It was recently announced that the odd-even policy is scheduled to return to Delhi in April. Since its trial in January, there has been heated debate over whether the experiment was successful. The impact of this policy on pollution levels is certainly an important question to answer. One thing is certain though – the odd-even policy brings much-needed attention to Delhi’s dangerously high levels of ambient air pollution.

Unfortunately, Delhiites are not the only Indians exposed to hazardous levels of air pollution. Although pollution levels outside of Delhi tend to get less media attention, residents of other north Indian cities may be breathing air that is even more dangerous than Delhi’s. Data from the National Air Quality Index web portal, an initiative by the Central Pollution Control Board to make real-time air quality data available for 17 cities, showed that Patna, Lucknow, Ahmedabad, Muzaffarpur, and Faridabad had even higher levels of some important pollutants, on average, than Delhi did in November.

PM2.5 is a silent killer

Why is the air in these places so dangerous? One important reason is that it contains many small particles which can enter deep into a person’s lungs, even into the bloodstream, causing serious health problems. These small particles are called PM2.5 – the name refers to the fact that dangerous particulate matter is 2.5 micrometers or smaller in diameter. Children growing up in an environment with high levels of PM2.5 are more likely to have asthma and stunted lung function than children growing up in places where the air is less polluted. They also have more frequent ear infections and respiratory infections, which get in the way of healthy growth and development. Among adults, PM2.5 is particularly harmful for people with heart and lung disease, and contributes to more frequent respiratory infections, which can reduce productivity.

The limited data that exists shows that pollution is a pernicious health problem across north Indian cities, but could pollution also be making people sick outside of major cities? A few months ago, we got a Dylos air quality monitor, a small machine that samples the air and estimates the level of PM2.5. What we found while traveling with the Dylos suggests that even in smaller towns and rural areas, air quality is often very, very poor.

We measured the air quality wherever we stayed, so our readings reflect exposure inside homes. In early November, in Sitapur, a district capital in Uttar Pradesh about 90 km north of Lucknow, we consistently measured PM2.5 levels five to eight times what the Indian government considers safe. In Bhavnagar, Gujarat, in mid-December, PM2.5 levels were two and a half times the limit. Even in Panaji, the capital of seemingly pristine Goa, PM2.5 levels were measuring substantially higher than those found in the United States’ most polluted city, Los Angeles, during the 1990s, when the US government started regulating PM2.5 under the Clean Air Act.

Real-time monitoring needed

So why aren’t odd-even experiments, or other policies to curb air pollution, being instituted in all of these places? Why is pollution outside of Delhi receiving so little attention when it seems to be such a dangerous problem? One reason could be that real-time air quality data for Indian towns and rural areas is almost non-existent. The National Air Quality Index, which was started in April 2015, only provides data for 17 large cities, and even the data from these air quality stations are not updated regularly. For instance, as we write this piece, the last air quality reading for the only National Air Quality Index monitoring station in Gujarat – in Ahmedabad – was recorded months ago, on November 8.

In principle, air quality data is measured for over a hundred other cities and towns through the National Air Quality Monitoring Programme, coordinated by the Central Pollution Control Board. In practice, however, it is not possible to access this data in a way that allows for real-time monitoring. Our colleagues looked at all of the State Pollution Control Board websites to try to find up-to-date data from these stations. Of the 27 state websites, only eight of them had any data on PM2.5 at all, and only Maharashtra’s State Pollution Control Board website had any data for this year.

As the government wakes up to the very real hazards of pollution in Delhi, we should not overlook the danger that air pollution poses to people outside the capital as well. Many more air quality stations need to be installed, and the resulting data should be made public in real time. Providing air quality data is necessary for drawing attention to the problem, understanding its scope, and hopefully, for measuring the results of much needed interventions to reduce pollution, just like the odd-even experiment in Delhi. The health of millions of people depends on it.

Diane Coffey is a visiting fellow at Princeton University, a visiting researcher at the Indian Statistical Institute, and co-executive director at r.i.c.e. Sangita Vyas is managing director at r.i.c.e.