Radiation Risks : The Sun, X-Rays, Radon Gas and Now Air Travel Pose Health Threats

NO DOSE OF radiation, no matter how small, is considered totally safe. In fact, many groups of experts, including the prestigious National Academy of Sciences, now claim that the chance of developing cancer from exposure to even low levels of radiation has been underestimated and may be three to four times higher than previously believed.

Only a decade ago, many scientists believed that it was outrageous, even alarmist, to warn the public of increased cancer risks from low-dose radiation. But today, experts generally recommend that people try to expose themselves to far less radiation whenever they can--after weighing the risks and benefits of common radiation sources such as X-rays, video screens and air travel.

The radiation danger of air travel is the most alarming recent discovery. A 1990 Department of Transportation report concluded that pilots, flight attendants and other frequent flyers receive far higher doses of cosmic radiation from the sun than previously believed, enough to translate into a high cancer risk.

The amount of cosmic radiation to which air passengers are exposed depends on the route and the altitude: the higher the flight and the farther north or south it goes, the greater the dose of radiation. On a one-way flight from Los Angeles to New York, for example, given ordinary flying conditions, the average person is exposed to about the same radiation emitted during one chest X-ray. Even so, occasional flights, even long ones, pose relatively little risk to most people.

The exception is during infrequent but unpredictable solar flares--isolated eruptions on the sun’s surface--when doses of radiation can jump several hundredfold. Some experts believe that pilots and flight attendants may annually receive larger doses of radiation than nuclear power plant workers. And although federal regulations require that workers at nuclear power plants be protected from radiation exposure, thus far no such precautions have been taken in the airline industry.

To rectify this, some radiation experts recently urged the Federal Aviation Administration to require the installation of a radiation detection and warning system on all commercial aircraft. “Such a device would monitor radiation, so crew and passengers could determine the exact dose of any flight,� says Dr. Robert Barish of New York University Medical Center. “More important, the device would be equipped with an alarm, which would sound at high radiation levels (such as solar flares) so the pilot could descend to safer altitudes.� The FAA is considering the request.

Given the huge distance between the earth and the sun, it is surprising that a few thousand feet can make such a difference in exposure to cosmic radiation. But even geographical altitude has an effect. Los Angeles residents are exposed to less than half as much ionizing radiation as those living in mile-high Denver. In Los Angeles, however, where sunbathing is a competitive sport, ultraviolet radiation is of particular concern. Skin cancer has recently become one of the most common types of cancer, striking one in seven people in the United States. One more time, just for the record: If you can’t avoid prolonged exposure to the sun, one way to reduce the risk of skin cancer is to use an effective sun block.

Even more serious than solar hazards is radon gas, which occurs naturally in the air, water and soil, especially in the Eastern states. Generally, radon gas leaks from the ground, and it often becomes trapped in buildings with poor circulation, especially homes with basements. “Radon is so potent a carcinogen that it doesn’t take much before you reach levels that can cause lethal damage to the body,� says Dr. Paul Papanek of the Los Angeles County Health Department.

A recent health department study estimates that 2% of Los Angeles County homes contain radon levels in the worrisome range. Breathing that amount of the gas is equivalent to smoking between one and two packs of cigarettes a day; for young children in particular, prolonged exposure can be hazardous. In Los Angeles County, lung cancer caused by radon kills about 300 people each year.

We recommend that people living in either a single-family house or in a ground-floor apartment test their homes for radon. There are many testing devices on the market, but the type most recommended is called an alpha track detector (about $20.) If dangerous levels are detected, the problem can be corrected by increasing circulation between the floor and the ground, sealing the foundation or re-insulating the basement. For additional information, call the American Lung Assn. at (213) 935-LUNG.

Another much-publicized source of radiation is the video display terminal, and here we have some good news: Although the data is not all in, it seems that users of well-maintained computers have little reason to worry about radiation. Studies commissioned by private industry and the government suggest that prolonged exposure to video screens, even during pregnancy, does not cause damage.

One source of radiation that you definitely should avoid during pregnancy is diagnostic X-rays, including routine dental X-rays. Even people who are not pregnant should avoid unnecessary X-rays. Fortunately, as the dangers of radiation became known, X-ray use has been curtailed. Even so, 300 million diagnostic X-rays will be taken this year and, according to some doctors, as many as one third of these will be unnecessary. Two types of routine X-rays--yearly mammograms for women over 40 and periodic dental X-rays--are highly recommended by most medical experts. In any case, X-rays should be done only for a specific reason. In the past, for example, doctors took routine chest X-rays of most hospitalized patients no matter what their illness. Current practice dictates that a person admitted to a hospital for suspected pneumonia will probably need a chest X-ray, but an otherwise healthy person in for a gall bladder removal will not.

To minimize radiation doses of necessary X-rays, avoid old or poorly maintained equipment and inexperienced operators. We recommend that people ask their doctors if the usefulness of an X-ray will outweigh the small but real risk of radiation.

Many of these radiation sources may not seem like real potential dangers, but until recently, the risk of radiation exposure has been grossly underestimated. Research has given us greater insight into how radiation affects and often harms us. We know enough about some types to reduce their risk, but other radiation still requires more research. At any stage, health research is effective only if we act on its findings.