Astonishing Facts About Sulfur Dioxide: What You Need to Know

by | Oct 13, 2023 | Environmental Impact Assessment

Home » Conservation » Environmental Impact Assessment » Astonishing Facts About Sulfur Dioxide: What You Need to Know

Sulfur dioxide is a toxic, colourless gas with a distinct and unpleasant odour. Its odour is frequently compared to those of a burning matchstick. When the gas oxidizes to sulphuric acid (H2SO4) by mixing with water vapour, it produces secondary particulate matter (PM2.5). It also interacts with ammonia (NH3) to form ammonium sulfate ((NH4)2SO4), a hazardous chemical. Sulfurous smog is caused by an elevated level of sulfur oxides (SOx) in the environment and is aggravated by moisture and particle matter (PM).

In this article, you will get to know some interesting facts about Sulfur Dioxide, its exposure risk, source of emission, and much more.

sulfur dioxide diagram

Sources Of Emissions Of Sulfur Dioxide: Unveiling The Culprits

Natural Sources

Large amounts of sulfur dioxide are released into the atmosphere during volcanic eruptions. The massive amounts of sulfur dioxide generated during a single discharge can significantly impact the worldwide climate. Similarly, sulfur dioxide is released into the atmosphere by hot springs. Even the interaction of hydrogen sulfide with oxygen in the air can yield sulfur dioxide. Hydrogen sulfide is emitted by marshes and other areas where biological degradation occurs.

Anthropogenic Sources

Sulphur dioxide emissions are caused mainly by the combustion of fossil fuels that, include coal, oil, and natural gas. Coal-fired power plants, in particular, are significant emitters of sulfur dioxide, accounting for half the annual emissions, according to the Tropospheric Emission Monitoring Internet Service (TEMIS). Furthermore, oil combustion accounts for another 25-30% of emissions. Sulfur dioxide emissions are caused mainly by power plants that use fossil fuels to generate energy. Industrial processes emit additional minor amounts of sulfur dioxide. These include metal extraction from ore and the use of high-sulfur fuels by locomotives, huge ships, and non-road equipment.

Certain dried fruits are kept using SO2 to avoid discolouration. SO2 is also employed as a fumigant and in bleaching products. Tobacco smoke, incorrectly or insufficiently vented gas equipment (like stoves, ranges, furnaces, or laundry dryers), gas or kerosene heating systems, wood or coal stoves, automotive exhaust from adjoining garages, and faulty chimneys can all produce sulfur dioxide gas in the home.

Who Are At Risk?

People who are susceptible to sulfur dioxide include:

  • People suffering from respiratory disorders such as chronic bronchitis, asthma, and emphysema will often suffer more severe health consequences at greater SO2 levels.
  • Since the lungs are still maturing, children are more vulnerable to SO2 exposure. Children are also more likely to develop asthma, which might worsen when exposed to SO2.
  • SO2 exposure may be more harmful to older people because they have a greater probability of having already present lung or cardiovascular problems.
  • Active persons of any age who work out or outside are more exposed to sulfur dioxide than less active people.

Exposure Information

SO2 can enter your body through the air or contact with your skin. People who reside near industrial sulfur dioxide sources may be in contact with it in the air. Suppose you engage in sectors where SO2 is generated, like copper smelting or power plants, or where it is utilized to manufacture sulfuric acid, paper, preservatives for food, or fertilizers. In that case, you are more susceptible. People whose homes have defective appliances or chimneys may also be subjected to sulfur dioxide.

The majority of SO2 infections happen by people breathing polluted outdoor air. People with breathing issues, including asthma, should pay more attention to these air alerts. Special precautions should be taken with children who have asthma to minimize their outdoor activities on days when pollution levels are high.

You can limit your exposure to sulfur dioxide from sources that are in your house by doing the following:

  • Use electronic (pilotless) ignition on gas appliances. This will get rid of the constant low-level pollutants emitted by pilot lights.
  • Instead of fans that recirculate air inside, use exhaust fans over gas burners vented to the outside. Keep your exhaust fans’ metal mesh filters cleaned (most can be washed in the dishwasher).
  • Whenever possible, choose vented appliances that are vented to the outside. Annually, have a skilled specialist inspect your devices.
  • Never use a gas stove or stove to heat your home.
  • Do not leave your automobile idling in the garage.
  • Indoor smoking is not permitted.

