A small black box spitting out negative ions and a bit of ozone is another cure-all on the market. A flick of the switch and away with sleeplessness, tension, migraine, nausea, breathlessness and asthma - just to mention a few of the claims.
The principle of operation of negative ion generators in not new. An electrical charge is applied to air-borne particles like dust and pollen, and these fall out, leaving clean air behind. Dust collectors using the electrical charge principle, are employed successfully in industry, and are usually referred to as electrostatic filters. Negative ion generators are very crude versions of electrostatic filters. To remove dust from air efficiently, all the air must come within the charged zone. This is the reason why effective electrostatic filters use charged plates with a large surface area, and circulate the air with a fan.
Negative ion generators release their electrical charge from small, sharp needles which have a tiny surface area. The air immediately close to the needles receives most of the charge, and the remaining air is left unaffected. Unfortunately, the poisonous gas, ozone, is produced whenever an electrical discharge takes place in air. Lightning in a storm and sparking electrical motors always produce ozone. Electrostatic filters and negative ion generators also produce ozone.
Negative ion generators made before the 1960s produced so much of this gas that they were considered unsafe in the United States and banned. It is interesting that much of the scientific research quoted about the effectiveness of negative ions dates back to the time when available generators produced large quantities of ozone, and when ozone was still erroneously considered by many as the invigorating component of sea-side and country fresh air.
The two most often cited researchers on negative ions are: Professor Felix G. Sulman, Head of the Department of Applied Pharmacology at the Hebrew University, Jerusalem, Israel, and Professor Albert P. Krueger, Emeritus Professor of Bacteriology at the University of California. Dr Krueger claims that the negative ions substantially improve the growth of plants and affect the production of some hormones in animals. It is interesting that the former claim has not been taken seriously by the plant-growing industry. The latter claim had sparked several research programmes (especially by Dr Sulmans department) on the effect of negative ions on humans.
Dr Sulman s research centres on the effect on humans of the hot desert winds. His theory is that the positive ions in these winds cause their unpleasantness, and that negative ions restore the balance. These winds have been called"evil winds" or "witches winds". We are told that in Australia, the northerly winds in Victoria and the westerlies in New South Wales are our very own witches winds. Dr Sulman has done some experiments to prove his hypothesis. In Jerusalem, it is well known that Dr Sulman carries out research aimed at helping "weather-sensitive" people who suffer during these desert winds. In one project, individuals with these complaints were treated with negative ions, and were then asked how they felt. Up to 30% of the group treated said they received relief from the treatment.
One glance at Dr Sulman s method reveals that the 30% success rate is no more than placebo effect. Simply, this means that 30% of the patients may have received benefit anyway, in the absence of any treatment.
In a later study, Dr Sulman set out to prove that changes in weather conditions are reflected in the hormone secretion of 500 females. He claimed to have carried out the study "double-blind" to eliminate any placebo effect. In a double-blind experiment, neither the experimenter nor the subject are told when the conditions are varied, thus eliminating bias. A close look at Dr Sulmans report reveals that the experimenter adjusted to the conditions until the required results were achieved Those reports would be excusable if produced by someone unskilled in the methods of science, but when published by no less than a professor of pharmacology, one can justly suspect bias. The results given in these reports are very scrappy, and give no assurance that the trials were conducted in a truly scientific fashion. Furthermore, Dr Sulman had an axe to grind, as he is financially linked to one of the big manufacturers of negative ion generators. Dr Sulman issues certificates recommending negative ion therapy based on his experimental "proof of their beneficial effects. Manufacturers of ion generators use Dr Sulmans claims as the hub of their sales promotion literature.
Because Dr Sulman presents no convincing evidence that his trials were conducted in a scientific fashion, so that the placebo effect was eliminated, his claims should not be taken seriously. Claims that negative ion generators help asthmatics have been refuted in at least two carefully conducted, independent and impartial studies (1,2, ) The Asthma Foundation of Victoria does not recommend the use of negative ion generators, and warns of the dangers of ozone. Negative ion generators have not earned a place as a genuine method of curing sickness in any branch of medicine.
Copyright 1996-2004 Australian Skeptics Inc.
Also read How Negative Ions Purify the Air
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