While scientists have known for a century that ionizing radiation can cause cancer, modern srudies strive to uncover potential negatives of radiation across the spectrum.
A corny German commercial ends in the predictable gag of a vacationing man so absurdly sunburned he can only wiggle his toes. Using a trite television spot to punctuate his crusade against ultraviolet radiation is what it has come to for Michael Repacholi, PhD, of the World Health Organization, an authority armed with infinite data and medical cases that underscore the dangers of sun exposure. If only there were ads where radon was the punch line. Maybe then, people would pay more attention to other radiation hazards.
Radon: Earthly Toxin
You can’t see, taste or smell it, but radon is just about everywhere.
The naturally occurring element results from the breakdown of uranium inside the earth and travels from soil into the air and groundwater. As a form of ionizing radiation, radon concerns health officials, particularly radon in homes (see sidebar).
The EPA reports that one in 15 American homes have elevated radon levels, resulting in as many as 22,000 lung cancer deaths per year. “There have been some big studies on radon showing quite clearly that radon in homes is contributing to 10 percent of all lung cancers worldwide,” says Dr. Repacholi. “It’s mostly because of increasing energy prices that people are sealing their homes more. Governments really must do something about this. They can mitigate high-exposure homes that already exist and have building regulations that require homes to have a radon seal under the basement or foundation.”
The EPA’s approach at the federal level has been centered on public education and voluntary efforts to promote risk reduction in homes and schools. The only place where there has been regulatory action has been at local and municipal levels, says Michael Boyd, a health physicist in the EPA’s Office of Radiation and Indoor Air. “Some states require that the results of any radon tests be disclosed to the buyer as part of a real estate transaction and there are some requirements for testing radon in schools. But I don’t see the federal government getting involved in writing regulations that are going to tell homeowners what they have to do.”
With only two thirds of the population reporting a general awareness of radon, the EPA has taken steps through education and not regulation to stop the problem before it starts—at construction. Through the two principal U.S. national building codes, the EPA promotes the voluntary use of radon-resistant techniques in new home construction, especially in high radon-potential areas. Since 1990, 1.2 million new homes have installed ventilation fans and other radon-resistant features. Safeguarding of older homes, however, is dependent upon the homeowner taking the necessary steps.
The WHO’s solution requires governments to take a heavier hand in regulating radon levels through building regulations. But Boyd says regulating what’s naturally present in the earth’s crust isn’t practical. “The alternative is intrusive regulations that would tell homeowners what they have to do in their own home, and I think that would be very unpopular and not a viable alternative.”
Ionizing Radiation: Medical Exposure
Ionizing radiation from medical exposure served as the catalyst in the NTP’s addition of ionizing radiation to their recent report.
“Whether it’s on our list or not, most people are well aware of the fact that there’s a danger in being exposed to ionizing radiation,” says Dr. Portier. It was at the request of the NCI and the FDA, he says, that the NTP evaluated full-body CT scans, which led to the listing of X-radiation, gamma radiation and neutrons as known human carcinogens.
“People are beginning to get full-body CT scans without a doctor and with very little understanding of the possible long-term health complications of it,” Dr. Portier says. “Whole-body CT scans involve significantly high exposure because what they’re doing is taking 200 or 300 X-rays and building a picture from those X-rays.”
In 2004, scientists estimated that a single full-body CT scan at age 45 increases cancer risk by one in 1,250. If the scan becomes an annual ritual until age 75, the risk goes up to one in 50.
G. Donald Frey, PhD, is concerned that the NTP listing might scare away people who need various medical tests. “It’s not just the radiation risk that you have to think about; it’s the benefit from the procedure also,” says Dr. Frey, a professor of radiology at Medical University of South Carolina. “It’s very hard to quantitate what the benefits are going to be or what the risks are going to be.”
It is not current practice, says Dr. Frey, for people undergoing diagnostic procedures to be informed of the amount of ionizing radiation to which they’re being exposed. He says the risk for most diagnostic procedures is so small that it is comparable to the level of risk involved in driving to the hospital for the scan. “For CT, the risk is larger, and there has been discussion about whether patients should be informed or not, and generally, that hasn’t happened.”
