Particulate matter measuring less than 2.5 micrograms (pm) in diameter (PM2.5) is a major concern among all air pollutants for human health since they can penetrate the lungs, impacting respiratory health. In 2015, Northern Africa and Western Asia, and Central and Southern Asia, recorded the highest PM2.5 concentrations estimated at 49 and 48 pg/m3, respectively (Figure 18). The Oceania subregion recorded the lowest concentrations.