The level of soot in the air is significantly high in six Indian cities, including Delhi, and there is an immediate need to check the source of pollution, according to an environment ministry study released Monday.

The finding came in a study commissioned by the ministry in six cities - Delhi, Mumbai, Bangalore, Pune, Kanpur and Chennai.

The particulate matter remains suspended in the air and can cause serious health problems.

The levels of certain types of soot - also known as particulate matter - in the air are significantly high irrespective of the type of locations. Winter and post monsoon seasons have been found most critical when standard rates are higher than in the summer months, the study said.

"Pollution due to particulate matter is severe and nitrogen oxide is the emerging pollutant. These two pollutants require immediate attention," the study noted.

The study also suggested measures to improve air quality in urban areas.

Suggestions included better maintenance of roads, paving of unpaved roads and footpaths and low-elevation concreting of unpaved surfaces along major roads with high traffic.

The use of fly ash bricks could be considered as an option for pavements that would also help in utilisation of fly ash, it suggested.