7-Year U.S. Study Finds No VDT Link to Miscarriages : Health: Differences among phone operators who do and do not work at terminals found negligible.
Women who are exposed to radiation from video display terminals do not appear to have a higher risk of miscarriages, according to a long-awaited federal government study published today in the New England Journal of Medicine.
However, several independent work-safety advocates said more research is needed to conclusively prove that VDT radiation is not hazardous.
The seven-year study, which compared the pregnancies of 323 young telephone operators who worked with VDTs and 407 who worked in similar jobs without VDTs, is the latest in a series of conflicting analyses of whether low-level radiation emitted by the machines affects the female reproductive system.
Conducted by the National Institute for Occupational Safety and Health, the study found that 14.8% of pregnant women who worked at VDTs reported miscarriages, compared to 15.9% for women who did not work at VDTs--a statistically negligible difference. Both figures fall within medical research estimates of a miscarriage rate of 11% to 20% for the general population of pregnant women.
NIOSH researchers studied operators between the ages of 18 and 33 who worked for Bell South and American Telephone & Telegraph in eight Southeastern states. Both groups were similar with respect to race, educational background and socioeconomic status.
“I think the study is reassuring for women who are concerned about working with VDTs and the subsequent risk of miscarriages,” said Teresa M. Schnorr, the principal author of the report. “This was the most detailed and the most focused study performed on miscarriages and VDT technology.”
For a decade, questions have been raised about the health effects of the cathode-ray tube that generates a visual display in a VDT, exposing the user to a low-level electromagnetic field. Past studies have suggested that appliances such as VDTs and electric blankets were responsible for increased rates of miscarriages. Some other, more recent studies of VDTs contradicted those findings.
The concern has been strong enough to persuade some U.S. computer makers to introduce terminals that are shielded to reduce some low-frequency electromagnetic radiation. Previously, such terminals were manufactured only for sale in Denmark and Sweden, where workplace safety regulations are substantially stricter.
Louis Slesin, editor of New York-based VDT News, said the NIOSH study is “good news for VDT operators.” But he added that the study should not be taken as a sweeping bill of health for workers exposed to electromagnetic fields.
The study was based primarily on the women’s own reports of their miscarriages. As a result, it did not study the impact of VDTs on the large number of miscarriages that occur in the first weeks of pregnancy before women detect them. Researchers say as many as half of all miscarriages occur in these initial weeks.
A study under way at the Mt. Sinai School of Medicine in New York is attempting for the first time to monitor VDT workers before they are pregnant and follow them through the first months of pregnancy.
Sheldon Samuels, director of health, safety and environment for the AFL-CIO’s industrial union department, said studies of miscarriages must consider ergonomic issues associated with VDTs.
For example, he said, the tendency of VDT work to isolate workers at their desks with little physical movement could influence “the physiology of reproduction.”
NIOSH researcher Schnorr said the study found no significant differences in miscarriage rates between women who used VDTs 25 hours a week or less and those who used them more than that.
