sprout of oxygen

I wonder, what happens on sudden increase of oxygen on the earth atmosphere? Do you think that it will be a boon to us? actually, the real answer was kind of bitter, increase in oxygen rate leads to a biggest curse that you've never met. even though it holds some merits on it. 

first of all, increase in oxygen rate on atmosphere, let more sunlight penetrate through the earth. which in turn results in a brighter climate. but this one merit can't paint curse as a boon. in fact, humans and animals' breath air with only 21% of oxygen while other 79% of air is of other gases like nitrogen.When oxygen rate increases , we were tend to breath pure oxygen.   And when we breath the pure oxygen it leads to emergence of free radicals on our body, which if  continued to  stay in our body, leads to cancer.and increase in the level of oxygen rate also increases combustion rate, due to which a candle will be able to fight with LED light💡 and forest fire runs faster than ever