Table 1.

Iranian values of the constructed proxies for PM_2.5 pollution (X) and the health impact (Y) on COVID-19, and both cross-correlation and Granger causality summaries identifying significant causal relationships between X→Y. Significance level **p < 0.05.

X	Y	lag	ρ(Y [t], X [t + lag])
25	65	−4	−0.12
23.7	140	−3	0.10
26.3	74	−2	0.53
31.5	98	−1	0.71**
31.4	199	0	0.51
29.8	223	1	0.16
30.3	159	2	0.04
30.1	262	3	−0.27
Granger-Causal		Y = f(X)	X = f(Y)
F		8.33	0.04
P		0.04	0.86