Synergistic Toxicity of Fine Particulate Matter and Ozone and Their Underlying Mechanisms.

The co-occurrence of fine particulate matter (PM) and ozone has emerged as a critical environmental challenge in recent years. The individual harmful impacts of PM and ozone exposure have been well studied; however, their combined toxicity under co-exposure conditions remains mechanistically undefined. This paper provides an extensive evaluation of the current pollution levels, epidemiological investigation, and new findings on the toxicological mechanisms of combined exposure to PM and ozone. The synergistic toxicity of PM and ozone depends on different factors, including the physicochemical properties of PM, the dose and duration of exposure, and the specific target organs. Through extensive research, we identified the main targets of toxic responses to PM and ozone exposure and summarized their synergistic toxic mechanisms. Given the current research priorities, there is an urgent need to improve scientific research regarding PM and ozone co-exposure with priority given to characterizing their properties and toxicological responses while updating relevant guidelines and standards.