I take a lot of hot showers, and sometimes I find myself wondering why I am able to breathe in the steam around me and not worry about any water-in-lungs related health concerns. How is breathing in steam different than breathing in small amounts of water droplets?
In: 6500
Couple reasons:
1. Water vapor is a gas, while droplets are liquids that are *suspended* in gas. Your lungs are very capable of propelling gasses out with each breath, but droplets will touch your lungs and “fall” out of suspension, becoming liquid water in your lungs. Small amounts will simply evaporate over a short period of time, but large amounts can be problematic as they’ll coat the surfaces of your lungs and pool, decreasing the surface available to exchange oxygen in air.
2. Vapor (a gas) condenses most readily on cold surfaces (like on the outside of a cold drink can), and less readily on warm surfaces. Your lungs are warm, so vapor doesn’t easily condense on the surfaces. Some will, but it takes a lot of vapor at a higher temperature than the body. At that point you’re likely more worried about steam burns, and you have other problems.
3. Droplets carry more water than vapor. A breath full of water droplets has more water than a breath with high concentration of water vapor. Lots of water is bad, less water is not really a problem because your lungs can expel it easily enough.
4. Your airway isn’t just a straight path to your lungs. Your airways, especially when breathing through your nose, are absolutely coated with little hairs that I can’t remember the name of. These provide a high surface area for water droplets to contact on before they get to your lungs, and they help filter out some droplets before they get to your lungs. When these get disturbed enough, they trigger a cough reflex, which helps propel the droplets out of your airway before they get into your lungs.
5. Your lungs are capable of absorbing some water. At a very basic level, your lungs are just a way to get a very large surface area between air (oxygen) and your blood, so that oxygen can be passed into your blood and CO2 can be passed out. It’s a mass transfer system, which depends on surface area. Your lungs work well for the same reason that a towel dries faster when you hang it up vs leaving it balled up. In the same way that they absorb and desorb O2 and CO2, your lungs can pass some water into and out of your blood stream. This is not the ideal way to hydrate yourself, but it helps your lungs deal with small amounts of water, especially if it’s well distributed on the surfaces of your lungs. A thin layer gets absorbed quickly, similarly to how if you were to mist-spray a towel, it would dry easily, but if you squirt-sprayed a spot on the towel it would take longer to dry. The water can easily evaporate into the air AND dissolve into your blood and tissue.
6. Water droplets carry things. Water in lungs health concerns often carry the complications of other stuff in the water, like viruses, bacteria, parasites, and just plain debris. Water vapor is a gas, and it doesn’t carry bacteria and viruses the same way as droplets.
Last note, if you can see the “steam”, it’s not a vapor anymore. Water vapor is clear and colorless. If you see the steam cloud, it means that the water vapor is mixing with the cooler air and condensing microdroplets in the air, creating that white cloud. These are technically droplets, and can stick to your lungs. The reason you aren’t dying from it is because it’s a small enough amount of water that your body is able to manage for reasonable periods of time. Also, when water evaporates and re-condenses, it’s very pure and far less likely to be carrying contaminants.
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