Table 3.

Effect of air pollutants on mortality by pandemic wave, individual-level covariates, and geographical area: percent increase in mortality risk (%IR), and 95% CI, per $1\text{-}{\mathrm{\mu }\mathrm{g}/\mathrm{m}}^3$ increment in air pollutants. Italy, 20 February 2020–15 June 2021 ($n=\mathrm{3,995,202}$ COVID-19 cases, $n=\mathrm{124,346}$ deaths).

	$n$	${\mathrm{PM}}_{2.5}$ %IR (95% CI)	${\mathrm{PM}}_{10}$ %IR (95% CI)	${\mathrm{NO}}_2$ %IR (95% CI)
All	3,995,202	0.7 (0.5, 0.9)	0.3 (0.2, 0.5)	0.6 (0.5, 0.8)
Wave
1st	201,210	1.1 (0.5, 1.6)	0.7 (0.4, 1.0)	0.7 (0.4, 1.0)
2nd	1,534,950	0.1 ($-0.4$, 0.5)	0.1 ($-0.2$, 0.4)	0.6 (0.4, 0.8)
3rd	2,259,042	0.9 (0.6, 1.3)	0.3 (0.0, 0.5)	0.7 (0.5, 0.8)
Age (y)
0–64	3,173,243	$-0.7$ ($-1.1$, $-0.2$)	$-0.5$ ($-0.7$, $-0.2$)	0.3 (0.1, 0.5)
65–74	369,907	$-0.2$ ($-0.9$, 0.5)	0.0 ($-0.5$, 0.5)	0.3 (0.0, 0.7)
75–84	282,527	1.0 (0.3, 1.6)	0.5 (0.0, 0.9)	0.9 (0.5, 1.2)
$85+$	169,525	1.7 (1.0, 2.5)	0.8 (0.4, 1.3)	0.8 (0.4, 1.1)
Sex
Female	2,021,052	0.9 (0.5, 1.2)	0.4 (0.2, 0.6)	0.6 (0.4, 0.7)
Male	1,974,150	0.6 (0.2, 0.9)	0.3 (0.1, 0.5)	0.7 (0.5, 0.9)
Clinical state at onset
Symptomatic	2,254,944	0.9 (0.6, 1.1)	0.4 (0.3, 0.6)	0.6 (0.4, 0.7)
Geographical area
Po Valley	1,888,148	0.5 (0.2, 0.8)	0.2 (0.1, 0.4)	0.3 (0.1, 0.4)

Note: Results of main model 6, adjusted for interactions between year and month, province, age classes, sex and ventiles of the generalized propensity score. Pandemic waves are defined as first: 20 February 2020–31 May 2020; second: 15 September 2020–15 December 2020; third: 16 December 2020–15/06/2021. CI, confidence interval; IR, increase of risk; ${\mathrm{NO}}_2$, nitrogen dioxide; ${\mathrm{PM}}_{2.5}$, particulate matter with aerodynamic diameter $\le 2.5$ micrometers; ${\mathrm{PM}}_{10}$, particulate matter with aerodynamic diameter $\le 10$ micrometers.