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.

For more information, contact your Chemtronics application specialist at 678-928-6534 or askchemtronics@chemtronics.com.

References

[1] Chen, Shiang-Jiuun, et al. “Possible Involvement of Glutathione and p53 in Trichloroethylene- and Perchloroethylene-Induced Lipid Peroxidation and Apoptosis in Human Lung Cancer Cells.” Free Radical Biology and Medicine, vol. 33, no. 4, 2002, pp. 464–472., https://doi.org/10.1016/s0891-5849(02)00817-1.

[2] Brusseau, Mark L., et al. “Chapter 15 - Subsurface Pollution.” Environmental and Pollution Science, 3rd ed., Academic Press, Amsterdam, 2019, pp. 248–249.

[3] Wexler, Philip, and Bruce D. Anderson. “Trichloroethylene.” Encyclopedia of Toxicology, 3rd ed., Elsevier/AP, Academic Press Is an Imprint of Elsevier, Amsterdam, 2014, pp. 827–830.

[4] U.S. Environmental Protection Agency (EPA). Toxicological Review of Tetrachloroethylene (Perchloroethylene). Feb. 2012, https://cfpub.epa.gov/ncea/iris/iris_documents/documents/toxreviews/0106tr.pdf.

[5] IARC Working Group on the Evaluation of Carcinogenic Risks to Humans. “Tetrachloroethylene.” Dry Cleaning, Some Chlorinated Solvents, and Other Industrial Chemicals., U.S. National Library of Medicine, 1 Jan. 1995, https://www.ncbi.nlm.nih.gov/books/NBK464345/.

[6] U.S. Environmental Protection Agency (EPA). Preliminary Information on Manufacturing, Processing, Distribution, Use, and Disposal: Tetrachloroethylene (Perchloroethylene). https://www.epa.gov/sites/production/files/2017-02/documents/perchloroethylene.pdf.

[7] Watts, R.J., and A.L. Teel. “Groundwater and Air Contamination: Risk, Toxicity, Exposure Assessment, Policy, and Regulation.” Treatise on Geochemistry, 2014, pp. 1–12., https://doi.org/10.1016/b978-0-08-095975-7.00901-3.

[8] Köppel, Claus, et al. “Acute Tetrachloroethylene Poisoning - Blood Elimination Kinetics during Hyperventilation Therapy.” Journal of Toxicology: Clinical Toxicology, vol. 23, no. 2-3, 1985, pp. 103–115., https://doi.org/10.3109/15563658508990621.

[9] Altmann, Lilo, et al. “Neurophysiological and Psychophysical Measurements Reveal Effects of Acute Low-Level Organic Solvent Exposure in Humans.” International Archives of Occupational and Environmental Health, vol. 62, no. 7, 1990, pp. 493–499., https://doi.org/10.1007/bf00381179.

[10] Aschengrau, Ann, et al. “Affinity for Risky Behaviors Following Prenatal and Early Childhood Exposure to Tetrachloroethylene (Pce)-Contaminated Drinking Water: A Retrospective Cohort Study.” Environmental Health, vol. 10, no. 1, 2011, https://doi.org/10.1186/1476-069x-10-102.

[11] Goldman, Samuel M., et al. “Solvent Exposures and Parkinson Disease Risk in Twins.” Annals of Neurology, vol. 71, no. 6, 2011, pp. 776–784., https://doi.org/10.1002/ana.22629.

[12] Getz, Kelly D., et al. “Prenatal and Early Childhood Exposure to Tetrachloroethylene and Adult Vision.” Environmental Health Perspectives, vol. 120, no. 9, 2012, pp. 1327–1332., https://doi.org/10.1289/ehp.1103996.

[13] Bove, Frank J, et al. “Evaluation of Mortality among Marines and Navy Personnel Exposed to Contaminated Drinking Water at USMC Base Camp Lejeune: A Retrospective Cohort Study.” Environmental Health, vol. 13, no. 1, 2014, https://doi.org/10.1186/1476-069x-13-10.

[14] Lucas, D., et al. “Assessment of Exposure to Perchloroethylene and Its Clinical Repercussions for 50 Dry-Cleaning Employees.” Journal of Occupational and Environmental Hygiene, vol. 12, no. 11, 2015, pp. 767–773., https://doi.org/10.1080/15459624.2015.1048346.

[15] Franchini, I., et al. “Early Indicators of Renal Damage in Workers Exposed to Organic Solvents.” International Archives of Occupational and Environmental Health, vol. 52, no. 1, 1983, pp. 1–9., https://doi.org/10.1007/bf00380601.

