| MadSci Network: Biophysics |
hi Cameron,
What's that smell? It's...pseudoscience! Scientists hate pseudoscience, because at first glance it can appear plausible, particularly if you don't have a strong science education. Most people have heard of ions. Many people are also aware that some forms of oxygen molecules that carry negative charge can be detrimental to cells. Some people may even have heard that charged surfaces can clean air by removing dust, spores and so on. So there's a general perception that charged particles in the environment might affect our health. Unfortunately this vague notion is all that the manufacturers of so-called "ionized air" devices have to offer. It doesn't take much more than a basic understanding of ions and molecules to realise that their claims are nonsense.
So - what's an ion? It's an atom or molecule that has lost or gained electrons, making it either positively- or negatively-charged, respectively. The simplest ion is the proton (H+), which is a hydrogen ion that has lost its single electron.
How do we make ions? Well, many substances will dissociate into ions when dissolved in water. A common example would be table salt, sodium chloride (NaCl), which in water dissolves to form sodium (Na+) and chloride (Cl-) ions. You'll notice that the charges balance and so a solution of sodium chloride is electrically neutral. You know this already, because you don't receive an electric shock when you dip your finger into salt solution.
In fact, you can't create a negative ion without a positive ion and the two don't like to be separated. On a hot stormy day when clouds rise rapidly, molecules in the air lose electrons and we get a charge imbalance - positive and negative charges accumulate in different regions of the thundercloud. When the potential difference between the regions becomes large, nature tries to restore charge equilibrium via an electrical discharge - which we know as lightning. A lightning strike itself can ionise molecules in the air, leading for instance to the generation of ozone. The smell of mountain air, a thunderstorm or the ocean is frequently attributed to ozone and many air ionizer manufacturers allude to this fact when proclaiming that ionized air is "natural" or "healthy" - but once again, they're not telling you the whole story.
OK - so we can generate ions in solution or using electrical discharges. In other words, ionization requires energy. The so-called sodium ion light does not provide the energy required for ionization. What you have is a rather expensive illuminated salt crystal. Even if ions were generated, we would need a mechanism to separate positive from negative (such as two metal plates on which they could accumulate) and a way to prevent electrical discharge due to the charge separation. And even assuming that we could do all of those things - what's the evidence for the effect of ions in the air on health?
We can go and search PubMed which is a repository of tens of millions of articles in scientific journals from the past few decades. Here are a few of the articles that I located using keywords such as "air negative ions", "air ioniser" "air purifier ions" and so on:
So finally to address your specific question - are there harmful ions in the atmosphere? There may be - ions are generated all the time, through processes such as radioactive decay. If you live over granite rock for example, you'll be exposed to some very nasty ions called alpha particles, which are positively charged helium nuclei. No amount of air ionizer will help you in that case! But remember that our bodies continually generate damaging negatively charged species of oxygen through our own metabolism. Our cells contain enzymes to deal with these species but over time, they do cause damage and may contribute to aging. Our cells too depend on ions for transport of solutes in/out of cells and other metabolic processes. So really, we're so saturated with ions that generating a few in the air isn't going to make a bit of difference.
I hope this was useful for you - science is so much more fun and interesting than pseudoscience!
Try the links in the MadSci Library for more information on Biophysics.