on Chemical Safety
CHEMICAL SAFETY TRAINING MODULES
PART VI: SOLVENTS
Exposure to solvents and other organic liquids is one of the most common chemical health risk at places of work.
Most of the organic solvents are combustible, often highly volatile and extremely flammable and they should always be handled with care. Some solvents produce vapours which are heavier than air. These may move on the floor or ground to a distant ignition source, such as a spark from welding or caused by static electricity. The vapours may also explode from smoking. Vapours of solvents can also accumulate in confined places and stay there for a long time, presenting risks for health and property.
Solvents enter the body by inhalation, by swallowing and through the skin. The effect depends on several factors, such as
Solvents, their vapours and mists have various effects on human health. Many of them have a narcotic effect, causing fatigue, dizziness and intoxication. High doses may lead to unconsciousness and death.
Exposure to large doses of solvents may slow down reaction-time and affect rational judgement. This may increase the risk of accidents both at work and outside, such as in the traffic on the way back home.
Solvents irritate the eyes and the respiratory tract.
Solvents clean and defat, not only metal plates in the process, but also the skin. This is a very common cause of skin disorders and dermatitis. Some solvents penetrate the skin and enter the blood circulation.
Solvents may damage the liver, kidneys, heart, blood vessels, bone marrow and the nervous system.
The solvents which pose the most serious risk to health should be substituted by less hazardous ones. If this is not possible with regard to the work process, at least the conditions during handling should be adjusted so that there is no risk of skin contact and that the concentration of vapour in the air is kept low. This may be achieved, for example, by using a closed process. Amongst the most hazardous solvents are benzene, carbon disulphide and carbon tetrachloride.
Solvents are excreted in urine and sweat or they may be exhaled.
Workplace controls and practices
Good work practices and training can help to reduce hazardous exposures.
For most of the hazardous solvents it is possible to find a substitute with the same characteristics but less drastic effects on health.
Ventilation is important and it should be considered carefully when using solvents.
Equipment (fire extinguishers, absorbant material, etc.) should be considered and provided for situations such as spillage or emergency.
Personal protective equipment such as aprons, gloves and masks with filters should be available where needed, and they should be used according to the recommendations.
Storage of this equipment should be in a clean place away from possible contact with solvent vapours.
Benzene is a colourless, flammable liquid with a pleasant odour. It is used as a solvent in many areas of industries, such as rubber and shoe manufacturing, and in the production of other important substances such as styrene, phenol and cyclohexane. It is essential in the manufacture of detergents, pesticides, solvents and paint removers. It is present in fuels such as in gasoline up to the level of 5%.
The Threshold Limit Value (TLV) in the workplace air over an 8-hour working day (as recommended in many countries) is 10 ppm (or 32 mg/m3). Some countries recommend even lower levels.
The odour threshold is 12 ppm. The odour serves only as a warning of exposure. If you are handling benzene without smelling it, this does not mean that there is no exposure.
Benzene enters the body through inhalation and it may pass through the skin.
Exposure to low concentrations of benzene vapour or to the liquid which has penetrated the skin may cause dizziness, lightheadedness, headache, loss of appetite and stomach upset.
Exposure can also irritate the nose and throat.
High exposures to benzene may cause irregularities in the heart beat which can lead to death.
Repeated exposure can damage the bone marrow, which is the blood-forming organ, causing a condition called aplastic anaemia. This may also lead to death.
Long-term health effects may follow when exposure to benzene has lasted for a long period of time; several months or years. Benzene is a cancer-causing substance: a carcinogen. There is sufficient evidence that benzene causes leukaemia in exposed workers. Many scientists say that there is no safe level of exposure to a carcinogen.
Benzene may cause birth defects in animals. Until further testing has been done it should be handled very carefully as a possible agent causing birth defects in humans as well.
In several countries there are severe restrictions for using and selling benzene.
Workplace controls and practices
As a solvent benzene can be substituted with a variety of less hazardous ones. Toluene is a similar solvent to benzene. It has the general adverse effects of solvents but it has been shown neither to cause cancer nor to damage the bone marrow. White spirit is often used as a substitute for more dangerous solvents. Less volatile solvents, such as xylene and mesitylene, have the same type of characteristics as toluene.
Gasoline should never be used as a substitute. It may contain benzene, tetraethyl lead or other hazardous substances.
Engineering control is the most effective way of reducing exposure where substitution is not possible. Operations with benzene can be enclosed and/or exhaust ventilation can be provided at the site of chemical release. Isolation of operations can also reduce exposure.
Personal protective equipment, for example, breathing protection, is sometimes necessary although less effective. However, recommendations are only guidelines and may not apply to every situation.
Benzene is filtered with a mask and filter type A (for organic solvents with boiling point over 650C). Improper use of the respirator is dangerous. The best choice would be a helmet with fresh air supply and a face piece operating with positive pressure, blowing clean air from inside the helmet or hood outward.
Not all types of gloves can resist the strong solvent power of benzene. Viton or PVA gloves are recommended although even they have limited resistance to benzene.
When clothing is contaminated it should be changed promptly to avoid intake through the skin.
Eating, smoking or drinking should not be allowed where benzene (or other hazardous solvents) are handled.
Handling and storage
Benzene vapour is heavier than air and may move along the floor to a distant ignition source. Smoking and open flames are prohibited where benzene is handled, used or stored. It should be stored in tightly closed containers in a cool well-ventilated area away from heat.
Metal containers need to be grounded to avoid ignition from sparks caused by static electricity. Attention should be paid to electrical equipment, this should be explosion-proof.
Benzene reacts violently with oxidizing agents, such as permanganates, nitrates, peroxides, chlorates and perchlorates.
If benzene is accidentally spilled, the following steps should be taken:
Large spills should be cleaned by experts from the fire department.
Classification and labelling
Benzene is classified as toxic and highly flammable in the EU countries. Labels on bottles or containers should carry symbols corresponding to `highly flammable' and `toxic', to indicate the risks. Risk (R) and safety advice (S) phrases are:
|R45||May cause cancer.|
|R48/23/24/25||Toxic: danger of serious damage to health by prolonged exposure through inhalation, in contact with skin and if swallowed.|
|S53||Avoid exposure - obtain special instructions before use.|
|S45||In case of accident or if you feel unwell, seek medical advice immediately (show the label where possible).|
During transport the containers must have UN number 1114 for identification and the symbol of hazard class, which for benzene is Class 3 (flammable liquids).
