Earth's Clouds Teem With Live Bacteria

Scientists have found living bacteria in clouds that grab up water vapor in the atmosphere to make cloud droplets. Tiny particles of dust, soot, and airplane exhaust are known to provide these surfaces. Isn't that dangerous? Can't that cause sickness in people because of all the nasty stuff in the clouds? I mean, rain comes from the clouds, so the rain falls and could carry nasty bacteria. I don't know much about it because I'm not a scientist, but i bet they'd tell us if it was dangerous.
The bacteria are good at collecting the water to form cloud droplets. Snow samples were taken from all over the world to be tested, and it was discovered that Antarctic snow has the least concentrations of biological nuclei. Sites like Montana and France had the highest.