News Excerpt
Recently the Supreme Court ordered the installation of anti-smog guns at all large construction sites to reduce dust pollution. To give effect to this order, the Delhi Pollution Control Board (DPCC) have been installed Guns at 14 of the 47 large projects in Delhi.

•    Smog: Smog is the mix of smoke and fog. Smog is formed by the particulate matter present in the atmosphere mainly due to the fossil fuels from automobiles, factories and power plants. Today, most of the smog is photochemical smog. Photochemical smog is produced when sunlight reacts with nitrogen oxides and at least one volatile organic compound (VOC) in the atmosphere.
•    Temperature Inversion: Smog is often dependent upon the temperature. When it is time for the temperature inversion, wind gets calm and creates the situation for the smog to get trapped over the area for few days. It becomes more severe in the areas which are farther away from the source of pollutant release.
•    Smog Towers: It is a structure of concrete that has multiple layers of filters. It purifies the air from all directions and could provide clean air to 75,000 people living in the 3 kilometer radius around it. It can clean up to 99.99% Particulate Matter (PM) present in the air with the help of pre-filter and activated carbon.

About Device
    The anti-smog gun is a cannon shaped device that sprays atomised water droplets in the air.  
    It converts the water into a fine spray with droplets size of 50-100 microns by passing it at high pressure through propellers. The gun is attached to a water tank built on a movable vehicle.
    It basically works as rain to bring down the suspended particles present in the air. It reduces air pollution by binding dust and other particulate matter and carrying them down to the ground level along with water.
    It can spray water up to the height of 150 feet with the capacity of 30-100 liters per minute to bring down the polluted particles from the atmosphere.
    Anti-smog guns should be mandatory in projects that require environmental clearance from the State or Centre, and have a built-up area of over 20,000 square meters.

Dust as Pollutant
Dust present in air as suspended particles. It can cause allergy and other respiratory diseases. It also affects plant growth by covering stomata on leaf surface and blocking them. It acts as the carrier of toxic compounds like heavy metals.
All the large construction sites in Delhi have to install Anti-smog gun to minimize the dust particle suspension. The environmental clearance is also required in these cases.

    Location selection: The trends of dust pollution vary on daily basis at any location. The real-time concentration of PM2.5 and PM10 and its time period also vary with reference to location. It is not practically possible and judicious to pump water all day. So, from all the polluted sites, we have to select locations which need these guns most.
    Use of Water: Anti-smog gun require water and power. Water is a scarce resource. So the efficiency of Gun is dependent on the availability of water.
    Policy: The cost sharing matter is still incompatible due to the lack of streamlined policy. Government and regulatory bodies are looking for ‘polluter pays policy’ to recover the cost of Gun. However, “The polluter pays policy” is yet to be inducted.

Way Forward
Fragmented policies and toothless environment bodies won’t help. The centre and states will have to work jointly and quickly.
Government should streamline the ‘polluter pays’ policy to clarify the cost, installation and operations of the anti-smog guns.