Dr. Frey recommends people discuss possible anxiety with their physicians in order to feel confident that any tests ordered are appropriate. Which is exactly what Dr. Portier did following recent heart surgery.
Concerned about undergoing three CT scans and numerous chest X-rays, Dr. Portier convinced his doctor to scratch an additional CT scan that was scheduled. “Doctors can be reasonable when you sit and talk to them about it.”
The EPA and other agencies are evaluating whether to update radiation protection guidance for diagnostic X-rays. Boyd says that while this guidance applies only to federal facilities, it provides a resource for universal dose reduction practices. “For cancer patients who have experience with radiation from either diagnostic or therapeutic sources, we’re not saying by any means that you should avoid those because the benefits are clearly demonstrated,” says Boyd. “But we believe there is room for promoting the optimal use of this equipment to avoid unnecessary exposures.”
The lesson with ionizing and ultraviolet radiation, says Dr. Portier, comes down to the dose. “It’s the amount and magnitude and frequency. Those are the things that will kill you.” He’s pleased the NTP’s current report hit one of “the big ones” with ionizing radiation, and he hints that the NTP is now considering looking at lifestyle factors, such as obesity and diet.
At the WHO, Dr. Repacholi also ponders what’s ahead. He says he is consistently surprised that science is unable to answer certain questions. “As a scientist myself, you expect science to be able to answer questions, but there are some things that maybe the effects are so subtle that you can’t pick it up in the studies. Or maybe the effects are there sometimes and not there other times, and maybe it’s not of any real consequence.”
Each day, people are exposed to cancer-causing ultraviolet radiation and radon, a radioactive gas found in the air and groundwater. There’s also radiation exposure from sunbeds, electromagnetic fields, therapeutic procedures and medical devices, such as CT (computed tomography) scans. The dangers associated with these exposures are mostly well known. But those in charge of protecting the public still feel there’s plenty most people don ’t know.
In January, the National Toxicology Program released its 11th Report on Carcinogens, a biennial list of the latest cancer hazards. The biggest buzz surrounding this year’s report was the inclusion of ionizing radiation, a type of radiation that causes cell damage by depositing high energy in body tissue. The addition of ionizing radiation was far more inevitable than surprising, but it nonetheless made the list of cancer-causing dangers a little longer.
And the longer the list, the harder the job for those like Dr. Repacholi, the head of radiation and environmental health at the WHO. Keeping the public safe takes all the help scientists can get—even if, however inadvertently, it comes from some cheesy television ad.
Ultraviolet Radiation: Catching Some Radioactive Rays
Components of UV radiation include UVA, UVB and UVC, with UVB considered the major cause of cancer. Christopher Portier, PhD, associate director of the NTP, says that although UVC is harmful, very little of it penetrates the atmosphere. And while substantial amounts of UVA reach the earth’s surface, it doesn’t have the same harmful effects as UVB. “It’s a balance between what gets through and how damaging it is that leads to skin cancers,” Dr. Portier says.
But whether exposure occurs from the sun or sunbeds, the public—one way or another—is getting burned.
“It’s a classic case of half the story and a lot of the same old scare tactics,” says John Overstreet, executive director of the Indoor Tanning Association, which represents the $5-billion-a-year industry. “An organization that has the ability to influence world health policy should at least tell the whole story. ”
Overstreet balks at the WHO’s recommendation in March that no one under 18 use sunbeds, a no-exceptions caution that went on to encourage lawmakers to regulate the industry. Five percent of all tanning customers are younger than 18, according to industry estimates.
The WHO based its recommendation on recent studies that tied a strong link between melanoma and sunbed use (sunbeds discharge both UVA and UVB radiation). “We definitely want governments to regulate this industry because there is a strong possibility that we’ll have an epidemic of skin cancers and melanomas just coming from sunbeds,” says Dr. Repacholi.
A 2003 study of Scandinavian women published in the Journal of the National Cancer Institute found that those between ages 20 and 50 who used tanning salons at least once a month had a 55 percent higher chance of developing melanoma. And for young women between 20 and 29, the increased risk soared to 150 percent.
