Short-term exposure to ambient air pollution and pneumonia hospital admission among patients with COPD: a time-stratified case-crossover study

Table 2 Distribution of air pollutants and meteorological conditions on case days in Guangdong, China during 2016–2019

Variable	Mean	SD	P₅	P₂₅	Median	P₇₅	P₉₅	IQR
Air pollutant
PM_2.5, μg/m³	32.1	17.9	11.5	19.2	28.0	40.9	65.2	21.7
PM₁₀, μg/m³	53.8	27.3	21.5	34.1	46.9	68.0	108.1	33.9
SO₂, μg/m³	8.2	3.7	4.1	5.4	7.3	9.9	15.2	4.5
NO₂, μg/m³	46.5	21.0	19.4	32.7	42.4	55.9	86.4	23.2
CO, mg/m³	0.85	0.23	0.55	0.70	0.80	0.95	1.27	0.26
O₃, μg/m³	94.9	50.5	20.7	58.4	89.0	125.8	190.3	67.4
Meteorological condition
Temperature, °C	23.8	5.4	14.4	19.8	24.3	28.3	31.2	8.5
Relative humidity, %	76.6	13.2	50.1	69.4	80.3	86.7	91.8	17.2

SD standardized deviation, P₅ the 5th percentile, P₂₅ the 25th percentile, P₇₅ the 75th percentile, P₉₅ the 95th percentile, IQR interquartile range, PM_2.5 particulate matter with an aerodynamic diameter ≤ 2.5 µm, PM₁₀ particulate matter with an aerodynamic diameter ≤ 10 µm, SO₂ sulfur dioxide, NO₂ nitrogen dioxide, CO carbon monoxide, O₃ ozone

ISSN: 1465-993X