Considerable changes in particulate matter (PM) during COVID-19 lockdown in major cities around the World demand changes in exposure assessment studies of PM. The present study shows variations in respiratory deposition dose (RDD) of both fine (PM_2.5) and coarse (PM₁₀) particles before, during and after Covid-19 lockdown phases at three sites (with different pollution signatures) in Delhi—Alipur, Okhla and Pusa Road. Exposure assessment study showed mean PM_2.5 RDD (± S.D.) (µg/min) for walk and sit mode during before lockdown (BL) as 2.41(± 1.20) and 0.84(± 0.42) for Alipur, 2.71(± 1.60) and 0.94(± 0.56) for Okhla, and 2.54(± 1.28) and 0.88(± 0.44) for Pusa road, which decreased drastically during Lockdown 1(L1) as 0.85(± 0.35) and 0.30(± 0.12) for Alipur, 0.83(± 0.33) and 0.29(± 0.11) for Okhla, and 0.68(± 0.28) and 0.23(± 0.10) for Pusa road, respectively. Mean PM₁₀ RDD (± S.D.) (µg/min) for walk and sit mode during before lockdown (BL) as 3.90 (± 1.73) and 1.36 (± 0.60) for Alipur, 4.74 (± 2.04) and 1.65 (± 0.71) for Okhla, and 4.25 (± 1.69) and 1.48 (± 0.59) for Pusa Road, respectively which decreased drastically during Lockdown 1(L1) as 2.19 (± 0.95) and 0.76 (± 0.33) for Alipur, 1.73 (± 0.67) and 0.60 (± 0.23) for Okhla and, 1.45 (± 0.50) and 0.50 (± 0.17) for Pusa Road, respectively. Significant decrease in RDD concentrations (Both PM_2.5 and PM₁₀) than that of BL phase have been found during Lockdown 1(L1) phase and other successive lockdown and unlock phases—Lockdown 2(L2), Lockdown 3(L3), Lockdown 4(L4) and Unlock1 (UL1) phases. Changes in RDD values during lockdown phases were affected by lesser traffic emission, minimized industrial activities, biomass burning activities, precipitation activities, etc. Seasonal variations of RDD showed Delhites are found exposed to more fine and coarse particles’ RDD (walk and sit modes) before and after lockdown, i.e. during normal days than during lockdown phases showing potential health effects. People in sit condition found less exposed to fine and coarse RDD comparison to those in walk condition both during normal and lockdown days.

在全球主要城市的 COVID-19 封锁期间，颗粒物 (PM) 的显着变化要求对 PM 的暴露评估研究进行改变。本研究显示了在德里的三个地点（具有不同的污染特征）的 Covid-19 锁定阶段之前、期间和之后，细颗粒 (PM _2.5 ) 和粗颗​​粒 (PM ₁₀ ) 的呼吸沉积剂量 (RDD) 的变化 — Alipur， Okhla 和 Pusa 路。暴露评估研究显示平均 PM _2.5锁定前 (BL) 期间步行和坐着模式的 RDD (± SD) (µg/min) 为 Alipur 的 2.41(± 1.20) 和 0.84(± 0.42)，Okhla 的 2.71(± 1.60) 和 0.94(± 0.56)， Pusa 路分别为 2.54（± 1.28）和 0.88（± 0.44），在封锁 1（L1）期间急剧下降，Alipur 分别为 0.85（± 0.35）和 0.30（± 0.12），0.83（± 0.33）和 0.29（± 0.11） ) 对于 Okhla，分别为 0.68(± 0.28) 和 0.23(± 0.10) 对于 Pusa 路。平均 PM ₁₀锁定前 (BL) 期间步行和坐着模式的 RDD (± SD) (µg/min) 为 Alipur 的 3.90 (± 1.73) 和 1.36 (± 0.60)，Okhla 的 4.74 (± 2.04) 和 1.65 (± 0.71)， Pusa Road 和 4.25 (± 1.69) 和 1.48 (± 0.59)，在封锁 1(L1) 期间急剧下降，Alipur 分别为 2.19 (± 0.95) 和 0.76 (± 0.33)，1.73 (± 0.67) 和 0.60 (± Okhla 为 0.23)，Pusa Road 为 1.45 (± 0.50) 和 0.50 (± 0.17)。RDD 浓度显着下降（PM _2.5和 PM ₁₀) 在 Lockdown 1(L1) 阶段和其他连续的锁定和解锁阶段——Lockdown 2(L2)、Lockdown 3(L3)、Lockdown 4(L4) 和 Unlock1 (UL1) 阶段发现。封锁阶段 RDD 值的变化受到交通排放减少、工业活动最小化、生物质燃烧活动、降水活动等的影响。RDD 的季节性变化表明德里人暴露于更细颗粒和粗颗粒的 RDD（步行和坐着模式）锁定之前和之后，即在正常的日子里，而不是在显示潜在健康影响的锁定阶段。与正常和禁闭期间步行条件下的人相比，坐姿条件下的人发现较少接触精细和粗略的 RDD。