Environmental Engineering Reference
In-Depth Information
the U.S. production history of the major chlorinated solvents. An approximate U.S. production of
chlorinated solvents in the early 1970s is represented by the following 1972 i gures (Considine, 1974):
Methyl chloroform
447 million pounds
Trichloroethylene
675 million pounds
Dichloromethane
500 million pounds
Perchloroethylene
500 million pounds
Methyl chloroform was substituted for trichloroethylene (TCE) beginning in the mid-1960s. The
change was largely due to the enactment of regulations that restricted the use of TCE. Methyl
chloroform production peaked in the mid-to-late 1980s. Reduced production was mandated by the
Montreal Protocol on substances that deplete the ozone layer, an agreement among the world's
nations to curtail the use of ozone-degrading compounds, including methyl chloroform. The
Montreal Protocol went into effect on January 1, 1989; it called for 100% reduction in the 1989
methyl chloroform production levels by January 1, 1996 (UNEP, 1999).
1.1.1 M
AJOR
A
PPLICATIONS
OF
C
HLORINATED
S
OLVENTS
The major chlorinated solvents were previously put to the following primary uses:
•
Degreasing
•
Extraction of oils or other food products
•
Text i le cle a n i ng
•
Wool processing
•
Preparation of inks, paints, varnish, and lacquer
•
Production of pharmaceuticals
•
Cleaning of electronics, semiconductors, and precision instruments
•
Cleaning of aircraft and other military hardware
•
Minor uses in veterinary and medical applications
•
A carrier for insecticides
•
Applying paints to automobiles and other metal surfaces
Solvent boiling point, solvent power (solvency), stability, availability, and cost were factors that
determined which solvents were used for particular applications. For example, perchloroethylene
boils at 121°C, whereas dichloromethane boils at 39.7°C. Therefore, dichloromethane may have
been preferred for cleaning electronics or other parts having plastics that are susceptible to melting,
and perchloroethylene may have been preferred for removing waxes and resins whose melting points
exceed the boiling point of other solvents.
1.1.1.1 Chlorinated Solvents in Historical or Current Use
1.1.1.1.1 Carbon Tetrachloride
Carbon tetrachloride is no longer produced for commercial use as an end product; it is still produced
as an intermediate for the production of other chemicals. It was phased out because of its toxicity and
its role as an ODC in the upper atmosphere. Carbon tetrachloride was the i rst of the major chlorinated
solvents to be used in North America, beginning in 1898; its production in Europe began in the 1890s
(Doherty, 2000a). It was used in i re extinguishers, in dry cleaning, as a grain fumigant, as a solvent for
the extraction of oils from seeds and animal products, in rubber production, in metal degreasing, in
rubber cement, in l oor wax, as a refrigerant, as a household cleaning agent, in insecticides, and in
numerous other applications (Irwin et al., 1997; Doherty, 2000a; European Chemicals Bureau, 2000b;
ATSDR, 2005). Carbon tetrachloride was used to make Freon compounds that were widely used as
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