Association between air pollution in the 2015 winter in South Korea and population size, car emissions, industrial activity, and fossil-fuel power plants: an ecological study

Table 2 Number of days the particulate matter 10 (PM₁₀) and carbon monoxide (CO) levels in the winter of 2015 exceeded government thresholds

	CO (days)			PM₁₀ (days)
	Mean ± SD	Min.	Max.	Mean ± SD	Min.	Max.
Population density (persons/km²)^a
Q1 (lowest)	8.3 ± 14.3	0	54	1.4 ± 1.2	0	4
Q2	28.4 ± 24.4	1	81	4.1 ± 4.7	0	23
Q3	41.8 ± 19.0	0	79	5.4 ± 5.3	0	21
Q4 (highest)	30.5 ± 21.1	0	66	2.2 ± 2.9	0	12
No. of car registrations^b
Q1 (lowest)	7.5 ± 13.9	0	54	2.0 ± 2.6	0	10
Q2	26.5 ± 24.1	0	77	3.0 ± 3.7	0	16
Q3	29.0 ± 19.3	0	72	2.9 ± 4.0	0	23
Q4 (highest)	43.2 ± 20.0	0	81	5.0 ± 5.2	0	21
No. of car accident^c
Q1 (lowest)	9.9 ± 14.6	0	54	2.1 ± 2.6	0	10
Q2	21.9 ± 23.0	0	77	2.1 ± 2.6	0	12
Q3	31.2 ± 19.6	0	72	3.6 ± 4.4	0	23
Q4 (highest)	43.0 ± 20.4	0	81	4.8 ± 5.2	0	21
Industrial power usage (Kwh/km²)^d
Q1 (lowest)	9.8 ± 13.8	0	46	1.6 ± 1.5	0	4
Q2	28.2 ± 26.5	0	81	4.2 ± 4.9	0	23
Q3	38.4 ± 18.6	1	78	5.0 ± 5.1	0	21
Q4 (highest)	33.8 ± 22.2	0	79	2.6 ± 3.7	0	16
Generation of electricity (Kwh)
No	27.0 ± 22.8	0	77	2.3 ± 2.8	0	14
Yes	37.1 ± 21.2	0	81	5.1 ± 5.4	0	23

^apopulation density(persons/km²): Q1 < 98.87, 98.87 ≤ Q2 < 459.19, 459.19 ≤ Q3 < 6329.12, 6329.12 ≤ Q4
^bNo. of car registrations(1000 cars): Q1 < 16.43, 16.43 ≤ Q2 < 48.90, 48.90 ≤ Q3 < 98.36, 98.36 ≤ Q4
^cNo. of car accident: Q1 < 213.00, 213.00 ≤ Q2 < 729.00, 729.00 ≤ Q3 < 1521.00, 1521.00 ≤ Q4
^dIndustrial power usage (Kwh/km²): Q1 < 300,926.80, 300,926.80 ≤ Q2 < 1,588,265.70, 1,588,265.70 ≤ Q3 < 8,306,667.40, 8,306,667.40 ≤ Q4

ISSN: 2052-4374