Q. According to the Environmental Protection Agency (EPA), which one of the following is the largest source of sulphur dioxide emissions? (UPSC Prelims 2024)
Answer: Power plants using fossil fuels
Notes: The correct answer is [D] Power plants using fossil fuels.According to data from the Environmental Protection Agency (EPA), sulfur dioxide (SO₂) emissions primarily originate from the combustion of fossil fuels containing sulfur.

• Power Plants (Option D – Correct): The largest source of SO₂ in the atmosphere is the burning of fossil fuels by power plants and other industrial facilities. Specifically, coal-fired power plants account for the vast majority of these emissions, as coal naturally contains varying amounts of sulfur that is released as gas during combustion.
• Extraction of metals from ores (Option C – Incorrect): While industrial processes such as smelting (extracting metal from copper, lead, and zinc ores) are significant point sources of SO₂, they contribute a smaller percentage compared to the electricity generation sector.
• Ships and Locomotives (Options A & B – Incorrect): While internal combustion engines in ships, locomotives, and heavy equipment burn high-sulfur fuel, global and regional regulations (such as IMO 2020 for shipping) have significantly reduced their share of total emissions compared to stationary power generation.

Environmental Impact: Sulfur dioxide is a primary precursor to acid rain, which can harm aquatic ecosystems and damage vegetation. In the atmosphere, SO₂ can also react to form particulate matter, which contributes to haze and respiratory health issues in humans.