That's true, but the article also mentions some possible causes: "The formaldehyde column is composed of different sorts of volatile organic compounds, and the

That's true, but the article also mentions some possible causes: "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." India also uses considerable quantities of wood in the home for cooking and heating.