Over the last year or so I've heard from friends, who subscribe to holistic medicine, talk about negative ions, saying that they are good for your mental/physical health. Being the only one among them with a chemistry background, I was suspicious when i heard this. Below are examples I've seen that use negative ions in a medicinal context:
Negative Ions Purify Air
Virtually all particles in the air have a positive charge, while negative ions have a negative charge. In which case, negative ions and particles magnetically attract to one another. When there is a high enough concentration of negative ions in the air, they will attract to floating particles in large numbers. This causes the particle to become too heavy to remain airborne. As a result, the particle will fall out of the air, and will then be collected by normal cleaning activities, such as vacuuming or dusting. - Ion-Imbalance
Negative Ions from the Beach
You may have experienced the power of negative ions when you last set foot on the beach or walked beneath a waterfall. While part of the euphoria is simply being around these wondrous settings and away from the normal pressures of home and work, the air circulating in the mountains and the beach is said to contain tens of thousands of negative ions -- Much more than the average home or office building, which contain dozens or hundreds, and many register a flat zero. -WebMD
Apparently they Help You Breath
People travel from all over the world to visit salt mines like the ones found in the Himalayas, Austria, and Germany. In Germany, the hot salt springs are so revered, companies often send overworked employees there to rejuvenate. Why are the salt mines so beneficial? Quite simply... the very dry, negative ion environment of a salt mine is key. Well... even if you're not able to travel to Asia or Europe to take advantage of salt mines, you can still take advantage of these negative ions to help improve the air you breathe. The solution involves pure Himalayan crystal salt...- Mercola
Well it's not surprising that two thirds of the above sources are trying to sell products (salt lamps, air purifiers).
Since we're dealing with ions here, I figure the chemistry world must have some sort of input. What's the chemical or biochemical support, or the evidence against, for the above claims? If there are negative ions present from waterfalls/oceans/salt rocks, what ions are we talking about?
To address @dissenter, one of these sites claims tourmaline is a source of negative ions...