Question

Of the following metals which one pollutes the air of a big city?
1. Copper
2. Chromium
3. Lead
4. Cadmium

Answer 1

Hint: One of the major causes of air pollution in cities is due to automobiles.

Complete answer:
Lead is the metal which pollutes the air of big cities. Due to the usage of lead petroleum, when lead is emitted out, it causes damage to air, and is a major pollutant. Proper maintenance of vehicles along with the usage of lead free petrol or diesel can reduce the pollutants emitted by automobiles.
So the correct answer is lead.

Additional Information:
Air Pollution is the occurrence or presence of any material or gas, in the air in such a quantity which is harmful to man, animals and their environment. Substances and factors which cause air pollution are called air pollutants. They can be both natural and anthropogenic.
Electrostatic precipitators and scrubbers in industries help in controlling air pollution. Use of catalytic converters in vehicles also controls air pollution by converting hydrocarbons emitted into carbon dioxide and water. It also converts carbon monoxide into Carbon dioxide, and nitrogen oxide into nitrogen gas. However, automobiles with catalytic converters must not be used with leaded petrol, because this inactivates the catalyst of the converter.

Notes:
Common air pollutants are -
> Gaseous material: Carbon monoxide, Sulphur dioxide, Nitrogen oxides and hydrocarbons.
Particulate matter: Aerosols, smoke, dust, mist and pollen grains.
> The Central Pollution Control Board (CPCB) says that particulate matter with size 2.5 micrometers or less in diameter is responsible for causing great harm to human health.
> The Air ( Prevention and Control of Pollution) Act, 1981, deals with the preservation of air quality and controlling air pollution.