<p>The Air Quality Index (AQI) in Delhi becomes a much discussed issue every Diwali when levels of pollutants in the air skyrocket.</p>.<p>But what is the AQI and how is it calculated?</p>.<p>The AQI was introduced in 2015, and since then, has been constantly used as an indicator of air quality, and by extension, air pollution in India.</p>.<p><strong>What is the AQI?</strong></p>.<p>A single composite index, the AQI helps communicate the severity of air pollution that is measured by recording the levels of multiple pollutants in the air.</p>.<p>Eight individual pollutants are monitored for the calculation of AQI, namely, PM10, PM2.5, nitrogen dioxide, sulphur dioxide, carbon monoxide, ground-level ozone, ammonia, and lead.</p>.<p><strong>How is AQI calculated?</strong></p>.<p>The sub-indices for the aforementioned individual pollutants at a particular monitoring station are calculated using their average concentration value over a 24-hour period (8 hours in case of carbon monoxide and ozone) and their health breakpoint concentration range.</p>.<p>The worst sub-index value is taken to be the AQI for that particular location.</p>.<p><strong>Infographic | <a href="https://www.deccanherald.com/national/north-and-central/infographic-delhis-aqi-on-diwali-since-2015-1156370.html" target="_blank">Delhi's AQI on Diwali since 2015</a></strong></p>.<p>However, in some cases, all eight pollutants may not be monitored at a particular location.</p>.<p>In such cases, AQI is only calculated if data is available for at least three of the eight aforementioned pollutants, with at least one of those three being PM2.5 or PM10. Further, a minimum of 16 hours' data is deemed necessary for the calculation of the values of sub-indices.</p>.<p>If the aforementioned criteria cannot be met, data is considered insufficient for the calculation of AQI.</p>.<p><strong>AQI ranges:</strong></p>.<p>AQI values within certain ranges are categorised by their impact on health.</p>.<p>An AQI value of 0-50 is considered 'good', while a value between 51-100 is considered 'satisfactory'. A value between 101-200 is considered 'moderate', 201-300 is considered 'poor', 301-400 is considered 'very poor', and 401-500 is considered 'severe'.</p>.<p>These labels — from 'good' to 'severe' — correspond to the health effects of air pollution.</p>.<p>'Good' AQI has minimal impact on health, while 'satisfactory' AQI causes minor breathing discomfort to sensitive people. 'Moderate', meanwhile, causes breathing discomfort to people afflicted by lung and heart diseases, as well as people with asthma. 'Poor' AQI casues breathing discomfort to most people if they are exposed to the polluted air for long enough. 'Very poor' air quality may cause respiratory illnesses among people on prolonged exposure, while 'severe' air quality affects healthy people and causes considerable harm to those having extant health problems.</p>
<p>The Air Quality Index (AQI) in Delhi becomes a much discussed issue every Diwali when levels of pollutants in the air skyrocket.</p>.<p>But what is the AQI and how is it calculated?</p>.<p>The AQI was introduced in 2015, and since then, has been constantly used as an indicator of air quality, and by extension, air pollution in India.</p>.<p><strong>What is the AQI?</strong></p>.<p>A single composite index, the AQI helps communicate the severity of air pollution that is measured by recording the levels of multiple pollutants in the air.</p>.<p>Eight individual pollutants are monitored for the calculation of AQI, namely, PM10, PM2.5, nitrogen dioxide, sulphur dioxide, carbon monoxide, ground-level ozone, ammonia, and lead.</p>.<p><strong>How is AQI calculated?</strong></p>.<p>The sub-indices for the aforementioned individual pollutants at a particular monitoring station are calculated using their average concentration value over a 24-hour period (8 hours in case of carbon monoxide and ozone) and their health breakpoint concentration range.</p>.<p>The worst sub-index value is taken to be the AQI for that particular location.</p>.<p><strong>Infographic | <a href="https://www.deccanherald.com/national/north-and-central/infographic-delhis-aqi-on-diwali-since-2015-1156370.html" target="_blank">Delhi's AQI on Diwali since 2015</a></strong></p>.<p>However, in some cases, all eight pollutants may not be monitored at a particular location.</p>.<p>In such cases, AQI is only calculated if data is available for at least three of the eight aforementioned pollutants, with at least one of those three being PM2.5 or PM10. Further, a minimum of 16 hours' data is deemed necessary for the calculation of the values of sub-indices.</p>.<p>If the aforementioned criteria cannot be met, data is considered insufficient for the calculation of AQI.</p>.<p><strong>AQI ranges:</strong></p>.<p>AQI values within certain ranges are categorised by their impact on health.</p>.<p>An AQI value of 0-50 is considered 'good', while a value between 51-100 is considered 'satisfactory'. A value between 101-200 is considered 'moderate', 201-300 is considered 'poor', 301-400 is considered 'very poor', and 401-500 is considered 'severe'.</p>.<p>These labels — from 'good' to 'severe' — correspond to the health effects of air pollution.</p>.<p>'Good' AQI has minimal impact on health, while 'satisfactory' AQI causes minor breathing discomfort to sensitive people. 'Moderate', meanwhile, causes breathing discomfort to people afflicted by lung and heart diseases, as well as people with asthma. 'Poor' AQI casues breathing discomfort to most people if they are exposed to the polluted air for long enough. 'Very poor' air quality may cause respiratory illnesses among people on prolonged exposure, while 'severe' air quality affects healthy people and causes considerable harm to those having extant health problems.</p>