Short-term exposure to trichloroethylene causes irritation of the nose and throat and central nervous system (CNS) depression, with symptoms such as drowsiness, dizziness, giddiness, headache, loss of coordination. High concentrations have caused numbness and facial pain, reduced eyesight, unconsciousness, irregular heartbeat and death.

Trichloroethylene is noticeable by smell at approximately 82 ppm and above. However, people can become accustomed to the odour and may not smell it until higher concentrations are reached. In one study, exposure to 110 ppm for 8 hours produced fatigue and drowsiness. Other studies have shown no significant effects following exposure to 200 or 300 ppm for less than 4 hours. At 160-250 ppm, the odour is persistent. Lightheadedness has been reported following exposure to 350-400 ppm for 3 hours. At 1000-1200 ppm, the odour is very strong and unpleasant. Lightheadedness, reduced hand-eye coordination and dizziness have been observed after several minutes. At 2000 ppm, the odour is difficult to tolerate, irritation of the nose and throat is strong, and drowsiness, dizziness and nausea occur within 5 minutes. Very high concentrations have produced death due to CNS effects, and, in rare cases, irregular heart beat. In one case, pulmonary edema (a potentially fatal accumulation of fluid in the lungs) was reported. The employee was welding a surface that had been washed in trichloroethylene. The pulmonary edema likely resulted from exposure to phosgene which is formed upon heating of trichloroethylene.

Effects on behaviour and coordination have been observed in some studies. In one study, exposure to 110 ppm resulted in decreased performance in tests measuring reaction time, dexterity, perception, and memory. Similar effects were not observed when the study was repeated. In general, no significant effects have been observed with exposures to 100 ppm or below. Numbness and discomfort of the face and jaw weakness (trigeminal nerve effects) and serious visual disturbances, including reduced eyesight and blurred or double vision, have been reported following exposure to high concentrations. Some of the effects may persist for several months. These effects may actually be caused by other chemicals (e.g. dichloroacetylene) are formed when trichloroethylene decomposes in the presence of strong alkaline materials.

Sometimes, permanent nervous system damage and/or liver injury have resulted from severe overexposure to trichloroethylene. In most cases, the individuals had intentionally inhaled very high concentrations of trichloroethylene for its intoxicating effects.

Trichloroethylene is a severe skin irritant, based on animal evidence. Prolonged contact with the liquid has caused reddening of the skin, irritation and blister formation.

The concentrated vapour, especially at elevated temperatures, can also cause severe redness and irritation. Several cases of very severe skin irritation have been reported in employees exposed to unspecified or high concentrations (up to 165 ppm) of trichloroethylene for a relatively short time (up to 5 weeks). In most cases, liver impairment and exposure to other several other potentially harmful chemicals were also reported.

Trichloroethylene can be absorbed through the skin. However, significant harmful effects are not expected to occur by this route of exposure.

Liquid trichloroethylene is a severe eye irritant, based on limited human information and animal evidence. One report indicates that a splash of trichloroethylene caused smarting pain and injury to the surface tissue of the eye.

Mild irritation has been reported by some volunteers exposed to 160 or 200 ppm vapour. Other sources report no eye irritation at 350-400 ppm. Severe eye irritation, with temporary clouding of the cornea, has been reported in people exposed to vapour concentrations so high they became unconscious. Serious disturbances in eyesight, including reduced eyesight and blurred, double and tunnel vision, have been reported in people with high inhalation exposure to trichloroethylene. See "What are the main health hazards associated with breathing in Trichloroethylene?" above, for additional information.

Ingestion causes a burning sensation in the mouth and throat, followed by abdominal pain and signs and symptoms central nervous system (CNS) depression, as described for inhalation exposure above. Accidental ingestion of 30 mL to 500 mL (2 tbsp to 16 ozs) has caused muscle weakness, vomiting and unconsciousness or delirium, with recovery within 2 weeks. Effects on the heart, liver and kidneys have also been reported. In one case, ingestion of less than 50 mL was reported to be fatal due to kidney and liver failure. Some of the harmful effects described, e.g. the liver effects, may be caused by other chemicals (stabilizers) added to trichloroethylene.

Trichloroethylene can probably be aspirated, based on its physical properties. Aspiration is the inhalation of the chemical into the lungs during ingestion or vomiting. Severe lung irritation, damage to the lung tissues and death may result. Ingestion is not a typical route of occupational exposure.

EFFECTS ON THE SKIN/SKIN SENSITIZATION: Repeated or prolonged contact with trichloroethylene can cause dry, red and chapped skin (dermatitis). A few case reports have described severe redness and irritation of the skin following relatively short exposures (up to 5 weeks) to unspecified or high vapour concentrations (up to 165 ppm). In most cases, impaired liver function and exposure to several other potentially harmful chemicals were also reported. In one case, the person later tested positive in a patch test using trichloroethylene, suggesting this person was allergic to trichloroethylene. However, it cannot be concluded that trichloroethylene is a skin sensitizer based on this one positive patch test.

EFFECTS ON THE CENTRAL NERVOUS SYSTEM (CNS): Long-term occupational exposure may cause signs and symptoms of CNS depression such as headaches, dizziness, altered mood, loss of memory and inability to concentrate or sleep. These effects have also been related to long-term occupational exposure to other organic solvents and are sometimes generally referred to as "organic solvent syndrome". It is difficult to draw specific conclusions regarding trichloroethylene from the available studies because, in general, a small number of people were studied, exposure levels were not defined, exposure to other potentially harmful chemicals may have occurred at the same time and, in some cases, comparisons were not made to unexposed individuals. In general, symptoms of CNS depression are commonly reported in employees exposed to average trichloroethylene levels of 100 ppm and above. One limited study reported symptoms such as dizziness, headache, insomnia, and altered mood in a small number of employees exposed to up to 40 ppm.

