Understanding Air Quality Index (AQI)

Air pollution, although is harmful for everyone, can be dangerous for people with chronic lung problems and allergies like asthma, patients with heart problems, elderly people and children. Air pollution leads to respiratory and cardiovascular diseases, reproductive and central nervous system dysfunctions, and also cancer. The Air Quality Index or commonly known as “AQI” is an index for reporting air quality on a daily basis. The purpose of the Air Quality Index (AQI) is to let the general people easily understand the local quality of air and its impact on their health.

How does the Air Quality Index (AQI) work?
The Air Quality Index (AQI) is a yardstick that starts from 0 to 500. The higher the Air Quality Index (AQI), the more polluted is the air and more is the adverse impact on health. The Environmental Protection Agency (EPA) calculates the Air Quality Index (AQI) for 5 air pollutants which are deemed most important. These air pollutants are ground-level ozone, particle pollution/particulate matter (PM2.5/pm 10), carbon monoxide, sulfur dioxide and nitrogen dioxide. The most dangerous of these air pollutants is PM2.5 which penetrates the respiratory system and leads to systemic problems.

Daily measurements are done for the listed major pollutants and these raw measurements are then converted into a separate Air Quality Index (AQI) for each of these pollutants using a standard formula. The highest of the values of these five air pollutants Air Quality Index (AQI) is reported as the Air Quality Index (AQI) for that day.

What are the categories of Air Quality Index (AQI)?
The Air Quality Index (AQI) is divided into six categories. The six categories are coded with different colours which makes it easier for the general public to quickly understand the Air Quality Index (AQI) levels and the consequent health issues. The categories of the Air Quality Index (AQI) are as mentioned below:

Values of IndexLevel of ConcernDescription of Air Quality
0-50GoodSatisfactory air quality; no risk
51-100ModerateMay cause minor breathing difficulties in sensitive people.
101-150Unhealthy for Sensitive GroupsMay cause respiratory problems in patients with asthma, heart disease, children and older adults.
151-200UnhealthySensitive groups experience serious health effects, although  general public may experience adverse health effects
201-300Very UnhealthyHealth alert with increased risk of adverse health effects for  everyone.
301-500HazardousHazardous air quality with everyone more likely to be affected.

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