Table 2.

Percentage of the concentration of pollutants and their changing share during lockdown and previous years in Kolkata City

Year	Month	Percentage of the concentration of pollutants and their changing share
		CO (%)	Share of change (%)	NO2 (%)	Share of change (%)	SO2 (%)	Share of change (%)	O3 (%)	Share of change (%)	PM10 (%)	Share of change (%)	PM2.5 (%)	Share of change (%)
2017	March	25.84	–	19.51	–	22.78	–	29.15	–	24.12	–	–	–
	April	27.41	–	32.14	–	24.73	–	34.48	–	29.55	–	–	–
	May	28.26	–	34.2	–	42.92	–	34.05	–	26.27	–	–	–
2018	March	24.31	−1.53	22.9	+ 3.39	21.48	−1.3	16.22	−12.93	26.3	+ 2.18	28.67	−
	April	29.12	+ 1.8	26.7	−5.44	30.86	+ 6.13	24.57	−9.91	24.74	−4.81	33.05	–
	May	34.88	+ 6.62	28.3	−5.9	17.9	−25.02	28.76	−5.29	24.86	−1.41	42.32	–
2019	March	25.73	+ 1.42	40.19	+ 17.29	25.33	+ 3.85	24.52	+ 8.3	29.26	+ 2.96	43.68	+ 15.01
	April	24.91	−4.21	28.17	+ 1.47	26.95	−3.91	15.61	−8.96	28.73	+ 3.99	42.47	+ 9.42
	May	21.87	−13.01	22.78	−5.52	28.58	+ 10.68	16.81	−11.95	34.89	+ 10.03	38.86	−3.46
2020	March	24.12	−1.61	17.4	−22.79	30.41	−5.08	30.11	+ 5.59	20.32	−8.94	27.66	−16.02
	April	18.57	−6.34	12.98	−15.19	17.46	−9.49	25.34	+ 9.73	16.98	−11.75	24.48	−17.99
	May	14.99	−6.88	14.74	−8.04	10.65	−17.93	20.37	+ 3.56	13.98	−20.91	18.82	–20.04