Even before the NTP listed sunlamps and sunbeds as known human carcinogens in its 2000 report, the American Academy of Dermatology endorsed a ban on the production and sale of indoor tanning equipment for non-medical purposes. The AAD asserts that since people get all the UV radiation they need in day-to-day activities to produce enough vitamin D, using tanning beds only pushes UV exposure levels past a healthy limit.
“You can’t ban cigarette smoking or alcohol for adults, but they are banned to children,” says Darrell Rigel, MD, clinical professor of dermatology at New York University School of Medicine and former president of the AAD. “Sunbeds are another risk to the child, and having government regulation for it is not unreasonable.”
But Overstreet says tanning salons already have safeguards to protect customers. A standard practice within the industry, he says, is for salons to obtain parental consent before letting teens fake bake. “People are raising this issue of teens as if it were some huge problem looming out there,” Overstreet says, “and it’s not, mostly because there are not that many people involved.”
Still, some states are putting standards into law. The Food and Drug Administration has regulated the manufacture of sunlamp products since 1980, but regulating tanning salons remains a state-by-state decision. Currently, 29 states have passed legislation that either bans or limits sunbed use by minors. California is among them with a new law that prohibits children under 14 from using tanning beds and requires written parental consent for teens ages 14 to 17.
Such laws are just the sort of thing the WHO is hoping will catch on, because “most sunbeds are unsupervised, so people are going to try to get a tan as soon as they can and get burned,” says Dr. Repacholi. He adds that skin cancer is a discriminating disease, with young people appearing to be more sensitive to UV radiation than adults. And with the 48 percent rise in melanoma cases over the past eight years, scientists say curbing such an alarming number begins with the public making better choices.
“We don’t want to be killjoys, but we want to make people aware,” says Dr. Repacholi. Part of that awareness comes from the extensive warning statements posted in tanning salons, indicating the risks associated with sunbed use.
“It’s a long piece of text that people don’t tend to read in this modern and busy time,” says W. Howard Cyr, PhD, of the FDA’s Center for Devices and Radiological Health. “What we want to do is have the warning statement in bullet form and much easier to read.”
Overstreet thinks his industry has been unfairly pegged as a scapegoat, and that regulating or banning sunbeds merely sends tan-seekers under the sun, where UV radiation exposure is more dangerous. But Drusilla Hufford, head of the Stratospheric Protection Division at the Environmental Protection Agency, says the lack of a regulatory structure to test sunlamps in individual salons means users don’t know what type of UV exposure or dose they’re getting. “You could be getting a massive dose of a type of radiation you would not get from the sun—at least not in that amount.” The FDA is working to reduce the dose of UV radiation from sunbeds, but Dr. Cyr says the proposal has stalled at the advisory committee level.
Greg Nail inherited his father’s Caucasian skin and enjoyed outdoor activities as a teenager, particularly baseball. Melanoma can take 10 to 30 years to develop, so Nail’s stage 3 melanoma diagnosis is likely due to his history of sun overexposure. Unknown is the role played by his frequent sunbed use, which began four years before his diagnosis in 1999.
“I had been told it was as safe as, if not safer than, the sun. But the people that tell you that don’t really know—they’re just clerks,” says the 43-year-old from Missouri who tanned three or more times a week. “As a melanoma survivor, I don’t resent the sunbed owners or makers. I resent false advertising that can cause illness and death.”
Positive Sun Exposure?
Health officials and dermatologists agree that moderation—of sunbeds and sunbathing alike—is the key. But new research published earlier this year in JNCI tells a different story.
A European study found that increased UV exposure was associated with a decreased risk of non-Hodgkin’s lymphoma, and an American study linked sun exposure to increased survival of melanoma. Marianne Berwick, PhD, led the American study and says while some melanomas are caused by sun exposure, others are the result of a genetic predisposition. “We think there’s some genetic factor working, but we have no idea what it is,” she says.
Dr. Berwick suggests the beneficial relationship between sun exposure and melanoma survival is the result of an increased production of vitamin D. The other hypothesis presented in the report involves the increased ability of cells to repair damaged DNA. “People have been so focused on the sun causing melanoma that they haven’t gone any further to dissect that. Once we understand it better, we’ll be able to better tell people what to do,” says Dr. Berwick, who is now conducting a similar study that will be completed in 2008.
