Table 3

 Distribution of total hours in the SPM categories

Length of exposure window (hours)Total hours in an SPM category (μg/m3)Hours that multiple SPM categories overlap*
0–99100–149150–199200–249250–299300–
Numbers in parentheses in each row show the percentages. *When periods were being classified into several SPM categories, and some of them overlapped, the higher one was selected.
11317039 (88.4)115448 (7.7)37703 (2.5)12897 (0.9)4830 (0.3)2099 (0.1)0 (0.0)
31239769 (83.2)160574 (10.8)56640 (3.8)20748 (1.4)8167 (0.5)4118 (0.3)63840 (4.3)
61154252 (77.5)208383 (14.0)77964 (5.2)30126 (2.0)12439 (0.8)6852 (0.5)110805 (7.4)
121021905 (68.6)277560 (18.6)111977 (7.5)46203 (3.1)20306 (1.4)12065 (0.8)173402 (11.6)
24842728 (56.6)361419 (24.3)161262 (10.8)70105 (4.7)33019 (2.2)21483 (1.4)268651 (18.0)
48619841 (41.6)447587 (30.0)227539 (15.3)105883 (7.1)52020 (3.5)37146 (2.5)409703 (27.5)