It was a wise decision in Delhi to replace the Diesel buses by CNG fueled buses as it reduces the Pollution contribution to the atmosphere at great extent. In coming days government is planning to add more buses for Public transportation. Although it may be a good decision for public transportation but create more severe situation for air quality of Delhi which is already suffering from worst condition. Increasing number of CNG fueled private or government buses are not reducing the environmental pollution and contributing towards indirect or invisible source of pollution.
Here it is to be noted that CNG as an alternative to diesel or petrol is less polluting but can not be misunderstood as Non-Pollution. If we will keep increasing vehicle using CNG as a fuel in an area, it may also lead towards worst situation for air quality. If air is polluted and quality is severe (as majority of the time we witness in Delhi) then comparing worst using CNG and more worst using diesel/petrol is not justified. The best suitable environment friendly transportation can be mass transit system like Metro rail or Mono rail which can be considered as substitute of Diesel and Petrol or CNG.
Are you driving BIKE? Have you felt the realm of warm air behind CNG buses in NCR? Many of the times I faced such issue when standing behind the CNG buses while waiting at traffic light. The exhaust of warm air has impact till 3 -4 feet in direct range. Be aware that the warm air of CNG buses is full of gaseous pollutants that is good enough to make someone unhealthy.
Methane and NOX are the main pollutant from CNG emission. If we compare the emission of Particulate Matter (PM) and NOX it is less for CNG buses, then to that of diesel buses. CNG generally has low particulate emissions, although the fuel still emits particles that are harmful to health. With higher passenger loads, the amount of PM can increase to levels comparable to diesel. CNG also emits higher quantities of formaldehydes and other nanoparticles with negative health impacts.
Particulate matter is a mixture of small particles and droplets, including acids, such as nitrates and sulfates, organic chemicals, metals, soil; or dust. Combustion can produce a large quantity of very fine particles 10 nanometers in diameter or smaller, but it is regulated by measuring the total quantity of all PM particles sizes. The human body cannot protect against exposure to ultrafine particles, which can enter the heart and lungs through inhalation and have serious health effects, including respiratory diseases and heart and lung conditions