Figure 2
Chemical exposure-response relations for reactive oxygen species (ROS) produced in the human respiratory tract upon inhalation of fine particulate matter (PM2.5).
It is shown as a function of PM2.5 concentrations with redox-active components as observed at various geographic locations around the world (Supplementary Tables 4–7). (A) ROS production rates induced by copper (Cu), iron (Fe), secondary organic aerosol (SOA), and quinones. (B) Characteristic concentration levels of different types of ROS and (C) total ROS concentration in the epithelial lining fluid after two hours of inhalation and deposition of ambient PM2.5. In panel (C), the green-striped horizontal bar indicates the ROS level characteristic for healthy humans (~100 nmol L−1), and the gray envelope represents the range of aerosol-induced ROS concentrations obtained with the approximate upper and lower limit mass fractions of redox-active components typically observed in ambient PM2.5. Total water-soluble fractions of iron and copper can range from ~5–25% and ~20–60%, respectively, in a wide range of different environments, which are represented by the error bars. (D) Fractional change of ROS concentrations upon removal of 50% of redox-active components from PM2.5 calculated for selected geographic locations with different PM2.5 concentration levels and composition (Supplementary Table 7).
