Final answer:
Ozone is beneficial at higher altitudes as it protects us from harmful UV rays, but at ground level, it is a harmful air pollutant.
Step-by-step explanation:
Ozone is beneficial to humans at higher altitudes as it forms a protective layer in the upper atmosphere, known as the stratospheric ozone layer. This layer shields us from the sun's harmful ultraviolet (UV) rays, which can cause skin cancer, cataracts, and other health issues. However, at ground level, ozone is a harmful air pollutant and a major component of smog, resulting from vehicle exhaust and other human activities.