How is ground level ozone harmful to humans?

Could you elaborate on the potential harm that ground-level ozone poses to human health? It seems like an invisible threat, yet the scientific consensus is clear on its dangers. I'm particularly interested in understanding how it affects respiratory systems, as well as any long-term health implications. Additionally, I'd like to know if there are specific populations, such as children or the elderly, that are more vulnerable to these harms. A concise yet thorough explanation would be greatly appreciated.