CHEMICAL DATA NOTEBOOK SERIES #79: TETRACHLOROETHYLENE
HAZARDOUS MATERIALS
Tetrachloroethylene is a nonflammable, toxic, irritating, colorless liquid with an ether-like, sweet odor. It is classified as a potential or probable carcinogen and is widely used as the solvent in dry cleaning operations. It also is used as a metal degreaser, as a drying agent for metal and wood, as a heat exchange fluid, and as a solvent in many industries. Chemically, tetrachloroethylene belongs to a family of hydrocarbon derivatives known as chlorinated hydrocarbons.
PROPERTIES
Tetrachloroethylene is nonflammable by most test methods and therefore has no flash point, flammable range, or ignition temperature. It has a specific gravity of 1.63, a molecular weight of 166, and a vapor density of 5.72. It boils at 249.8°F, freezes at — 8.32°F, and is nonsoluble in water. While it is considered to be nonreactive with water, it will react with it under some circumstances to produce some dangerous by-products. Its chemical formula is CC12 = CC12 (sometimes written as C12C = CC12).
Tetrachloroethylene’s structure is exactly the same as that of ethylene, except chlorine atoms have been substituted for all four hydrogen atoms of ethylene (see Fire Engineering, August 1987). This substitution totally changes the chemical composition and therefore the chemical properties of the original material, so virtually no chemical (or physical) properties remain the same.
HAZARDS
Tetrachloroethylene’s major hazard is to health. It is a probable human carcinogen, and constant exposure to its vapors and liquid could be very dangerous. One manufacturer with a rating system similar to the NFPA’s 704 system rates it a “3” in the health category, whereas the NFPA rates it a “2” in that category.
Tetrachloroethylene vapors are detectable at levels near 5 ppm (parts per million of air) and are recognizable at 50 ppm. Its TLV-TWA (threshold limit value-time weighted average, developed by the ACGIH, or American Conference of Governmental Industrial Hygienists) is 50 ppm, while OSHA’s (Occupational Safety and Health Administration) PEL (permissible exposure limit) is 25 ppm. The different limits set by the ACGIH and OSHA represent a major problem in protection. For years, the only guideline was the TLV-TWA values listed for certain chemicals. OSHA now is publishing values for its version of safe limits, and the result is confusion among employers who are regulated. Every chemical in the employer’s workplace must be investigated, and both its TLV-TWA and PEL noted. The only safe approach is to use the lower value to determine when protection must be provided to all exposed employees.
The STEL (short-term exposure limit, also set by the ACGIH) is 200 ppm for 15 minutes.
Tetrachloroethylene vapors represent the greatest hazard to unprotected exposed persons. Contact with the eyes causes irritation, but permanent eye injury is unlikely unless the exposure is to very high concentrations of vapor for long periods of time and such exposures are repeated often.
Inhaling high concentrations of vapors can depress the central nervous system and cause narcosis, unconsciousness, respiratory failure, and eventually death. The symptoms of inhalation of high concentrations of vapors vary from individual to individual. Some individuals may exhibit dizziness, drowsiness, fatigue, intoxication, and other symptoms of mental incapacitation, while others may undergo periods of total irresponsibility and exhilaration—laughing at almost anything that happens. Some will have flushed red faces or experience headaches (some painful and some reported as a “fullness” in the head), nausea, a ringing in the ears, a “runny” nose, sinus pain, sweaty palms, and vomiting. All these symptoms could appear in the same individual over the course of the exposure. If death does not occur, damage to the central nervous system, kidneys, liver, lungs, and spleen is possible.
The effects of various concentrations of tetrachloroethylene vapors have been recorded for different individuals. The vapor concentration and the time of exposure determine the effects. At 600 ppm, the eyes and nasal passages become significantly irritated. Ten minutes of exposure at this level can be extremely dangerous or even fatal, since the exposure can cause the exposed person to lose all inhibitions. This lack of inhibition could cause the individual to ignore the irritation and dizziness, to remain in an unprotected condition, and possibly to lose consciousness. Mild irritation of the eyes occurs far below the 600-ppm level, and all exposed personnel should have the proper personal protective equipment. The fact is that when working with tetrachloroethylene, employees already should be wearing the proper personal protective equipment as part of safety requirements.
