Question

Why is excessive use of CFCs a cause of concern?

Answer 1

According to me CFC i.e. chloro fluro carbon is very poisonous gas that is used in refrigerators, air conditioner, etc which can affect our health adversely.

That's why it's a cause of concern

Answer 2

CFCs stands for chloroflurocarbons which are used as refrigerants and in fire extinguishers. Excessive use of CFCs lead to decline of ozone in the atmosphere.
This is already done damage by creating a large ozone hole over Antarctica region.

The United Nations Environment Programme (UNEP) has forged an agreement to freeze CFC production.