Which statement correctly describes ozone in the upper atmosphere versus ground level?

Which statement correctly describes ozone in the upper atmosphere versus ground level?

• A. Atmospheric ozone is the good kind that protects us from UV; ground-level ozone is the bad kind and the main ingredient of smog
• B. Ground-level ozone is the good kind that protects us from UV; atmospheric ozone is the bad kind and the main ingredient of smog
• C. Both atmospheric and ground-level ozone are equally beneficial to health
• D. Ozone has no role in air quality

Answer: (A)

Ozone behaves very differently depending on where it is in the atmosphere. In the upper atmosphere, the stratosphere, ozone forms a protective layer that absorbs most of the sun’s harmful ultraviolet radiation, helping reduce skin cancer risk, cataracts, and other UV-related damage. Near the ground, in the troposphere, ozone is a pollutant created by reactions between sunlight and emissions like nitrogen oxides and volatile organic compounds; this ground-level ozone contributes to smog and can irritate the lungs, worsen asthma, and harm crops. That contrast makes the statement describing the upper-atmosphere ozone as the protective kind and the ground-level ozone as the smog-forming pollutant the best description. The other ideas don’t fit because ground-level ozone doesn’t shield us from UV, and the term atmospheric ozone typically refers to the protective stratospheric layer in this context. Ozone clearly does play a significant role in air quality, but in opposite ways depending on location.

Ozone behaves very differently depending on where it is in the atmosphere. In the upper atmosphere, the stratosphere, ozone forms a protective layer that absorbs most of the sun’s harmful ultraviolet radiation, helping reduce skin cancer risk, cataracts, and other UV-related damage. Near the ground, in the troposphere, ozone is a pollutant created by reactions between sunlight and emissions like nitrogen oxides and volatile organic compounds; this ground-level ozone contributes to smog and can irritate the lungs, worsen asthma, and harm crops.

That contrast makes the statement describing the upper-atmosphere ozone as the protective kind and the ground-level ozone as the smog-forming pollutant the best description. The other ideas don’t fit because ground-level ozone doesn’t shield us from UV, and the term atmospheric ozone typically refers to the protective stratospheric layer in this context. Ozone clearly does play a significant role in air quality, but in opposite ways depending on location.