Air pollution contributed to the deaths of at least 1.2 million Indians in 2017 – but a unique pilot scheme to combat air pollution in the western state of Gujarat could prove to be a model for the rest of the country. The BBC spoke to experts to find out more about the world’s first ever such experiment.

The concentration of tiny particulate matter (known as PM2.5) in India is eight times the World Health Organization’s standard.

These particles are so tiny that they can enter deep into the lungs and make people susceptible to respiratory and cardiovascular diseases, making them extremely deadly.

Air pollution in India is caused by fumes from cooking on wood or dung indoors in villages, and a combination of traffic exhaust, soot and construction dust and factory emissions in the cities.

Now Gujarat has launched the world’s first “cap and trading” programme to curb particulate air pollution.

Put simply, the government sets a cap on emissions and allows factories to buy and sell permits to stay below the cap.

It is being launched in the dense, industrial city of Surat, where textile and dye factories are a major source of pollution. Since 2011, local pollution control authorities have been working on the impact of emissions trading in Surat, along with the University of Chicago and Harvard University…