Data generated by CPCB of ambient air quality in various cities and towns of India under National Air Quality Monitoring Programme (NAMP) have been analyzed. A decreasing trends has been obseved in ambient sulphur dioxide levels in many cities like Delhi, Hyderabad, Kanpur, Lucknow, Mumbai etc. This may be due to various interventions like reduction of sulphur in diesel, use of CNG as the vehicular fuel in Delhi and Mumbai etc.

During recent years a number of different species of lichens have been found (species richness) and the presence of indicator species has been studied to characterize regional air quality impact on lichen populations. The following review describes some of the pollutants affecting lichens, mechanisms of pollutant accumulation by lichens, physiological responses to pollution, and methods of study utilizing lichens.

Rice is the most important Kharif crop of Punjab. With the increase in production of rice there is concomitant increase in the production of residue (rice straw), which is approximately 18.75 MT. About 80 percent of the rice residue it burnt in the fields, particularly after harvesting rice by combine harvesters.

Residue burning practice is followed in major Indian states of Uttar Pradesh and Punjab. Agricultural residue burning in the fields and used otherwise for rural domestic needs is responsible for a large number of toxic emissions, which are a health hazard.

Crop residue burning results in the emission of many a toxic pollutants. These emissions can travel long distances affecting thereby the entire region. Due to these emissions the air quality of the region worsens, which results in nose and throat itching and burning, and irritation of the airway tract.

Open field burning of plant material has been a long standing traditional agricultural practice by farmers and foresters. When farmers burn their agricultural lands, the products of combustion are emitted directly into the open air. Heavy smoke, consisting of particulate matter, from these fires clouds the skies.

Rice-wheat is a major crop rotation in the Indo-Gangetic region. Tillage is one of the major crop production operations and is an important contributor to the total cost of production. It is a common observation that direct tilling of any crop into combine-harvested rice stubbles from a reasonable rice yield is not possible without any prior burning or removal of straw.

Harvesting a crop generates a huge amount of crop residue. Uttar Pradesh tops the list of the Crop Residue Producing States followed by Punjab, Madhya Pradesh and so on. A large part of this crop residue is burnt in the open fields since the farmers do not have any worthwhile use of this waste. Burning of residues give rise to emissions of aerosols, major gases and trace gases.

Property changes associated with differences in chemical structure between vegetable oil and petroleum based diesel fuel may ask for change in the engine operating parameters such as injection timing, injection pressure etc. These operating parameter changes can cause difference in performance and exhaust emissions than the optimized settings chosen by the engine manufacturer.