Synonyms: perchloroethene, tetrachloroethene, tetrachloroethylene, may also be referred to as “Perc”
PCE is an organic chemical introduced in the environment by human activity. Specifically, it is a widely used solvent, especially in dry cleaning activities. PCE is also used as a degreaser and in some consumer products (e.g., shoe polish, typewriter correction fluid). Although not theoretically impossible, there is no evidence that PCE forms or occurs naturally in the environment. Thus, its detection in an environmental sample (e.g., groundwater, surface water, soil, indoor, or ambient air) is associated with PCE spills or accidental release.
PCE is toxic to humans at very low concentrations. The Environmental Protection Agency has established a Maximum Contaminant Level for PCE in water of 5 parts per billion (or micrograms per Liter). At this low amount, practically PCE cannot be perceived by smell or taste. For example, people may smell PCE in air at concentrations above 1 ppm (parts per million).
PCE is a halogenated organic compound composed of 2 atoms of carbon and 4 atoms of chlorine (two chlorine atoms linked to each carbon). The two carbons are linked with each other by a double chemical bond. Thus, PCE does not contain any hydrogen atoms.
PCE is a colorless liquid with a sweetish smell which is not flammable under normal temperature and pressure. It is part of a class of chemicals also known as halogenated volatile organic compounds (HVOCs). This means that PCE evaporates (goes from liquid into gaseous form when in contact with air).
PCE is also part of a class of chemicals referred to as “chlorinated solvents”. Due to the presence of one or more chlorine atoms in their structure chlorinated solvents are heavier than water. Chlorinated solvents are also referred to as Dense Non-Aqueous Phase Liquids (DNAPLs).
Basically, when spilled into the environment, part of the spilled PCE will evaporate, while another part will infiltrate through the ground into the subsurface.
Thus, PCE may travel in the subsurface as a DNAPL, as a dissolved phase into groundwater, and as a gaseous phase. As a DNAPL PCE may accumulate on the bottom of groundwater table in a dip. DNAPL flow direction is in general independent from groundwater flow direction, as it relates to sloping of underground low permeable layers. In contrast, the dissolved PCE phase will travel with groundwater. During subsurface transport, some PCE may be absorbed to soil particles. However, PCE does not strongly sorb to soil.
What makes PCE a problematic pollutant is its resistence to degradation/biodegradation, unlike, petroleum hydrocarbons (which usually degrade fast in the environment).
Through skin absorption (please note that PCE is not efficiently absorbed through the skin):
Through breast feeding – since PCE accumulates in milk due to its lipophilic nature
Exposure to PCE may cause a variety of health effects depending on the amount of PCE and exposure time. Such effects may include:
In chronic exposures:
In acute exposures (to high amounts of PCE):
Please note that the data related to such exposure pollution is usually obtained through animal studies and may not be verified in humans, however the potential to cause similar problems in humans remains.
PCE is reasonably anticipated carcinogen, which means that it was proven to cause tumors in mice and it has the potential to cause cancer in humans, especially when exposure to high amounts of PCE has occurred. The following type of cancers may be associated to exposure to PCE: