India suffers some of the worst air pollutions in world history. Delhi’s pollution is infamous, but air pollution is a national problem.

Every district across the Gangetic Plain has annual exposures higher than the National Ambient Air Quality Standards (NAAQS) of 40 micrograms per cubic metres.

In central and west India, 82% and 50% of districts exceed the NAAQS. In the rest of the country, over 80% of districts meet the NAAQS, but essentially the entire country fails to meet the stricter WHO guidelines of 10 micrograms per cubic metres for particle air pollution. Although certainly bad, in terms of the total population exposed to health-damaging ambient pollution, Delhi is just a drop in the bucket.

When people are asked what causes the terrible pollution, most think of large and small industries, vehicles and power plants. There is also growing recognition of the importance of non-industrial sources, such as dust and burning of garbage and crop stubble.

What is left out of most people’s perception and, perhaps consequently, out of most discussions of ambient air pollution control strategies in the country is the importance of household sources in the mix.

A number of studies have shown that burning of biomass and coal for cooking and heating, and kerosene for lighting in households is actually the largest cause of pollution in India. Such household fuels also create large pollution exposures in and around households. Indoor or household air pollution is accounted separately and has health impacts that rival those from ambient pollution nationally.

Our new paper, published in April this year[1], models air pollution across the country using the best available information about all emission sources to estimate what would be the effect on total air pollution exposures by eliminating household sources alone, an admittedly major undertaking but nevertheless perhaps doable in the next decade or so with sufficient effort.

Surprisingly, we found that the country could meet the NAAQS averaged over the entire population by control of just this one source category alone. Perhaps we should not be surprised since so many studies have found it to be largest single category of emissions. The national exposure could be brought to 38 micrograms per cubic metres, just meeting the NAAQS. Not in Delhi, of course, but nevertheless with major national health benefits, estimated to be a reduction in 13% of total premature mortality.

It is a simple lesson in some ways — you cannot have a clean environment when two-thirds of households are still burning polluting fuels two to three times a day.

When the US and Europe first addressed air pollution in the middle of the last century, cooking with biomass or coal was a distant memory. Regulations in Los Angeles to deal with pollution in the 1950s did not have to consider household cooking.

India, however, has developed a large modern economy at a time when it has not yet cleaned up households. Thus, both kinds of sources exist together and need to be considered in policy measures.

China also has terrible air pollution due to a significant degree to household sources, although with more coal burning than India. Since 2013, China has embarked on a set of policy measures across source categories to reduce pollution and recent data indicate that pollution levels are dropping nearly everywhere, although by no means becoming yet clean.

They adopted a number of measures, one being a major programme to eliminate solid fuels in households, including a required 75% reduction in three years in some areas. They seem to rely mainly on electricity and piped natural gas, although LPG plays a role as well.

It is not that India is doing nothing in the household fuel sector, indeed the massive Pradhan Mantri Ujjwala Yojana has had major success in connecting poor households to LPG, although more effort is needed to enhance and ensure use for cooking. This has happened, however, independently from strategies to control ambient pollution.

What is needed now is to incorporate improvements in household fuel use across the board, including cooking, bathwater and space heating, and full elimination of kerosene, into the National Clean Air Programme along, of course, with strategies to control other sources.

Ambient pollution affects everyone. Pollution may start in a chulha inside the kitchen but soon goes outdoors and becomes part of the pollution for the country along with that from vehicles and industry.

Sagnik Dey from Centre for Atmospheric Sciences and School of Public Policy, Indian Institute of Technology Delhi and Kirk R. Smith, Collaborative Centre for Clean Air Policy, New Delhi.