Which of the following statements about the Volatile Organic Compounds (VOCs) are correct? i) They cause acid rain ii) They may cause cancer iii) They play an important role in the formation of photochemical smog Select the correct answer from the options given below:

Which of the following statements about the Volatile Organic Compounds (VOCs) are correct? i) They cause acid rain ii) They may cause cancer iii) They play an important role in the formation of photochemical smog Select the correct answer from the options given below: Correct Answer ii) and iii)

Volatile organic compounds are compounds that have a high vapour pressure and low water solubility. Many Volatile organic compounds are human-made chemicals that are used and produced in the manufacture of paints, pharmaceuticals, and refrigerants. Volatile organic compounds are typically industrial solvents or by-products by chlorination in water treatment, such as chloroform. Volatile organic compounds are often components of petroleum fuels, hydraulic fluids, paint thinners and dry cleaning agents.

Key Points

• Volatile organic compounds are gases that are emitted into the air from products or processes. Some are harmful in themselves, including some that cause cancer. In addition, they can react with other gases and form other air pollutants.
• The more reactive volatile organic compounds combine with nitrogen oxides in photochemical reactions in the atmosphere to form ground-level ozone, a major component of smog. Volatile organic compounds are also precursor pollutant to the secondary formation of fine particulate matter. (PM 2.5)
• When Volatile organic compounds react with nitrogen oxides and create ozone molecules, they also create fine particulates. 
• Also, the gases emitted by volatile organic compounds when are emitted into the air, some are harmful by themselves and some can cause cancer as well.
• The presence of volatile organic compounds plays an important role in the formation of ground-level ozone, photochemical oxidants, and smog episodes, and they are harmful to the ecosystem. Aromatic volatile organic compounds have a high photochemical ozone creation potential. Hence, the 2nd option is the correct answer.

• Photochemical smog is a mixture of pollutants which includes particulates, nitrogen oxides, ozone, unreacted hydrocarbons, etc. The smog often has a brown haze due to the presence of nitrogen dioxide. It causes painful eyes.
• Acid rain- rainfall made so acidic by atmospheric pollution that it causes environmental harm, chiefly to forests and lakes. The main cause of acid rain is industrial burning of coal and other fossil fuels, the waste gases which contain acids sulphur and nitrogen oxides which combine with atmospheric water to form acids.