Question

1. Synthesis question: To simplify the presentation of air-quality data to the general public, many governments have created an air-quality index that summarizes with a simple number how clean or dirty the air is. For your national government (or for the USA if your own government doesn’t have one), search the web for info about the air-quality index. How is it defined in terms of concentrations of different pollutants? How do you interpret the index value in terms of visibility and/or health hazards?

Answer 1

Solution –

Air quality indexes

Air quality indexes are a measure of how polluted the air in that particular area is. They measure different substances and their concentrations.

They help in predicting the future pollutions and can help us to take the proper measures to counter them.

They also shows the related health hazards that are accompanying the pollution and warnings related to them. E.g., If the pollution level is dangerously high then patients with breathing or lung problems should stay home and avoid outdoor activities.

One such country is India. They have published air quality indexes in September 2014 under swachh bharat abhiyan.

They mainly measure the following 8 parameters to assess the air quality.

• Particulate matter 10 (PM₁₀)
• Particulate matter 2.5 (PM_2.5)
• Nitrogen dioxide (NO₂)
• Sulphur dioxide (SO₂)
• Carbon monoxide (CO)
• Ozone (O₃)
• Ammonia (NH₃)
• Lead (Pb)

After monitoring the above parameters, the air quality is categorised under 6 major categories (0 to 500)

• Good (0 – 50) – Minimal impact
• Satisfactory (51 – 100) – Minor breathing discomfort to sensitive people.
• Moderately Polluted (101 – 200) – Breathing discomfort to people with asthma or lung disease.
• Poor (201 – 300) – May cause illness by long exposures.
• Very poor (301 - 400) - May cause illness by long exposures, effect more severe in children and senior citizens.
• Severe (401 - 500) – Serious impact on health of even healthy persons.

Under each category, the following concentration of substances

AQI Category (Range)	PM10 (24hr)	PM2.5 (24hr)	NO2 (24hr)	O3 (8hr)	CO (8hr)	SO2 (24hr)	NH3 (24hr)	Pb (24hr)
Good (0–50)	0–50	0–30	0–40	0–50	0–1.0	0–40	0–200	0–0.5
Satisfactory (51–100)	51–100	31–60	41–80	51–100	1.1–2.0	41–80	201–400	0.5–1.0
Moderately polluted (101–200)	101–250	61–90	81–180	101–168	2.1–10	81–380	401–800	1.1–2.0
Poor (201–300)	251–350	91–120	181–280	169–208	10–17	381–800	801–1200	2.1–3.0
Very poor (301–400)	351–430	121–250	281–400	209–748	17–34	801–1600	1200–1800	3.1–3.5
Severe (401–500)	430+	250+	400+	748+	34+	1600+	1800+	3.5+