EFFECTS ON THE CRANIAL NERVES: Nerves of the face and head (cranial nerves) have been affected by long-term exposure to trichloroethylene or chemicals formed when it decomposes. In particular, the trigeminal nerve, which provides feeling and movement to part of the face, has been affected. To a lesser extent, the optic nerve, which provides sight, has also been affected. In one study, some evidence of trigeminal nerve impairment was seen in employees with long-term exposure to no more than 35 ppm. Evidence of trigeminal nerve damage was also observed in employees with long-term occupational exposure to approximately 40 ppm. Effects were more pronounced with longer exposures. Several other studies, with higher exposures, have also reported trigeminal nerve effects. Symptoms such as facial numbness, jaw weakness, altered reflexes and facial discomfort have been reported. In one study, trigeminal nerve disorders were not observed in employees with long- term exposure to 38 to 172 ppm.

Vision disturbances, including blurred, double or tunnel vision and poor eyesight, have occasionally been reported following long-term exposure to trichloroethylene. These effects are caused by impairment of the optic nerve and other cranial nerves. The trigeminal and optic nerve effects may be caused by dichloroacetylene, a chemical formed when trichloroethylene decomposes in the presence of strong alkaline materials.

EFFECTS ON HEARING: Limited information suggests that long-term exposure to trichloroethylene may harm hearing. Concentrations which have produced hearing effects are probably high enough to have also produced significant symptoms of central nervous system (CNS) depression.

OTHER NERVOUS SYSTEM EFFECTS: A metal degreaser exposed to 1.5 to 32 ppm for 1 to 2 hours/day for over 20 years experienced loss of feeling in hands and feet persisting for 4 years after retirement. This individual also had several high level short-term exposures which may have contributed to his symptoms. Repeated skin contact (while cleaning contact lenses) resulted in a reduced sense of touch, decreased mobility of the fingers, and an inability to grasp small objects with thumb and forefinger. These effects were reversible after several months.

EFFECTS ON THE HEART: A number of studies have investigated the effects of occupational exposure to trichloroethylene on the heart. Many of the studies are limited by factors such as the small number of people studied and lack of exposure information. In general, the studies suggest that workplace exposures to 100 ppm may cause irregular heart beat in a small number of people occupationally exposed.

EFFECTS ON THE LIVER AND KIDNEYS: There is limited evidence that exposure to trichloroethylene may cause liver and kidney injury in some people following long-term occupational exposure. No firm conclusions can be drawn from the available studies because most only involved a very small number of exposed individuals, exposure levels were not defined and/or there may have been exposure to other potentially harmful chemicals. Liver and kidney effects were not observed following long-term occupational exposure at concentrations up to 40 ppm.

The International Agency for Research on Cancer (IARC) has concluded that there is limited evidence for the carcinogenicity of trichloroethylene in humans. The overall IARC evaluation is that trichloroethylene is probably carcinogenic to humans (Group 2A). IARC has also concluded that there is sufficient evidence that trichloroethylene is carcinogenic in experimental animals. Three well-designed studies of people with occupational exposure to trichloroethylene showed higher levels of liver and biliary tract cancers and non-Hodgkins lymphoma. Numerous other studies were either negative or had significant limitations, including small sample size, limited exposure data and exposure to other chemicals.

Limited human information does not show that occupational exposure to trichloroethylene causes harmful effects on reproductive function in men or women. Similar results have been observed in studies of people exposed to trichloroethylene in drinking water. The available studies are limited by factors such as the small number of individuals studied, lack of exposure information and exposure to other potentially harmful chemicals at the same time. Trichloroethylene has not been shown to cause reproductive toxicity in animals.

No changes in sperm count or sperm shape were observed in 15 men occupationally exposed to trichloroethylene for more than 20 hours/week. In another study, a higher number of miscarriages were not observed in the partners of men occupationally exposed to trichloroethylene. In studies in which women were exposed to trichloroethylene more miscarriages are sometimes observed. However, the exposure to other potentially harmful chemicals at the same time prevents interpretation of this observation. Two poorly conducted and reported studies have reported menstrual disorders in women occupationally exposed to trichloroethylene. This effect was observed in the presence of symptoms of central nervous system depression.

Very limited human information does not indicate that occupational exposure to trichloroethylene is harmful to the unborn child. One study did not show more birth defects in the children of men occupationally exposed to trichloroethylene. There is some evidence that exposure to trichloroethylene in drinking water may cause certain types of birth defects. Although the available information is far from conclusive. One animal study has shown teratogenic effects (abnormal heart development) in the offspring of rats orally exposed to trichloroethylene in drinking water. Harmful effects were not observed in the mothers. Other studies have not shown teratogenic, embryotoxic or fetotoxic effects following oral or inhalation exposures that did not also produce significant harmful effects in the mother.

When ethanol (commonly found in alcoholic beverages) is consumed shortly before or after exposure to trichloroethylene, the skin of the face and arms becomes very red. This condition is called "degreaser's flush".

Trichloroethylene is rapidly absorbed into the bloodstream following inhalation and ingestion and rapidly distributed to organs, including the liver, kidneys and cardiovascular and nervous systems. A small amount is absorbed through the skin. Some trichloroethylene is eliminated unchanged and as carbon dioxide in exhaled breath. Some trichloroethylene is broken down in the body mainly to trichloroacetic acid and trichloroethanol, which are excreted primarily in the urine. Trichloroethylene is excreted from the body at a moderate rate, mostly in the urine.