The facts on Dichloromethane

Older data (CAREX) from 1990 show occupational exposure to dichloromethane (also known as methylene chloride or chloroform) for approximately 250,000 workers in the EU (15 Member States). However, the use of dichloromethane has since been significantly restricted (REACH Regulation, Drinking Water Directive).

Current estimates of occupational exposure to dichloromethane in the EU are not available. The main routes of exposure in the workplace are the respiratory tract and the skin. Dichloromethane has a harmonised classification according to CLP as carcinogenic category 2. The IARC classifies the substance as a Group 2A carcinogen (probably carcinogenic to humans). Dichloromethane is suspected of causing pancreatic, lung and liver cancer.

Where risks occur

Dichloromethane is primarily used as a paint stripper, degreaser, propellant, refrigerant and extraction solvent. It is highly volatile, dissolves many organic substances and is therefore also used as a solvent for resins, fats, plastics and bitumen. It also serves as an adhesive for special applications (acrylic glass, polystyrene).

Dichloromethane is highly volatile, meaning that when used over a large area, high concentrations can quickly build up in the air and be inhaled. During such large-scale applications, like degreasing or bonding of (plastic) surfaces, high concentrations of dichloromethane may still occur in the air breathed. High intensity exposures are possible for workers who use paint strippers (construction industry, renovation) and during tasks like tank cleaning, degreasing, confined space maintenance. Medium intensity exposures are typical in chemical manufacturing, pharmaceutical production and solvent formulation while low intensity exposures can be expected in analytical, research and healthcare laboratories, for laboratory staff and in the pharmaceutical industry (extraction agents), and when carrying out plastic surface treatments with degreasing agents and adhesives.

More about the substance

Dichloromethane is an aliphatic, saturated halogenated hydrocarbon which, in its pure form, is a colourless liquid with a chloroform-like odour. It has a low boiling point of 40°C and a vapour pressure of 470 hPa (at 20°C) and is highly volatile. When products containing dichloromethane are used, approximately 85% of the substance is released into the environment. Under normal conditions of use, dichloromethane is not flammable; however, there may be a risk of explosion in closed containers.

Due to the restrictions on use under the REACH Regulation, paint strippers containing more than 0.1% by weight of dichloromethane may only be used commercially by specially trained personnel. The combustion of dichloromethane can produce gaseous, highly toxic phosgene.

Hazards that may occur

If the substance is absorbed in liquid form, e.g. through the skin, it primarily affects the central nervous system and causes symptoms such as headaches, dizziness, nausea, numbness, and impaired concentration. In the body, dichloromethane is converted into carbon monoxide, thereby causing carbon monoxide poisoning. Irritation of the respiratory tract and eyes, loss of appetite, poor concentration and fatigue may also occur.

Prolonged skin contact leads to the breakdown of fatty tissue, thereby causing rashes and itching of the skin. Dichloromethane vapours are heavier than air and therefore accumulate near the ground. Inhalation of vapours can cause damage to the optic nerve and the liver (hepatitis).

The most relevant effect of long‑term exposure is carcinogenicity. Dichloromethane is suspected of causing cancer of the pancreas, lung and liver.

The latency periods for the development of cancer following exposure to dichloromethane can range from 20 to 30 years.

What you can do

First and foremost, you should check whether products containing dichloromethane can be replaced by less hazardous or non-hazardous alternatives. There are a wide variety of alternative products, particularly for use as a propellant. If no substitute is available, appropriate health and safety measures must be implemented, especially for large-scale applications, to protect exposed workers. Vapours must be captured and extracted at the source or close to the ground using extraction systems. The number of exposed persons and the duration of exposure must be kept to a minimum. Exposed workers must be regularly instructed, in a comprehensible manner, on the risks of dichloromethane and the implementation of protective measures. Once all the measures mentioned have been exhausted, the uptake of dichloromethane into the body can be further reduced through the use of suitable personal protective equipment (PPE) and work clothing. PPE and work clothing must be capable of being cleaned and stored hygienically. When using respiratory protection and gloves, the manufacturer’s instructions regarding suitability, handling, maintenance, cleaning and breakthrough time must be followed.

References: OECD, ECHA; EU-OSHA, Gestis, EC, UBA.