hopefully never. :\
World Pollution Day is observed on December 2nd every year. It aims to raise awareness about the environmental challenges posed by pollution and promote solutions to mitigate its effects.
2nd december
Pollution is the main problem of our world's peoples, the animals are both affected due to the problem of pollution's we cannot stop pollution then we all will die one day or other day.
The world is pollution free.
According to the World Health Organization, around 7 million people die every year as a result of air pollution. This equates to approximately 19,178 deaths per day worldwide.
3 December observed the anti pollution day
There is major air pollution in Mexico, the USA, and South America. Walking the streets of some mega cities for a day is the equivalent of smoking 60 cigarettes. Hope this answer is what you needed!
see light pollution
Mumbai
As you live you life try not to make or be the cause of pollution - this will help the world.
11th july
Thousands of animal die a day from pollution please