Just a two-minute exposure to 1,000 ppm of tetrachloroethylene vapors produces the same effects as 600 ppm at 10 minutes. An exhilarating feeling may come over the unprotected individuals at this time, and they cannot be trusted to take the proper precautionary steps to protect their lives. Unconsciousness at this level of exposure can occur within 20 to 45 minutes.
At 2,000 ppm, narcosis can be induced very quickly. Exposure to 5,000 ppm becomes unbearable in under five minutes, and exposed individuals have been reported to be “mentally confused” for several minutes after the exposure ended. Experiments on laboratory animals produced death at levels above 10,000 ppm in as few as 12 minutes. I also must mention here that at least one study showed that exposure of from nine to 38 ppm over long periods of time (dry cleaning establishments) caused no ill effects.
Fatalities from inhaling tetrachloroethylene vapors can occur from exposure to levels far below those known to kill laboratory animals in experiments. The above-mentioned 10-minute exposure to vapors at the 600-ppm level can produce intoxication similar to that caused by ingesting alcohol. Anyone in a drunken state working around hazardous materials is unsafe by definition, and impaired reasoning probably could cause these individuals to make decisions that could kill them or their fellow workers.
The feeling of exhilaration can cause an exposed person to feel indestructible and to remain exposed to the tetrachloroethylene vapors until being overcome. Mental incapacitation and/or confusion also can lead to decisions that can be fatal in one manner or another.
The literature does not mention addiction to tetrachloroethylene vapors, but I believe that it is possible. Some workers exposed to tetrachloroethylene vapors in percentages that do not cause serious side effects might consider it pleasant. Workers deliberately might expose themselves to vapors at a level that produces a “buzz” or mild “high.” Workers also might use their seniority on the job to have tasks assigned to them that expose them to just enough vapors to reproduce the high feeling. This easily could get out of hand and progress to the point w here the worker’s life is in danger or, at the very least, his/her internal organs are damaged. Signs of an employee’s addiction to tetrachloroethylene or any other workplace solvent or chemical must be closely monitored.
Ingesting tetrachloroethylene irritates the mouth, esophagus, stomach, and gastrointestinal tract. Damage to the liver and kidneys as well as depression of the central nervous system are possible. Tetrachloroethylene is considered to have a low to moderate level of toxicity. At least one study has established an LDso of 2,629 mg/ kg (milligrams of the substance per kilogram of body weight).
Contact with the skin, especially long exposures, can cause reddening and burning severe enough to produce blisters. Chronic contact with the skin can cause drying, cracking, inflammation, and scaling due to the defatting action of the tetrachloroethylene. It also may be absorbed through the skin, so prolonged and repeated skin contact produces symptoms somewhat similar to ingestion. Avoid all contact with tetrachloroethylene, since it is classified as a probable human carcinogen.
Tetrachloroethylene, according to at least one source, is corrosive to metals such as aluminum, iron, and zinc. It also attacks some forms of plastics and rubber.
Although tetrachloroethylene is considered to be a stable chemical, it decomposes very slowly in water to form hydrochloric acid and trichloroacetic acid. If the volume of water present is large, no harmful effects of these reaction products should be present.
Tetrachloroethylene forms a shocksensitive explosive if mixed with powdered lithium or barium and a somewhat less sensitive explosive when mixed with powdered beryllium. It reacts violently with nitric acid, potassium hydroxide, and sodium hydroxide. It also reacts violently with liquid oxygen, other strong oxidizers, and metals such as magnesium and potassium.
When tetrachloroethylene decomposes at high temperatures, chlorine, hydrogen chloride, and phosgene gases all are possible decomposition products. Chlorine is a toxic, corrosive oxidizer; hydrogen chloride is an irritant that dissolves in water to form hydrochloric acid; and phosgene is a deadly poison.
