Europe's new Sentinel-5P satellite, which was launched last October to track air quality worldwide, has noticed that the air in India looked different from other places in the world. After sampling the air, scientist concluded that the differences were due to the presence of formaldehyde, as reported by the BBC.
Compared to the major constituents like nitrogen and oxygen, the formaldehyde signal is actually very small; in every billion air molecules just a few will be HCHO. But it can be a signifier of more general pollution problems, says Isabelle De Smedt from the Royal Belgian Institute for Space Aeronomy (BIRA-IASB).
"The formaldehyde column is composed of different sorts of volatile organic compounds, and the source can be from vegetation - so, from natural origin - but also from fires and pollution," she told BBC News.
"It depends on the region but 50-80% of the signal is from some biogenic origin. But above that you have pollution and fire. And the fire can be from coal burning or wildfires, but in India, yes, you have a lot of agricultural fires."
The scientists doing the survey believe that some of the issue is cultural. India uses a lot of wood fires for cooking and heating. The chemicals released from the burning wood mixes with nitrogen dioxide (NO₂, from fossil fuel burning) and sunlight and the reaction produce ground-level ozone. Combine that with the mountain regions that prevent the winds from dispersing the pollutants and you have a recipe for poor air quality.
Fortunately, advances in air quality detecting allow us to spot trouble spots earlier and begin working to correct them. Still, might want to rethink your next campsite cookout.