Feature

Electromagnetic Hazards

Are we suffering from the effects of electromagnetic radiation? Despite claims to the contrary, it appears not.

By Vicki Hyde, NZSM

One section of the Auckland Regional Council's main headquarters is evacuated because of a "magnetic radiation" scare. A naturopath warns of "dangerous neutrons" leaking out of a stereo speaker. A family shifts their children to another school because of worries about nearby power pylons.

Concern about the effects of electrical and magnetic fields has been growing in recent years, aided by media coverage that has been at times alarmist and inaccurate, according to researchers.

Martin Gledhill, of the National Radiation Laboratory says that the facility has fielded a couple of dozen telephone calls on the issue following a recent Frontline television item on the apparent hazards of electrical and magnetic fields.

The documentary was "very poor, presenting the subject in a sensational manner with scant regard for objectivity", said a laboratory release, adding that it caused many people unnecessary alarm.

Gledhill has known of people who have got rid of everything from bar heaters to bathroom extractor fans in the belief that they were in danger from these devices.

"It does get people concerned," he says. Researchers in the area recognise that a lack of knowledge has contributed to those concerns.

"It's rather misleading to call these fields radiation at all," avers Gledhill. Power lines and electrical equipment don't propagate radiation as such, he says, but act in much the same way as if you wave a bar magnet around. The term "radiation" tends to ring alarm bells, producing visions, as one expert put it, of mushroom clouds.

In the ARC scare, staff and equipment were shifted from one area when computers were found to be malfunctioning. The problems were caused by interefence from transformers on the floor below. Similar sorts of interference can come from any-sized electrical equipment operating on the same frequencies; even small fans and hairdryers can cause it.

Tests in the building showed a field strength of 1-60 milligauss; the NRL considers up to 5000 milligauss to be acceptable in the workplace.

Health Concerns

Much of the initial concern raised about electric and magnetic field effects stemmed from a number of epi-demiological studies of varying quality. There were reports that childhood leukemia figures rose with exposure to strong electrical fields and that miscarriages increased with exposure to radiation from computer VDUs.

The problem with such reports is that they generally provide conflicting data, even in those cases where the studies are carefully designed. Follow-up studies have called into question the very low sample numbers used in initial reports.

In addition, there were other possible factors not taken into account, such as the stress, office enviroment and lengthy periods of sitting undertaken by a typical VDU worker. A study in Canada of 56,000 births showed no relationship between exposure to computer VDUs and pregnancy problems, but this has had far less coverage than the initial reports.

Another study suggested that the herbicides used to prevent grass growth around large pylons were more likely to have been involved in possible health effects than the electromagnetic fields present.

The National Radiation Laboratory has monitored both electrical and magnetic field strengths in industrial and domestic situations. The laboratory's exposure guidelines are extremely conservative, based on levels established by the International Radiation Protection Association.

One local study of workers in the plastic welding industry looked at the high levels of radiation in the radio frequencies used in this industry. The guidelines were being exceeded in some case, but no health effects attributable to this were found.

Gledhill has been looking at low-level magnetic fields and their potential effects. Wiring codes have been used as a rule-of-thumb indication of magnetic field strength in various studies. The codes are based on the number and relative thickness of power lines within 50 metres of a domestic residence.

Dangerous Assumptions

A survey Gledhill undertook in Christchurch has shown that similar-looking high voltage lines can have startlingly different loads, depending on the time of day, time of year and where the measurements are made.

"The results do suggest that proximity to low or high voltage power lines, or substations, is not necessarily a good indicator of residential magnetic field levels," Gledhill remarks.

The initial study into childhood leukemia and electromagnetic fields assumed that the wiring codes accurately represented the current carrying capacity of the lines and the strength of their associated magnetic fields. While a very weak correlation between such codes and leukemia has been found, a recent epidemiological survey using actual measured magnetic fields found no relationship to the incidence of childhood leukemia.

"The evidence is pretty sketchy if there are any effects or not," Gledhill says.

A recent conference on public health held at Lincoln University included a report of a Dunedin survey which described no discernible effects from electromagnetic fields. The survey is being combined with other international reports which have similar results.

Despite the reassurances, there is public pressure for the adoption of a "prudent avoidance" approach. In this, strategies are used to implement reasonable, low-cost steps to avoid exposure. The problem with this, according to Gledhill, is defining what are reasonable, low-cost strategies.

"Do we spend a million dollars on this, or would we be better off spending the money to put crash barriers down motorways?" he says.

At least with barriers we know we'll be saving lives, Gledhill adds, instead of trying to protect ourselves against something that is not actually causing any harm.

Vicki Hyde is the editor of New Zealand Science Monthly.