But Dr. Berwick advises continued caution in the sun. “Just because you need some sun exposure doesn’t mean you should use that as an excuse to throw caution to the wind.” And while more people are getting melanoma, she says the mortality rate has not followed suit, which suggests people are getting the sun-induced melanomas that grow slowly. “But we don’t know that, and nobody wants to say the sun will give you melanoma but it’s not the really bad one.”
In 2000, the EPA launched the SunWise Program in an effort to inform schools, children and parents about the effects of sun overexposure. Almost 11,000 schools now participate, and organizers say that since the program began, there has been an 11 percent reduction in the kinds of sunburns that increase the lifetime risk of skin cancer and melanoma.
The EPA also has a history of regulating substances, including CFCs (chlorofluorocarbons), responsible for creating a hole in the stratosphere’s layer of ozone that screens out harmful UV radiation. Hufford says the EPA has phased out class 1 compounds used in refrigerators, freezers, air conditioners and fire extinguishers.
“Now we have to do the work to phase class 2 compounds out of domestic production,” says Hufford. “The trouble is the chemicals we’re working on live a long time in the stratosphere, so scientists think it will probably be 50 years before the ozone layer completely recovers, so it’s not solved by any means.”
Electromagnetic Fields: Are They Harmful?
If you’ve ever been frustrated when your cell phone becomes outdated six months after buying it, imagine how radiation researchers feel.
Some of the newest data about the potential dangers of cell phones don’t shed light on any cell phones used today. Rather, the data are merely long-overdue results from tests conducted on outdated analog phones that have since been rendered obsolete by digital networks.
Dr. Repacholi heads the Electromagnetic Fields Project, which launched in 1996, and says in the race to study potential radiation hazards in new products, scientists don’t have the resources of cell phone and computer manufacturers. “We’ve tried to be smart about the sort of research we recommend, recognizing that you’ve got to come up with good general studies that will be applicable to new technologies as they come up.”
Electromagnetic fields are forms of non-ionizing radiation (contains enough energy to move atoms but not enough to alter them chemically) that include power lines, electrical appliances, computers and cell phones. Results of the EMF Project’s health risk assessment are expected by 2007.
Dr. Portier says the NTP has been working closely with the WHO’s International Agency for Research on Cancer to make sense of the literature on power lines and cell phones. “We concluded, as did IARC, that power lines are possible human carcinogens, but that’s the lowest level of positive you can get. We see something in the human data that no one understands, and we can’t get any controlled animal studies to repeat it. We have no idea why it’s occurring, but it’s consistent over many studies.”
As for cell phone research, studies have consistently lacked evidence of a cancer risk. But Dr. Portier is skeptical—especially since it’s the cell phone industry that is often footing the bill for the research.
“We [at the NTP] have regretfully concluded that every single one of these studies has been partially funded by the cellular phone manufacturers,” Dr. Portier says. “We don’t feel there is an entirely independent assessment out there, so we’re going to start our own studies.”
Results from an IARC-coordinated study, known as Interphone, are expected within the year’s end, says Elisabeth Cardis, PhD, chief of IARC’s Unit of Radiation and Cancer. Thirteen countries (though not the United States) are participating in the study, which Dr. Cardis says should be fairly definitive in terms of cancer risk.
“I don’t think we have data [on radiofrequency fields] at this point that can make us go in one direction or another. I’m hoping that a year from now, between the Interphone study and all the experimental studies, we’ll have a much better idea as to whether or not there is a risk. And if there is a risk, how big a risk? Then it will be easier to evaluate whether or not radiation protection has to change.”
Limits are in place for the amount of radiofrequency energy absorbed by the head when using a cell phone. The Federal Communications Commission requires all wireless phones sold in the United States to have a SAR (specific absorption rate) no greater than 1.6 watts per kilogram. But this SAR standard, set by the Institute of Electrical and Electronics Engineers, conflicts with the 2.0 W/kg limit set by the International Commission on Non-Ionizing Radiation Protection and endorsed by the WHO.
Norm Sandler, director of global strategic issues for Motorola, the second-leading mobile phone maker worldwide, says an expert panel review is currently under way to address the discrepancy. “It seems they are moving toward adoption of a recommendation that IEEE essentially harmonize with ICNIRP.”