Health & Safety Overview of Tetrachloroethylene (PCE, PERC) & Trichloroethylene (TCE)

Tetrachloroethylene (PCE) and Trichloroethylene (TCE) are chlorinated liquid hydrocarbons, primarily used as degreaser agents for the cold cleaning of fabricated metal parts. They serve as general solvents for resins, fats, oils, waxes, rubber, paints, cellulose esters and ethers, and varnishes [1]. In the industry, both chemicals are of occupational concern because of their high toxicity levels and widespread usage; they have recently become the primary pollutants in most of the state and federal Superfund sites [2]. Moreover, traces of these harmful compounds have been found to occur in underground and surface water sources as a result of inappropriate manufacturing, consumption, and disposal practices [3].

Chlorinated solvents are usually difficult to biodegrade, and they pose a significant and continuing threat to the United States’ potable water supplies, as well as the worker’s welfare. Both PCE and TCE have been associated with toxic effects in the kidney and liver, and can also cause depression in the central nervous system, reproductive dysfunction, higher cancer incidence, among other diseases. In this regard, business owners and consumers, who are still employing these compounds, should keep an eye on the latest legislation and potential implications when using the chemicals, as well as identifying available alternatives.

What is Tetrachloroethylene?

Tetrachloroethylene, also known as perchloroethylene (PCE or PERC), is a nonflammable colorless liquid used for dry cleaning operations and as a starting material to synthesize other compounds. It has been associated with mild side effects after short-term exposure such as upper respiratory irritation, reversible mood, dizziness, sleepiness, headaches, and coordination impairment. Likewise, long-term exposure leads to severe adverse reactions such as cognitive damage, kidney & liver diseases, immunotoxicity, reproductive issues, and potential cancer development. As a result, the US Environmental Protection Agency (EPA) and other international organizations have classified it as likely to be carcinogenic to humans [4].

In the United States, PCE production peaked at 350 million kg in 1980 when it was introduced as a replacement alternative to trichloroethylene (TCE) for metal cleaning, vapor degreasing, textile processing, dry cleaning, and as a chemical precursor [5]. Since then, tetrachloroethylene production has been declining because of its toxic and rapid evaporation attributes, which have made it detectable in ground and surface water sources, air, soil, food, and even breast milk samples. The latest industrial reports indicate that 215 manufacturing companies have been continuously producing close to 65 million lbs. of PCE annually, and 22 other facilities import 26.5 million lbs. of the chemical into the country [6].

Recently, Superfund site investigations have been conducted involving the nearby communities to take robust response actions against tetrachloroethylene contamination. The first water source detection occurred in the 1990s during a routine sampling practice, and the number has been increasing since then with evidence of this substance in nearly 28% of the sites today. The major concerns resulting from inappropriate disposal of hazardous chemicals are the long-term cleanup efforts, leakage to other groundwater sources, and health risks for both humans and animals [7].

Tetrachloroethylene (PCE) Toxicity Case Studies 

Multiple case studies about the side effects of tetrachloroethylene (PCE) have been reported throughout the years due to its prevalence in the market. The toxic levels and exposure pathways may change depending on the type of clinical trial that was conducted or public release addressing major contamination evidence. Table 1 presents, in chronological order, the most relevant incidents related to tetrachloroethylene exposure, including the conditions in which they occurred, as well as the average toxic levels for each case.

Table 1. Case Studies on Tetrachloroethylene (PCE)

What is Trichloroethylene?

Trichloroethylene (TCE) is a volatile organic solvent used in multiple manufacturing industries (e.g., aircraft, spacecraft, electronic) to remove grease from metal parts. This colorless liquid has been associated with negative health effects such as upper respiratory irritation, kidney & liver dysfunction, developmental defects, immunosuppression, neurobehavioral changes, cancer development, among many others. Although TCE can be highly convenient for vapor degreasing of metal parts, governmental entities have listed it as a hazardous chemical substance that could leach into water supplies, feed, and air [33].

Along with Perchloroethylene, Trichloroethylene has also been widely produced and commercialized since the 1920s. On a global scale, roughly 80-90% of TCE production goes exclusively to the degreasing industry, being used in paints, adhesives, varnishes, and lacquer formulations. In the United States, TCE production peaked at 280 million kg in 1970 when it had been used in the food industry for decaffeination; in cosmetics as an extractant; in pesticides for spotting fluids; and even in pharmaceutics as a volatile anesthetic. Industrial working settings are the most usual way to get exposed to trichloroethylene, which has led to serious occupational health concerns[34].

Environmental fate testing shows that TCE can easily penetrate surface soils through volatilization, which makes it likely to migrate into groundwater sources. As a result of its prevalence in the environment, the general population − especially workers − can get exposed via ingestion, inhalation, and contact. Up to 2011, this toxic compound has been identified in more than 760 Superfund sites, and the ATSDR reported that between 9 to 34% of the drinking water supply sources in the country exhibited some TCE contamination [35]. Moreover, the National Health and Nutrition Examination Survey suggests that nearly 10% of Americans have detectable levels of TCE in their blood [36].

Trichloroethylene (TCE) Toxicity Case Studies 

The Environmental Protection Agency (EPA) has consistently released studies about the hazards that TCE can impose on humans, animals, and the environment. These reviews classify all health hazards in different categories according to the human tissues that are being or could be affected. Table 2 presents, in chronological order, the most relevant incidents related to trichloroethylene exposure, including the conditions in which they occurred, as well as the average levels of the compound for each case.

Table 2. Case Studies on Trichloroethylene (TCE)

Safety Regulations for PCE and TCE

As a response to the numerous human studies on PCE and TCE, many organizations have set recommendations addressing their usage. The most relevant national and international guidelines, regulations, and advisories regarding tetrachloroethylene and trichloroethylene are summarized in Table 3. The values represent the threshold levels that employers, importers, recyclers, and sellers should follow to avoid legal sanctions and protect the public and workers from adverse health effects from exposure. For the EPA and DOE guidelines, each consecutive AEGL and PAC number is associated with a progressively severe effect that involves a higher exposure level to the chemicals.

Table 3. Regulations and guidelines applicable to tetrachloroethylene [63] and trichloroethylene [64]

In the upcoming years, these regulations could significantly alter the production, usage, transport, storage, and disposal of cleaning products that contain chlorinated chemicals. Official statements about maximal levels permitted in food, water, plants, atmosphere, soil, and animal and human tissues are continuously modified and may not reflect the regulatory status for the chemicals in the future. Companies and customers who employ PCE and TCE for their daily operations should pay special attention to the general discontinuation, management efforts, and feasible alternatives in the market.

Alternatives to Tetrachloroethylene- and Trichloroethylene-Based Degreasers

Tetrachloroethylene- and Trichloroethylene-based degreasers have been popular for industrial cleaning applications because they quickly dissolve oils and greases, evaporate quickly, and have a relatively low cost. As regulations on these compounds continue to tighten on the path to a full ban, Chemtronics continues to engineer alternatives with all the advantages of PCE and TCE, but without the harmful health effects.

Chemtronics Electro-Wash Tri-V Precision Cleaner and Max-Kleen Tri-V Heavy-duty Degreaser are nonflammable cleaners that quickly remove flux, grease, oils, dirt, dust, and other contaminants from electronic components, metal parts, tools, and assemblies. They remove all types of oil and grease while evaporating quickly and leaving no residues. Tri-V nPB replacement chemistry is an innovative chemistry that does not contain n-propyl bromide, TCE, hazardous air pollutants, or ozone-depleting compounds.

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