions remain about cell phone link to cancer

Tag : Interphone

"It's fair to say that the data aren't all in yet," says Dr. DavidL. McCormick, a biologist and director of the Illinois Institute ofTechnology Research Institute in Chicago, who has studied theissue. "There are a small number of epidemiological studies thathave suggested a possible increase in cancer risk. But comparablestudies in other populations haven't confirmed these findings."
That's not to say anyone should panic. Cell phones do produce atype of radiation, but it's of the type called nonionizing radiofrequency  a form of energy on the electromagnetic spectrum. Atthe high end of the spectrum, ionizing radiation, such as thatemitted by X-ray machines, has well-known dangers. But the weaksignals released by nonionizing radio frequencies do not cause DNAdamage, and there is no explanation for how such energy could causecancer, McCormick says.
Little evidence found
Most studies have not consistently demonstrated a link between cellphone use and cancer, including two studies conducted by theNational Cancer Institute. Several other studies coordinatedthrough the International Agency for Research on Cancer, called theInterphone studies, have also failed to show an association.Numerous laboratory studies on animals have also found no evidencethat DNA is damaged by low levels of radio frequency, McCormicksays.
But the sheer number of people using cell phones and the volume ofuse, as well as a few studies that found a potential link betweenbrain cancer and cell phones, have kept the safety questionlooming.
The National Academy of Sciences released a report in Januarycalling for more research on cell phones and health risks. Theauthors concluded that many of the past studies were not conductedover a long-enough period of time to assess the risk of braincancer, which typically develops slowly.
Nor have the studies examined the effects of cellphone use onchildren, whose nervous systems are still developing, or on whetherthe radio frequency emissions can cause other types of healthproblems, such as cancers elsewhere in the body or central nervoussystem damage that may affect learning or behavior, says Dr. LeekaKheifets, a professor of epidemiology at the University ofCalifornia, Los Angeles' School of Public Health, who was a memberof the NAS panel.
"At this point, it looks unlikely that cell phones are causingbrain tumors, particularly from short-term exposures," Kheifetssays. "But we have not looked at all kinds of health outcomes yet.The focus has been on brain tumors."
'Unexpected results' seen
Kheifets and researchers in Denmark recently examined cell phoneuse in children and found "unexpected results." The researchersexamined 13,159 Danish children born in 1997 and 1998 who areparticipants of a study called the Danish National Birth Cohort.The children's mothers were surveyed during pregnancy and againwhen the children were 18 months old and 7 years old.
The study found that children who used cell phones, and whosemothers used cell phones during pregnancy were 80 percent morelikely to have behavioral problems such as emotional symptoms,inattention, hyperactivity and problems with peers compared withchildren who had no cell phone exposure as fetuses or in earlychildhood. Children whose mothers used cell phones during pregnancybut who had no other cell phone exposure were 54 percent morelikely to have behavioral problems.
The study, which will be published this month in the journal Epidemiology , is the first to find a behavioral effect and so must beinterpreted with caution. But Kheifets says, "In general, kids aremore susceptible to environmental hazards. We have littleinformation on cell phones, and children are using cell phones atyounger ages."
Research on children and long-term studies should provide moreclarification on any health risks, says Dr. Siegal Sadetzki, anepidemiologist at Gertner Institute, Chaim Sheba Medical Center, inIsrael.
Uncertainty remains
Sadetzki's research has found heavy cell phone users were at 50percent higher risk for a parotid tumor, which arises in thesalivary gland near the ear and jaw, typically where cell phonesare held. Parotid tumors can be cancerous or benign. The study wassignificant because it tracked heavy users for more than 10 yearsand found a relationship between the side of the head the phone wastypically placed against and where the tumor formed.
She says she doesn't think her study, which was published inFebruary in the American Journal of Epidemiology , contradicts previous studies that showed no cause for alarm. Theresearch was conducted in Israel, which has a population of heavyusers who were among the first to adopt cell phone technology.