Table 2.

NO2, PM2.5, and PM10 concentration (μg/m3) during the study period (1 February to 11 May) in 2019 and.

	NO2 (μg/m3)			PM10 (μg/m3)			PM2.5 (μg/m3)
	2019	2020	Δ NO2 (%)	2019	2020	Δ PM10 (%)	2019	2020	Δ PM25 (%)
Antwerpen	33.83	22.76	−32.72	31.76	25.40	−20.02	18.96	12.81	−32.44
Barcelona	35.77	22.71	−36.50	24.23	19.74	−18.52	–	–	–
Brussels	31.04	18.32	−40.98	20.73	15.69	−24.28	14.48	9.36	−35.32
Chicago	52.35	46.56	−11.08	25.73	20.99	−18.42	9.21	8.56	−7.03
Denver	60.18	53.41	−11.26	27.48	20.91	−23.92	8.44	6.35	−24.81
Detroit	50.68	40.54	−20.01	17.93	16.06	−10.44	9.18	8.15	−11.22
Frankfurt	28.37	22.14	−21.95	20.84	14.86	−28.71	13.55	9.47	−30.10
London	41.83	25.39	−39.31	25.40	16.33	−35.73	15.58	9.88	−36.56
Los Angeles	48.81	48.73	−0.16	18.55	21.28	14.70	7.42	8.46	13.98
Madrid	35.69	24.16	−32.32	16.78	14.95	−10.88	9.00	8.69	−3.40
Milan	44.14	34.45	−21.96	31.44	31.79	1.13	21.21	22.61	6.57
New York	50.98	43.94	−13.80	–	–	–	7.44	6.30	−15.33
Paris	44.16	26.25	−40.55	25.03	18.17	−27.40	16.87	13.07	−22.55
Philadelphia	42.35	43.67	3.11	17.34	14.84	−14.40	7.99	7.76	−2.96
Rotterdam	31.96	21.20	−33.66	23.73	18.33	−22.78	13.61	8.71	−36.01
Utrecht	24.29	17.06	−29.77	21.18	17.11	−19.21	13.98	9.79	−29.95