HALOGENATED HYDROCARBON SOLVENTS
This type of solvent is used in industry although various consumer products may also contain them.
Some of these solvents, such as chloroform, may originate from natural processes; others exist only as result of man-made chemical production. For example, natural sources of carbon tetrachloride have not been reported in the literature. Likewise, methylene chloride, 1,2-dichloroethane and trichloroethylene do not occur naturally in the environment, but are released from man-made sources and have become air, water and soil pollutants.
The persistence of these pollutants in the environment is described by the term `half-life', which gives the period in which half of the amount of pollutant has decomposed in various chemical reactions. The half-lives vary from a few hours to years, even hundreds of years in the air for some fully halogenated chlorofluorocarbons (freons).
Montreal Protocol (1989) is an international agreement to regulate the disposal of substances that may deplete the ozone layer. In this agreement the government promise to reduce or ban the use and release into the environment of specified halogenated hydrocarbons. Carbon tetrachloride and 1,1,1-trichloroethane are among those substances.
Most of the chlorinated hydrocarbons have narcotic effects, they may affect the heart and damage the liver. Some of them may penetrate the skin sufficiently to cause health hazards. It should be kept in mind that toxic effects may result from repeated exposure to amounts too low to produce acute symptoms and too low to give a warning of danger. Also there is a wide range of human responses to these chemicals: some workers may be seriously affected by exposure to concentrations that seem to have no effect on others.
Among halogenated compounds ethylene dibromide (mainly used as soil fumigant), vinyl bromide (used in plastic industry) and epichlorohydrin (used epoxy resin production) are classified by IARC (International Agency for Research on Cancer) as probably carcinogenic to humans. The following solvents are classified as possibly carcinogenic: bromodichloromethane, carbon tetrachloride, chloroform, 1,2-dichloroethane, 1,3-dichloropropene, methylene chloride and tetrachloroethylene. Some compounds of this group have also demonstrated, in addition to carcinogenic effects, changes in the reproductive process in animal tests. More research and follow-up of the long term effects of human exposure are necessary.
Halogenated hydrocarbon solvents decompose producing toxic and corrosive gases when brought into contact with open flames or hot surfaces. Some of the halo-solvents are also highly flammable.
In Europe about one million people (in European Union countries) risk exposure to these solvents at work. In the USA it has been estimated that five million workers are exposed to four of the most commonly used solvents: methylene chloride, trichloroethane, trichloroethylene and tetrachloroethylene. An undetermined amount of secondary exposure of occupational origin is caused to the general public.
Occupational exposure to these solvents can be expected in the following industrial activities:
1. Properties, use and health effects of some solvents
1.1. Carbon tetrachloride
Synonyms and trade names: methane tetrachloride, tetrachloromethane, Fasciolin, Freon 10, Necatorine, Tetrafinol, Tetraform, Tetrasol
Carbon tetrachloride is a non-combustible, colourless liquid with an ethereal odour. When the odour is detected, the recommended occupational exposure limit value has already been exceeded. Stabilizers are added to commercially used grades to prevent slow decomposition due to light. Carbon tetrachloride is insoluble in water, miscible with most organic solvents and has a good dissolving ability. For example, it can dissolve asphalt, benzyl chloride polymers, chlorinated rubber, ethyl cellulose, resins, waxes and fats. It is used as a solvent in the manufacture of cables and semiconductors. Carbon tetrachloride is an intermediate in the production of chlorofluorocarbon refrigerants for air conditioning and cooling equipment. It is used in the production of paints and plastics and in the formulation of petrol additives. Previously it was been used in fire extinguishers, but this is not recommended as heat may decompose it and the resulting products are highly toxic. Formerly it was used in dry-cleaning, degreasing, and as a grain fumigant. These uses, as well as its use in consumer products, are now restricted in many countries. Carbon tetrachloride was first produced commercially in 1907. Production and extensive use have declined since reaching its peak in 1974 because of the adverse effects to human health and to the environment.
There are numerous reports of injury and death following both acute and chronic exposure to carbon tetrachloride. The intoxications result from the inhalation of vapour, but it is also readily absorbed through the gastrointestinal tract and is able to penetrate through the intact skin. Volunteers exhaled easily measurable amounts of carbon tetrachloride after an experiment involving a 30 minute thumb immersion in this substance. Carbon tetrachloride is irritant to the skin, the eyes, nose, and throat. Exposure to this solvent and its vapour causes nausea, vomiting and abdominal pain, which some individuals experience already at low vapour concentrations. Carbon tetrachloride has anaesthetic properties affecting the central nervous system causing dizziness, vertigo, headache, depression, mental confusion and poor coordination. Higher concentration levels lead to unconsciousness and heart problems. Health effects may be immediate or delayed. Chronic exposure damages the kidneys, liver, and bone marrow, causes visual disturbances, and bronchitis. Carbon tetrachloride produces toxic effects on offspring in animal tests and it may have adverse effects on human reproduction. IARC has classified carbon tetrachloride as possibly carcinogenic to humans.
The ingestion of fat or alcohol together with carbon tetrachloride enhances the toxic health effects.
Effects on the environment
Although natural sources of carbon tetrachloride are not known, it is formed by sunlight-induced reactions involving other man-made chlorinated substances in the upper parts of the atmosphere (troposphere). It has been suggested that the presence of carbon tetrachloride in upper parts of the atmosphere is of concern as it may contribute to the depletion of the protecting ozone layer. Estimates of the atmospheric half-life of carbon tetrachloride vary between 15 and 100 years. Carbon tetrachloride is mentioned in Montreal protocol among chemicals that deplete the ozone layer and are subjects to effort of reducing the use by substituting with less hazardous solvents.
Carbon tetrachloride can be found at trace concentrations in water. However it is not formed during the purification of drinking-water using chlorine. It rapidly evaporates to the atmosphere from industrial effluents. Carbon tetrachloride residing in water is resistant to biological and chemical degradation. Hence, carbon tetrachloride is a marine pollutant.
