*3.7. Pollution Days/Non-Attainment Days*

Any day with one or more pollutants exceeding CAAQS (Grade II) standards is considered as a non-attainment/pollution day. In NWC, the proportion of non-attainment days were 23.3%, 23.9%, 16.2%, and 8.9% during 2015 to 2018, respectively. The proportion of non-attainment days decreased by 61.77% (24%, 47.1%, 79.1%, 77.9%, and 73.9%) in NWC (SN, XJ, GS, NX, and QH) during 2015 to 2018 (Table 1). The highest reduction in the proportion of non-attainment days occurred in spring (79.6%), summer (63.1%), autumn (60.4%), and winter (37.6%), respectively.
