Earlier it was a big problem in Delhi.But it has minimised to some extent after the construction of metro in the city and after controlling emission norms, use of CNG fuel.

• 这个问题曾对德里地区带来很大的影响，但自从市区盖了地铁，有效控制废气排放量和压缩天然瓦斯的使用量，污染问题已获得明显改善。