CAS 108-90-7 (Monochlorobenzene); 95-50-1 (1,2-dichlorobenzene)
Monochlorobenzene and 1,2-dichlorobenzene are both flammable, colourless liquids with a sweet odour. They are soluble in benzene and alcohols but are insoluble in water. The vapours are heavier than air and may travel a considerable distance from the evaporation source. Ignition and flash-back to the source may lead to a fire, releasing toxic and corrosive gases. Chlorobenzenes are chemically active and used as intermediates in many industrial processes, such as in the production of pesticides, silicones and dyes. Monochlorobenzene is a process solvent for methylene diisocyanate, the latter being used as a solvent in adhesives, polishes, waxes, pharmaceutical products and natural rubber. 1,2-Dichlorobenzene is used as a solvent for a wide range of organic materials and non-ferrous metal oxides. It is also used as a solvent carrier in the production of toluene diisocyanate, as a fumigant and insecticide. Other applications include degreasing of hides and wool, in metal polishing products, industrial odour control and in cleaning agents meant for drains.
Chlorobenzenes irritate the skin and the eyes. Inhalation of chlorobenzene vapour causes headaches, dizziness, drowsiness and stomach irritation. It also affects the central nervous system. Chlorobenzene intoxication causes pain and numbness of fingers, and muscle spasms. High doses damage the kidneys and liver, and lead to unconsciousness. Chlorobenzenes may affect the blood causing anaemia. Acute leukemia has been attributed to 1,2-dichlorobenzene exposure by absorption through the skin (case studies).
Effects to the environment
Chlorobenzenes enter the environment from manufacture and dispersion in different formulations, but natural sources have not been identified. Chlorobenzene decomposes mainly in biological processes, such as microbial activity. In the air, photodegradation takes place. Chlorobenzene in water will be redistributed to the air and sediment. The amount of chlorobenzene in sediment may be 1000 times higher than that of the contaminated water.
Chlorobenzenes are moderately toxic to the aquatic life: discharge to the waters should be prohibited. They are marine pollutants.
Synonyms and trade names: methane trichloride, methyl trichloride, trichloromethane, Freon 20, R20 (refrigerant)
Chloroform is a very volatile, colourless, non-flammable liquid with a burning sweet taste. It has a characteristic odour but when it is detected, the recommended exposure limit value (10 ppm) has already been exceeded. Chloroform is miscible with most organic solvents but it is only very slightly soluble in water. Pure chloroform decomposes slowly in sunlight producing highly toxic gases (phosgene, chlorine and hydrogen chloride). To prevent this decomposition, commercial chloroform contains a stabilizing agent, usually 0.5-1% of ethanol.
Chloroform is used in the formulation of pesticides, in drugs and flavours, and as an intermediate in the production of fluorocarbon refrigerant, such as HCFC 22. Chloroform is a source material for polymer production, such as `Teflon' (PTFE). It is also used as a solvent and an insecticidal fumigant. Chloroform was once used as an inhalation anaesthetic but has now been replaced by safer substances.
Chloroform is well absorbed into animals and humans by ingestion and inhalation. It penetrates the skin, especially when it is wet or humid. Chloroform is distributed throughout the whole body, highest concentrations being found in fat, blood, liver, kidneys, lungs and the nervous system. Chloroform is irritating to the skin and may cause chemical burns. It is more irritating to eyes than most of the commonly used solvents, and splashes may cause inflammation. Acute effects depend on the concentration and duration of exposure and include headaches, drowsiness, dizziness, nausea and feeling of being drunk. Higher concentrations lead to unconsciousness, respiratory depression and heart failure. Liver and kidney damage arise from continued exposure. Chloroform has caused cancer in test animals. It has been shown to harm the reproductive process and the fetus in animal tests. Pregnant and nursing mothers should not come to contact with this solvent.
IARC has assessed chloroform and classified it as possibly carcinogenic to humans.
Effects on the environment
Chloroform is released into the environment from industrial production processes, transport and use. It is present in water as a result of chlorination of drinking-water and from industrial sources. Due to its high volatility it is rapidly transferred from surface water and surface soils into the air. It will stay in the atmosphere for several months before chemical transformation reactions have completed the decomposition. It may also be a product of atmospheric reactions involving other solvent vapours, such as 1,1,1-trichloroethylene vapours. The concentrations in tap water can considerably contribute to the quality of indoor air and to the general daily intake.
In soil, chloroform is highly mobile and may reach ground water.
Chloroform is also a marine pollutant; discharge into sea of this substance,of ballast water, tank washing or other residues or mixtures containing chloroform should be prohibited.
Synonyms and trade names: ethylene dichloride, glycol dichloride, EDC, Gaz olefiant, Freon 150, Dutch Liquid
1,2-Dichloroethane is a volatile, highly flammable, oily and colourless liquid. It has a sweet taste and an odour similar to chloroform. The vapour is heavier than air and may move along the ground to a distant ignition point with possible flash-back to the container. 1,2-Dichloroethane may explode when its vapour comes into contact and mixes with powdered metals such as dusts of magnesium or aluminum. It reacts violently with ammonia; furthermore mixtures of 1,2-dichloroethane and nitric acid may detonate due to heat, impact or friction. 1,2-Dichloroethane is miscible with other chlorinated hydrocarbons and soluble in most commonly used solvents, but it is only slightly soluble in water.
1,2-Dichloroethane corrodes aluminum, iron, zinc and some plastics. These materials are not suitable for storage containers of 1,2-dichloroethane.
The production volume of 1,2-dichloroethane is one of the largest of all globally produced chemicals. It is available for industrial use in various volumes: in tank wagons, drums, cans and bottles. The commercial end-products are stabilized to prevent the slow decomposition of 1,2-dichloroethane by air, moisture and light: usually by adding small amounts of alkylamines. If not stabilized, it may contain toxic and corrosive gases (chlorine and hydrogen chloride).
The main use of 1,2-dichloroethane is in the production of other chemicals such as vinyl chloride, 1,1,1-trichloroethane, ethylamines, and tri- or tetrachloroethylenes.
Gasoline may contain this solvent. It is used in textiles, varnishes and paint formulations, as well as in the processing of pesticides and resins. As a solvent it is used in the extraction of fats and oils and in degreasing operations.
When used as a fumigant it may contain carbon tetrachloride (up to 25%) to reduce the risk of a fire hazard.
Poisonings by inhalation or skin exposure have frequently been reported from workplaces where 1,2-dichloroethane is used as a solvent or fumigant.
Accidental ingestion of 20-50 g of 1,2-dichloroethane has been identified as a cause of a death, with a delay from 6 hours to 6 days. Symptoms may also be delayed.