Unknown Facts About The Harmful Threats Of Sulfur Dioxide

1. Acid Rain

When discharged into the atmosphere, SO2 can combine with oxygen and water to generate sulphuric acid. Sulphuric acid, a primary component of acid rain, can significantly harm trees, crops, streams, and other environments.

2. Foliage Loss

At high amounts, sulfur dioxide in the atmosphere can cause severe damage to plants. The poisonous gas can induce bleaching or dark colouration on broad-leaved plant leaves and browning and wilting of conifer needles.

3. Visibility And Air Quality

SO2 is one of the numerous sulfur oxides that can generate tiny particulate matter when combined with other atmospheric chemicals. This can result in a relatively low-lying haze that reduces sight, blocks sunlight, and impairs plant growth. Not only are cities affected by SO2-related fog, but numerous wilderness regions and national parks in the United States are also affected by air pollution.

The long-term impacts caused by atmospheric SO2 are apparent to the human eye, with scientists warning that excessive air pollution is causing the Taj Mahal in India to turn yellow.

4. Respiratory And Other Illnesses

Sulfur dioxide (SO2) and other sulfur oxides can severely harm the human lungs and respiratory tract. Breathing in SO2 can cause acute lung injury and exacerbate pre-existing illnesses, including bronchitis and asthma.

The mucous membranes and skin of the nose, eyes, throat, and lungs are irritated by sulfur dioxide. High SO2 concentrations can cause respiratory system inflammation and irritation, especially after vigorous physical exercise. Symptoms can involve pain while breathing a long breath, coughing, throat inflammation, and difficulty breathing. In susceptible groups, high SO2 concentrations can impair lung function, exacerbate asthma attacks, and exacerbate pre-existing cardiac disease. This gas can also combine with chemical compounds in the air to form tiny particles that can enter the lungs and have similar health effects.

5. Affects National Parks

Sulfur dioxide substantially impacts Hawai’i Volcanoes National Park since high quantities are hazardous to human health. At Hawai’i Volcanoes National Park and other national parks, sulfate particles can also cause haze and decrease vision.  SO2 can be converted to acid in the environment and fall to Earth as rain, snow, fog, or dry particles. This air deposition can harm vegetation, wreak havoc on soils, acidify streams and lakes, and monuments, constructions, and sculptures at our national cultural monuments.

Bottom Line

Sulfur is one of 118 recognized chemical elements, and while it is a naturally occurring component, it can have significant environmental repercussions in some conditions. When sulfur-containing materials like fossil fuels are burned, the element interacts with oxygen to form sulfur dioxide (SO2). SO2, classified as a pollutant by the Environmental Protection Agency, is a poisonous gas that endangers the environment and human health.

Most of the sulfur dioxide discharged into the environment originates from power plants, particularly those burning coal. Petroleum refineries, cement manufacture, paper pulp manufacturing, and metal melting and processing plants are all sources of sulfur dioxide. Locomotives, huge ships, and specific non-road diesel equipment currently burn high-sulfur fuel, emitting sulfur dioxide into the atmosphere. Volcanic eruptions in nature can emit sulfur dioxide into the atmosphere. Sulfur dioxide may trigger respiratory disorders such as bronchitis and may irritate your nose, throat, and lungs. Coughing, wheezing, phlegm, and asthma attacks may result. When you exercise, the consequences are exacerbated. Sulfur dioxide is believed to be connected to heart disease.

Also Read: Physicochemical Methods of Wastewater Management



  • Dr. Tanushree Kain

    Tanushree is a passionate Environmentalist with a Doctorate in Environmental Sciences. She is also a Gold medalist in Master of Science (M.Sc), Environmental Sciences. She has 6 years of experience as a guest faculty in Environmental Sciences. With her combination of technical knowledge and research expertise, she can create clear, accurate, and engaging content that helps users get the maximum information regarding environmental topics.

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