Largest study on cellphones, cancer finds no link

MARIA CHENG

AP Med­ical Writer

LONDON — Dan­ish researchers can offer some reas­sur­ance if you’re con­cerned about your cell­phone: Don’t worry. Your device is prob­a­bly safe.

The biggest study ever to exam­ine the pos­si­ble con­nec­tion between cell­phones and can­cer found no evi­dence of any link, sug­gest­ing that bil­lions of peo­ple who are rarely more than a few inches from their phones have no spe­cial health concerns.

The Dan­ish study of more than 350,000 peo­ple con­cluded there was no dif­fer­ence in can­cer rates between peo­ple who had used a cell­phone for about a decade and those who did not.

Last year, a sep­a­rate large study found no clear con­nec­tion between cell­phones and can­cer. But it showed a hint of a pos­si­ble asso­ci­a­tion between very heavy phone use and glioma, a rare but often deadly form of brain tumor. How­ever, the num­bers of heavy users was not suf­fi­cient to make the case.

That study of more than 14,000 peo­ple in mul­ti­ple coun­tries, in addi­tion to ani­mal exper­i­ments, led the Inter­na­tional Agency for Research on Can­cer to clas­sify elec­tro­mag­netic energy from cell­phones as “pos­si­bly car­cino­genic,” adding it to a list that also includes things such as cof­fee and gaso­line engine exhaust.

But that des­ig­na­tion does not mean the phones nec­es­sar­ily pose a risk. Cell­phones do not emit the same kind of radi­a­tion as that used in some med­ical tests or found in other sources such as radon in soil.

Two U.S. agen­cies — the Food and Drug Admin­is­tra­tion and the Fed­eral Com­mu­ni­ca­tions Com­mis­sion — have found no evi­dence that cell­phones are linked to cancer.

Yet fears of a link per­sist, despite the fact that can­cer rates have not risen since cell­phones were introduced.

In the lat­est research, pub­lished online Thurs­day in the jour­nal BMJ, researchers updated a pre­vi­ous study exam­in­ing 358,403 cell­phone users aged 30 and over in Den­mark from 1990 to 2007. They found cell­phone users did not have a higher can­cer risk com­pared with those with­out cellphones.

Can­cer rates in peo­ple who used cell­phones for about 10 years were sim­i­lar to rates in peo­ple with­out a cell­phone. Cell­phone users were also no more likely to get a tumor in the part of the brain clos­est to where phones are usu­ally held against the head. The study was paid for by the government’s Dan­ish Strate­gic Research Council.

“Our study pro­vides lit­tle evi­dence for a causal asso­ci­a­tion, but we can­not rule out a small to mod­er­ate increase in risk for sub­groups of heavy users,” said Patrizia Frei, of the Insti­tute of Can­cer Epi­demi­ol­ogy in Copen­hagen, Den­mark, one of the paper’s authors.

“This is encour­ag­ing news, but it doesn’t mean we’re at the end of the road,” said Hazel Nunn, head of Health Evi­dence and Infor­ma­tion at Can­cer Research U.K., which was not linked to the study.

About three-quarters of the world’s pop­u­la­tion, more than 5 bil­lion peo­ple, use a cell­phone. That makes it dif­fi­cult for sci­en­tists to com­pare can­cer inci­dence in peo­ple who use the devices ver­sus those who do not.

Oth­ers dis­puted the Dan­ish study’s find­ings. The advo­cacy group Mobile­Wise, which believes cell­phones pose a health risk, said the study wasn’t long enough to con­sider the long-term risk, since brain tumors can take decades to develop.

In an accom­pa­ny­ing edi­to­r­ial in BMJ, Anders Ahlbom and Maria Fey­cht­ing of Sweden’s Karolin­ska Insti­tute wrote that one of the study’s strengths was its use of objec­tive data from cell­phone records. Pre­vi­ous stud­ies have been crit­i­cized for rely­ing on peo­ple to recall their cell­phone habits from decades earlier.

In about 30 other stud­ies done in Europe, New Zealand and the U.S., patients with brain tumors have not reported using their cell­phones more often than unaf­fected people.

The edi­to­r­ial writ­ers pointed out that research on cell­phones and can­cer was not sparked by any evi­dence of a con­nec­tion, but from con­cerns that some­thing about the rela­tion­ship between radio fre­quency fields and human phys­i­ol­ogy had been “over­looked or mis­un­der­stood.” Research into the safety of cell­phones is now “exten­sive,” they wrote.

Nunn said stud­ies with longer-term data were still needed and that there was lit­tle infor­ma­tion on children’s expo­sure to cellphones.

There was no bio­log­i­cal evi­dence for how cell­phones might cause can­cer, unlike, for exam­ple, the proof that tobacco is car­cino­genic, she added.

Cell­phones send sig­nals to nearby tow­ers via radio waves, a form of energy sim­i­lar to microwaves. But the radi­a­tion pro­duced by cell­phones can­not directly dam­age DNA and is dif­fer­ent from stronger types of radi­a­tion like X-rays or ultra­vi­o­let light. At very high lev­els, radio fre­quency waves from cell­phones can heat up body tis­sue, but that is not believed to dam­age human cells.

Nunn said peo­ple should not change their cell­phone habits based on the cur­rent evi­dence, except per­haps for lim­it­ing their kids’ use of the devices.

“There are a lot more wor­ry­ing things in the world than mobile phones,” she said.

Posted by AP News on Oct 20 2011. You can follow any responses to this entry through the RSS Feed. Comments can be made below.