NONFIRE RELEASE
A spill of any sizable amount of tetrachloroethylene should trigger the community’s emergency action plan. Environmental experts must be involved in the incident because of the potential harm it can cause to the environment.
Consider evacuation downwind. There is no danger of fire or explosion, since tetrachloroethylene is nonflammable. Its toxic properties, however, must be considered. Wind and weather conditions determine evacuation distances.
Tetrachloroethylene vapors are considerably heavier than air (the vapor density is 5.72), and they will hang together and flow a great distance downwind (if the wind is not very strong). In the absence of a breeze, they will seek low spots in the terrain and flow away from the source. Vapors accumulating in low spots or confined areas are very hazardous for anyone entering the area without eye and respiratory protection.
Until covered, tetrachloroethylene vapors may be “swept” from the air with a high-pressure water spray or fog. If you use this technique, contain all runoff water.
Contain any release of tetrachloroethylene to prevent the spread of contamination. Construct containment ponds around the spill by pushing up soil or sand to form dikes. You also may dig a containment pit (assuming the proper equipment is available) and dig trenches to lead the liquid to the pit. A containment pit usually is better than a pond, since the pit’s surface area usually is smaller than that of a pond. The smaller the area exposed to the atmosphere, the slower the generation of vapors through evaporation will be.
You also can slow the evaporation of tetrachloroethylene by covering the surface with sheets constructed from a compatible material, or the surface of the liquid can be covered widi firefighting foam to slow evaporation. Remember, as the foam breaks down and more is applied, it adds to the volume of material in the pond or pit. Also, since foams contain water, there is the possibility of some slow reaction with water at the surface.
Another covering technique is to gently flow a layer of water across the surface of the tetrachloroethylene in the pit or pond. Tetrachloroethylene is heavier than water and therefore will allow the water to float on its surface. The water very effectively will control evaporation. The volume of water in the covering layer should dilute any reaction with the water effectively.
IDENTIFICATION NUMBERS AND RATINGS
CAS
(Chemical Abstract Services)
127-18-4
STCC
(Standard Transportation Commodity Code)
4940355
RTECS
(Registry of Toxic Effects of Chemical Substances)
KX3850000
UN/NA
(United Nations/North America)
1897
CHRIS
(Chemical Hazard Response Information System)
EDC
RCRA
(Resource Conservation and Recovery Act)
U210
DOT
(U.S. Department of Transportation)
ORM-A
NFPA 704 Rating
2–0-0
IMO
(International Maritime Organization)
6.1, poisonous material
Once the tetrachloroethylene is contained, it may be salvaged by the carrier, the seller, the buyer, or a professional salvage firm by suctioning or pumping the liquid into secure containers. Any remaining product may be absorbed by using cement powder, clay, diatomaceous earth, fly ash, Fuller’s earth, peat, perlite, sand, sawdust, soil, straw, vermiculite, or other commercial sorbents. Once these materials have absorbed the remaining tetrachloroethylene, dispose of them in accordance with the proper federal, state, and local regulations. This also is true for any earth that has become contaminated and has to be removed. These sorbents now contain the hazardous material and must be treated as such.
Make every attempt to prevent tetrachloroethylene from entering sewers and waterways. Dam all entrances to the sewer system; and if any material enters the sewer, immediately warn all sewage treatment facilities and downstream users of the contaminated water.
If tetrachloroethylene enters a river or stream, it will sink to the bottom and will be moved along by gravity and the other forces moving the water. Pumping the insoluble liquid as it moves downstream or as it accumulates in deep spots in the waterway may remove it from the stream or river bed. If the waterway can be diverted until all the tetrachloroethylene is contained in the water in a holding area, the product may be salvaged much more effectively. Use activated charcoal, peat moss, or other adsorbing agents to remove relatively small amounts of the contaminant from the water, and aerate, strip, or sparge the water to remove remaining tetrachloroethylene. The environmental authorities want to be sure that all the product has been removed from the water, especially if it is a source of drinking water for those who live downstream.
