Exposure to electromagnetic fields linked to cancer, Hopkins studies show

June 25, 1991|By Jonathan Bor

In yesterday's editions of The Sun, the name of researcher Dr. Genevieve Matanoski of the Johns Hopkins School of Hygiene and Public Health was misspelled in an article about electromagnetic radiation and cancer.

The Sun regrets the error.

A study of telephone linemen has added to the growing body of evidence that suggests low-level radiation from electric cables and devices may be responsible for some cancers.

Cautioning that the verdict on electromagnetic fields is years away, Dr. Genevieve Matanowski of the Johns Hopkins School of Hygiene and Public Health reported yesterday that telephone linemen who were exposed to the strongest fields were almost twice as likely to get leukemia as were linemen with average exposures.

FOR THE RECORD - CORRECTION

Leukemia is a rare cancer, striking an estimated 7 of every 100,000 Americans, so Dr. Matanowski said linemen exposed to the strongest fields may not actually be in serious jeopardy of developing the often-fatal disease. But she said the "totality of evidence" -- this study and others that preceded it -- seems to justify the recent concern over electromagnetic radiation.

"The evidence is starting to point to something going on," Dr. Matanowski, an epidemiologist, said in an interview. She presented her findings yesterday to a gathering of the Bioelectromagnetics Society in Salt Lake City.

For the leukemia study, Dr. Matanowski and colleagues pored through records of 1.5 million past and present employees of AT&T, finding 124 men who died of leukemia between 1975 and 1980. Those employees were matched with 337 male telephone workers who did not die of leukemia.

Among the findings:

* Men working as cable splicers and central office technicians had 1.7 times the risk of dying from leukemia than did men working at two other jobs characterized by less intense exposure to electromagnetic fields (EMF). Cable splicers string bundles of wire along main telephone routes; central office technicians maintain the equipment that switches telephone signals from one line to another.

* Cable splicers and central office technicians were exposed not only to stronger fields, but also to radiation that peaked and dipped in recurring cycles throughout the day. This may suggest that the spiking radiation may be as important -- if not more so -- than the average radiation to which the workers are exposed.

* Cable splicers, who work amid the strongest radiation, are exposed on average to fields measuring 4.3 milligauss. But the fields peak as high as 99.2 milligauss. [A milligauss is a unit of electromagnetic radiation.] In contrast, people at home are typically exposed to between 1.1 and 1.5 milligauss.

* The men exposed to the weaker fields, those classified as installers and outside plant technicians, worked amid radiation comparable in strength to what people experience at home. Installers work inside houses and offices, while outside plant technicians link homes and offices with the main telephone cables.

It was impossible to determine if the workers' exposure came mainly from the telephone lines or from their proximity to electric power lines, which carry much higher voltage, according to one of the researchers.

The study was funded by the Electric Power Resesarch Institute (EPRI), which in turn receives its money from electrical utilities. In the wake of the Hopkins report, EPRI's leadership withheld comment, releasing only a summary of the findings.

Dr. Matanowski said the study did not try to prove that radiation caused the workers' cancer, and scientists are still puzzled at how such a mechanism would work.

The question is far less clear, she said, than it is with ionizing radiation, the type released by nuclear power plant accidents and atomic explosions. In that case, scientists have observed how the radiation splits apart the DNA in human cells, setting off the growth of cancer cells.

Dr. Matanowski also said she would be more comfortable blaming electromagnetic fields for cancer if her study found a much stronger association -- say, a 10-fold increase in cancer risk -- and if such a finding were repeated in other studies.

The Environmental Protection Agency said last summer there was considerable evidence from more than a dozen scientific studies over the past decade that high exposure to electromagentic fields is "a possible, but not proven cause of cancer in humans."

Dr. Matanowski said she could not compare the telephone workers' exposure to any other sources -- say, home appliances or high-voltage power lines. Exposure depends on the strength of the current, a person's distance from the source and -- possibly -- cycles of peak radiation.

But one close parallel, she said, may be the electric blanket. That's because the blanket touches the person's body, and because the current ebbs and flows as the blanket works to maintain a pre-set temperature.

James Dushaw, safety and health director of the International Brotherhood of Electrical Workers, said he found the study interesting but said further research is needed to determine if factors other than the radiation are responsible for the elevated cancer risk.

"The country's been electrified for 100 years," Mr. Dushaw added. "If there is a health risk, it's not one that is readily apparent."

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