Today, many bongs, ornate or basic, are equipped with little glass ice catchers just above the beaker. Putting ice in a bong can cancel out some of the heat from the smoke, making your rip much smoother and less painful.
I personally love putting ice in a new bong that has not been broken into yet or just after I have thoroughly cleaned out my downstem, just to be gracious on my lungs. But when I started seeing articles and hearing through word-of-mouth the rumors that the ice can cause bronchitis and other serious lung issues, I used my ice more sparingly. So, I did my research, since I do not want to take the chance of causing extreme damage to my lungs. So, according to everything I have read in health blogs, articles from doctors, and stuff written by stoners everywhere, here is the truth about the effect of putting ice cubes in your bong...
The whole logic behind the theory is that the hot smoke flowing through the ice cubes causes water vapor to collect in your lungs, leading to severe bronchitis and other lung related issues. The water vapor is so cold that it can freeze, causing strain and stress to your lungs. According to both personal users and medical professionals, this has been proven to happen in people who already suffer from previous respiratory issues. This does not mean it does not affect people with perfectly fine lungs. When you first take the ice cubes out of the freezer, you often see that little, white smoke-looking stuff when they touch any form of heat. You also might see that when you first put it in the bong, since they are often on the warmer side. This white smoke will last for the first few rips until the heat from the lighter starts to melt the ice. That white vapor is exactly what you don't want to be inhaling.
Many people say a way around this is putting your bong out in the sun for a little to let the ice melt, or to let the ice melt previous to putting it in the bong to prevent it from filling up with too much water from the melting process. An even better alternative, which I have now almost completely switched to, is filling your bong up with cold water instead of involving ice at all. I believe this makes my rip even smoother because the water was cold to begin with, so there is less heat from the very start. There also is absolutely no water vapor created, or any extra water coming from melting ice. I one-hundred-percent recommend it! There are also some bongs that are designed to prevent the actual vapor from getting in your lungs, and I have read that those also can make a difference in how often it is healthy to actually put ice in the bong.
So, overall, yes, exposing yourself to massive amounts of water vapor could cause it to freeze in your lungs and lead to respiratory problems. In saying this, if you put a couple cubes in your brand new bong to create a more pleasant rip, as long as you let the ice melt a little first, it will not cause harm, yet it is not recommended to do something like this every smoke sesh. One also has to take into account that everyone's body reacts a little bit differently, and what works for some stoners might not work for others. Just because you see that 420 guy on YouTube take a massive rip in a bong stacked with ice cubes does not mean that would not negatively affect your lungs, even if it didn't hurt his.