Disease? Nothing compared to the Black Death or Bubonic Plague - no, not even AIDS.
The reason the Black Death or Bubonic Plague claimed so many lives in the 1300's is because medical science hadn't advanced in contemporary society to the health care options we have now in developed countries. What do you think the death-toll for AIDS would be if it wasn't for drugs like AZT and Emtriva. The real issue is the number of diseases and their overall mortality patterns that have infected mankind in the 20th century.
Pollution? The progress across the past 50 years in US cities air and water has been almost miraculous. Does the Cuyahoga River catch fire anymore? Has lead in the US environment plunged?
There's been a lot of research conducted by credible scientists about pollution, climate change and recent weather trends.
http://news.nationalgeographic.com/news/2007/03/070306-pollution-storms.html
Asia Pollution Changing World's Weather, Scientists Say
Pollution in Asia is altering global weather patterns by creating larger clouds and more intense storms, a new study says.
The findings are the first definitive link between human activities and significant shifts in storm patterns that influence weather worldwide, the researchers write.