Harmful impact of air pollution on severe acute exacerbation of chronic obstructive pulmonary disease: particulate matter is hazardous

Figures & data

Table 1 Comprehensive Air-quality Index (CAI)

Category	Description	Values	Health effects
A	Good	0–50	A level that will not impact patients suffering from diseases related to air pollution
B	Moderate	51–100	A level that may have minimal impact on patients in cases of chronic exposure
C	Unhealthy	101–250	A level that may have harmful impacts on patients and members of sensitive groups, and that may also cause the general public unpleasant side effects
D	Very unhealthy	251–500	A level that may require emergency measures for patients and members of sensitive groups, and that may have harmful impacts on the general public

Table 2 The relationship between CAI value and air pollutants

Category	A	B	C	D
Description	Good	Moderate	Unhealthy	Very unhealthy
Values	0–50	51–100	101–250	251–500
PM10 (µg/m^3)	0–30	31–80	81–150	151–600
PM2.5 (µg/m^3)	0–15	16–50	51–100	101–500
O3 (ppm)	0–0.030	0.031–0.090	0.091–0.150	0.150–0.600
NO2 (ppm)	0–0.030	0.031–0.060	0.061–0.200	0.201–2
SO2 (ppm)	0–0.020	0.021–0.050	0.051–0.150	0.151–1
CO (ppm)	0–2	2.01–9	9.01–15	15.01–50

Abbreviations: CAI, Comprehensive Air-quality Index; PM₁₀, particulate matter with a diameter of less than 10 µm; PM_2.5, particulate matter with a diameter of less than 2.5 µm; O₃, ozone; NO₂, nitrogen dioxide; SO₂, sulfur dioxide; CO, carbon monoxide.

Table 3 Monthly average data related to air pollutants

	CAI	PM10 (µg/m^3)	PM2.5 (µg/m^3)	O3 (ppm)	NO2 (ppm)	SO2 (ppm)	CO (ppm)	Temperature (°C)	Humidity (%)
Jan	77.1±29.3	50.2±18.9	27.4±11.7	0.012±0.006	0.031±0.011	0.006±0.001	0.7±0.2	−2.0±4.2	54.7±12.4
Feb	81.5±45.0	56.2±41.6	26.3±10.7	0.016±0.006	0.030±0.010	0.007±0.002	0.6±0.2	0.4±3.6	54.9±13.5
Mar	101.2±50.2	67.6±28.2	32.4±12.4	0.024±0.007	0.031±0.011	0.007±0.002	0.6±0.2	6.7±4.0	47.9±11.9
Apr	88.3±34.8	61.3±26.4	26.3±10.0	0.031±0.010	0.027±0.008	0.006±0.002	0.6±0.1	14.0±2.8	53.8±16.5
May	85.8±41.3	57.8±27.3	25.8±10.7	0.038±0.008	0.023±0.007	0.007±0.001	0.5±0.1	19.3±2.7	53.7±14.6
Jun	70.9±10.6	42.1±13.6	25.8±8.7	0.039±0.007	0.023±0.006	0.006±0.001	0.4±0.1	22.5±23.6	61.3±11.5
Jul	66.8±17.9	32.5±14.8	21.3±10.2	0.034±0.015	0.020±0.006	0.005±0.001	0.4±0.1	23.9±26.0	72.0±11.3
Aug	62.1±16.2	37.4±15.1	24.0±11.2	0.034±0.011	0.020±0.007	0.006±0.001	0.4±0.1	28.3±27.1	66.8±6.7
Sep	63.3±13.8	35.3±13.9	20.2±9.4	0.028±0.008	0.024±0.009	0.005±0.001	0.4±0.1	24.6±22.7	60.4±10.8
Oct	58.1±37.9	44.4±23.4	22.8±15.1	0.019±0.006	0.028±0.011	0.006±0.001	0.5±0.2	18.7±15.8	61.3±11.4
Nov	79.1±26.0	44.2±20.1	24.3±12.4	0.012±0.007	0.029±0.009	0.006±0.001	0.6±0.2	4.3±7.8	65.0±12.6
Dec	70.0±27.8	48.0±16.5	28.5±11.8	0.009±0.006	0.032±0.009	0.006±0.001	0.7±0.2	4.1±1.4	59.5±12.4

Notes: The average from January to May is from 2015 to 2017; the average from June to December is from 2015 to 2016. Numbers are presented as mean ± SD.

Abbreviations: CAI, Comprehensive Air-quality Index; PM₁₀, particulate matter with a diameter of less than 10 µm; PM_2.5, particulate matter with a diameter of less than 2.5 µm; O₃, ozone; NO₂, nitrogen dioxide; SO₂, sulfur dioxide; CO, carbon monoxide.

Figure 1 Monthly average data related to air pollutants and number of inpatients per day. (A) Monthly average CAI, PM₁₀, and PM_2.5. (B) Monthly average humidity and temperature. (C) Monthly average number of inpatients (patients admitted to hospital for AECOPD) per day.

Notes: The average from January to May is from 2015 to 2017; the average from June to December is from 2015 to 2016.
Abbreviations: CAI, Comprehensive Air-quality Index; PM₁₀, particulate matter with a diameter of less than 10 µm; PM_2.5, particulate matter with a diameter of less than 2.5 µm.

Table 4 The association between CAI and severe AECOPD events

CAI category	A	B	C	D	Total
CAI description	Good	Moderate	Unhealthy	Very unhealthy
Total number of days	94	696	82	10	882
Total number of inpatients (cases)	24	311	33	6	374
Average number of inpatients per day (cases/day)	0.26	0.45	0.40	0.60

Abbreviations: CAI, Comprehensive Air-quality Index; AECOPD, acute exacerbations of chronic obstructive pulmonary disease.

Table 5 Risk of severe AECOPD events with cutoff values of CAI 50 and 100

Cutoff value	Factors	RR	95% CI	P-value
CAI 50	CAI≤50	1
	CAI>50	1.612	1.065–2.440	0.024
	Temperature (°C)	0.989	0.979–0.999	0.034
	Humidity (%)	0.994	0.986–1.001	0.110
CAI 100	CAI≤100	1
	CAI>100	1.025	0.736–1.429	0.882
	Temperature (°C)	0.989	0.979–0.999	0.033
	Humidity (%)	0.993	0.986–1.001	0.074

Abbreviations: AECOPD, acute exacerbations of chronic obstructive pulmonary disease; CAI, Comprehensive Air-quality Index; RR, adjusted relative risk.

Figure 2 Association of PM₁₀, CAI and severe AECOPD events after adjustment for humidity and temperature. (A) The association of PM₁₀ and severe AECOPD events. (B) The association of CAI and severe AECOPD events.

Abbreviations: PM₁₀, particulate matter with a diameter of less than 10 µm; CAI, Comprehensive Air-quality Index; AECOPD, acute exacerbations of chronic obstructive pulmonary disease.