Manufacturing impurities in chlorinated solvents have been considered to be sources of contamination in groundwater. Chlorinated solvents are manufactured in a variety of grades; the technical grade is used at many industrial and manufacturing facilities. Compounds present as manufacturing impurities in technical grade chlorinated solvents vary, and their quantity is extremely small or not measurable, because chlorinated solvents historically have been manufactured to a high degree of purity. The purity of currently manufactured TCE ranges from 99.9% for reagent grade to 98.0% for the technical grade. Impurities in technical grade 1,2-dichloroethane, also known as ethylene dichloride (EDC), manufactured within the last 10 years with purities of 99.9991% and 99.9955% contained PCE between about 0.0001% and 0.0006%, respectively.

In a number of litigation cases where TCE released from a vapor degreaser is the major contaminant in groundwater, there is an accompanying minor concentration of PCE. The assumption made in these cases is that the PCE impurity in technical grades of TCE is the source of the PCE in groundwater. This assumption is based on the release of these two compounds together from a distillation bottom residue where PCE is concentrated, relative to the TCE, because of its much higher boiling point at atmospheric pressure.

There is no peer reviewed literature that can be cited to prove that PCE is a significant impurity in either the distillation bottoms produced from a vapor degreaser or technical grade TCE. PCE, if present as a manufacturing impurity, is present in such small amounts that significant concentrations would not be generated in groundwater. When PCE and TCE are present together in groundwater, the source of the PCE is likely not an impurity in the manufactured TCE.