CBSE Class 12th English (Core) Question Paper (Set-3), given here
1. Air pollution is an issue which concerns us all alike. One can willingly choose or reject a food a drink or a life comfort but unfortunately there is little choice for the air we breathe. All what is there in air is inhaled by one and all living in those surroundings.
2. Air pollutant is defined as a substance which is present while normally it is not there or present in an amount exceeding the normal concentrations. It could either be gaseous or a particulate matter. The important and harmful polluting gases are carbon monoxide carbon dioxide ozone and oxides of sulphur and nitrogen. The common particulate pollutants are the dusts of various inorganic or organic origins. Although we often talk of the outdoor air pollution caused by industrial and vehicular exhausts the indoor pollution may prove to be as or a more important cause of health problems.
3. Recognition of air pollution is relatively recent. It is not uncommon to experience a feeling of suffocation in a closed environment. It is often ascribed to the lack of oxygen. Fortunately however the composition of air is remarkably constant all over the world. There is about 79 per nitrogen and 21 per cent oxygen in the air-the other gases forming a very small fraction. It is true that carbon dioxide exhaled out of lungs may accumulate in a closed and over-crowded place. But such an increase is usually small and temporary unless the room is really air-tight. Exposure to poisonous gases such as carbon monoxide may occur in a closed room heated by burning coal inside. This may also prove to be fatal.
4. What is more common in a poorly ventilated home is a vague constellation of symptoms described as the sick-building syndrome. It is characterized by a general feeling of malaise head-ache dizziness and irritation of mucous membranes. It may also be accompanied by nausea itching aches pains and depression. Sick building syndrome is getting commoner in big cities with the small houses which are generally over-famished. Some of the important pollutants whose indoor concentrations exceed those of the outdoors include gases such as carbon monoxide carbon dioxide oxides of nitrogen and organic substances like spores formaldehydes hydrocarbon aerosols and allergens. The sources are attributed to a variety of construction materials insulations furnishings adhesives cosmetics house dusts fungi and other indoor products.