1,2-Dichloroethane is readily absorbed into the body through the skin, by inhalation of the vapour and by ingestion. The first symptoms of acute intoxication are headache, dizziness, weakness, muscular spasms and vomiting, irritation of mucous membranes of the eyes and the respiratory tract. The exposure can also lead to changes in the blood and in the heart rhythm (cardiovascular insufficiency) which may be lethal. Kidneys and liver changes have also been recorded as a result of exposure.
1,2-Dichloroethane has produced cancer in animal tests and IARC has classified it as possibly carcinogenic to humans.
Effects on the environment
1,2-Dichloroethane is a man-made chemical: it does not naturally occur in nature, and hence it can only be found as a result of releases from production processes. Large amounts may be released through the disposal of waste from vinyl chloride industries, since it is the main component of the afore-mentioned waste products (EDC-tar).
Being volatile it evaporates from water into the atmosphere where it decomposes fairly quickly in sunlight to form oxides and acidic gases of hydrogen chloride. The decomposition is sufficiently rapid to prevent the accumulation of the compound in the atmosphere.
1,2-Dichloroethane is slightly toxic to the aquatic environment. It is also considered to be a marine pollutant. It poses a real hazard only in the case of an accident or inappropriate disposal. In some countries authorization for disposal is needed.
1.5. bis(2-Chloroethyl) ether
Synonyms: dichloroethyl ether, 2,2-dichlorodiethyl ether bis(2-Chloroethyl) ether is a colourless, combustible liquid with a pungent odour. It reacts in contact with water or steam producing toxic and corrosive fumes. bis(2-Chloroethyl) ether may decompose forming peroxides in sunlight and during storage, particularly if the container has been opened. Peroxides are explosive and in liquid form may be detonated by friction, impact or heating.
bis(2-Chloroethyl) ether is used as a solvent for special lacquers, resins and oils. Due to the strong dissolving power it is also used as a penetrant in spot removing and dewaxing agents. It is chemically active: contact with metal powders, strong acids, or sodamide, produces heat inducing a fire hazard. Inhibitors have been added to commercial formulation to prevent formation of peroxides and polymerization.
bis(2-Chloroethyl) ether is poisonous by any type of entry route into the body. It may penetrate the skin even as a diluted solution in amounts large enough to cause toxic effects without noticeable irritation. The respiratory reaction following inhalation of the vapour may be severe and symptoms delayed. Direct contact with the liquid or vapour irritates the skin, eyes and mucous membranes, causing coughing, nausea, and vomiting.
Some observations of cancer have been recorded in animal tests.
Effects on the environment
bis(2-Chloroethyl) ether is a marine pollutant, its release to the sea is prohibited by the International Convention since 1973.
Synonyms and trade names: propylene dichloride, ENT 15,406
1,2-Dichloropropane is a colourless, highly flammable liquid. The vapour is nearly four times heavier than air and may travel along the ground and ignite from a distant source. It is soluble in water to a certain extent (2.7 g/l), as well as in ethanol. In the presence of moisture it forms highly corrosive hydrochloric acid.
1,2-Dichloropropane should be kept separate from aluminum, o-dichlorobenzene and 1,2-dichloroethane. Strong acids induce the decomposition of 1,2-dichloropropane. Contact with strong oxidizing agents, such as nitric acid and chlorates may lead to fire and explosion.
1,2-Dichloropropane is used as a component in spot and paint removers, dry cleaning and furniture finishing products. It is a solvent for metal degreasing, for oil, resin and gum processing. Other applications of this substance are rubber compounding and vulcanizing operations. It is also a source material and intermediate of chemical industry processes, such as the manufacture of tetrachloroethylene and propylene oxide. It is used in the extraction processes of fats, oils, lactic acid and petroleum waxes. 1,2-Dichloropropane in mixtures with 1,3-dichloropropene in soil fumigants is used to control nematodes in vegetables, potatoes and tobacco.
It has been used in agriculture as a fumigant for grain, fruit and nut crops, peach trees and insect control. 1,2-Dichloropropane is also an additive for antiknock fluids in fuels for motor vehicles.
This solvent should not be used without proper precaution, ventilation, protective clothing and methods of disposal, although it is not among the most toxic of the halogenated solvents.
Inhalation of the vapour and skin contact are frequent routes of occupational exposure. Inhalation of low concentrations causes irritation of the respiratory tract, coughing and sneezing. High concentrations are narcotic and, depending of the dose, they lead to other symptoms such as weight loss, drowsiness and vertigo. Headache may be persistent and delayed from the original exposure. The vapour and the liquid irritate the eyes. Several cases of dermatitis and skin reactions have been reported from repeated exposure of workers using 1,2-dichloropropane and mixtures of solvents containing it.
Effects on the environment
1,2-Dichloropropane is persistent in the soil: in an experiment 98% of the applied 1,2-dichloropropane was recovered 12-20 weeks after soil treatment. 1,2-Dichloropropane may be taken up by plants and food crops in small amounts.
The solvent may leak from the soil to contaminate the ground-water. It is a marine pollutant.
Trace amounts of 1,2-dichloropropane have been measured in the atmosphere. It decomposes slowly with a half-life of over 313 days.
1,2-Dichloropropane is water soluble and has a low octanol-water partition coefficient; this suggests that bioaccumulation does not take place.
1.7. Methylene chloride
Synonyms and trade names: dichloromethane, methylene dichloride, methane dichloride, Aerothene MM, Freon 30, Solmethine
Methylene chloride is a colourless, non-flammable, volatile liquid. Under specific conditions it may burn. Its commercial formulations for paint stripping are particularly flammable. It is slightly soluble in water and miscible with many other solvents, such as acetone, chloroform carbon tetrachloride and alcohol.
Methylene chloride is a widely used solvent where quick drying (i.e. high volatility) is required: adhesives, cellulose acetate fibre production, blowing of polyurethane foams, and metal and textile treatment. It dissolves oils, fats, waxes, many plastics, bitumen, and rubber, this property is used also in paint stripper formulations. It is used as an aerosol solvent, and for extraction operations in pharmaceutical industry. It was previously used in fire-extinguishing products.
