What are organic sulfur compounds?

Organic sulfur compounds are chemical compounds that contain at least one sulfur atom in their structure and also have organic components. They occur both naturally and synthetically. Many are known for their characteristic intense odors, which are noticeable even in very low concentrations. They are used in the chemical industry, petroleum processing, the food industry (flavors), and as precursors for pharmaceuticals and pesticides.

Formation

Natural organic sulfur compounds are formed, for example, during the microbial degradation of organic matter, in volcanic gases, or in plants (e.g., Allium species such as garlic). Industrially, they are often obtained through thiolation, sulfidation, or petrochemical processes. In refineries, sulfur compounds are produced as by-products of crude oil processing and often have to be removed before further processing.

Detection

Organic sulfur compounds are often colorless to yellowish liquids or gases and are characterized by extremely low odor thresholds – often in the ppb range. Many smell foul, garlicky, or sulfurous. They are often volatile, highly flammable, and react with oxidizing agents. Due to their strong odor perception, some are specifically used as odorants for natural gas.

Limit values

Occupational exposure limits depend heavily on the specific compound. For example, ethanthiol has an OEL of 1 ppm (2.5 mg/m³) in the EU, while dimethyl sulfide has a limit of 10 ppm (25 mg/m³). Significantly lower limits apply to highly toxic sulfur compounds such as carbon disulfide.

Hazards

Many organic sulfur compounds are toxic, irritating, or harmful to the environment. Even in low concentrations, they can cause headaches, nausea, and respiratory irritation. In higher concentrations, some are neurotoxic. Due to their often unpleasant odor, they can cause odor nuisance and severely impair air quality. They are environmentally relevant due to their potential formation of sulfur dioxide during combustion.