Finnish study on residential magnetic fields and cancer (1996)

In October/November of 1996 the British and European media widely reported that a new Finnish study exonerated powerlines from adult cancers. Unfortunately the media and others took this study at face value and did not bother to critically examine the findings. Researchers, Dr. Pia Verkasalo and coworkers from the University of Helsinki, Finland, claimed that their large scale epidemiological study found that "The results of the present study suggest that typical residential magnetic fields generated by high-voltage power lines are not related to cancer in adults." Their findings were published in the October 26, 1996 issue of British Medical Journal.

As reported in New York based Microwave News, (Nov/Dec 1996) Verkasalo and co-workers found "no major increases" in risk among the cohart for 21 varieties of cancer. "The previously suggested associations between magnetic fields and tumors of the nervous system, lymphoma, leukemia and breast cancer in women were not confirmed," they wrote.

The study included 8,415 cancer cases from a group of 383,000 adults living within 500 metres of all 110-400 kVhigh voltage power-lines in Finland. No actual field measurements were taken. Exposures were calculated from power company records.

Verkasalo however later reported at the U.S. Department of Energy's EMF review in November, that there was a statistically significant risk ratio of 4.8 for chronic lymphatic leukemia among those adults exposed 12 or more years before diagnosis. "It's not clear what this means," Verkasalo said.

Verkasalo did find a statistically significant increase in female colon cancer but said that this "may well be due to chance." There was also a slight increase in some other cancers but they were not statistically significant.

A careful evaluation of this study makes apparent some major weaknesses which makes the researcher's conclusions fundamentally flawed.

1) The researchers wrongly assumed that the only exposure to magnetic fields was from high voltage powerlines over 110,000 volts. This is wrong. It is widely accepted that peoples' main exposures are from other sources, such as home wiring and appliances, underground distribution lines, substations and occupational exposure.

2) The researchers calculated magnetic fields into five bands. According to British researcher Alasdair Philips, the first four bands are at similar levels to ones in Finnish homes, which are from sources other than powerlines. This means that in four out of five of their analysis bands, their calculated exposure for individuals from high voltage powerlines is not an accurate assessment of the fields the people were actually exposed to. Only the highest band would have any chance of seeing a significant risk.

3) Virtually no homes in Finland are located within 100 metres of high voltage power lines.This is significant because at 100 metres, the fields from the powerlines would have been reduced greatly.

4) The study did not consider the electric field component, which is being shown to have a real impact on cancer risk. (see Section 3.0)

As a result of the above, the Finnish study's calculated exposure levels would have had little relevance to actual magnetic field exposures and no relevance to electric field exposures, which most likely would come from other sources than powerlines anyway.

The only thing the Finnish study does show is that the many large and expensive epidemiological studies that looked at magnetic fields only have really "had their day". They show that there is an effect, maybe on a susceptible sub-group in the population, and the effect is NOT very large for magnetic fields alone.

(Information supplied courtesy of Alasdair Philips at Powerwatch, 2 Tower Road, Sutton, Ely, Cambs, CB6 2QA, UK )