The acute toxicity of methylene chloride is one of the lowest in the family of halogenated hydrocarbon solvents. Liver and kidney damage are less likely at low exposure levels. However, methylene chloride is used mainly in mixtures in which other components may increase adverse effects. The worker and his entourage are mainly exposed through the inhalation of vapours. Its narcotic effects and the drunkenness-related symptoms depend on the degree of exposure. In the body methylene chloride is transformed to release carbon monoxide, which replaces oxygen in the blood. This has resulted in heart failure deaths, which have been reported in spray painting. Methylene chloride is irritating to the eyes. It may penetrate the intact skin, is irritating on repeated contact and moderately toxic if ingested.
Repeated exposure to methylene chloride has been shown to be carcinogenic in animal tests and IARC has classified this compound as possibly carcinogenic to humans.
Methylene chloride passes through the placenta and has been found to accumulate in the fetal tissue and breast milk. Increased rates of spontaneous abortions were reported among female pharmaceutical workers, indicating a hazardous effect in pregnancy.
Effects on the environment
An estimated 80% of the total world production of methylene chloride evaporates into the atmosphere from where it reacts with a 77-day half-life.
Its degradation in surface waters is slow and it is removed from the water by evaporation into the air. Its presence in drinking-water results from chlorination of water or is due to contamination. Methylene chloride has not been found to accumulate in sediment or in the aquatic organisms.
Synonyms and trade names: tetrachloroethane, sym-tetrachloroethane, acetylene tetrachloride, Bonoform, Cellon
1,1,2,2-Tetrachloroethane is a heavy, mobile, non-flammable liquid. Its suffocating odour does not provide any warning as it is smelled only at concentrations exceeding the occupational exposure limit. It is only slightly soluble in water, but is soluble in a wide range of organic solvents, such as alcohol, acetone, chloroform and ether.
Tetrachloroethane decomposes slowly in the presence of moisture, producing corrosive gases. It reacts with alkali metals and their alloys, many metal powders, sodium or potassium hydroxide, bromoform and nitrogen tetroxide producing explosive compounds.
1,1,2,2-Tetrachloroethane is used in the production of tetrachloroethylene and trichloroethylene. It has a relatively high boiling point and is a solvent in paints and lacquers. It is also used in metal degreasing and finishing (e.g. in jewelry production), in some dyes, in the extraction of fats and oils, and in the production of insecticides and herbicides. It dissolves sulphur, gums and resins, bitumen, pitch and tarry materials, and has been used in fumigation products for greenhouses and grain.
At present it has been replaced in most of its applications by less toxic solvents and is recommended to be used only in closed processes.
1,1,2,2-Tetrachloroethane is considered to be one of the most poisonous of the common chlorinated hydrocarbon solvents. Exposure may arise from inhalation of the vapour or skin contact. The slow removal processes of the human body contribute to the high toxicity. It is a powerful central nervous system, kidney and liver poison with a narcotic effect. In animal tests it has been shown to be two to three times as effective as chloroform in causing narcosis. Cases of chronic intoxication from artificial silk and leather manufacturing have shown two main types of effects: those originating from the central nervous system, such as tremor, vertigo and headache, and those originating from the gastrointestinal tract and the liver, such as nausea, vomiting, stomach pain and jaundice from liver damage. Tetrachloroethane causes changes in the blood. The adverse effects may be delayed.
Tetrachlorethane has shown adverse effects on the fetus in animal tests.
Effects on the environment
Tetrachloroethane is a marine pollutant and it may bioaccumulate in the human food chain.
Synonyms and trade names: perchloroethylene, ethylene tetrachloride, tetrachloroethene, 1,1,2,2-tetrachloroethylene, Antisal 1, Dee-Solv, Didakene, Dow-Per, ENT 1860, NeMa, Perchlor, Persec, Tetlen, Tetracap, Tetravec, Tetropil
Tetrachloroethylene is a colourless, non-flammable liquid, miscible with many organic solvents but insoluble in water. The odour is pleasantly ethereal, resembling that of chloroform. It saturates the sense of smell and does not provide a warning, as a person can suffer from overexposure without smelling it. Commercial grades contain stabilizers as pure tetrachloroethylene is decomposed slowly by light and in contact with moisture. Stabilized products are very stable up to 140oC. Under proper conditions tetrachloroethylene reacts violently with some metals, strong alkalis and nitrogen tetroxide gas. Like all other halogenated solvents, tetrachloroethylene decomposes in an open flame or on a very hot surface producing corrosive and toxic gases.
Waste should be collected as tetrachloroethylene can be recycled.
Tetrachloroethylene is an important solvent in dry cleaning fluids; its share is more than 90% of solvents used in this sector. As a solvent it is also applied in metal degreasing, rubber and resin production and it can dissolve silicones. It has been used to replace hazardous heat transfer liquids, PCBs, in transformers.
The most common route of occupational exposure is via inhalation of the vapour which is readily absorbed from the lungs into the blood circulation. The symptoms of exposure to low concentration are related to the effects on the central nervous system - where it causes dizziness, confusion, headache and nausea. Inhalation of high concentrations may lead to unconsciousness.
Table 1. Experienced correlation of symptoms and air concentration by inhalation of tetrachloroethylene
|50 ppm||Occupational exposure limit, faint odour (8 hours)|
|100 ppm||Faint but apparent odour, very faint to not perceptible by prolonged exposure, no physiological effects (8 hours)|
|200 ppm||Moderate to faint odour level depending of the length of exposure; faint to moderate eye irritation, minimal lightheadedness|
|400 ppm||Unpleasant, strong odour; irritation of eyes and slight irritation of nose, definite incoordination (2 hours)|
|600 ppm||Odour is very strong and unpleasant but tolerable; definite irritation of eyes and nose; dizziness, loss of inhibitions (10 minutes)|
|1000 ppm||Intense, irritating odour; markedly irritating to the eyes and respiratory tract, considerable dizziness (2 minutes)|
|1500 ppm||Almost intolerable odour; complete incoordination within minutes leading to unconsciousness within 30 minutes|
The acute toxicity is relatively low when compared to many other commonly used chlorinated solvents. The adverse health effects that are experienced depend on the increased concentration inhaled and the length of the exposure period. Repeated exposure to (concentrations over 100 ppm) tetrachloroethylene over months or years may lead to adverse effects on the nervous system, respiratory tract, liver and kidneys, and heart functions (cardiac arrhythmias).
Tetrachloroethylene degreases the skin causing irritation by repeated contact.
