The Body Electronic
Part II: VDT Hazards
REBECCA ROSEN LUM
Labor-saving devices are supposed to help, not hurt. But the computer, the wunderkind of productivity tools has been associated with health hazards ranging from inflamed wrists to miscarriages. In the second of two articles, Rebecca Rosen Lum explores the controversy surrounding prolonged use of video display terminals.
Caught off guard may be the best way to describe the computer world's response to the spate of ailments befalling video display terminal users. Reports of eye problems and a scattering of unexplained "clusters" of birth defects and miscarriages have sent unions rushing to the bargaining table to secure protection for employees.
By far the most controversial and hotly debated safety issue for unions and business is the possible hazard to computer users due to electromagnetic emissions from their terminals. The least controversial and best-researched of disorders linked to long hours at the VDT are eye problems.
While no studies have linked monitor use with permanent eye damage, temporary ailments caused by hours of intense focusing combined with glare can be quite debilitating, as San Francisco resident Steven Michael discovered.
Michael had been working at the San Francisco Newspaper Agency for 10 years when the computer revolution arrived. The 45-year-old finance department supervisor and his colleagues trained for months in a temporary office that offered adjustable workstations, anti glare screens and directed lighting as they mastered what he calls "a very complex system."
Computer literate, they brought their new skills back to their old office. "It's in a very old building," he says, "with fluorescent lighting, white walls and no-glare screens"--an ergonomic minefield. Michael watched his staffs new confidence quickly erode as eye problems and headaches became the norm.
"My headaches started within days," he says, "And once they started, it was non-stop. It wasn't like I had good days and bad days. It was very wearying." Worse still, hours after Michael had left the office, the headaches stubbornly persisted. Literally, if I went to read the news paper, the page was just an indecipherable sea of black and white. I couldn't focus, I couldn't read. It would last for several hours. The next day, it would start all over again."
Months later, when glare screens arrived, relief swept the department. "They've made an enormous difference," he says. "The next day we didn't have people aching all over with migraine headaches. My question about glare screens is, how do you live without them?"
Apparently, many do. Some 90 percent of computer users suffer from eye strain and vision problems, according to the National Institute for Occupational Safety and Health. Eye fatigue, blurred vision, chronic headaches and "after images" are common among the 15 to 19 million VDT users in the workplace.
Clinical Studies
A recent study by Dr. James Sheedy of the University of California at Berkeley revealed unexpectedly high numbers of 20- to 40-year-old VDT users suffering from eye problems. Dr. Sheedy, who is chief of the university's School of Optometry VDT Eye Clinic, says one-third of his clinic's patients have an accommodative eye problem, compared to 15 to 20 percent in other clinical populations. Focusing closely on a VDT screen without interruption may be the culprit, he believes.
He recommends pausing "to look off into the distance--every 10 minutes for 10 seconds, say, to allow the accommodative mechanism to fully relax. Looking off into the distance relaxes the muscle that needs to contract (to enable us) to look up close."
He blames the changing workplace, which is all too frequently not geared to computer use, for much of the eyestrain VDT users experience, but adds that most eye problems can be avoided by applying what researchers have already learned.
"Overhead lights used to be no problem when people looked down (at their desks)," he says. "Now, with VDTs, people are looking straight ahead, and overhead fluorescent lighting is a problem." Wearing a visor at work is a good idea for those who operate a VDT with bright lights in their peripheral vision, he adds. Ergonomists also recommend positioning the VDT at a 90-degree angle to windows, dimming the lights to a moderate level, retrofitting fluorescent lights with "baffles" that reduce glare, fitting windows with anti-glare screens or blinds and putting a glare screen on your monitor.
What about the resolution of the image itself? The image on the VDT is created by phosphors that glow when scanned by the terminal's electron beam. The image lasts only as long as the phosphors glow, which is actually an extremely brief time. It must be re-illuminated, or "refreshed," by another electron beam quicker than the eye can perceive in order for the image to appear continuous. The "refresh rate," then, refers to the number of times the electron beam scans the phosphors per second. "Flicker" occurs when the refresh rate is sluggish enough that the eye can perceive the changes (the eye can pick up changes somewhere in the range of 20 Hz to 100 Hz (100 Hz equals 100 times per second). Flicker rates that are barely perceptible to the eye nevertheless cause the eye to continuously readjust, bringing fatigue. Designers say European labor unions, much stronger than in the United States, have pressed for, and won, a commitment from industry to produce monitors with a minimum refresh rate of 70 Hz. There is no standard in the United States; the average runs between 56 and 60 Hz (although some industry insiders say the refresh rate of American-made products will soon match that of the European to enable American companies to compete more effectively overseas).
What does all this mean for the personal computer owner who, on a shoe-string budget, invests in a used computer?
It means the image on a monitor more than five years old may look like a Chaplin flick compared to the crisp images generated by today's screens.
"I wouldn't say most people are working on state-of-the-art equipment," says Laura Stock, director of the Berkeley, Calif., VDT Coalition. "Looking at a flickering screen can lead to a seasick feeling."
In the workplace, it is in an employer's best interest to consider such issues as image resolution and lighting. "Some employers are," she says, adding, "Some resist being told to do something they didn't choose to do, even if in the long run it saves them money in workers compensation and productivity."
Dr. Sheedy says, "We need to know more about lighting and lighting geometry on vision and visual performance, about what is happening to the eyes and the binocular system. But much of the discomfort people are experiencing can be eliminated knowing what we know now. The problems are partly caused by a lack of application."
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Cathode-Ray Tube |
The Radiation Debate
Sentiments run high when those in the science community, computer world and industry discuss another danger tagged to VDT monitors--pulsed electromagnetic emissions.
