Perchloroethylene(PCE) , also known under its systematic name tetrachloroethylene and many other names, is a chlorocarbon with the formula Cl2C=CCl2. It is a colourless liquid and has a sweet odor detectable by most people at a concentration of 1 part per million (1 ppm).
Uses
The liquid is mostly applied in industries, including appliance, automotive and the aerospace industries. This liquid is useful for vapor degreasing of metal parts during various production stages.
Because of its high boiling point and long cleaning cycle, difficult greases and waxes can be removed by, essentially, being melted. Lightweight parts have longer vapor contact time for more effective cleaning. Also, the high boiling point helps enable more penetration of the liquid in order to clean more thoroughly. Because Perchloroethylene is more stable than other chlorinated solvents, it is easier to use when cleaning parts with moisture entrapped. Perchloroethylene has a low vapor pressure and high vapor density, which results in lower emissions compared to other cleaning choices, such as trichloroethylene.
It has been marketed in an aerosol formulation, particularly for the automotive industry, including brake cleaning. Additionally, Perchloroethylene can be used as a water repellent for clothes, as a spot remover, as a silicone lubricant and as an insulating fluid in some electrical transformers.
Production
Production of tetrachloroethylene was 405 million lbs in 1986. Major releases to air and water are from dry cleaning and industrial metal cleaning or finishing. Water pollution can occur from tetrachloroethylene leaching from vinyl liners in some types of pipelines used for water distribution, and during chlorination water treatment.
From 1987 to 1993, according to EPA’s Toxic Chemical Release Inventory, perchloroethylene releases to land and water totalled over 1 million lbs. These releases were primarily from alkali and chlorine industries which use it to make other chemicals. The largest releases occurred in Louisiana and South Carolina.
Regulation
In 1974, Congress passed the Safe Drinking Water Act. This law requires EPA to determine safe levels of chemicals in drinking water which do or may cause health problems. These non-enforceable levels, based solely on possible health risks and exposure, are called Maximum Contaminant Level Goals(MCLG). The MCLG for PCE has been set at zero because EPA believes this level of protection would not cause any of the potential health problems described below
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