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

The co-occurrence of fine particulate matter (PM_2.5) and ozone has emerged as a critical environmental challenge in recent years. The individual harmful impacts of PM_2.5 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_2.5 and ozone. The synergistic toxicity of PM_2.5 and ozone depends on different factors, including the physicochemical properties of PM_2.5, the dose and duration of exposure, and the specific target organs. Through extensive research, we identified the main targets of toxic responses to PM_2.5 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_2.5 and ozone co-exposure with priority given to characterizing their properties and toxicological responses while updating relevant guidelines and standards.