Table 2.

Air quality index categorization for PM_2.5 polluants (μgm⁻³).

AQI	Concentration divisions of PM2.5 polluants (μgm−3)	∗Risk analysis (AQI)
0–50	0.0–12	Good
50–100	12.1–35.4	Marginal (moderate)
101–150	35.5–55.4	Unhealthy for sensitive group
151–200	55.5–150.4	Poor (unhealthy)
201–300	150.5–250.4	Very poor (very unhealthy)
301–400	250.5–350.4	Hazardous
401–500	350.5–500	Very hazardous
>500	>500	Very critical

US EPA, 2012a, US-EPA, 2012b.