Currently, only the mass of sub 2.5 μm and sub 10 μm particles (PM_2.5, PM₁₀) in ambient air is regulated and monitored closely, but the same increase in PM_2.5 can cause different degrees of health effects in different cities (sometimes more harmful effects per unit mass in less polluted cities) (Li et al., 2019). In addition to mass concentration, other measurement metrics are needed to connect particle pollution data and health effects. In our measurements made in traffic-influenced environments in Helsinki, Finland (a relatively clean city), and Delhi-National Capital Region (Delhi-NCR), India (a polluted area), we noted a large difference in the median particle size for lung-deposited surface area (LDSA). In Helsinki, the median size was 80 nm, corresponding to soot particles emitted from diesel engines. However, the median size increased to 190 nm during a long-range transport event of air mass. In Delhi-NCR, surprisingly, the median size was even larger, 410 nm. These larger particles were likely to originate from regional sources rather than local traffic. The LDSA to PM_2.5 ratio for particles in Helsinki was 2–4 times the amount in Delhi-NCR, potentially linked with the higher toxicity of a unit of particulate mass in Helsinki.

当前，仅对环境空气中的亚2.5μm和亚10μm颗粒（PM _2.5，PM ₁₀）的质量进行严格控制和监视，但PM _2.5的增加量相同会在不同城市造成不同程度的健康影响（在污染较少的城市中，每单位质量的有害影响有时会更大）（Li等人，2019）。除了质量浓度以外，还需要其他测量指标来连接颗粒物污染数据和健康影响。在芬兰赫尔辛基（一个相对干净的城市）和印度德里国家首都辖区（德里-NCR）（一个污染区域）的交通影响环境中进行的测量中，我们注意到肺沉积表面积（LDSA）。在赫尔辛基，中位粒径为80 nm，与柴油机排放的烟尘颗粒相对应。但是，在空气质量的长距离传输过程中，中值尺寸增加到了190 nm。令人惊讶的是，在德里NCR，中位尺寸甚至更大，为410 nm。这些较大的粒子很可能来自区域性来源，而不是本地流量。LDSA到PM赫尔辛基_2.5的颗粒比是德里NCR的2-4倍，这可能与赫尔辛基每单位颗粒质量的较高毒性有关。