Image: Traffic jam in Delhi, Wikimedia

Air Quality in India: How Sensors Harm and Help

Special thanks to Puneet Kishor and Aatish Bhatia for bringing the WHO study to my attention and, overall, for being an active part of this ongoing conversation about sensor journalism.

You can’t trust the air quality in India.

That’s what the World Health Organization is saying in its latest assessment, which ranked Delhi as the world’s most polluted city in a survey released during May 2014. (The Guardian has also covered this story.) The main causes for pollution were growing vehicle population and the rising emissions from coal-based thermal power plants.

According to the Central Pollution Control Board (CPCB), which oversees pollution control in India, 43.5%of children in Delhi have reduced lung function and breathing problems.

Unreliable data

Poor air quality in India is a serious issue with adverse health impacts, but the data about air quality are ultimately unreliable for a myriad of reasons.

The main metrics of concern is the presence of PM 2.5, airborne particles less than 2.5 microns in size. These are small enough to penetrate deep into our lungs and bloodstreams and have been connected to lung cancer and heart attacks. While air sensors are available, there are key reasons why the data collected from them and the sensor themselves do not give an accurate snapshot of the state of India’s air quality:

Inconsistent calibration of air sensors

PM 2.5 sensors in use are currently not calibrated against each other. On top of that, air sensor manufacturers “self-certify” their own products. Because there is no way to assess the quality of existing tools, manufacturers that compete against each other in selling their tools cannot be eliminated on technical grounds. Instead, the determining factor for which sensor is chosen over another is cost, and the lowest bid usually wins.

““All we have is a financial bid where we have to choose on the basis of L1 (lowest bid),” says George.””
“…a check the CPCB undertook about two and-a-half years ago, when it compared some India-made PM 2.5 samplers with international ones. “There was a 100 per cent difference in reading…””

Lack of established standards

India does not have its own established air quality standards. So, even if you had proper readings from calibrated sensors, there would be nothing official to compare them against.

“Although the government mandates companies to adhere to specifications defined by the US Environment Protection Agency (EPA), India doesn’t have standards of its own, it doesn’t check if these samplers measure what they claim to.”
“…airborne particles less than 2.5 microns in size. Small enough to penetrate deep into our lungs and bloodstreams, they have been connected to lung cancer and heart attacks. Studies show there is no safe level of PM 2.5, though CPCB terms as “safe” readings up to 60 ig/m3. On October 12, a Sunday, between 3 pm and 4 pm, ITO in New Delhi had a PM 2.5 reading of 206.”

Feedback loops

While air quality data gets reported back to pollution boards, the information does not regularly get back to the general public.

““Another advantage of a CM system is it throws up a lot of data. “In the manual system, there is a lag in data,” says a CPCB official. “If you look at the public’s response to air pollution, it is very lackadaisical. One reason for that is the lack of timely information. What is the use of telling people the air was very polluted a week ago?””

Data fabrication

Companies are required to install continuous monitoring units, which send data directly to pollution control boards. Unfortunately, “data fudging” is a pervasive problem.

“Companies are installing these machines only to meet statutory requirements,” says a manager at Chemtrols, a distributor and installer of CM units, not wanting to be named. “90 per cent of them are fabricating data, not so much on SO2 and CO2 but on particulate matter.””

Prioritization of bigger cities

Most air quality assessment focuses on densely populated urban areas, leaving out those who live outside the city.

While data is collected for 12 pollutants in a few big cities, in the rest of India, data is collected for far fewer, like PM 10, NO2, SO2.”

Turning policy into protocol

Despite the existence of national policy to develop more work around assessing air quality, there has been little momentum toward this goal.

“There is a failure of the research establishment here. “The Air Act was passed in 1981. Since then, where is the work to set safety norms on exposure to pollutants?” asks the former CPCB official. “On testing methodologies? On better instruments?””


Alternatively, there might be a way to enable people to use low-cost sensors to gather extra data in locations not covered by continuous monitoring (CM) units outside of bigger cities in India or to engage local communities to engage with air quality issues by taking measurements of particulate matter in the air.

As far as tools go, the AirBeam is a personal air quality monitor designed to use Bluetooth, an app, and a website to build awareness about air pollution within its network of users. The sensor claims to be able to measure PM 2.5, which seems to be what is needed in India. It runs on an open source platform called AirCasting, which is meant to encourage DIY air monitoring and uses information about local environments to “inform, educate, share, and ultiamtely improve health in communities around the world.”

Image: HabitatMap

The DustDuino is another open source tool that measures PM 2.5 and PM 10 indoors and outdoors. The tool draws air in from its surroundings and uses a $15 USD optical sensor (an LED and a lens) to determine the concentration of dust in a partially closed chamber. The sensor data is received by an Arduino board and transmitted to Xively, a data repository and data sharing platform.

Still the Dustduino is not without its unknowns, some of which include (from the website) “whether it needs to be co-located with higher-quality instruments for calibration, and whether it could be used extreme environments. There are also some limitations — the sensor may not produce high-quality information at time intervals shorter than an hour.”


Research & Policy

To address the lack of research and actionable policy on air quality in India, Urban Emissions is conducting an independent study of air quality in six Indian cities (Pune, Chennai, Indore, Ahmedabad, Surat, and Rajkot).

“While state and national authorities are taking necessary action and introducing interventions in varying capacities to curb these emissions and reduce ambient pollution levels, a lack of coherent policy as well as unplanned growth across sectors (construction, transport, industry) is hindering these efforts.”

The study aims to identify common pollutants in India “detailing the geographic, demographic, monitoring, emission sources, emission totals, and health impacts associated with the observed PM 10 pollution levels in the cities.” As yet, there is more research to be done around these same factors for PM 2.5.

The availability of alternative tools doesn't constitute the effectiveness of those tools. The existence of policy doesn't ensure the enactment of that policy in tangible, measurable ways. However, the problem of air pollution in India remains, and the health of its citizens is at risk.

What ends up happening in India will likely need to be a multi-pronged approach, as in the impetus won’t and mustn’t be on a single player (i.e. the government OR businesses OR academics OR the public). In creating feedback loops that connect air quality data to the public, the media can and should play a vital role in distributing information to those that the data most concern.

Further, there could and should be opportunities where concerned publics can self-report information and suspicions about air quality around them. As an advocate for sensor-based journalism, it is of interest to me to both support the improvement of environmental sensors and to keep a critical eye on the way the discourse is shaped around them.

Moving away from the language of top-down or bottom-up strategies for environmental monitoring, I’d like to suggest a term that I first came across in the work of Tuan-Yee Ching, an urban planner and architect from MIT. India’s solutions might end up being a middle-out approach, one that combines government authorization (sometimes even funding or resources) as well as community engagement and organization. Environmental issues such as air quality are not unique to India, and it may serve those at the top, middle, bottom, and periphery to think about approaching these problems in new ways.


Ching, Tuan-Yee. Smart Cities: concepts, perceptions, and lessons for planners. Massachusetts Institute of Technology. Thesis. 2013.

India’s air quality figures can’t be trusted.” The Guardian. Published October 20, 2014. Accessed October 30, 2014.

Urban Emissions, Study of Air Pollution in Six Indian Cities

Rajshekhar, M. “Why India’s numbers on air quality can’t be trusted.” Economic Times. Published October 14, 2014. Accessed October 30, 2014.

World Health Organization, Ambient (outdoor) air pollution in cities database 2014.