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From 2014.igem.org
Chlorinated Solvents
Uses of Chlorinated Solvents
Chlorinated solvents are organic solvents containing chlorine atoms in their molecular structure. They have a huge range of uses by individuals, professionals, and industry.
The chlorinated solvent methylene chloride (also known as dichloromethane or DCM) has been used in industry for over 80 years. Its unique combination of properties - low boiling point, high solvency power, relative inertness, low toxicity and non flammability - has led to its wide variety of applications. It is the most widely-used of the chlorinated solvents, particularly for pharmaceutical production, and is as well used as an extraction medium/process solvent.(Eurochlor). For these reasons, our team has chosen to use DCM as the case study chemical for which we will develop a bioremedication mechanism eventually applicable to all chlorinated solvents.
Who produces chlorinated solvent waste, and why? Eurochlor, the EU body responsible for the European Chlorinated Solvents Association) analyses the uses and impact of chlorinated solvents in three categories: industrial, professional, and consumer. Today the four most commonly used chlorinated solvents are dichloromethane (DCM - also known as methyl chloride [CH2Cl2]), trichloroethylene (aka trichloroethene [C2HCl3]), perchloroethylene (aka tetrachloroethene [C2Cl4]), and to a lesser extent, trichloromethane(aka chloroform[CHCl3]). Hover over each application to reveal more information...
Industrial Uses
Adhesives & Sealants ↴ - Foam Blowing and Fire Extinguishers
- Food Manufacture
- Recycling
- Decorating
- Extraction Solvent
- Cleaning
- Textile Industry
- Functional Fluid
Coatings and adhesives sometimes require the dissolving power of chlorinated solvents to solubilize the wide variety of thermoplastic ingredients. DCM and trichloroethylene feature rapid drying rates and low flammability that make them ideal for use in rubber cements, styrenics, and epoxies.
Chlorinated solvents are commonly used as propellants in fire extinguishers and in foam blowing as they are capable of producing a cellular structure in materials such as polymers, metals, and plastics.
The food industry uses over 3000 metric tons of chlorinated solvents annually, despite efforts to reduce this figure. Unfortunately gentler extraction methods used in process such as decaffineation of coffee often leaves some of the essential substance behind, and new technologies such as supercritical carbon dioxide extraction and liquid carbon dioxide extraction remain prohibitively expensive for many companies.1. .
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Textiles manufacturing produces over 10.5 metric tons of chlorinated solvent waste annually. Unfortunately attempts to replace the use of chlorinated solvents with other harmful substances have so far proved difficult: aqueous scouring, an alternative to cleaning textiles using chlorinated solvents, is more energy intensive and less effective; common replacements generally use additives which bring their own environmental problems; modern technologies remain prohibitively expensive.
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Professional Uses
- Packaging & (Re)-Filling
- Adhesives
- Aerosols
- Laboratory Use
- Manual Cleaning
- Decorating
- Dry Cleaning
- Film Cleaning and Copying
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Consumer Uses
- Aerosols
- Glue
- Decorating
- Washing and cleaning products
- Pest Control
Despite controversies chlorinated solvents remain present in a range of aerosol products including hairspray and deodorant
.Chlorinated solvents are used in a wide variety of adhesive products available to consumers, including carpet glue, spray and tube adhesives, superglue, and wood parquet glue.
Chlorinated solvents are common ingredients in materials such as paint spray and paint stripper - although since 2010 DCM is no longer permitted in home use paint strippers, in part due to problems encountered with disposal, chlorinated solvents continue to be used for this purpose in non-EU countries.
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Chlorinated solvents are used in various plant protection products, both for large-scale agriculture and for home-use, and in other pest control sprays.
Disposal of Chlorinated Solvents
Information...
Atmosphere
The Environmental Protection Agency has expressed fears that even short lived halocarbons may have a significant detrimental effect on the global atmosphere, as well as concerns about our relative lack of understanding of the environmental effects of these compounds2. Several chlorinated solvents are listed by the U. S. Environmental Protection Agency (U.S. EPA) as a hazardous air pollutant (HAP) under the U.S. Clean Air Act. However, various environmental NGOs and organisations maintain that current regulation of chlorinated solvent disposal is inadequate - for example, chlorinated solvents are not regulated under the Montreal Protocol despite evidence that they may contribute to ozone depletion.
