The carbon-stained lungs of Delhi moved a step closer to cleaner air when on July 1 diesel, which has a lower sulphur content of 0.05 per cent, was introduced in National Capital Region. Sulphur is a major pollutant in diesel and its reduction can lower the levels of pollution. The introduction of the new diesel comes after a Supreme Court ruling which directed that the fuel quality and emission levels in the entire NCR should conform to Euro II standards from July 1.