1. Automobile exhaust

2. Tobacco smoke

3. Wood burning

4. Using varnished wooden furniture

5. Using products made of polyurethane

Select the correct answer using the code given below :

(a) 1, 2 and 3 only

(b) 2 and 4 only

(c) 1, 3 and 4 only

(d) 1, 2, 3, 4 and 5

1. Ans: a

Explanation:

Benzene is a naturally occurring colourless liquid at room temperature (25 oC) and pressure (760 mm Hg). It has a characteristic aromatic odour, a relatively low boiling point (80.1oC) and high vapour pressure, which causes it to evaporate rapidly at room temperature. 

Benzene is released into the environment from both natural and man-made sources, although the later is the most significant source. 

Benzene in air exists predominantly in the vapour phase, with residence time varying between few hours to a few days depending on the environment and climate.

Degradation of benzene in air occurs mainly by reaction with hydroxyl, alkoxy and peroxy radicals. Toluene and Xylene are also present in most of the sources along with Benzene.

Benzene is a highly volatile aromatic compound usually component of mineral oil, petrol, coking plant and other products. Benzene is extensively utilized as industrial solvent in manufacturing of lacquers varnishes and paint. 

Benzene escapes from mineral oil and petrol during storage, transport, loading, unloading or during filling of petrol in motor vehicles. High concentration of Benzene are encountered in the vicinity of petrol filling stations, fuel tank storage sites, coking plant in the vicinity of refineries. 

Major Benzene emission originates from the motor vehicles . 

Sources of BTX Emission 

Transport : 

• (I) Vehicular Pollution : a) Vehicular exhaust b) Fuel filling station c) Fuel adulteration 
• (II) Railways 
• (III) Airways

 Industries 

• (I). Major industrial units (Refinery, Petrochemical etc ) 
• (II). Industrial estates 
• (III). Medium scale chemical industries 

Domestic Emissions 

• (I). Domestic combustion units 
• (II). Commercial combustion units

Emissions from combustion sources:

• Medical waste incinerators 
• Sewage sludge incinerators 
• Hazardous waste incinerators
• External combustion solid, liquid and gaseous fuels in stationary sources heat and power generation Stationery internal combustion 
• Secondary lead smelting Iron and Steel foundries 
• Portland cement production Hot-mix ashalt production 
• Open burning of biomass, scrap tires

About 50% of benzene is absorbed by inhalation & absorption of it via skin is limited. The high lipophilicity and low water solubility of benzene favour its distribution to fat-rich tissues. Benzene distributed by blood accumulates in fat-rich tissues like adipose tissue bone marrow & liver. 

Polyurethane is a plastic material, which exists in various forms. It can be tailored to be either rigid or flexible, and is the material of choice for a broad range of end-user applications such as:

• Insulation of refrigerators and freezers
• Building insulation
• Cushioning for furniture
• Mattresses
• Car parts
• Coatings
• Adhesives
• Rollers and tyres
• Composite wood panels
• Shoe soles
• Sportswear

Hence, option a is correct.

Read: Previous Year UPSC Environment Questions (PYQs) With Explanation 2020