Have a look at http://en.wikipedia.org/wiki/Maslow%27s_hierarchy_of_needs
Pre industrialisation, most people lived in the bottom bit - even struggling to get into the bottom bit. Until 50 years ago, famine was rife. Now it is fairly close to nonexistant, except for disturbances caused by local conflicts.
The same for disease. Sure Ebola is making a lot of news, but that's not even 0.1% of what the 1918 flu pandemic was.
Booming industry has brought us this wealth, and that is largely driven by low-cost energy.
As people get more wealthy, and use more energy, their aspirations improve. One of the things they want is a cleaner environment. Wealthy societies can spend more on clean ups.
USA and UK uses more energy (including oil) than ever before, yet the rivers and air are cleaner now than 50 years ago.
London air is now far cleaner than it was in the 1960s and the streets cleaner than they were in 1900.
The clean up is happening without the UN telling people what to do.