[16] Verplanke, Anton J.W., et al. “Occupational Exposure to Tetrachloroethene and Its Effects on the Kidneys.” Journal of Occupational & Environmental Medicine, vol. 41, no. 1, 1999, pp. 11–16., https://doi.org/10.1097/00043764-199901000-00003.

[17] Andrea Trevisan, Isabella Maccà, Fr. “Kidney and Liver Biomarkers in Female Dry-Cleaning Workers Exposed to Perchloroethylene.” Biomarkers, vol. 5, no. 6, 2000, pp. 399–409., https://doi.org/10.1080/135475000750052411.

[18] Gennari, Piero, et al. “Gamma-Glutamyltransferase Isoenzyme Pattern in Workers Exposed to Tetrachloroethylene.” American Journal of Industrial Medicine, vol. 21, no. 5, 1992, pp. 661–671., https://doi.org/10.1002/ajim.4700210506.

[19] Brodkin, C A, et al. “Hepatic Ultrasonic Changes in Workers Exposed to Perchloroethylene.” Occupational and Environmental Medicine, vol. 52, no. 10, 1995, pp. 679–685., https://doi.org/10.1136/oem.52.10.679.

[20] Goldman, John A. “Connective Tissue Disease in People Exposed to Organic Chemical Solvents.” JCR: Journal of Clinical Rheumatology, vol. 2, no. 4, 1996, pp. 185–190., https://doi.org/10.1097/00124743-199608000-00005.

[21] Garabrant, D. H. “Scleroderma and Solvent Exposure among Women.” American Journal of Epidemiology, vol. 157, no. 6, 2003, pp. 493–500., https://doi.org/10.1093/aje/kwf223.

[22] Emara, Ashraf M., et al. “Immunotoxicity and Hematotoxicity Induced by Tetrachloroethylene in Egyptian Dry-Cleaning Workers.” Inhalation Toxicology, vol. 22, no. 2, 2010, pp. 117–124., https://doi.org/10.3109/08958370902934894.

[23] Chaigne, Benjamin, et al. “Primary Sjögren's Syndrome and Occupational Risk Factors: A Case-Control Study.” Journal of Autoimmunity, vol. 60, 2015, pp. 80–85., https://doi.org/10.1016/j.jaut.2015.04.004.

[24] Olsen, Jørn, et al. “Low Birthweight, Congenital Malformations, and Spontaneous Abortions among Dry-Cleaning Workers in Scandinavia.” Scandinavian Journal of Work, Environment & Health, vol. 16, no. 3, 1990, pp. 163–168., https://doi.org/10.5271/sjweh.1800.

[25] Windham, Gayle C., et al. “Exposure to Organic Solvents and Adverse Pregnancy Outcome.” American Journal of Industrial Medicine, vol. 20, no. 2, 1991, pp. 241–259., https://doi.org/10.1002/ajim.4700200210.

[26] Eskenazi, Brenda, et al. “A Study of the Effect of Perchloroethylene Exposure on Semen Quality in Dry-Cleaning Workers.” American Journal of Industrial Medicine, vol. 20, no. 5, 1991, pp. 575–591., https://doi.org/10.1002/ajim.4700200502.

[27] Aschengrau, Ann, et al. “Prenatal Exposure to Tetrachloroethylene-Contaminated Drinking Water and the Risk of CONGENITAL ANOMALIES: A Retrospective Cohort Study.” Environmental Health, vol. 8, no. 1, 2009, https://doi.org/10.1186/1476-069x-8-44.

[28] Calvert, G. M., et al. “Mortality and End-Stage Renal Disease Incidence among Dry-Cleaning Workers.” Occupational and Environmental Medicine, vol. 68, no. 10, 2010, pp. 709–716., https://doi.org/10.1136/oem.2010.060665.

[29] Ruckart, Perri Zeitz, et al. “Evaluation of Exposure to Contaminated Drinking Water and Specific Birth Defects and Childhood Cancers at Marine Corps Base Camp Lejeune, North Carolina: A Case-Control Study.” Environmental Health, vol. 12, no. 1, 2013, https://doi.org/10.1186/1476-069x-12-104.

[30] Bove, Frank J, et al. “Evaluation of Mortality among Marines and Navy Personnel Exposed to Contaminated Drinking Water at USMC Base Camp Lejeune: A Retrospective Cohort Study.” Environmental Health, vol. 13, no. 1, 2014, https://doi.org/10.1186/1476-069x-13-10.

[31] Bulka, Catherine, et al. “Relations between Residential Proximity to EPA-Designated Toxic Release Sites and Diffuse Large B-Cell Lymphoma Incidence.” Southern Medical Journal, vol. 109, no. 10, 2016, pp. 606–614., https://doi.org/10.14423/smj.0000000000000545.