Removing tetrachloroethylene from a pond or lake is easier than removing it from a moving stream of water. Aquatic life and the surrounding ecosystem will be damaged, and the environmental experts will test exhaustively until they are sure the water has been decontaminated.
FIRE SCENARIO
Although tetrachloroethylene will not burn, it still poses serious hazards if involved in a fire. In addition to producing the hazardous thermal decomposition products listed above, tetrachloroethylene acts like any liquid during a fire. As heat energy is absorbed, the liquid evaporates faster, producing larger and larger volumes of toxic vapors. The more vapors produced, the more thermal decomposition products are formed. Since chlorine is one of these products and it is an efficient oxidizer, enough of it may form to intensify the fire, making it more difficult to extinguish.
Any container of tetrachloroethylene exposed to the heat of impinging flames or heat radiated by a fire experiences a rapid rise in internal pressure caused by the increased evaporation rate of the heated liquid. If the rising pressure is not vented properly, the container may catastrophically fail, spewing shrapnel and its contents great distances.
SYNONYMS
Ankilostin
Antisol
Antisill
carbon bichloride
carbon dichloride
Didakene
Dowper
ENT 1,860
ethene, tetrachloro
ethylene tetrachloride
Fedal-Un
NCI-c04580
Nema
PCE
Per
Perawin
Perc
Perchlor
perchlorethylene
perchloroethylene
Perclene
Perclene D
Perclone
Percosolve
Perdene
Perk
Persec
TCE
Tetlin
Tetracap
tetrachlorethylene
tetrachloroethene
1,1,2,2-tetrachloroethylene
Telravec
Tetraleno
Tetralex
Tetropil
Cool all containers of tetrachloroethylene with water delivered by unmanned appliances from as far away as possible. Never allow yourself to be caught between the fire and any heated containers.
After the fire has been extinguished, call in professional salvage teams to move and remove all containers. All cleanup activities should be performed by professional salvage and/or cleanup companies. Firefighters should not be involved in these activities, since they have not been professionally educated, trained, or equipped for these tasks. Firefighters also should keep their protective equipment, especially their selfcontained breathing apparatus, in place during overhaul. Many materials continue producing potentially toxic vapors long after the fire has been extinguished.
PROTECTIVE CLOTHING AND EQUIPMENT
Select all protective clothing and equipment to provide the maximum respiratory, eye, and skin protection against tetrachloroethvlene. Regular turnout gear that is impervious to penetration by liquids may provide skin protection, as may rubber boots, gloves, aprons, coveralls, and hoods. Chemical-resistant goggles that protect against splashes may be required under a face shield. Positive-pressure, self-contained breathing apparatus is needed to provide respiratory protection.
Use properly maintained total encapsulating suits whenever the liquid or high concentrations of vapor are present. Compatible materials include polyvinyl alcohol, Teflon®, and Viton®.
One source places chlorinated polyethylene and Viton/neoprene on the list of compatible materials. Contact the manufacturer of your department’s encapsulating suits to determine the suit’s capacity to protect against tetrachloroethvlene. Also, contact tetrachloroethvlene manufacturers for their recommendations.
FIRST AID
Inhalation. Move the victim to fresh air and keep him/her calm and warm. If breathing has stopped or has become labored, administer artificial respiration, being aware that such action might expose the first-aid giver to the material in the victim’s lungs and/or vomit. Seek immediate medical attention.
Eye contact. Flush the eyes immediately for at least 20 minutes, lifting the eyelids occasionally. Seek immediate medical attention.
Skin Contact. Wash the affected body areas with large amounts of soap and water. If irritation continues after washing, seek medical attention.
Ingestion. If the victim is conscious, keep him/her calm and warm. Seek expert medical advice before inducing vomiting. Never try to make an unconscious person drink anything or vomit. Immediate medical attention is absolutely necessary when tetrachloroethylene is ingested.*
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