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Sulfur Dioxide


CAS No. 7446-09-5

Sulfur dioxide (SO₂) is a colorless gas with a characteristic, irritating, pungent odor.  Exposure to sulfur dioxide may cause irritation to the eyes, nose, and throat. Symptoms include:  nasal mucus, choking, cough, and reflex bronchi constriction, and when liquid: frostbite  Workers may be harmed from exposure to sulfur dioxide. The level of exposure depends upon the dose, duration, and work being done.

Sulfur dioxide is used in many industries. It’s used to manufacture sulfuric acid, paper, and food preservatives.  Some examples of workers at risk of being exposed to sulfur dioxide include the following:

  • Factory workers in industries where it occurs as a by-product, such as copper smelting or power plants
  • Industry workers that manufacture sulfuric acid
  • Workers in plants that produce paper
  • Food processing to preserve foods, such as dry fruits
  • Workers who manufacture fertilizers

NIOSH recommends that employers use Hierarchy of Controls to prevent injuries. If you work in an industry that uses sulfur dioxide, please read chemical labels and the accompanying Safety Data Sheets for hazard information. Visit NIOSH’s page on Managing Chemical Safety in the Workplace to learn more about controlling chemical workplace exposures.

The following resources provide information about occupational exposure to sulfur dioxide. Useful search terms for sulfur dioxide include “sulfur oxide,” “sulfurous acid”, “anhydride,” and “sulfurous oxide.”

NIOSH Chemical Resources

Related NIOSH Resources

  • NIOSHTIC-2 search results on sulfur dioxide—NIOSHTIC-2 is a searchable database of worker safety and health publications, documents, grant reports, and journal articles supported in whole or in part by NIOSH.
  • NIOSH Worker Health Study Summaries—NIOSH conducts research to prevent illnesses and injuries in the workplace. The NIOSH Worker Notification Program notifies workers and other stakeholders about the findings of these research studies.

Selected Publications

Related Resources