[32] Carton, Matthieu, et al. “Occupational Exposure to Solvents and Risk of Head and Neck Cancer in Women: A Population-Based Case-Control Study in France.” BMJ Open, vol. 7, no. 1, 2017, https://doi.org/10.1136/bmjopen-2016-012833.

[33] Environmental Protection Agency (EPA). “Trichloroethylene - US EPA.” Trichloroethylene, EPA, https://www.epa.gov/sites/production/files/2016-09/documents/trichloroethylene.pdf.

[34] International Agency for Research on Cancer. Dry Cleaning, Some Chlorinated Solvents, and Other Industrial Chemicals. Vol. 63, IARC, 1995.

[35] Agency for Toxic Substances and Disease Registry. “Trichloroethylene (TCE).” Centers for Disease Control and Prevention, Centers for Disease Control and Prevention, 22 June 2020, https://wwwn.cdc.gov/TSP/ToxProfiles/ToxProfiles.aspx?id=173&tid=30.

[36] Wu, C, and J Schaum. “Exposure Assessment of Trichloroethylene.” Environmental Health Perspectives, vol. 108, no. suppl 2, 2000, pp. 359–363., https://doi.org/10.1289/ehp.00108s2359.

[37] Barret, L., et al. “Evoked Trigeminal Nerve Potential in Chronic Trichloroethylene Intoxication.” Journal of Toxicology: Clinical Toxicology, vol. 19, no. 4, 1982, pp. 419–423., https://doi.org/10.3109/15563658208992496.

[38] Troster, A. I., and R. M. Ruff. “Neuropsychological Sequelae of Exposure to the Chlorinated Hydrocarbon Solvents Trichloroethylene and Trichloroethane.” Archives of Clinical Neuropsychology, vol. 5, no. 1, 1990, pp. 31–47., https://doi.org/10.1093/arclin/5.1.31.

[39] Burg, Jeanne R., and Ginger L. Gist. “Health Effects of Environmental Contaminant Exposure: An Intrafile Comparison of the Trichloroethylene Subregistry.” Archives of Environmental Health: An International Journal, vol. 54, no. 4, 1999, pp. 231–241., https://doi.org/10.1080/00039899909602480.

[40] Kilburn, Kaye H. “Is Neurotoxicity Associated with Environmental Trichloroethylene (TCE)?” Archives of Environmental Health: An International Journal, vol. 57, no. 2, 2002, pp. 113–120., https://doi.org/10.1080/00039890209602925.

[41] Reif, John S., et al. “Neurobehavioral Effects of Exposure to Trichloroethylene through a Municipal Water Supply.” Environmental Research, vol. 93, no. 3, 2003, pp. 248–258., https://doi.org/10.1016/s0013-9351(03)00131-2.

[42] Seldén, Anders, et al. “Trichloroethylene Exposure in Vapour Degreasing and the Urinary Excretion of N-Acetyl-β-D-Glucosaminidase.” Archives of Toxicology, vol. 67, no. 3, 1993, pp. 224–226., https://doi.org/10.1007/bf01973312.

[43] Brüning, Thomas, et al. “Glutathione Transferase Alpha as a Marker for Tubular Damage after Trichloroethylene Exposure.” Archives of Toxicology, vol. 73, no. 4-5, 1999, pp. 246–254., https://doi.org/10.1007/s002040050613.

[44] Green, T. “Biological Monitoring of Kidney Function among Workers Occupationally Exposed to Trichloroethylene.” Occupational and Environmental Medicine, vol. 61, no. 4, 2004, pp. 312–317., https://doi.org/10.1136/oem.2003.007153.

[45] Lee, L J-H. “Increased Mortality Odds Ratio of Male Liver Cancer in a Community Contaminated by Chlorinated Hydrocarbons in Groundwater.” Occupational and Environmental Medicine, vol. 60, no. 5, 2003, pp. 364–369., https://doi.org/10.1136/oem.60.5.364.

[46] Jung, Hyun Gul, et al. “Trichloroethylene Hypersensitivity Syndrome: A Disease of Fatal Outcome.” Yonsei Medical Journal, vol. 53, no. 1, 2012, p. 231., https://doi.org/10.3349/ymj.2012.53.1.231.

[47] Raaschou-Nielsen, O. “Cancer Risk among Workers at Danish Companies Using Trichloroethylene: A Cohort Study.” American Journal of Epidemiology, vol. 158, no. 12, 2003, pp. 1182–1192., https://doi.org/10.1093/aje/kwg282.

[48] Radican, Larry, et al. “Mortality of Aircraft Maintenance Workers Exposed to Trichloroethylene and Other Hydrocarbons and Chemicals: Extended Follow-Up.” Journal of Occupational & Environmental Medicine, vol. 50, no. 11, 2008, pp. 1306–1319., https://doi.org/10.1097/jom.0b013e3181845f7f.