Photochemical Smog
Global Warming
Dichloromethane has a Global Warming Potential (GWP) ten times greater than that of carbon dioxide, whilst trichloromethane has a GWP 30 times greater. At the time of writing the GWPs of tetrachloroethene and trichloroethene are not known, but are expected to be comparable to those for DCM and TCM.Acid Rain
In the lower atmosphere degradation of chlorinated solvents is initiated by a reaction with the hydroxyl radical, and forms a variety of products including hydrochloric acid, formic acid, and phosgene (the colourless gas infamous for its use as a chemical weapon during World War One). These compounds dissolve in cloud and rain water and are ultimately deposited from the atmosphere in acid rain and snow.Further, trichloroacetic acid (TCA) can be formed as a minor product in the atmospheric deg-radation of some chlorinated solvents. Studies have shown that TCA is broadly distributed in precipitation, surface water and soil on a global scale. Since the observed levels in soil in some areas have been found to exceed the accepted 'safe' levels (2.4 μg/kg for terrestrial organisms) the European Commission instructed producers of the relevant solvents to carry out extensive studies of the origin and fate of environmental TCA. Although the results of these studies suggest that TCA levels in soils could not be explained by precipitation alone, the European Union Risk Assessment on nevertheless concluded that “it is considered unlikely that depo-sition of TCA from the atmosphere will by itself lead to levels of TCA in soil that pose a risk for ter-restrial organisms”.
Biosphere
The No Observed Effect Concentration (NOEC) for the most sensitive species of plants was 46 μg/m
The Environmental Protection Agency has expressed fears that even short lived halocarbons may have a significant detrimental effect on the global atmosphere, as well as concerns about our relative lack of understanding of the environmental effects of these compounds1. Several chlorinated solvents are listed by the U. S. Environmental Protection Agency (U.S. EPA) as a hazardous air pollutant (HAP) under the U.S. Clean Air Act. However, various environmental NGOs and organisations maintain that current regulation of chlorinated solvent disposal is inadequate - for example, chlorinated solvents are not regulated under the Montreal Protocol despite evidence that they may contribute to ozone depletion.
Photochemical Smog
Global Warming
Dichloromethane has a Global Warming Potential (GWP) ten times greater than that of carbon dioxide, whilst trichloromethane has a GWP 30 times greater. At the time of writing the GWPs of tetrachloroethene and trichloroethene are not known, but are expected to be comparable to those for DCM and TCM.Acid Rain
In the lower atmosphere degradation of chlorinated solvents is initiated by a reaction with the hydroxyl radical, and forms a variety of products including hydrochloric acid, formic acid, and phosgene (the colourless gas infamous for its use as a chemical weapon during World War One). These compounds dissolve in cloud and rain water and are ultimately deposited from the atmosphere in acid rain and snow.Further, trichloroacetic acid (TCA) can be formed as a minor product in the atmospheric deg-radation of some chlorinated solvents. Studies have shown that TCA is broadly distributed in precipitation, surface water and soil on a global scale. Since the observed levels in soil in some areas have been found to exceed the accepted 'safe' levels (2.4 μg/kg for terrestrial organisms) the European Commission instructed producers of the relevant solvents to carry out extensive studies of the origin and fate of environmental TCA. Although the results of these studies suggest that TCA levels in soils could not be explained by precipitation alone, the European Union Risk Assessment on nevertheless concluded that “it is considered unlikely that depo-sition of TCA from the atmosphere will by itself lead to levels of TCA in soil that pose a risk for ter-restrial organisms”.
