Loading...
ST9302-CS 980928Discoveries Monday, September 28, 1998 RECHARGING THE DEBATE ~-: ' - almost two decades, experts have been 'Electromagnetic fields remain. a controversial health concern By Karin Jegalian ~al! Writer of T~e DE~u Morning News In the extreme, electricity is clearly dangerous. Electric chairs and lightning strikes prove that. But people also benefit from electricity; hearls and brains couldn't work without it. And defibrillators use it to save lives. Yet whether the most familiar EPIDEMIOLOGY form of electricity -- the kind that flows through wires into almost every building -- poses any dangers is not entirely clear. Ever since the finding 19 years ago r~etic fields created ~~__ other sources can slightly ~ /,~r~-~= ':'-' I risk. Two scientific reports, one thi;' ' :) years ago, agree about much · Jisagree about its interpretation. <:.:~ ~.. ~ of measurement for ~ magnetic fields is the ~ mllllgau~ (roG). The , ~ magnetic flel~ f~t ~ ~lovolt) ~wer line is ~ ~ approximately 12.5 ~ ~ roG. A neighbo~ ~ ~ ~wer line can ~ ~ produce indoor fields y ~ ~or~r~. Yet whether the most familiar EPIDEMIOLOGY form of electricity-- the kind that flows through wires into almost every building -- poses any dangers is not entirely clear. Ever since the finding 19 years ago that children who live near power lines seem more at risk for leukemia, scientists have tried to see whether electromagnetic fields, or EMFs, can have subtle, long-term health effects. Yet after two decades and countless studies, scientists still cannot say whether EMFs from power lines and ap- pliances can hurt people. Two years ago, the issue seemed set- tled when a panel of the National Acade- my of Sciences reassured the public that EMFs from power lines and appliances are safe: "No adverse health effects seen from residential exposure to electromag- netic fields,' declared an academy press release. But this summer, a group of 25 scien- tists and other experts presented a report Please see Scientists on Page Scientists seek reason for betw n wer lines, leu] BY Living near power lines rais- Usually, soml es ~he risk-- slightly-- of chtld-~ causes cancer me~ ho~~ leukemia, scientists agree, ne~lc material, ~ Buttheydon~agreeth~elec~'o- in cells. But el~ _m.?~c fields frmn tl~ power fields, or EMFs, ~ llnea ate to bIam~ [ ~ j generated by pow the how the ~ eoaM ea~es imble of that : --~ dam--- ~ ~ la~ ' 80 some btol~ ~ea~ convincingly ahow: wliether ~ ~ that the ktnda o! flelda 8tven off ~ Pleame aee MOR! ink. , ieaua es up the ge )wn es DNA~ ~tromasnetk the ~ ~ ~n~ ~d ~ ~ ~e~ ~t enco~ HOME (For appliances in use; figures represent highest magnetic field measurements) 1. Hair d~er (6 inches away) 700 mG 2. Blender (1 foot) 20 mG 3, Can opener (1 foot) 300 mG 4. Dishwaeher (1 foot) 30 mG 5. Microwave oven (1 foot) 200 mG 6. Electric range (1 foot) 30 mG 7. Color TV (2 feet) 8 mG 8, Ceiling fan (4 feet) ImG 9. Vacuum cleaner (1 foot) 200 mG 10. Conventional clock-face alarm clock (1 foot) 30 mG 11. Baby monitor (6 inches) 15 mG 12. Color computer monitor (2 feet) 3 mG SOURCES: Information Ventures IncJEMF-I ink at http'.//Infoventures. microserve.com/emf/; Consumer Reports Atypical U.S. home has a background magnetic rmld, away from appllance~, of between 0.5 and 4 milligauss, with an average of 0.9 mG. Th~Dall~sllorninI ~ev~W.,~laI~Pinknt ...... · ' More tudic needed , nUsts debate the r electromagnetic fields to explain EMFs' linl4 )ntinued from Page 6D. ~out EMFs and health to the Nation- ~ Institute of Environmental Health ciences, in which the group classi- led EMFs as a "possible human car- :inogen.' The group's position seems to dif- fer from that of the National Acade- my panel, but experts say that the reports agree more than they may seem. "A lot of the elementS [of the re- portsl are more similar than you'd think from the bottom line," says Da- vid A. Savitz, an epidemiologist at the University of North Carolina in Cha- pel Hill who served on the National Academy panel. In fact, both panels agreed that exposure to EMFs is associated with a small increase in the risk for child- hoed leukemia. And both agreed that experimentS exposing animals and cells to fields typical of those that come through power lines have not explained how EMFs could cause can- :er or other health problems. The groups disagreed on how much credence to give to human pop- flation studies that suggest a link )etween EMFs and disease vs. labera- .ory studies that show no link. Nobody is suggesting doing away vath electricity. Electricity is inescap- able. Being invisible, it can also seem mysterious. And cancer in children is so dreaded that even the potential for a small increase in the risk of it alarms many people. Congress in 1992 instructed the National Institute of Environmental Health Sciences, a division of the Na- tional Institutes of Health, to evaluate the scientific evidence about the po- tentisl health effectS of environmen- tal F_NIFs. The World Health 0rgamza- Uon also has an EMF project to assess possible risks, with more than 40 countries and six international orga- mzations participating. The 26membar NIH group decided this summer that "limited evidence" supports a link between EMFs and chfldhcod leukemia, and a majority of the panel members said "limited evidence" also supports a link t-ween the exposure of adults to EMFs at work and a different kind of leuke- mia, The group said that no more than "inadequate evidence" links F3dF exposure to other cancers. "If there is a [aSk, it seems to be mall," concludes Ben Greenebaum, a physicist at the University of Wiscon- sin-Parkside and the editor of the journal Bioelectromagnetics. Several studies have replicated the 1979 finding that children who have leukemia tend to be exposed to high- er levels of magnetic fields in their homes than the average child. '~l'he evidence that there are effects is clear. The basis is not clear," says David O. Carpenter, a neuro~cientist at the State University of New York in Albany. Because scientists haven't been able to explain how exposure to E, MFs from power lines could cause cancer, some suspect that the reason children who live near power lines are more Likely to get leukemia is because they share some other characteristic -- some other environmental exposure perhaps -- that really causes the can. cer. The ~ group could have ranked EMFs in one of five categories -- as a "known," "probable" or "possible" carcInogen; as "probably not" a car. cinogen; or it could have said that the data are not clear. Some materials that have achieved the ranking of "known" or "probable" carcinogens are ionizing radiation (such as that from X-rays), dioxins (found in some herbicides and created when certain plastics are burned), ultraviolet light (which causes skin cancer), arsenic, benzene, lead and, notoriously, ciga- rette smoke. Not one of the 26 mem- bers of the .NIH group deemed EMFs a "known" or "probable" carcinogen. Charles F. Stevens, who headed the National Academy of Sciences panel two years ago, studies how mol- ecules respond to electrical impulses in the brain. He thinks EMFs are safe but concedes that the link between leukemia and power lines "could not be ascribed to a statistical bhp." "It looks like there has to be some link," says Dr. Stevens, a researcher at the SaLk Institute in La Jolla, Calif. Despite that link, the National Academy panel was swayed by the absence of a convincing explanation for it. "We had a different perception of what was important. There was a consensus statement; the reasoning was that epidemlology was not com- pelling in itseff," says Dr. Sevi~z, a member of that panel. He points out that the NIH group Included more epidemiologista than the National Academy panel, which was dominat- ed instead by physicists, chemists and other lab researchers. The National Academy report in 1996 reviewed more than 500 studies and concluded that "no conclusive and consistent evidence shows that exposures to residential electric and magnetic fields produce cancer." The NIH group reviewed about 9e0 stud- Electric drills produce 100 to 200 mG when they are 6 inches away from the user. les. "Both reports looked at the data in a very unbiased way, I would say," says Richard Luben of the University of California, Riverside, who served on both comnnttees. '~'b.e... [Nation- al Ins'diute of Environmental Health Sciencesl had about three years' more data to work with." Also, the National Academy panel set a higher standard that the tx~si- hie risl~ from EMF had to reach. The standard it set -- "conclusive and conSiStent" evidence linking EMF ex- IX)sure and disease -- is "a scientific standard that is very difficult to achieve,' says Christopher J. Portier, a statistician at the National Institute of Environmental Health Sciences, in Research Triangle Park, N.C. A "con- clusive and consistent" evaluation would be equivalent to ,-ailing E.MFS a "known" or "probable" carcinogen, he says. But proving that something is not a carcinogen can be an arduous task, too. Only one, relatively obscure, Please see EFFECTS on Page 8D. to childhood Continued from Page 6D. the growth of tumors once cancerous cens ar~. Other scientists suggest that earlier assumptions underesti- mated how much EMFs can penetrate Into htLman cells. A small statistical link ties living near power lines with childhood leu- kemia, but a statistical association be- tween two things cannot alone prove that one causes the other. For exam- ple, the birth rate in Europe has de- clined during the last century. So has the population of storks. "Does that prove storks deliver ba- bies? You need additional studies," deadpans Christopher J. Portier, a statistician at the National Institute of Environmental Health Sciences in Research Triangle Park, N.C. Some experts believe the burden of proof should lie with those who think that EMFs can be dangerous. Others won't accept that EMFs are safe until the link between power line exposure and leukemia is ex- plained by another agent. "If people can show what that other tiring is, then they can convince me, but no one's found it," says David O. Carpen- ter, a neurescientist at the State Uni- versity of New York in Albany. The magnetic aspect of electro- magnetic fields tends to be empha- sized when health effects are consid- ered. Many scientists say that skin and bones -- not to mention drywall and cement -- block electric fields. A recent study suggests that may be wrong. "The argument that's usu- ally given that an electric field is blocked [from penetrating the body] is based on poor calculations," says cancer ' Tal Tsun wu, a physicist at Harvard University in Cambridge, Mass. "The electric field is attenuated, but the reduction is not very much." Previous calculations of riel etration accounted for only sph~,,,.al cells. Cell membranes do shield the interiors of spherical cells from elec: trical fields generated by power lines. But cell membranes cannot skteld the body's elongated cells -- like mus- cle cells and nerve cells, Dr. Wu says. He and Ronold W.P. King, also a phys- icist at Harvard, published their cal- culatious In August in Physical Drs. Wu and Krug, however, do not presume to say whether the penetra- tion of the fields into cells affects health. "We are giving basic information for biologists to think about," Dr. Wu In the past 25 years, e~dmataS of the strength of fields required for any biological effect have ratcheted slow- ly down, notes Ben Greenebaum~ a physicist at the University of W sin-Parkside. He says that ch, have been ob6erved in physical mod~ els at magnetic field levels 1,0fl0 tim_es stronger than the typical background field levels in a home. That may seem irrelevant to most human exposure, but in the past, sci- entists would not have expected ef- fects even at tho~e levels. And for short periods of time, people are ex- posed to such high fields. Hair dryers and blenders can generate such fields, end so may occasional bursts Please see CURRENTS' on Page SD. 8 D ~[~e~all~ornino~rfl~ Monday, September 28, 1~8 SCIENCE Effects of electromagnetic fields not quite understood Continued from Page 7D. chemical from the approximately ~00 evaluated by the International Agen- cy for Research on Cancer has been deemed "probably not" carcinogenic, Dr. PorUer points out. Dr. Greenebaum is even more ada- merit. "You can never say there's ex- actly zero risk," he says. Dr. Stevens agrees. '~Fnere is no way in the world that you can prove that EMFs are safe. You don't know whether you didn't do the right test or whether there's [actually] no ef- fect,' he says, referring to animal studies that do not show a link be- tween EM~ exposure and cancer. The most that can be said is, "I didn't fInd any harm," he says. But an experi. ment conducted under some other circumstances -- perhaps one that combines exposures to ~ with other carcinogens or one that includ- ed occasional bursts in current flow -- might find an effect. Faced with human population studies showing a link between can- cer and EMFs and animal studies that don't show a l/nk, some scientists are more inchned to trust the human population studies; others, the animal studies. '~l'hare are a whole variety of rea- sons why you would not get a positive