It's not in your imagination. Mosquito populations are thriving.
If you could see an alien planet from Earth, you wouldn't necessarily need to look for cities. You could just check for oxygen in the atmosphere.
Pollution in cities is pretty much an accepted thing, but what about pollution in the country? Learn about pollution on this Moment of Science.
To really behold the stars these days, you have to travel far from cities and towns to escape urban glow. The magnificent sight of the Milky Way, for example, can now only be seen in rural areas. But why do we shine light up into the sky in the first place? We need light shining down on streets and walkways–not up into the sky!