Vehicles and industries are mainly responsible for the deterioration of air quality in the state. Both create noise and emit air pollutants. Impact of vehicular emission and noise is widespread while that due to industrial emission is limited to areas around the industries. Advanced manufacturing techniques have considerably reduced both noise and emission and automobiles. Cleaner production process have emerged which reduce emissions from some industries. But the benefits are being offset by the rapid increase in the numbers of vehicles as well as industries. This growth is pronounced in urban areas. Air quality is therefore under increased stress around urban areas.

                 Even increasing use of fossil fuel in the transportation and industrial sectors is adversely affecting the air quality in Kerala. These driving forces are also responsible for the increase in ambient noise. The number of vehicles on the roads in Kerala has increased more than 20 times since 1975.Kerala now has over 25 lakh licenced vehicles on the road when the total length of the carriage way is only 21347km. The vehicle population in the different districts of Kerala is given on the table.

               The last decade has been rapid increase in the number and diversity of vehicles on the roads of Kerala. The number of vehicles increased 2000% from 119720 in 1975 to 2315372 in 2002. The corresponding increase in road length has been only 44% from 14870 km to 21347km. 40% of the vehicles in the state are registered in the three districts of Eranakulam, Thiruvananthapuram and Kozhicode. Personal transport vehicles constitute 72% of the total vehicles in the state and 77% of these personal vehicles are scooters and motor cycles.

              Vehicular emission and noise from this vehicles are sever in the three major cities of Kerala namely, Thruvananthapuram, Kochi and Kozhicode. Development of road infrastructure has not kept pace with rapid increase in number of vehicles. This has resulted in traffic congestion and the resultant increase in air quality deterioration.

                 Kerala's industrial growth has been very lower when compared to rest of India. The number of industries, which can be categorized as Large or Medium, is about 640. Most of these units are in the private sector and a majority of them are located at Kochi. There are about 2.5lakh SSI units, which are dispersed in the different districts of the state. Kerala state pollution control board brought nearly 600 large/medium scale industries and about 2500 SSI units under the consent regime of Air (Prevention and Control of Pollution) Act. Majority of the smaller units, comprise of stone crusher. District wise list of air polluting industries in Kerala is given in table.

                     Bulk of the major/medium industries and the maximum number of vehicles are in Ernakulam.This has an adverse impact of the ambient air quality of the area.Kanjikode in the Palakkad is another instance where air quality degradation is observed due to the large number of electric furnace based industries being located there.Rest of the district have industries which mostly fall in the small or SSI category.Large and medium industries are sparse and are spread apart.Impact on air quality is therefore less or localized.

                 On the energy sector,Kerala has shifted its focus from hydel sources to fossil fuel for the generation of electicity.The new power plants use either naptha or diesel to generate electricity.791MW,out of a total generation of 2621 MW,is now generated from fossil fuels.70% of the additional power generation capacity created since 1997-98 consists of plants running on fossil fuel.During power shortage in summer the industries and commercial establishments depend on captive power plants or portable generators..This increased dependence on fossil fuel has increased the air pollution.

                   Urbanisation is occurring, in Kerala, at a slower pace than in other states. However Thiruvananthapuram, Kochi and Kozhikode have been experiencing growth in urban spread. As per census 2001, urban population of the state is 25.9% of the state's population. The percentages for Thiruvananthapuram, Kochi and Kozhikode districts are 34,48 and 38 respectively. Unplanned growth has resulted in degradation of air quality due to crowding and traffic congestion. Air quality deterioration in urban areas is due to increased use of fossil fuels and personal transport. Improper collection and disposal of garbage is causing the waste to rot before it is removed. Scientific disposal facilities are inadequate even in the major cities. Garbage is mostly burned in the open causing air pollution. Vehicular movement and unrestrained use of loud speakers are mainly responsible for the noise in the urban areas.

           Ambient air is monitored by Pollution Control Board for Suspended Particulate Matter (SPM), Respirable Suspended Particulate Matter (RSPM), Sulphur Dioxide (SO₂ ) and Oxides of Nitrogen (NO_X ) from stations located in industrial, residential and sensitive areas. Observations at these stations show that SPM and RSPM regularly exceed allowable limits. SO₂ and NO_X levels are observed to be almost always within the prescribed limits. The measurements at the cities of Thiruvananthapuram, Eranakulam and Kozhikode are given in table. Similarly the air quality at a commercial locality and in an industrial belt are presented as shown here. 

            The observations show that SPM and RSPM levels exceed ambient air quality standard (200 and 100 µg/m³ , 24 hour value) at all stations. SO₂ and NO_x are observed to exceed the recommended 24 hour limit of 80 µg/m³ in industrial areas.

Ambient Air Quality: The ambient air quality standards of major cities of Kerala during 2008 as indicated by the National Ambient Air Quality Monitoring are given below. The Ministry of Environment and Forests has revised the National Ambient Air Quality Standards.Details are given in  here                  

Air Quality Levels in selected Locations in Kerala 2008  are given in here.  

Revised National Ambient Air Quality standards (NAAQS) 2009 are given in here. 

National Ambient Air Quality Status & Trends 2019 are given in here.   

 Guidelines for the Measurement of Ambient Air Pollutants is given in here.

  Air Quality Report are given in here.