Negative Ions
Ions are atoms or molecules that have an electrical charge. So, atoms are made up of protons and electrons. Electrons are negatively charged and protons are positively charged. An ion will either have an unequal number of either protons or electrons and whichever one it has more of will determine the negative or positive charge of an ion. Some cations are positively charged meaning they have more protons than electrons and some anions have more electrons than protons which will give them a negative charge. Cations and anions attract one another because they hold opposite charges. When they combine they form ionic compounds.
Ions with only one atom are called monatomic ions. Ions with two or more atoms are called molecular ions or polyatomic ions.
Ok, so what? What about the products that claim to contain negative ions?
Right, before I get to that there are some rather innocuous claims about ions in nature that I should probably cover.
First, the claim is that negative ions appear in greater numbers than positive ions in natural settings, particularly near moving water.
I can add a link to a pdf of a study in the show notes that shows that waterfalls create negative ions. They also create positive ions and different waterfalls create different sizes and quantity of both positive and negative ions.
So I don’t know if there is more research to say that natural areas have more negative ions and if you believe what websites that are more aimed at “complementary medicine” say then you will find them all over the place in nature. It would appear after some amount of reading that it makes sense that places that stir up the water and put some water vapour into the air could have a higher concentration of negative ions but they likely also have a higher concentration of positive ions because of the way that positive and negative ions are very mobile in fluids and vapours. This is actually called the Lenard effect and is described by the American Meteorological Society as the separation of charges accompanying the aerodynamic breakup of water drops.
The AMS goes on to say, “Experiments have shown that the degree of charge separation in spray processes depends upon the drop temperature, presence of dissolved impurities, speed of the impinging air blast, and contact with foreign surfaces. The largest fragments of the broken drops are observed to carry positive charges and the fine spray of drops carried off in the impinging air current carries a net negative charge.”
There is also evidence that our homes have fewer ions because inside our homes we are shielded from one of the major sources of ions which are cosmic rays. One of the reasons ions may be said to be found in nature is because in cities, homes, and communities we are surrounded by buildings and metal and other air pollutants that can block or attract the ions which turns them into neutral atoms or molecules.
Moving onto the health claims, I am considerably more skeptical and tried to find studies that will help me understand if they work and hopefully how they work if they do. There are a lot of claims about the benefits of negative ions and alternatively, positive ions are often painted as harmful so I’d like to lump these claims into a few groups. There are extreme claims that I think are not only unsupported but maybe even dangerous if someone puts too much weight behind them, there are claims for which some research has been done and there is potentially a real effect, and there are claims that are daily mild but don’t have enough research to say conclusively. There are also a number of products that claim to be beneficial due to their collection or distribution of negative ions.
Claims
Negative ions have antidepressant effects – some evidence suggests that being subjected to a high density of negative ions has at some antidepressant effects on people suffering from seasonal affective depression. The studies that showed this, however, were not blinded and subjects knew that they were being exposed to negative ions and that may have affected the results
Negative ions make your brain work better – there is evidence that people in a high-density ion environment have quicker reaction times and reported being more energetic than a control group. Some EEG results supported better brain function in high-density negative ion environments while participants claimed they felt more relaxed and alert. Seemingly, there were opposite results from people studied who were placed in a high-density positive ion environment. This study measured multiple outcomes and that increased the chances that any one outcome may have a disproportionate change showing an effect.
All the studies about negative ions had fairly small sample sizes
They measured ions at the source and distance to subjects was not controlled and neither were other air components, which means that the subjects may not have gotten the expected amount of ionic air.
In 2013 a meta-analysis by Vanessa Perez, Dominik D Alexander, and William H Bailey found, “No consistent influence of positive or negative air ionization on anxiety, mood, relaxation, sleep, and personal comfort measures was observed.”
The effect on depression seems to be plausible but the meta-analysis recommends future research to, “evaluate the biological plausibility of this association”
An article from Healthline.com with the title, The Effect of Negative Ions lists a few effects that are supposedly supported by evidence. They include, help regulating sleep patterns and mood, reducing stress, improving immune system function, increased metabolism of carbs and fats, and killing bacteria. A 2018 systemic review of these claims found, “Some studies have suggested that NAIs had multiple health benefits on humans/animals, might inhibit the growth and/or kill some microorganisms and promote plant development, but some of the results need to be further verified, some references might overestimate its benefits and no consistent or reliable evidence in therapeutic effects were achieved.”
Products
Salt Lamps – do not produce negative ions
Tourmaline – will produce negative ions if heated
Ionic air purifier – will produce negative ions also produces ozone which is a pollutant
Ion bracelet – Any inert product cannot have negative ions without energy being put into it. Negative ions are a product of atoms losing a proton and having more electrons left over. For an ion lamp or air purifier to work, it needs heat or electricity. Most of the ionic bracelets or necklaces or other non energized products simply don’t have the negative ions that are claimed unless they’ve been irradiated. Which is to say that they have been exposed to enough radiation that they will contain negative ions. One of the ways that they seem to do this is actually to gather radiated soil or powder of some kind and mix it into the fabric or material of the product.
I highly recommend the video in footnote 6 from Thought Emporium for an actual demonstration of how radioactive the products are and how risky they are.
All the sources in one place
https://en.wikipedia.org/wiki/Ion
http://glossary.ametsoc.org/wiki/Lenard_effect
Are Negative Ions Good For You? By Veritasium
Negative Ion Products Are Actually Radioactive https://youtu.be/C7TwBUxxIC0
Reddit Thread on Negative Ions
Has anyone heard of "negative ion" health claims? from skeptic
Looking for someone to concisely refute (or support) the claim that "negative ions" are generated near water active sources and are responsible for health benefits. from askscience
Studies https://acp.copernicus.org/preprints/11/25297/2011/acpd-11-25297-2011-print.pdf
https://pubmed.ncbi.nlm.nih.gov/23320516/
Pseudoscience websites
Are Negative Ions Good For You?
Seemingly middle of the road articles