Both statements are correct 

About Ozone: 

• Ozone is a gas composed of three atoms of oxygen. Ozone occurs both in the Earth’s upper atmosphere and at ground level. It can be good or bad, depending on where it is found. 
• The stratospheric ozone also called Good Ozone occurs naturally in the upper atmosphere. There, it forms a protective layer that shields us from the sun’s harmful ultraviolet rays. 
• On the other hand, Ozone at ground level is a harmful air pollutant, because of its effects on people and the environment, and it is the main ingredient in “smog”. 
• Ozone generally disintegrates after sunset. It is because, in the absence of sunlight, NOx further reacts with ozone to neutralize it. 

Source: Article