I doubt safety is playing a big role. After all, even the most unsecure city in China is still way safer than the most secure US city

And Guangzhou isn't that dirty - compared to other "big" chinese cities it is, at least.

Humid weather is something quite common in that region of the world... the more South the worse I would say. Singapore is probably the most damp big city in the world, still people don't complain much about it.

I would say go ahead, and enjoy your time there!