For the month of June we also began monitoring the air quality data from Ahmedabad. It is the home of the Indian Prime Minister and a city whose development progress was held up as an example of what he could achieve for India. We wanted to know how it fared when it came to air quality.
In June, Indian metro cities (excluding Kolkata, for which we’re still waiting for live data, three months after the scheme launched) recorded 29 days where the air quality was found to be Good and 69 days where the air quality was found to be Satisfactory.
After Chennai recorded the most number of days that were classified as Severe in May (although we weren’t entirely convinced by the numbers), Delhi recorded the most days that had a Severe rating in June. Here’s how the air quality broke down for the six cities in June:
Bangalore and Hyderabad both topped the list when it came to the most number of days with Good air quality.
Missing Data Days
After the National Air Quality Index was unable to provide data on 27 out of 155 days in May, we hoped that they would turn things around and start providing accurate data on all days for all cities.
This month, there were 17 out of 180 days that were missing data, so it would appear that things are getting more reliable. We’ll have to wait until next month to see if this trend continues.
Where Chennai was much improved, recording just two missing data days compared to 14 in May, Bangalore continued its poor record with 13 missing data days.
Air Quality Over Time
Delhi saw a large rise in pollution towards the end of June after PM2.5 levels spiked and hit a maximum index of 500 (the index does not give readings beyond 500). There didn’t seem to be any reason for the pollution to get twice as bad and we don’t have full confidence in the numbers being reported – we believe it should be lower.
Not that the gaps in the lines are when data is missing for these days.
US Consulate Air Quality Readings of Indian Cities
The most reliable and up to date air quality information for Indian cities comes from the US Consulate website. The US has consulates in Delhi, Mumbai, Kolkata, Hyderabad and Chennai and updates the air quality date every hour.
The caveat of course is that air quality readings are only valid for the local area and since the US Consulates are often located in the centre of the cities, the readings tend to be higher than the official figures.
The other caveat which makes comparing official data to US Consulate data difficult is that the US Consulates provide hour by hour meter readings rather than a daily average. The readings below were all taken in the morning between 9 and 12 noon but the air quality could vary throughout the day.
Delhi is consistently reporting high levels of pollution according to US Consulate data. What’s surprising is that it reports that Hyderabad also consistently reports high levels of pollution, which in many ways is at odds with the official data which suggests that Hyderabad is one of the least polluted cities. It just goes to show how placement of monitoring stations can effect the measurements.
When we break down the chart above to see how many days were at given pollution levels, we can see how far behind Delhi is compared to the other Indian cities. The city is reporting plenty of days that are Unhealthy and even Very Unhealthy when it comes to air pollution.
The overwhelming number of days reported by the US Consulates are given as Moderate, which the US defines as:
Unusually sensitive individuals may experience respiratory symptoms.
It’s encouraging to see that Mumbai, Chennai and Kolkata all reported a number of days when the air quality was Good. However, this could be because the cities all received a fair amount of rainfall during June and there is a link between rainfall and reduced air pollution.
Previous Monthly Air Pollution Surveys