Why is the ozone so bad?

I'm curious, could you elaborate on the issue of ozone pollution? Specifically, why is ozone considered so harmful? What are the main reasons behind its negative impact on our environment and health? Does it have any direct correlation with human activities? How significant is this issue globally, and what measures are being taken to mitigate its effects? I'm particularly interested in understanding the scientific basis behind these concerns and how we can collectively work towards a more sustainable future.