Table 4.

Deaths attributable to ${\mathrm{PM}}_{2.5}$ and ${\mathrm{NO}}_2$ concentrations above predefined thresholds^a: results from both single-pollutant and two-pollutant models. Each cell reports attributable cases and 95% confidence interval. Italy, 20 February 2020–15 June 2021 ($n=\mathrm{3,995,202}$ COVID-19 cases, $n=\mathrm{124,346}$ deaths).

${\mathrm{PM}}_{2.5}$ thresholds	${\mathrm{NO}}_2$ thresholds				Single pollutant ${\mathrm{PM}}_{2.5}$: Deaths (95% CI)
	10: Deaths (95% CI)	20: Deaths (95% CI)	30: Deaths (95% CI)	40: Deaths (95% CI)
5	9,163 (394; 17,182)	2,121 ($-\mathrm{3,840}$; 7,616)	186 ($-\mathrm{1,984}$; 2,187)	$-131$ ($-832$; 512)	10,514 (7,007; 13,902)
10	10,762 (4,338; 16,728)	3,278 ($-\mathrm{1,017}$; 7,304)	612 ($-946$; 2,072)	$-15$ ($-544$; 481)	6,513 (4,321; 8,650)
15	9,235 (5,391; 12,838)	3,598 (999; 6,065)	917 ($-43$; 1,830)	100 ($-267$; 450)	3,080 (2,036; 4,105)
20	6,963 (4,907; 8,908)	3,349 (2,015; 4,628)	1,053 (522; 1,565)	213 (2, 418)	1,023 (673; 1,370)
25	594 (462, 720)	319 (242, 394)	100 (76, 124)	17 (13, 21)	14 (9, 19)
Single pollutant ${\mathrm{NO}}_2$	10,155 (8,295; 11,973)	4,187 (3,410; 4,951)	1,136 (924; 1,346)	239 (194, 285)	—

Note: Results of main model 6, adjusted for interactions between year and month, province, age classes, sex, and ventiles of the generalized propensity score. —, no data; AQG, air quality guidelines; CI, confidence interval; ${\mathrm{NO}}_2$, 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; WHO, World Health Organization.

^a WHO 2021 AQG levels: $5{\mathrm{\mu }\mathrm{g}/\mathrm{m}}^3$ for ${\mathrm{PM}}_{2.5}$, $10{\mathrm{\mu }\mathrm{g}/\mathrm{m}}^3$ for ${\mathrm{NO}}_2$; WHO 2005 AQG levels: $10{\mathrm{\mu }\mathrm{g}/\mathrm{m}}^3$ for ${\mathrm{PM}}_{2.5}$, $40{\mathrm{\mu }\mathrm{g}/\mathrm{m}}^3$ for ${\mathrm{NO}}_2$; EU (European Union) air quality standards: $25{\mathrm{\mu }\mathrm{g}/\mathrm{m}}^3$ for ${\mathrm{PM}}_{2.5}$, $40{\mathrm{\mu }\mathrm{g}/\mathrm{m}}^3$ for ${\mathrm{NO}}_2$.