India's emissions of the air pollutant sulphur dioxide increased by 50 per cent since 2007, while China's fell by 75 per cent, claims a study which found that India is yet to implement emission controls like its neighbour.
The study led by researchers at University of Maryland in the US suggests that India is becoming, if it is not already, the world's top sulphur dioxide emitter.
Sulphur dioxide is an air pollutant that causes acid rain, haze and many health-related problems. It is produced predominantly when coal is burned to generate electricity.
The rapid decrease of sulphur dioxide emissions in China far exceeds expectations and projections.
This suggests that China is implementing sulphur dioxide controls beyond what climate modellers have taken into account.
China and India are the world's top consumers of coal, which typically contains up to three per cent sulphur, researchers said.
Most of the two countries' sulphur dioxide emissions come from coal-fired power plants and coal-burning factories.
In particular, Beijing suffers from severe haze problems because of the many coal-burning factories and power plants located nearby and upwind.
Starting in the early 2000s, China began implementing policies such as fining polluters, setting emission reduction goals and lowering emissions limits.
According to the results of the current study, these efforts are paying off.
Despite China's 75 per cent drop in sulphur dioxide emissions, recent work by other scientists has shown that the country's air quality remains poor and continues to cause significant health problems.
This may be because sulphur dioxide contributes to only about 10 to 20 per cent of the air particles that cause haze, according to Li.
By contrast, India's sulphur dioxide emissions increased by 50 per cent over the past decade.
The country opened its largest coal-fired power plant in 2012 and has yet to implement emission controls like China.