Tetrachloroethylene has caused cancer in animal tests and is classified as possibly carcinogenic to humans.
Tetrachloroethylene passes into breast milk and through the placental barrier to the fetus. It has shown effects on reproduction in animal tests.
ACGIH has established biological exposure indices (BEI) for tetrachloroethylene: it can be measured from exhaled air (BEI 5 ppm) or blood samples (BEI 0.5 ppm) prior to the last shift of the workweek, or from urine at the end of the workweek (BEI as trichloroacetic acid 3.5 mg/litre).
Effects on the environment
Tetrachloroethylene has no natural sources. However, it has been found to be present in small amounts in samples of air and of surface waters, including drinking-water. It has been also found in foods, such as dairy products, meat, oils and fat, fruits and vegetables, and fresh bread.
Tetrachloroethylene has shown toxic effects in the aquatic environment and it is in the list of compounds known to be marine pollutants. If present in soil, it penetrates into the groundwater.
The time which tetrachloroethylene vapour remains in the atmosphere is estimated to have a half-life of 68 days. The effects on the ozone layer are under discussion.
Synonyms and trade names: methyl chloroform, methyl trichloromethane, Chloroethena, Chlorothene, Aerothene TT, Alpha-T, Genklene, Inhibisol
1,1,1-Trichloroethane is a colourless, volatile liquid with a vapour that is heavier than air and it has a sweet odour. It is poorly soluble in water but dissolves in other solvents, such as acetone, benzene, ethanol, and carbon tetrachloride. In contact with water or humidity, trichloroethane decomposes slowly yielding corrosive acids.
In normal working conditions 1,1,1-trichloroethane presents no risk of flammability. However when heated, and particularly when in contact with some metal salts, it decomposes producing very toxic and corrosive gases. This may be the case if welding takes place in confined places containing trichloroethane vapour. Commercial products are stabilized to avoid corrosion of the storage container. The stabilizers (3-8%) may have toxic health effects. 1,1,1-Trichloroethane undergoes a hazardous reaction when in contact with a strong alkali, such as calcium hydroxide, producing extremely flammable, volatile and hazardous compounds.
1,1,1-Trichloroethane has similar properties to those of the more hazardous solvents: carbon tetrachloride and trichloroethylene. It has replaced the use of the latter and is extensively used as a solvent for rubber, bitumen, mineral and vegetable oils, stearic acid, lanolin, polystyrene, polyvinyl acetate, acrylic resins and in metal cutting oils as a coolant and in lubricants. 1,1,1-Trichloroethane finds uses in dry cleaning formulations, in the cleaning of metal and plastic surfaces, as a solvent in printing inks and consumer products such as adhesives and correction fluids like Tipp-Ex®. It can be found in aerosols and as an additive to raise the flash point of many flammable solvents.
It was previously used as a solvent in insecticides, and in the treatment of citrus fruits and strawberries.
1,1,1-Trichloroethane is generally accepted to be among the least toxic to humans among the chlorinated hydrocarbon solvents. It is mainly absorbed through inhalation, although it may also enter the body through the skin and as result of ingestion. It has fairly low acute and chronic toxicity, and is relatively safe when used as a solvent. Concentration levels under 1350 mg/m3 (250 ppm) are estimated to cause no adverse effects. The odour is smelt before the occupational exposure limit is exceeded and may serve as a warning.
The potential adverse health effects in both short term and repeated exposure vary from changes in behaviour to symptoms originating from the central nervous system depression: unconsciousness and heart failure, kidney, liver and lung damage at high concentrations (above 350-500 ppm). Inhalation of the vapour cause headache, dizziness and drowsiness. The seriousness of the effects depends on the individual susceptibility and the dose.
Skin and eyes are irritated if in direct contact with liquid or vapour.
1,1,1-Trichloroethane is volatile and the vapour is nearly five times heavier than air. Poorly ventilated or confined spaces, such as tanks and vaults, may contain very high concentration of solvent vapour. This has lead to serious accidents.
Alcohol drinking combined with exposure to 1,1,1-trichloroethane may increase the toxic effects.
Effects on the environment
1,1,1-Trichloroethane spillage evaporates (estimation is over 99% of lost solvent) to the atmosphere, decomposing there slowly. The estimated time it resides in the atmosphere is about 6 years. It also reaches the upper parts of the atmosphere in significant amounts, where decomposition releases reactive chlorine, resulting in the depletion of the protective ozone layer. It could produce global warming but with lesser potential than the chlorofluorohydrocarbons (freons). The large scale releases of this solvent into the atmosphere is the reason for the concern of global atmospheric effects. 1,1,1-Trichloroethane is included in Montreal Protocol on substances that deplete the ozone layer and its use is going to be reduced, and finally will be substituted by other solvents.
1,1,1-Trichloroethane is heavier than water and is not water soluble. It is not absorbed onto soil particles and thus leaks readily into groundwater, staying there as persistent contamination.
1,1,1-Trichloroethane has been detected in trace concentrations in all water sources: groundwater, drinking water, rain water, seawater and sewage. It has been found in seawater organisms and fresh- and seawater birds and in their eggs. It has been classified as a marine pollutant.
Although being a widely distributed contaminant in nature, 1,1,1-trichloroethane is considered not bioaccumulate.
Synonyms and trade names: ethane trichloride, beta-T
1,1,2-Trichloroethane is a non-flammable liquid with a pleasant odour, practically insoluble in water but miscible with ethanol, chloroform, ether and chlorinated solvents. It is mainly used in the manufacturing of vinylidene chloride but may act as a specialty solvent for adhesives, fats and resins. Exposure is possible for workers in blast furnace, steel mill, engineering and scientific instrument manufacturing. Due to hazardous liver toxicity and suspicious carcinogenity, its use has been replaced, often by the less toxic 1,1,1-trichloroethane.
Effects on the environment
Industrial waste and effluents, such as EDC-tar from polyvinyl production, are sources of this solvent in the environment as it does not occur there naturally.
1,1,2-trichloroethane is also a marine pollutant.
