It appears, in the glacial time 14 thousand years ago the air was polluted much more strongly, than now. Investigations of scientists from the Institute of polar investigations in Ohio have proved it. They have analyzed layers of land ice in Greenland, and it appeared that the ice, formed at that time, contained in one hundred times larger quantity of solid impurities, than the ice and snow that was formed these days. Antarctic ice, age of which matched to age of Greenland ice, was in four times more dirty than the modern one. According to scientists, actively erupting volcanous were the source of pollution,
Source: Almanac M.D.A.
My commentings: Nothing prove that the source of air pollution during the epoch of last glaciation (finished, at different estimates, 12-10 thousand years ago) were actively erupting volcanous (at least, I, geologist do not know about it). In works on ice drilling in Arctic and Antarctic regions I have met another opinion - the sources of air pollution at that time were dust storms. But the fact of such storms is confirmed nothing too. The both explanations are only tryings of scientists, who don't believe in existence of highly-developed antediluvian civilizations, somehow to explain these phenomenas.
All fall into place, however, if to recognise that before the last flood which, according to the majority of existing dating, took place about 12,5 thousand years ago, there were not less highly-developed civilizations on the Earth, than now.
Read about it in detail in my work "Drilling of ice confirms the existence of antediluvian civilizations"