result" in any given study, s~ys Dr. Carpenter. "there's not a lot of rea- sons why there would be a positive effect unles~ it's real." Unlike other fields of inquiry, where studies showing no link be- tween two factors may be i/noted, the hypothesis linking EMFs and dis- ease has received so much attention that "negative studies" -- those show- ing no link between EMPs and health -- are published with just as much fanfare as "positive studies" that sug- gest a Link. One reason for d~perate results, even among human population stud. les, may be that it's hard to accurately determine the exposure any person gets from EMFs. "Studies have focused on the mea- surement of fields in one plece -- on the ~ob or at home," Dr. Cm'penter says. "But in my judgment, we have such inaccuracy in assessing expo sures that I think we are undere~. mating the risk." EMF comments and information · The National Institute of Environmental Health Sciences is accept- ing public comment as it prepares its report to Congress. Comments must be received by Oct. ? at EMF-RAPID Report/LCBRA, c/o Dr. Mary Wolfe, NIEHS, National Institutes of Health, P.O. Box 12233, MD EC-16, Research Triangle Park, N.C. 27709. Christopher J. Pottier, an NIEHS statistician, says the agency will report to Congress in mid-November or early December. · For information on EMF RAPID, the Electric and Magnetic Fields Research and Public Information Dissemination Program, or to take a look at the NIEHS group's report, go to www.niehs.nih.gov/emfrapid on the World Wide Web. Dr. Stevens is much more skepti- cal about any r~ks from EMFs. '~he problem is there's nothing that you can do that at an extreme caWt kill you. If you drink enough water, tt~l kill you," he says. "If you're in a bright enough Light, ttql cook you." Others, like Dr. Carpenter, will not be convinced that EMFs are harmless until someone can show another rea- son why kids who live near power lines seem more at risk for leukemia. Several alternative explanations have been considered and dis- counted. Poverty is not a link. Herbi- cide use under power lines does not account for the leukemia cases either, Dr. Pottier notes. Neither can higher traffic density -- with its increased pollution from cars -- explain away the data, Dr. Stevens says. Dr. Carpenter and Dr. Stevens stand on opl~ite sides in the cre- dence they give to EMFs' potential dangers. But they agree that the ele- vation in leukemia risk observed in children who live near power lines is about ~0 percent above the average. Both compare the risk to the in- creased risk of lung cancer in second- hand smokers. Childhood leukemia is rare, strik- ing one in 10,000 children each year. "Even ff you're doubling the risk of leukemia, it's still a remote chance," says Dr. Carpenter. "But if you look at it another way, you ask, what is the proportion of kids w/th leukemia who got it from exposure to EMF?... And childhoed cancer is such an enor- mous trauma," Even ff ~ directly increase the risk for leukemia by ~0 percent, Dr. Stevens sees no re~son for alarm. He says that three studies have shown that eating hot dogs increases the chance of childhood cancer by more than that. (Scientists attribute this to nitrites, used to flavor the hot dogs.) For example, a 1994 study by Dr. Sav- itz's /roup tied eating one or more hot dogs a week with a doubled risk for brain tumors in children. Dr. Ste- vens notes that smoking increases the risk of lung cancer by 20 t/roes. "Look how long it took to prove that smoking causes cancer. Even if there's a cause and effect" EMFs with disease, he says, "we'll never find out." The scientific consensus is that ff F_~IFs pose any danger, they pose a small one. Same diseases they most probably do not cause -- like lung cancer or cancer of the stomach or intestines. Using electricity is no doubt much safer, from the perspec- tive of fire risk and clean air, than using candies for light or using a fireplace for warmth. And Dr. Car. penter says worrying about power lines, however large they are, half a mile from e potential home is "ludi. crous.' He has "the usual apphances' in his home. But he did move his 12- year-old son's bed to a part of the bedroom where electric fields are weaker. Dr. Stevens, however, WOL do that. "I still have an electric man- ket. I use an electric razor," he says. "But I wouldn't want to ~ive near a power line," he adds, "only because they're ugly."