Synonyms and trade names: ethylene trichloride, acetylene trichloride, trichloroethene, TCE, Tri, Algylen, Benzinol, Blancosolv, Chlorilen, Circosolv, Dow-tri, Fleck-Flip, Lanadin, Perm-A-Chlor, Petzinol, Trethylene, Triasol, Trichloran, Tri-Clene, Trilene, TRI-plus, Vestrol, Vitran
Trichloroethylene is a volatile, colourless liquid. The odour is slightly sweetish and it is smelt at concentrations low enough to provide a warning of exposure. Trichloroethylene is poorly soluble in water but dissolves in ethanol, diethyl ether and other chlorinated hydrocarbons. It is non-flammable in normal working conditions and combustible under specific conditions. Accidents have been recorded when toxic and corrosive decomposition gases have been inhaled. These gases may be formed in contact with hot surfaces and open welding flames. Stabilized commercial products do not undergo any chemical changes in contact with air, humidity or light, this being prevented by stabilizers (below 1%). However, some of the stabilizers used are very toxic.
Contact with strong alkaline substances, such as soda lime, particularly if heated above 70oC, or the presence of epoxides cause trichloroethylene to react producing a highly reactive and explosive gas (dichloroacetylene), which is acutely damaging and causes permanent nerve injury both to man and animals.
Trichloroethylene is a good solvent and is used in the degreasing of metals, textiles, leather and wool. Commercial grades are available and some of them are for specified use such as the cleaning of ferrous metals. Aluminum and magnesium metals should not be cleaned with the same grade but with a neutral, stabilized grade designed for non-ferrous metals.
Trichloroethylene is used in extraction processes and as a solvent for various materials, such as waxes, oils, resins, rubber, lacquers and paints, printing inks, adhesives, fluid silicones, cellulose esters and ethers, and sulphur. Another use of trichloroethylene has been dry-cleaning, in insecticides and fungicides, where it is a vehicle for the active ingredients, and as an anaesthetic in medical and dental use.
Less toxic solvents have replaced trichloroethylene in several places of usage.
Trichloroethylene from industrial processes can be recovered by distillation and may be recycled.
Exposure to trichloroethylene occurs mainly through inhalation and skin contact. The over-exposure symptoms are related to the effects on the central nervous system causing headache, drowsiness, depression, vertigo and lack of coordination. It also causes alcohol intolerance.
Some sudden deaths have been caused by heart arrhythmia. Repeated exposure may cause changes in behaviour, in intellectual functions and in reaction speed as well as memory impairment. Termination of exposure usually results in rapid recovery of normal behaviour. There are reports of damage to liver and kidneys.
Trichloroethylene is an irritant to skin, mucous membranes and the eyes.
Trichloroethylene has induced cancer in animal tests. Until now, there has been no evidence of the carcinogenic effects in humans. However, more research is being done in this field.
For biological monitoring, ACGIH has given biological exposure indices (BEI) values to trichloroethylene metabolite products measured in urine (trichloroacetic acid and trichloroethanol, 300 mg/g creatinine) and blood (free trichloroethanol, 4mg/litre), analysed from samples taken at the end of the work shift.
Effects on the environment
Trichloroethylene does not exist in unpolluted nature but may be detected in the environment as a result of human activities. An estimated 60% of the annual world production is lost to the environment (hundreds of millions of tons evaporation into the atmosphere yearly). It decomposes in the atmosphere by photo-oxidation (reacting with ozone) with a half-life estimated to be from 8 hours to 5 days.
The lifetime before decomposing is expected to be short for trichloroethylene, ranging from a week to ten days, and it does not therefore represent an ecological threat.
It has been detected in trace amounts in surface waters, soil and sediment. Consumer products such as dairy products, meat, oils and fat, beverages, fruit and vegetables have also been found to contain trace amounts but there is no direct evidence of its bioaccumulation in the human food chain.
Trichlorethylene is a marine pollutant.
Synonym names: allyl trichloride, glycerol trichlorohydrin
1,2,3-Trichloropropane is a combustible liquid. The vapour is heavier than air; it may travel along the ground to a distant ignition point and may form explosive mixtures with air.
Inhalation and penetration through the skin are common exposure routes at work. 1,2,3-Trichloropropane is irritating to the skin and the respiratory tract and acts as a severe irritant to the eyes.
It has a narcotic effect, a headache being the symptom of exposure to low concentrations. High concentrations lead to unconsciousness. Repeated exposure may cause liver damage.
Effects on the environment
1,2,3-Trichloropropane is a marine pollutant.
2. Preventive measures
1. To prevent adverse effects on users and workers, one should select, among the many possibilities available, the solvent which has the least serious health effects combined with the required solvent characteristics.
2. Prevent the contact of the worker with the solvent and its vapour. This can be achieved by closed systems, isolated working areas where the solvent is likely to be released, ventilation at the source, protective clothing and respiratory equipment.
Gloves should be tested with the solvent before recommending their use, as the solvents are often a commercial formulation and not the pure substance.
3. Prevention should be accompanied by monitoring. The solvent vapour levels may exceed the recommended occupational exposure limits without being smelt by the worker. For effective monitoring, filters have been developed for solvents, they can be attached to the clothing in the breathing zone and analysed in the local laboratory. Medical monitoring may also be part of the preventive planning.
4. As solvents are absorbed through the skin in considerable amounts the worker should pay attention to work practices and equipment.
Labelling the containers, training the users, pointing out the need to follow the given instructions should form a part of preventive measures.
Halogenated solvents which are used in closed or partly closed systems can often be collected and recycled cost-effectively. In open use they are lost, mainly through evaporation.
|Carbon tetrachloride, skin||5 ppm;||31 mg/m3; A3|
|Chlorobenzene (monochlorobenzene)||10 ppm;||46 mg/m3|
|Chloroform||10 ppm;||49 mg/m3; A2|
|1,2-Dichlorobenzene (o-dichlorobenzene)||25 ppm;||150 mg/m3|
|1,2-Dichloroethane (ethylene dichloride)||10 ppm;||40 mg/m3|
|1,2-Dichloroethylene||200 ppm;||793 mg/m3|
|bis(2-Chloroethyl) ether, skin||5 ppm;||29 mg/m3|
|1,2-Dichloropropane (propylene dichloride)||75 ppm;||347 mg/m3|
|1,3-Dichloropropene, skin||1 ppm;||4.5 mg/m3|
|Methyl bromide, skin||5 ppm;||19 mg/m3|
|Methylene chloride (dichloromethane)||50 ppm;||174 mg/m3; A2|
|1,1,2,2-Tetrachloroethane, skin||1 ppm;||6.9 mg/m3|
|Tetrachloroethylene (perchloroethylene)||25 ppm;||170 mg/m3; A3|
|1,1,1-Trichloroethane (methyl chloroform)||350 ppm;||1910 mg/m3|
|1,1,2-Trichloroethane, skin||10 ppm;||55 mg/m3|
|Trichloroethylene||50 ppm;||269 mg/m3; A5|
|1,2,3-Trichloropropane, skin||10 ppm;||60 mg/m3|
|skin||Refers to potential significant exposure through skin, mucous membranes and eyes|
|A2||Suspected human carcinogen|
|A3||Causing cancer in animal tests|
|A5||Not suspected as human carcinogen|
|Synonym names are in parenthesis|
Attention should be paid to storage. Some of the solvents are flammable and all of them decompose in an open flame producing very toxic gases. Decomposition can also happen during improper incineration of the waste products.
