Q. Which of the following are some important pollutants released by steel industry in India?

1. Oxides of sulphur
2. Oxides of nitrogen
3. Carbon monoxide
4. Carbon dioxide

Select the correct answer using the code given below. (UPSC Prelims 2014)
Answer: 1, 2, 3 and 4
Notes: The correct answer is [D] 1, 2, 3 and 4. The steel industry is one of the most energy-intensive and polluting sectors, releasing a variety of gaseous and particulate emissions during different stages of production.

• Oxides of Sulphur (SO_x) (Statement 1 – Correct): These are primarily released during the "Sintering" process and the burning of coal or coke in blast furnaces. The sulphur present in the raw iron ore and coal reacts with oxygen to form sulphur dioxide (SO₂), a major contributor to acid rain.
• Oxides of Nitrogen (NO_x) (Statement 2 – Correct): NO_x is generated due to high-temperature combustion in blast furnaces and internal combustion engines used within the plant. These pollutants contribute to the formation of ground-level ozone and photochemical smog.
• Carbon Monoxide (CO) (Statement 3 – Correct): This is a byproduct of the incomplete combustion of fossil fuels (coking coal) and the chemical reduction of iron ore in the blast furnace. It is a highly toxic gas that interferes with oxygen transport in the blood.
• Carbon Dioxide (CO₂) (Statement 4 – Correct): The steel industry is a massive source of CO₂. It is released both as a direct chemical byproduct of the reduction of iron oxide with carbon and from the vast amounts of energy (heat and electricity) required to run the plants.

In addition to these gases, the steel industry also releases significant amounts of Particulate Matter (PM) and heavy metals like lead and cadmium. Modern "Green Steel" initiatives in India are currently focusing on using hydrogen instead of coal to reduce these emissions.