What is dichloromethane?

Dichloromethane, also known as methylene chloride, is a colourless, volatile liquid with a sweet, chloroform-like odour. It is mainly used in industry as a solvent, for example in paint strippers, adhesives, degreasing agents and in pharmaceutical manufacturing. Due to its high solvency and moderate evaporation rate, it is suitable for many applications, but is increasingly regulated due to health risks.

Formation

Dichloromethane is produced industrially by chlorinating methane or chloromethane at elevated temperatures. In addition to DCM, other chlorination products such as chloroform and tetrachloromethane are also produced, which are separated by distillation.

Detection

DCM is a clear, highly volatile liquid with a characteristic sweet odour that is noticeable at low concentrations. It is poorly soluble in water but highly soluble in most organic solvents. Due to its high volatility, it evaporates quickly at room temperature and can rapidly reach high concentrations in the air if ventilation is inadequate.

Limit values

The occupational exposure limit (OEL) for dichloromethane in the EU is 100 ppm (350 mg/m³) as a time-weighted average over eight hours. Short-term exposure should be minimised. Due to its potentially carcinogenic properties, additional occupational safety measures are required in many countries.

Hazards

DCM can be harmful to health if inhaled, swallowed or in contact with the skin. It irritates the eyes and respiratory tract and can cause dizziness, headaches, nausea and central nervous system disorders. In the body, DCM can be metabolised to carbon monoxide, which can impair the oxygen supply to the blood. Long-term exposure poses a cancer risk. In the environment, DCM is volatile and can contribute to air pollution, but it degrades relatively quickly in water.