[49] Zhang, L., et al. “Alterations in Serum Immunoglobulin Levels in Workers Occupationally Exposed to Trichloroethylene.” Carcinogenesis, vol. 34, no. 4, 2012, pp. 799–802., https://doi.org/10.1093/carcin/bgs403.

[50] EPA. “General Health State of Women Professionally Exposed to Trichloroethylene Vapours.” EPA, Environmental Protection Agency, https://hero.epa.gov/index.cfm/reference/details/reference_id/724197.

[51] SAIHAN, E.M., et al. “A New Syndrome with Pigmentation, Scleroderma, Gynaecomastia, Raynaud's Phenomenon, and Peripheral Neuropath.” British Journal of Dermatology, vol. 99, no. 4, 1978, pp. 437–440., https://doi.org/10.1111/j.1365-2133.1978.tb06184.x.

[52] Sallmén, Markku, et al. “Reduced Fertility among Women Exposed to Organic Solvents.” American Journal of Industrial Medicine, vol. 27, no. 5, 1995, pp. 699–713., https://doi.org/10.1002/ajim.4700270506.

[53] Chia, Sin-Eng, et al. “Semen Parameters in Workers Exposed to Trichloroethylene.” Reproductive Toxicology, vol. 10, no. 4, 1996, pp. 295–299., https://doi.org/10.1016/0890-6238(96)00058-5.

[54] EPA. “Final Report: Evaluation of Priority Health Conditions in a Community with Historical Contamination by Trichloroethylene.” EPA, Environmental Protection Agency, https://hero.epa.gov/hero/index.cfm/reference/details/reference_id/730414.

[55] Henschler, D., et al. “Increased Incidence of Renal Cell Tumors in a Cohort of Cardboard Workers Exposed to Trichloroethene.” Archives of Toxicology, vol. 69, no. 5, 1995, pp. 291–299., https://doi.org/10.1007/s002040050173.

[56] Anttila, Ahti, et al. “Cancer Incidence among Finnish Workers Exposed to Halogenated Hydrocarbons.” Journal of Occupational and Environmental Medicine, vol. 37, no. 7, 1995, pp. 797–806., https://doi.org/10.1097/00043764-199507000-00008.

[57] Blair, A., et al. “Mortality and Cancer Incidence of Aircraft Maintenance Workers Exposed to Trichloroethylene and Other Organic Solvents and Chemicals: Extended Follow Up.” Occupational and Environmental Medicine, vol. 55, no. 3, 1998, pp. 161–171., https://doi.org/10.1136/oem.55.3.161.

[58] Raaschou-Nielsen, O. “Cancer Risk among Workers at Danish Companies Using Trichloroethylene: A Cohort Study.” American Journal of Epidemiology, vol. 158, no. 12, 2003, pp. 1182–1192., https://doi.org/10.1093/aje/kwg282.

[59] Coyle, Yvonne M., et al. “An Ecological Study of the Association of Environmental Chemicals on Breast Cancer Incidence in Texas.” Breast Cancer Research and Treatment, vol. 92, no. 2, 2005, pp. 107–114., https://doi.org/10.1007/s10549-004-8268-z.

[60] Zhao, Yingxu, et al. “Estimated Effects of Solvents and Mineral Oils on Cancer Incidence and Mortality in a Cohort of Aerospace Workers.” American Journal of Industrial Medicine, vol. 48, no. 4, 2005, pp. 249–258., https://doi.org/10.1002/ajim.20216.

[61] Krishnadasan, Anusha, et al. “Nested Case-Control Study of Occupational Chemical Exposures and Prostate Cancer in Aerospace and Radiation Workers.” American Journal of Industrial Medicine, vol. 50, no. 5, 2007, pp. 383–390., https://doi.org/10.1002/ajim.20458.

[62] Sung, Tzu-I., et al. “Increased Risk of Cancer in the Offspring of Female Electronics Workers.” Reproductive Toxicology, vol. 25, no. 1, 2008, pp. 115–119., https://doi.org/10.1016/j.reprotox.2007.08.004.

[63] Agency for Toxic Substances and Disease Registry (ATSDR). “Toxicological Profile for Tetrachloroethylene.” Centers for Disease Control and Prevention, 22 June 2020, https://wwwn.cdc.gov/TSP/ToxProfiles/ToxProfiles.aspx?id=265&tid=48.

[64] Agency for Toxic Substances and Disease Registry (ATSDR). “Toxicological Profile for Trichloroethylene.” Centers for Disease Control and Prevention, 22 June 2020, https://wwwn.cdc.gov/TSP/ToxProfiles/ToxProfiles.aspx?id=173&tid=30.