Controversy focuses on low-level electromagnetic emissions, known as non-ionizing radiation because, unlike X-rays, they cannot break apart atoms. But, some scientists maintain, that doesn't mean they're safe.
While it was once assumed that low-level electromagnetic fields--produced by hair dryers, toasters, electric blankets and computer terminals--couldn't cause cell changes, a recent study by the Office of Technology Assessment revealed that even very weak pulsed electromagnetic fields can produce mutations and other biological changes in cells and organisms.
At the second international conference on VDTs and health in Montreal last September, researcher Hakon Frolen of the University of Agricultural Science in Sweden linked non-ionizing radiation exposure soon after conception to the high rate of fetal deaths among laboratory mice in his study.
Furthermore, a 1982 case-control study by researchers at northern California's Kaiser Permanente medical group revealed that women who work at VDTs for 20 hours or more each week stand an 80 percent higher chance of suffering a miscarriage than women who do not work at VDTs. Although researchers emphasized that they could not determine the reason for the elevated risk, they reported that "this risk could not be explained by age, education, occupation, smoking, alcohol consumption, or other maternal characteristics" and called for more research.
This study, as well as anecdotal reports of "clusters" of miscarriages among pregnant VDT users in the United States, Canada and Europe, resulted in public pressure for more research into possible VDT hazards.
One such study of VDTs and pregnancy outcomes, the first of its kind, is under way at the Mt. Sinai School of Medicine. It will track women who work with VDTs from conception on, rather than rely on the memories of participants, as do retrospective studies.
Most recently, public health researcher Dr. Lars Brandt of Denmark found no correlation between VDTs and negative pregnancy outcomes in his epidemiological study of 6,212 women and 6,541 pregnancies.
Men At Risk
But women of childbearing age are not the only users who risk harm by putting in long hours in the glow of the VDT. A study funded by the Department of Energy revealed that men between the ages of 21 and 35 had 10 percent slower motor responses after being subjected to low-level electromagnetic fields. In fact, researchers have found that many changes in cell structure seem to occur after exposure to low-frequency emissions at low doses, or at certain frequencies that scientists call "power windows."
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Miscarriages among VDT workers |
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Hrs of VDT Work in first Trimester of Pregnancy Kaiser Permanente study |
Discussing the possible hazards of electromagnetic fields, watchdog Louis Slesin, editor of VDT News, says, "I'm especially concerned about children, because they use computers at school, they do video games after school, do their homework on a computer at home and watch television. They're getting more exposure than some workers."
While industry heads have scoffed at possible health threats posed by electromagnetic emissions in VDTs, last November IBM quietly introduced in this country a low-radiation monitor they already were marketing in Europe.
Entrepreneurs are also putting products on the market. George Lechter, the MIT-educated engineer who founded Safe Computing Company, sells a high-resolution liquid-crystal monitor, or LCD which produces no electromagnetic radiation. (Most computer terminals are cathode-ray tubes, which produce pulsed electromagnetic fields.)
Lechter and his associates recently tested several CRT monitors in a Needham, Mass., computer center. They measured very low frequency and extremely low frequency magnetic emissions from a user distance of two feet in front of each VDT. The monitors, he said, clocked in at astonishingly high levels, ranging from 0.5 milligauss to 8.1 milligauss--and those in a monitor marketed to children.
What worries Lechter about those measurements are studies like that of University of North Carolina researcher David Savage, which linked childhood tumors, including central nervous system tumors and leukemia, with exposures of one to two milligauss generated by power lines near the participating children's homes.
Critics Speak Up
Critics like Slesin lambast the federal government for not having conducted similar tests in controlled conditions long ago. "We could all test our gas mileage, but it's easier for the EPA to do it," he says. "The government is asleep on this. Nobody wants to know the numbers."
Writer Paul Brodeur sent pulsed waves of his own through the popular science community recently with the publication of his article "The Annals of Radiation" in theNew Yorker magazine and with his bookCurrents of Death, in which he claims not only that ample evidence points to the dangers of low-frequency electromagnetic fields, but that the government, industry and the media have been covering up the fact.
But the Center for Office Technology, an industry group, released its own paper criticizing Brodeur's challenge. In it, they accuse Brodeur of stacking the deck with selective findings. COT's executive director, Dr. Bruce Dickerson says "Radiation from VDTs have been studied both here and abroad. The overwhelming conclusion is that the radiation emitted by VDTs pose no threat to human health." Brodeur "did an incomplete job of evaluating the literature," he adds. "The vast majority of scientists do not concur with him."
Keeping Safe
Ironically, there is no standard screening, testing, or licensing for computer monitors as there is for televisions, which also use a cathode ray tube--and from which viewers are encouraged to keep a distance of 10 feet.
So what can workers and VDT home users do to protect themselves while the controversy rages? The New York Committee for Occupational Safety and Health suggests limiting the number of hours spent at the VDT. (Sweden mandates a maximum workday of four hours at the VDT.) It further suggests women who work at VDTs on the job seek alternative assignments during pregnancy.
Because a Polish study revealed exposure to VDT levels of radiation affected the testicles of laboratory mice, NYCOSH further suggests that men who want to father a child protect themselves as well.
NYCOSH also warns against sitting within four feet of the backs or sides of neighboring computers, where the flyback transformer generates the highest level of electromagnetic emissions.
While all concerned are calling for more research, the thorny issue seems to be how far manufacturers and employers should go to protect VDT users until more is known. Asks the VDT Coalition's Laura Stock, "Do you err on the side of caution or do you let people be the guinea pigs?"
Rebecca Rosen Lum is a San Francisco-based freelance writer.
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Computer Hazards--Legislation and Litigation |
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