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IAQUK Resources - Methylene Chloride

Sources of Pollution

 

Methylene Chloride is a widely used chemical solvent with a diverse number of applications.  It was introduced as a replacement for more flammable solvents over 60 years ago.  Predominantly Methylene Chloride is used as a solvent, but because it has a low level of solubility, it can also be used as a water-repellent.

 

The World Health Organisation analysed the use and determined that 23% was primary used for solvent properties. It is also used as an aerosol propellant (20%). Methylene Chloride is volatile and essentially non-flammable, however it can form an explosive mixture when mixed with oxygen; processing solvent in the manufacture of steroids, antibiotics, vitamins, and tablet coatings (20%); as a degreasing agent (8%); in electronics manufacturing (7%); and as a polyurethane foam blowing agent (5%).

 

Methylene Chloride has been used in the manufacture of photographic film, as a flame retardant in conjunction with flammable alkane propellants, used as an extracting and degreasing agent, in electronics and manufacturing. In the food industry, it has been used to decaffeinate coffee and tea as well as to prepare extracts of hops and other flavourings.  It can be found in spray shoe polish, water repellent/protectors, spot removers, wood floor and panel cleaners, contact cement, super glues, spray adhesives, adhesive removers (general purpose, tile and wallpaper), silicone lubricants (excluding vehicles), specialised electronic cleaners (for TV, VCR, razor, etc.) also wood stains, varnishes and finishes, paint thinners, paint removers, aerosol spray paints, primers, aerosol rust removers, outdoor water repellents, glass frosting/artificial snow, spray lubricant for cars, transmission cleaners, battery terminal protector, brake quieter/cleaner and gasket removers.

 

The amount of Methylene Chloride used varies within the products and some manufacturers have removed the component completely from their product.  The use of Methylene Chloride has slowly started to decline with more low risk components being replaced within products.   50% of Methylene Chloride dispensed into the air will still be present after 53 to 127 days.   Methylene Chloride has been banned in many products, particularly when applied as an aerosol.

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Health effects

Overexposure most often affects the nervous system (brain), skin, eyes, nose and throat. Methylene Chloride can affect your brain the same way drinking alcohol does. Overexposure for a short time causes headaches and nausea, dizziness, clumsiness, drowsiness and other effects like those of being drunk. These effects can increase your risk of being injured. Drinking alcohol within a few hours of exposure increases these effects and makes them last longer.

 

The symptoms of short-term exposure usually clear up within a few hours after exposure stops. Repeated, frequent overexposure to Methylene Chloride and other solvents over months and years can have long-lasting and possibly permanent effects on the nervous system. The symptoms include fatigue, sleeplessness, poor coordination, loss of short-term memory, and personality changes such as depression, anxiety and irritability.

 

Methylene Chloride can irritate your eyes, nose, and throat.  Methylene Chloride can make pre-existing angina (heart pain) worse and cause other heart symptoms in people with heart disease. In healthy people, Methylene Chloride is not likely to affect the heart. Extremely high exposure levels, however, can cause heart failure and sudden death.

 

Methyene Chloride is not likely to damage the liver or kidney if exposures are kept at legal limits and there are no noticeable effects on the nervous system. Methylene Chloride causes cancer in animals and potentially can cause cancer in humans. It is regulated as a cancer-causing chemical in the workplace.

 

Methylene Chloride does not appear to be more harmful to the developing fetus than to the adult. It does not cause birth defects or other developmental harm when tested in pregnant animals. Like most organic solvents, when inhaled, Methylene Chloride can reach the developing fetus through the placenta and can enter the breast milk. You should avoid overexposure if you are pregnant or breastfeeding.

 

Methylene Chloride breaks down into carbon monoxide (CO) in your body. CO can cause nervous system effects like those described above. Smoking also puts CO in your blood, so smokers can have these symptoms at lower Methylene Chloride levels than non-smokers.

 

CO also stresses the heart, and people with angina (chest pains) from coronary artery  disease are extremely sensitive to CO; Methylene Chloride can make angina worse, even with exposures below the limits. People with heart or lung conditions, smokers, people who are overweight or pregnant, and people with other exposure to carbon monoxide should limit their exposures to Methylene Chloride.

Technical - Methylene Chloride - CH 2CI2


  • 2 hydrogen and 2 chlorine atoms linked to a central carbon atom
  • Colourless liquid
  • Moderate sweet aroma
  • CAS Number: 75-09-2
  • LTEL - 100ppm (350 mg/m³)
  • STEL - 300ppm (1060mg/m³)
  • Risk Phrases: R20, 22, 40
  • Safety Phrases: S23, 24, 25, 36, 37

Methylene Chloride (DCM or Dichloromethane).

 

Other names: HCC 30, Methane Dichloride, Methylene Chloride, Methylene Dichloride, Aerothene MM, DCM, Narkotil, Solaesthin, Solmethine, NCI-C50102, R 30, Methylene Bichloride, Freon 30.  thylene Chloride is a colourless, volatile liquid with a moderately sweet aroma. It is a man made substances and there are believed to be no natural sources of Methylene Chloride.  It was first prepared in 1840 by the French chemist Henri Victor Regnault. Regnault was interested in the thermal properties of gases and discovered that not all gases expand equally. Regnault often experimented with synthesizing gas and applying heat.

 

Methylene Chloride is currently produced by chlorinating methane gas at high temperature.  It will form an explosive mixture in an atmosphere with high oxygen content, or in the presence of liquid oxygen, nitrite, potassium, orsodium.  When heated to decomposition, it emits highly toxic fumes of phosgene.

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