Groundwater
The Environmental Protection Agency has expressed fears that even short lived halocarbons may have a significant detrimental effect on the global atmosphere, as well as concerns about our relative lack of understanding of the environmental effects of these compounds1. Several chlorinated solvents are listed by the U. S. Environmental Protection Agency (U.S. EPA) as a hazardous air pollutant (HAP) under the U.S. Clean Air Act. However, various environmental NGOs and organisations maintain that current regulation of chlorinated solvent disposal is inadequate - for example, chlorinated solvents are not regulated under the Montreal Protocol despite evidence that they may contribute to ozone depletion.
Photochemical Smog
Global Warming
Dichloromethane has a Global Warming Potential (GWP) ten times greater than that of carbon dioxide, whilst trichloromethane has a GWP 30 times greater. At the time of writing the GWPs of tetrachloroethene and trichloroethene are not known, but are expected to be comparable to those for DCM and TCM.Acid Rain
In the lower atmosphere degradation of chlorinated solvents is initiated by a reaction with the hydroxyl radical, and forms a variety of products including hydrochloric acid, formic acid, and phosgene (the colourless gas infamous for its use as a chemical weapon during World War One). These compounds dissolve in cloud and rain water and are ultimately deposited from the atmosphere in acid rain and snow.Further, trichloroacetic acid (TCA) can be formed as a minor product in the atmospheric deg-radation of some chlorinated solvents. Studies have shown that TCA is broadly distributed in precipitation, surface water and soil on a global scale. Since the observed levels in soil in some areas have been found to exceed the accepted 'safe' levels (2.4 μg/kg for terrestrial organisms) the European Commission instructed producers of the relevant solvents to carry out extensive studies of the origin and fate of environmental TCA. Although the results of these studies suggest that TCA levels in soils could not be explained by precipitation alone, the European Union Risk Assessment on nevertheless concluded that “it is considered unlikely that depo-sition of TCA from the atmosphere will by itself lead to levels of TCA in soil that pose a risk for ter-restrial organisms”.
Marine Environment
Chlorinated solvents are generally highly volatile and only sparingly soluble in water. Even if traces of solvents are briefly present in aqueous waste streams, they volatilise from rivers and lakes with a half-life of about a month or less, unless they are trapped in groundwater. Nevertheless, presence of chlorinated solvents is a concern due to its potential impact on marine life...
The Environmental Protection Agency has expressed fears that even short lived halocarbons may have a significant detrimental effect on the global atmosphere, as well as concerns about our relative lack of understanding of the environmental effects of these compounds1. Several chlorinated solvents are listed by the U. S. Environmental Protection Agency (U.S. EPA) as a hazardous air pollutant (HAP) under the U.S. Clean Air Act. However, various environmental NGOs and organisations maintain that current regulation of chlorinated solvent disposal is inadequate - for example, chlorinated solvents are not regulated under the Montreal Protocol despite evidence that they may contribute to ozone depletion.
Photochemical Smog
Global Warming
Dichloromethane has a Global Warming Potential (GWP) ten times greater than that of carbon dioxide, whilst trichloromethane has a GWP 30 times greater. At the time of writing the GWPs of tetrachloroethene and trichloroethene are not known, but are expected to be comparable to those for DCM and TCM.Acid Rain
In the lower atmosphere degradation of chlorinated solvents is initiated by a reaction with the hydroxyl radical, and forms a variety of products including hydrochloric acid, formic acid, and phosgene (the colourless gas infamous for its use as a chemical weapon during World War One). These compounds dissolve in cloud and rain water and are ultimately deposited from the atmosphere in acid rain and snow.Further, trichloroacetic acid (TCA) can be formed as a minor product in the atmospheric deg-radation of some chlorinated solvents. Studies have shown that TCA is broadly distributed in precipitation, surface water and soil on a global scale. Since the observed levels in soil in some areas have been found to exceed the accepted 'safe' levels (2.4 μg/kg for terrestrial organisms) the European Commission instructed producers of the relevant solvents to carry out extensive studies of the origin and fate of environmental TCA. Although the results of these studies suggest that TCA levels in soils could not be explained by precipitation alone, the European Union Risk Assessment on nevertheless concluded that “it is considered unlikely that depo-sition of TCA from the atmosphere will by itself lead to levels of TCA in soil that pose a risk for ter-restrial organisms”.
