Extract From "Are Ions Good for You?"

(From Compliance Engineering Nov/Dec 2002)

Almost from the very first detection of air ions, there has been speculation about possible hygienic, physiological, or other types of effects. The first paper may have appeared as early as 1923. Very few, if any, of these first papers deserve the designation of scientific papers, which should only deal with properly described and properly conducted investigations. Almost all reported investigations were purely anecdotal. In my opinion, one of the reasons for this was that usually the investigations were carried out by physicians and other laypeople without the guidance of physicists with a proper knowledge of atmospheric electricity.

For example, in the 1930s, it was rather common in to treat a variety of ailments, such as asthma, bronchitis, and other airways-related problems, by letting the patients (apparently) inhale negative ions. Some of the administrants of these treatments, usually medical practitioners, reported rather astonishing results. At a certain point in these experiments, somebody had the good sense to ask a real expert to examine the ionizers to find out what they were actually doing. The all-time-ever expert on atmospheric electricity, Hans Israël, agreed to do this. Years later, I heard Hans Israël summarize his investigation. It appeared that the ionizers used by some of the doctors with the most beneficial results did not even contain a high-voltage supply; that is, they did not produce ions at all.

The Negative-Ion Myth
The previous story is a good example of a negative-ion myth. Repeatedly, it has been reported that negative ions are good and that positive ions are bad, usually with little if any scientifically rigorous documentation.

One of the oldest claims concerning the effect of ions is that air rich in negative ions is fresh and that air rich in positive ions is stuffy. Of course, it is difficult to prove or disprove such statements, as freshness and stuffiness are subjective quantities for which there is no physical method of measurement. Therefore, let us be subjective. Let us assume that most people will agree that the air at a mountaintop deserves to be called fresh. Now, it just so happens that this air is rich in positive ions, the concentration being maybe 3–4 times greater than at sea level. The freshness and the positive ions have nothing to do with each other. The freshness could be caused by the air being unpolluted and cool, and the high positive-ion concentration is simply a result of the electrode effect.

Let us also assume that most people will find that during a thunderstorm (before the rain sets in) the air may be considered less than fresh, maybe even stuffy. This same air is rich in negative ions. The stuffiness might be explained by high humidity and other thermophysical factors, and the high negative-ion concentration is simply an effect of the strong negative field from the base of the thundercloud to the ground.

Another example of the negative-ion myth concerns the effects of ions on the cilia in the respiratory tract. From 1957 through 1963, a series of papers were published by Krueger et al., who suggested that air with an excess of positive ions caused a deceleration of cilia activity and of t