● With its very large population of `color{violet}"vehicular traffic"`, `color{Brown}"Delhi"` leads the country in its levels of `color{violet}"air-pollution"` – it has more cars than the states of `color{violet}"Gujarat and West Bengal"` put together.

● In the `color{violet}"1990s'`, Delhi ranked `color{violet}"fourth"` among the `color{violet}"41 most polluted"` cities of the world.

● Air pollution problems in Delhi became so serious that a `color{violet}"public interest litigation"` (PIL) was filed in the Supreme Court of India.

● After being censured very strongly by the `color{violet}"Supreme Court"`, under its directives, the government was asked
to take, within a `color{violet}"specified time period"`, appropriate measures, including switching over the `color{violet}"entire fleet"` of `color{violet}"public transport"`, i.e., buses, from diesel to `color{brown}"compressed natural gas (CNG)"`.

● All the `color{violet}"buses of Delhi"` were converted to run on `color{violet}"CNG"` by the end of `color{violet}"2002"`.

● This was because `color{violet}"CNG is better"` `color{violet}"than diesel"`.

● The answer is that CNG `color{violet}"burns most efficiently"`, unlike petrol or diesel, in the automobiles and very `color{violet}"little of it"` is `color{violet}"left unburnt"`.

● Moreover, `color{violet}"CNG is cheaper"` than petrol or diesel, `color{violet}"cannot be siphoned off"` by thieves and `color{violet}"adulterated"` like petrol or diesel.

● The main problem with switching over to CNG is the `color{violet}"difficulty of laying"` `color{violet}"down pipelines"` to deliver CNG through `color{violet}"distribution points/pumps"` and ensuring `color{violet}"uninterrupted supply"`.

Simultaneously `color{violet}"parallel steps"` taken in Delhi for `color{violet}"reducing vehicular pollution"` include:

● `color{violet}"Phasing out"` of old vehicles, use of `color{Brown}"unleaded petrol"`

● Use of `color{Brown}"low-sulphur"` petrol and diesel

● Use of `color{Brown}"catalytic converters"` in vehicles

● Application of `color{Brown}"stringent pollution level norms"` for vehicles, etc.

● The Government of India through a `color{Brown}"new auto fuel policy"` has laid out a `color{violet}"roadmap"` to cut down vehicular pollution in Indian cities.

● More `color{violet}"stringent norms"` for fuels means steadily reducing the `color{violet}"sulphur and aromatics content"` in petrol and diesel fuels.

● `color{Brown}"Euro II norms"`, for example, stipulates that `color{violet}"sulphur"` be controlled at `color{violet}"350 parts-per-million"` (ppm) in diesel and `color{violet}"150 ppm"` in petrol.

● `color{violet}"Aromatic hydrocarbons"` are to be contained at `color{violet}"42 per cent"` of the concerned fuel.

● The goal, according to the roadmap, is to reduce `color{violet}"sulphur to 50 ppm"` in petrol and diesel and bring down the level to `color{violet}"35 per cent"`.

● Corresponding to the fuel, `color{violet}"vehicle engines"` will also need to be `color{violet}"upgraded"`.

● The `color{Brown}"Bharat Stage II"` (equivalent to `color{violet}"Euro-II norms"`), which is currently in place in `color{violet}"Delhi, Mumbai, Kolkata"`, `color{violet}"Chennai, Bangalore, Hyderabad"`, `color{violet}"Ahmedabad, Pune, Surat"`, `color{violet}"Kanpur"` and `color{violet}"Agra"`, will be applicable to all automobiles throughout the country from `color{violet}"April 1, 2005"`.

● All `color{violet}"automobiles and fuel"`-petrol and diesel – were to have met the `color{Brown}"Euro III emission"` specifications in these 11 cities from `color{violet}"April 1, 2005"` and have to meet the `color{Brown}"Euro-IV norms"` by `color{violet}"April 1, 2010"`.

● The rest of the country will have `color{Brown}"Euro-III emission norm"` compliant automobiles and fuels by `color{violet}"2010"`.

● Thanks to the efforts made, the `color{violet}"air quality of Delhi"` has significantly `color{violet}"improved"`.

● According to an estimate, a `color{violet}"substantial fall"` in `CO_2` and `SO_2` level has been found in Delhi between `color{violet}"1997 and 2005"`.

● In India, the `color{Brown}"Air (Prevention and"` `color{Brown}"Control of Pollution) Act"` came into force in `color{violet}"1981"`, but was amended in `color{violet}"1987"` to include `color{violet}"noise as an"` `color{violet}"air pollutant"`.

● `color{Brown}"Noise"` is `color{violet}"undesired high level"` of sound.

● We have got used to associating loud sounds with `color{violet}"pleasure and entertainment"` not realizing that noise causes `color{violet}"psychological and physiological"` disorders in humans.

● The `color{violet}"bigger the city"`, the `color{violet}"bigger the function"`, the `color{violet}"greater the noise"`!!

● `color{violet}"Brief exposure"` to extremely high sound level, `color{violet}"150 dB"` or more generated by take off of a `color{violet}"jet plane or rocket"`, may damage ear drums thus permanently `color{violet}"impairing hearing ability"`.

● Even `color{violet}"chronic exposure"` to a relatively `color{violet}"lower noise level"` of cities may permanently `color{violet}"damage hearing abilities"` of humans.

● Noise also causes `color{violet}"sleeplessness"`, `color{violet}"increased heart beating"`, `color{violet}"altered breathing pattern"`, thus considerably `color{violet}"stressing humans"`.

● `color{violet}"Reduction of noise"` in our industries can be affected by use of `color{violet}"sound absorbent materials"` or by `color{violet}"muffling noise"`.

● Stringent following of laws laid down in relation to noise like`color{violet}" delimitation of horn-free zones"` around hospitals and schools, `color{violet}"permissible sound-levels"` of crackers and of loudspeakers, `color{violet}"timings"` after which loudspeakers cannot be played, etc., need to be `color{violet}"enforced"` to protect ourselves from noise pollution.