[12] The output of these processes is a mixture of chloromethane, dichloromethane, chloroform, and carbon tetrachloride as well as hydrogen chloride as a byproduct.

DCM was first prepared in 1839 by the French chemist Henri Victor Regnault (1810–1878), who isolated it from a mixture of chloromethane and chlorine that had been exposed to sunlight.

[14] DCM's volatility and ability to dissolve a wide range of organic compounds makes it a useful solvent for many chemical processes.

[18] Dichloromethane extract of Asparagopsis taxiformis, a seaweed fodder for cattle, has been found to reduce their methane emissions by 79%.

[19] It has been used as the principal component of various paint and lacquer strippers, although its use is now restricted in the EU and many such products now use benzyl alcohol as a safer alternative.

[21] Tertiary amines can react with DCM to form quaternary chloromethyl chloride salts via the Menshutkin reaction.

[23] At increased temperatures, pyridines including DMAP, react with DCM to form methylene bispyridinium dichlorides.

[24] Hydroxybenzotriazole and related reagents used in peptide coupling react with DCM in the presence of triethylamine, forming acetals.

[1][28] Symptoms of acute overexposure to dichloromethane via inhalation include difficulty concentrating, dizziness, fatigue, nausea, headaches, numbness, weakness, and irritation of the upper respiratory tract and eyes.

[28] People with existing liver, nervous system, or skin problems may worsen after exposure to methylene chloride.

These workers had been working alone, in poorly ventilated bathrooms, with inadequate or no respiratory protection, and no training about the hazards of DCM.

[40] On March 15, 2019, the US Environmental Protection Agency (EPA) issued a final rule to prohibit the manufacture (including importing and exporting), processing, and distribution of DCM in all paint removers for consumer use, effective in 180 days.