On the 50th floor of Chicago's Sears Tower, government scientists have measured radio-frequency radiation at considerably higher levels than the maximum reported during the controversial microwave bombardment of the U.S. Embassy in Moscow.
At the corner of Wisconsin Avenue and Fessenden Street in Northwest Washington, the intensity of radio-frequency radiation recorded by government researchers already exceeds the Soviet Union's safety standard for its general population.
Findings like these have been reported again and again as government researchers, employing computerized electronic measuring instruments, survey major cities across the United States, tracing levels of radio-frequency radiation to which Americans are exposed in their daily lives.
The significance of these findings remains unclear because American researchers have yet to establish whether microwave and other radio-frequency radiation may have harmful effects at such relatively low intensities.
The data collected so far in government surveys indicate that most radiation levels in American cities are far below U.S. safety standards, but that they sometimes exceed the far more stringent Soviet standards.
In the Washington area, about 40,000 people - mainly those who live near television and FM radio-freguency radiation exceeding Soviet safety standards. Their exposure is apparently far less than the amount permitted under U.S. standards.
Some findings at industrial plants suggest, however, that even the less strict American standards may be violated by some plastics, wood products, rubber and other manufacturing companies. Scientists at the National Institute for Occupational Safety and Health recent reported that about 75 per cent of the workers at plants they surveyed are exposed to radio-frequency radiation exceeding U.S. occupational safety guidelines.
The NIOSH researchers say their findings are based on more than 1,000 measurements of radiation levels at about a dozen plants at scattered locations during the past three years. Radio-frequency radiation is widely used for industrial sealing and heating in manufacturing such products as plastic bags, shoe soles and shower curtains.
Several NIOSH scientists said in an interview that they cannot yet assess whether a health hazard exists for workers at these manufacturing plants for two complex reasons. One factor is that they took measurements through a different technique than normally used in similar research. The other is that their measurements centered on frequency ranges whose biological effects are among the least understood.
With American research into biological effects of mircowave and other radio-frequency radiation still apparently in its infancy, scientists and government officials are, for the most part, uncertain over where to draw a line between safe and hazardous levels of radio-frequency radiation.
Some researchers suggest that current U.S. safety standards may be too lax, but some also suggest that Soviet safety standards may be too stringent. In either case, many researchers say, attempts to set safety standards remain problematic because of the relative sparsity of scientific data on the biological effects of low-intensity radio-frequency radiation.
While radio-frequency radiation is considered harmful at acute intensities, the effects of low-level radio-frequency radiation on laboratory animals and people are still subjects of uncertainty, debate and continuing research. Though scientific definitions vary, microwaves are generally said to form part of the radio-frequency segment of the electromagnetic spectrum. It is as yet unknown whether microwaves are more or less likely to have biological effects the other radio-frequency radiation.
Despite the uncertainties surrounding this field, concern is mounting among government officials and others, partly because of the increasing prevalence of microwave and other radio-frequency radiation as a result of their widespread use in communication, military manufacturing, medical and other technology. Officials of the Environmental Protection Agency say that the number of sources of microwave and radiowave radiation is estimated to be increasing by about 15 per cent annually.
The intensity of radio-frequency is generally measured in terms of what is known as its power density. U.S. occupational safety standards limit exposure to such radiation to a maximum of 10 milliwatts per square centimeter. A milliwatt is one one-thousandth of a watt. There is as yet no U.S. safety standard for general exposure for the public, though it would presumably be more stringent.
The Soviet occupational safety standard, by contrast, is 10 microwatts per square centimeter. This is 1,000 times more stringent than the U.S. standard. The Soviet safety standard for the public at large is 1 microwatt is one one-million of a watt.
The discrepancies between the U.S. and Soviet safety standards have prompted much debate in recent years, though no resolution has occurred. The differing standards were out-growths of divergent approaches to research. Historically, Soviet scientists have given far more attention than have Americans to possible biological effects of low-intensity radio-frequency radiation, although American attitudes toward this issue have begun to shift in recent years.
According to State Department officials, the intensity of the microwave radiation beamed at the U.S. Embassy in Moscow, possibly for intelligence purposes, reached a maximum in August, 1975, and several months afterward of 18 microwatts per square centimeter. This level is higher than Soviet safety standards but far below U.S. standards.
Herbert Pollack, a medical consultant for the State Department, noted in an interview that the maximum was recorded near an open window. As a result, he said, most embassy employees were exposed to considerably less radiation even when the microwave radiation was at its peak.
Pollack conceded it is possible that the microwave radiation may have occasionally risen "a dash higher" than the maximum recorded by U.S. measuring devices. But any such increase, he added, would have been too slight and would have occured too infrequently to be significant.
The state Department has reported no evidence of health problems linked with microwave radiation at the Moscow embassy. An epidemiological study is now under way to investigate further whether U.S. employees stationed at the embassy since 1953 have undergone any ill effects that can be traced to microwave exposure.
Considerably higher levels of radio-frequency radiation than the maximum reported at the Moscow embassy have been measured by EPA researchers at office buildings in American cities, including Chicago's Sears Tower. The radiation stems mainly from the buildings' proximity to television or radio broadcast outlets.
The intensity of radio-frequency radiation near a window on the 50th floor of the Sears Tower, the world's tallest building, was recorded at almost 66 microwatts per square centimeter, more than three times greater than the maximum at the Moscow embassy. The level, though higher than Soviet safety standards, is far below U.S. standards.
Similarly, a level of 97 microwatts per square centimeter was recorded on the 38th floor of a Miami office building situated near a broadcast transmitter, and a level slightly over 10 microwatts per square centimeter was measured on the 54th floor of the Pan Am Building in New York.
These preliminary findings by EPA researchers appear to indicate that the intensity of radio-frequency radiation in office buildings in American cities may often exceed Soviet safety standards, though they fall below current U.S. standards.
EPA scientists stress, however, that such measurements probably do not accurately reflect the amount of radio-frequency exposure to which a person working in an office building might be subjected. The readings were generally taken near windows. If a shade were drawn or if measurements were made elsewhere in a building, the researchers note, the level of radiation recorded would be much lower. Researchers have yet to estimate typical exposure levels in office buildings.
A more thorough survey is now under way, however, by EPA researchers who are measuring intensities of radio-frequency radiation close to ground levels in a number of American cities, including Washington. These readings are being made with 21-foot antennas mounted on a research van. The findings are intended to indicate the amount of exposure to radio-frequency radiation most Americans undergo.
D.E. Janes, a government scientist who is overseeing the EPA survey, said in an interview that the findings so far indicate that between 95 and 98 per cent of the public is exposed to less than 1 microwatt per square centimeter of radio-frequency radiation, the Soviet standard. "We don't know what the other 2 to 5 per cent of the people are exposed to," Janes added.
In the metropolitan Washington area, the EPA researchers estimated, about 40,000 people - approximately 1.5 per cent of the population - are exposed to more than 1 microwatt per square centimeter of radiation.
Of 40 readings made in the Washington area, two exceeded the Soviet safety standard. One was at Wisconsin Ave. and Fessenden St. NW, where the level was 3.5 microwatts per square centimeter. The other was made in the Westwood section of Bethesda, off River Road, where the reading was 2.2 microwatts per square centimeter.
In other cities, Janes said, there have been a few higher readings near ground level, including a measurement of 10.1 microwatts per square centimeter in Chicago and another in Las Vegas of about 20 microwatts per square centimeter. EPA measurements have already been completed in Atlanta, Boston, Miami and Philadelphia. Research are now surveying cities on the West Coast.