Table 2.

Pearson's correlation coefficients among environmental variables, Hong Kong 1997–2002

	Temperature	Humidity	Rainfall	PM10	PM2.5	SO2	NO2
Whole year
Humidity (%)	0.22
Rainfall (mm)	0.12	0.35
PM10 (μg/m3)	−0.33	−0.48	−0.27
PM2.5 (μg/m3)	−0.21	−0.35	−0.24	0.90
SO2 (μg/m3)	0.13	−0.15	−0.09	0.37	0.47
NO2 (μg/m3)	−0.38	−0.37	−0.20	0.78	0.75	0.49
O3 (μg/m3)	−0.09	−0.40	−0.20	0.48	0.36	−0.17	0.35
Cold season (October–March)
Humidity (%)	0.15
Rainfall (mm)	0.03	0.27
PM10 (μg/m3)	0.01	−0.44	−0.24
PM2.5 (μg/m3)	0.05	−0.29	−0.21	0.90
SO2 (μg/m3)	0.01	−0.18	−0.12	0.53	0.59
NO2 (μg/m3)	0.00	−0.33	−0.18	0.69	0.70	0.69
O3 (μg/m3)	0.27	−0.36	−0.15	0.33	0.21	−0.24	0.08
Warm season (April–September)
Humidity (%)	−0.32
Rainfall (mm)	−0.16	0.46
PM10 (μg/m3)	−0.18	−0.38	−0.23
PM2.5 (μg/m3)	−0.03	−0.28	−0.21	0.89
SO2 (μg/m3)	0.23	−0.21	−0.13	0.39	0.48
NO2 (μg/m3)	−0.31	−0.25	−0.12	0.80	0.74	0.51
O3 (μg/m3)	−0.30	−0.43	−0.20	0.60	0.47	−0.11	0.52

PM₁₀, aerodynamic diameter <10 μm; PM_2.5, aerodynamic diameter <2.5 μm; SO₂, sulphur dioxide; NO₂, nitrogen dioxide; O₃, ozone.