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The burning of fuels in industrial activities and transportation leads to a plethora of combustion products, which contribute towards air pollution including toxic trace organics. Exposure to these toxic air pollutants can cause serious health effects. These include damage to the immune system, as well as respiratory, neurological, reproductive (e.g. reduced fertility) and other health problems.
Ambient air pollutants can be divided into two categories: criteria pollutants and air toxics. Criteria pollutants are often considered a group of 'traditional' air pollutants. These have a demonstrable health hazard. The criteria pollutants constitute mainly carbon monoxide, sulphur dioxide, photochemical oxidants (as ozone), oxides of nitrogen, lead and particles. Air toxics are pollutants present in the environment in low concentration (other than criteria pollutants) that are known, or suspected to be as toxic and persistent. The term 'air toxics' and 'hazardous air pollutants' (HAP) are used interchangeably. Trace organics belong to the category of air toxics. The trace organics include Volatile Organic Compounds (VOCs) including Benzene, Toluene, Xylene (BTX) and Polycyclic Aromatic Hydrocarbons (PAHs). Some PAHs are semi volatile in nature & therefore, these can be present in particulate as well as vapour phase while others are mostly adsorbed onto particles in the environment. The Central Pollution Control Board has set up facilities for Polycyclic Aromatic Hydrocarbons (PAHs) and VOCs including BTX measured in Delhi and its zonal labs in Vadodara, Kolkata, Kanpur and Bangalore. PAHs monitoring at selected locations and some traffic intersections has also been carried out . Based on monitored data, it has been possible to compare the levels of PAHs with other cities of the world and also to prepare action plans for PAH reduction in the diesel and in the environment. Because of initiatives taken for controlling air pollution from different sources, particularly automobiles and fuel quality, the increasing trend of toxic organic pollutants in the city has been arrested. Polycyclic Aromatic Hydrocarbons content has been restricted to 10% in diesel to be supplied all over India from 2005. The initiatives taken for improvement of fuel quality, introduction of compressed natural gas (CNG) and tightening of emission norms for vehicles have checked unabated increase of pollution as evident through monitoring data.
I appreciate the efforts put in by my colleagues Dr. S. K. Tyagi , Scientist, 'C' and Dr. B. Sengupta , Member Secretary , CPCB for collecting and collating relevant information for this Newsletter.
We hope, it will be useful to all concerned with protection and improvement of air quality.
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