Several years ago I wrote a post about how frequently steam plumes are used as illustrations to articles on pollution. In the US, if you see a cloud coming out of a smokestack, adds are about 100:1 its steam, not smoke. Look how many of the results today in Google images for "air pollution" are actually plumes of water vapor.
One trick environmental sites will play is to Photoshop the contrast and darkness of the steam plume to try to make it look smokier. Here is a good example
This photoshopping of steam plumes to make them look like smoke is prevalent enough that I have written about it a few times. That is why this image tickled me. I don't know the artist. He may be making the opposite plea (e.g. turning smoke to steam) but I'll interepret it the way I like:
Postscript: This is my all-time favorite image in this category:
This image was used by Battelle labs (update: still is) to illustrate their air pollution expertise. The sad-faced girl with the inhaler is classic, but what makes this my favorite is the water vapor plume from the nuclear plant (you can see the nuclear reactor dome). The water vapor from a nuclear plant cooling tower has only pure water -- it has no combustion products and no particulates that might give this poor girl asthma. It does not even have any CO2 in it, if that is your particular bogeyman.