The vapours of these solvents are heavier than air and settle on the floor. Storage space should not be chosen in cellars or basements where ventilation of heavy vapours can be difficult. Light and moisture have a decomposing effect on these solvents; the released products are corrosive to metal containers. Stainless or iron steel containers are generally recommended, copper, aluminum or its alloys and galvanized iron are not recommended materials for storage containers for many of the halogenated solvents. Plastic should not be used unless it has been tested previously. The same applies to tubes and hoses for transfer as these solvents attack and soften many polymers, resins, coatings and rubber.
CLASSIFICATION OF HALOGENATED HYDROCARBONS IN EU
|Carbon tetrachloride||T; N||23/24/25-40-48/23-52/53-59||(1/2-)23-36/37-45-59-61|
|Chlorobenzene (phenyl chloride)||Xn; N||10-20-51/53||(2-)24/25-61|
5% £ conc.<20%
|1,2-Dichlorobenzene, conc.³ 20%||Xn; N||22-36/37/38-50/53||(2-)23-60-61|
|1,2-Dichloroethane (ethylene dichloride)
(dichloroethyl ether), conc.³ 7%
|1,3-Dichloropropene||T; N||10-20/21-25-36/37/38-43-50/53||(1/2-)36/37-45-60-61||C, D|
|1,1,2,2-Tetrachloroethane, conc.³ 7%
|Tetrachloroethylene (perchloroethylene)||Xn; N||40-51/53||(2-)23-36/37-61|
|1,1,1-Trichloroethane (methyl chloroform)||Xn; N||20-59||(2-)24/25-59-61||F|
|1,1,2-Trichloroethane, conc.³ 5%||Xn||20/21/22||(2-)9|
Synonym names are in parenthesis
S-phrases in parenthesis indicate that they must be included to a label for consumer products.
|N||Dangerous for the environment|
Meaning of Notes
|Note C||Some organic substances may be in a specific isomeric form or as a mixture of isomers with a general designation. In this case the label states clearly whether the substance is a specific isomer or a mixture of isomers. For example `Xylene' is specified: `o-Xylene' or `Xylene, mixture of isomers'.|
|Note D||Some substances which polymerize readily or decompose spontaneously are normally placed on the market in a stabilized form. However, such substances are sometimes placed on the market in a non-stabilized form. This must be stated on the label with the name of the substance: `Methacrylic acid (non-stabilized)'.|
|Note E||Substances with specific effects on human health (classified as
carcinogenic, mutagenic and/or toxic to reproduction) if they are also classified as `Very
toxic (T+)', `Toxic (T)' or `Harmful (Xn)'. The word also shall precede the risk
phrases R20, R21, R22, R23, R24, R25, R26, R27, R28 when in a combination, for example:
R45-23: May cause cancer. Also toxic by inhalation.
R46-27/28: May cause heritable genetic damage. Also very toxic in contact with skin and if swallowed.
|Note F||The substance may contain a stabilizer. If the stabilizer changes the hazardous properties of the substance as listed, a label must be compiled in accordance with rules for the resulting hazardous preparations.|
RECOMMENDED GLOVE MATERIALS
|Substance||Use gloves made of|
|Acetone||Butyl rubber; Polythene|
|Benzene||PVA; Viton; (Polyurethane; Butyl/Neoprene)|
|Carbon tetrachloride||polyvinyl alcohol, Teflon, Viton|
|Chlorobenzene (monochlorobenzene)||Viton, Teflon|
|Chloroform||polyvinyl alcohol, Viton, Teflon|
|1,2-Dichloroethane (ethylene dichloride)||polyvinyl alcohol, Viton, Teflon|
|1,2-Dichloropropane (propylene dichloride)||polyvinyl alcohol, Viton, Teflon|
|1,3-Dichloropropene||polyvinyl alcohol, Viton, Teflon|
|Ethanol||Butyl rubber; Nitrile rubber; Neoprene; Natural rubber; Viton|
|Hexane||Viton; Neoprene; PVA; Nitrile|
|Isopropanol||Natural rubber; Neoprene; Nitrile rubber; PVC|
|Methyl bromide||butyl rubber, neoprene, polyethylene|
|Methyl cellosolve||Butyl rubber; PVA;|
|Methylene chloride (dichloromethane)||polyvinyl alcohol, nitrile|
|Methyl ethyl ketone (MEK)||Butyl rubber; (PVA; Viton; Polythene)|
|Methyl isobutyl ketone (MIK)||PVA|
|Naphtha||Polyurethane; Nitrile rubber|
|Tetrachloroethylene (perchloroethylene)||polyvinyl alcohol, Viton, Teflon|
|Toluene||PVA; Viton; (Butyl rubber)|
|Toluene diisocyanate (TDI)||PVA; Butyl rubber; Nitrile rubber|
|1,1,1-Trichloroethane (methyl chloroform)||Viton; (Natural rubber; Butyl rubber; Polythene)|
|Trichloroethylene||Viton; (Natural rubber; Butyl rubber; Polythene)|
|1,2,3-Trichloropropane||butyl rubber, polyvinyl alcohol, Viton|
|Turpentine||PVA; Nitrile rubber|
|Xylene||PVA; Nitrile rubber|
(Viton) name in parenthesis: these gloves give a limited protection
FIRST AID ADVICE
related to halogenated solvents
Check the Chemical Safety Data Sheet ( See the Cards by CAS Number, in alphabetical order or by risk phrases) and the label for first aid advice. If not available follow the general first aid procedure:
Continue to Part VII: Metals