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School of Process, Environmental and Materials Engineering Essay Sample

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School of Process, Environmental and Materials Engineering Essay Sample

Executive Summary:

In the production stage of ethylene oxide, it is normally stored in special automated chemical process plants.  Ethylene oxide has been produced since the early 1900s, originally by the reaction of ethylene chlorohydrin with base and in recent years more commonly by catalytic oxidation of ethylene. It has been used as a chemical intermediate in the production of ethylene glycol, glycol ethers, nonionic surfactants and other industrial chemicals. Although much smaller amounts are used in sterilizing, medical instruments and supplies in hospitals and industrially and for the fumigation of spices, it is during these uses that the highest occupational exposure levels have been measured.

There is limited evidence in humans for the carcinogenicity of ethylene oxide.

There is sufficient evidence in experimental animals for the carcinogenicity of ethylene oxide.


Charles Wurtz, a French chemist, was the first who was able to prepare Ethylene oxide by treating 2-chloroethanol with a base. It was used in the World War I as a precursor to both the chemical weapon mustard gas and ethylene glycol, which serves as a coolant. Later on, another French chemist named Theodore Lefort discovered on how to prepare ethylene oxide directly from ethylene and oxygen, using silver as a catalyst. Since then, almost all ethylene oxide that is produced industrially was made from this method.1

Ethylene oxide is used for sterilization since it can kill bacteria, mold, and fungi when it is on its gaseous form. In 1930, this has been used to preserve spices through sterilization. It is also used to sterilize medical supplies such as surgical implements, bandages, and sutures. Another usage of Ethylene oxide is it acts an intermediate in producing other chemicals. One of its major uses is the production of ethylene glycol. Ethylene glycol is used as an antifreeze and coolant for automotives. It is also used in the production of polyester polymers.1

This chemical is the simplest of the cyclic ethers. It is a colorless gas at room temperature and normal pressure. 3 It has an ether-like odor 4. Ethylene oxide has a molecular weight of 44.1 with a melting point of -111 degree Celsius and a boiling point of 10.7 degree Celsius. It has a vapor pressure of 1,314 mm HG at 25 degree Celsius and a log octanol-water partition coefficient of 0.30.

Ethylene oxide is soluble in water, ethanol, acetone, benzene, diethyl ether, and most organic solvents. It is relatively stable in aqueous solutions or when diluted with carbon dioxide or halocarbons, but it may undergo slow polymerization during storage. Ethylene oxide is highly reactive and potentially explosive when heated or in the presence of alkali metal hydroxides a highly active catalytic surfaces. It reacts readily with acids resulting in ring opening. Vapors may be flammable or explosive if there is inadequate heat dissipation. Incomplete combustion releases carbon monoxide. 13

The solubility of ethylene oxide gas in various compounds has been measured and reported at atmospheric pressure and 22 to 23 degree Celsius. These compounds include hydrocarbons, oils, water, alcohol, and waxes. 11

The solubility of gases in liquid ethylene oxide varies, increasing in the order nitrogen, argon, methane, and ethane. Increase in temperature tends to increase the solubility. 11

Liquid Ethylene oxide is an electrically conductive fluid and static electricity charges cannot accumulate in metal containers using proper bonding and grounding techniques.10

Ethylene oxide has a high odor threshold almost > 250 ppm and sense of smell does not provide adequate protection against its toxic effects. The effects of exposure are concentration and time dependent. Concentrations of several hundred ppm may be tolerated for a few mintures without significant immediate health effects. Similar concentrations may cause sever injury, especially if inhaled for longer periods. The concentration to kill is 50% of was 5000ppm for a one hour exposure, and about 1460 ppm for a four hour exposure. 3

Ethylene oxide ranked as one of the most hazardous compounds (worst 10%) to ecosystems and human health. 13 Ethylene oxide is a substance, which due to its epoxide structure, is counted among the very reactive compounds. This reactivity also includes organic structures within cells and cell nuclei. In this case, alkalation and reactions with DNA, RNA and proteins occur. Cytotoxicity, carcinogenicity and mutagenicity of ethylene oxide, which have been demonstrated by many in vitro tests, are attributed to these properties.

Epidemiological data from many sources indicated that workers exposed to ethylene oxide at their working place had an increased incidence of leukemia and other tumours. In view of the known positive potential of ethylene oxide for genotoxic carcinogenicity, it is recommended that use is acceptable only when pharmaceutically absolutely necessary, and then at a limit of 1 ppm. This limit is based on the current limit of detection for ethylene oxide. Any deviation upwards from this limit must be justified and defended, taking into account the clinical risk or benefit assessment for the particular products under consideration.

This research study discusses the raw materials of ethylene oxide, its different methods for manufacturing, the hazard effects of the chemical to the human body, and safety measures that needs to consider preventing adverse effects during exposure to this chemical.

Process Selection, Process Evaluation and process Flow Diagrams

Ethylene oxide is produced industrially by the oxidation of ethylene with either pure oxygen or air. The primary difference between the two processes is the sequencing of absorbers and desorbers in the separation train. Ethylene and oxygen (or air) are reacted at 10-30 atmospheres and 400-500F in a fixed bed catalytic reactor. The catalyst bed consists of large bundles of many tubes that contain supported silver catalyst spheres or rings. The tubes are 6-12 meters long and 20-50 millimeters in diameter.

In the oxygen process, the reactor off-gas is fed to CO2 scrubbers, then to ethylene oxide scrubbers, which absorb the ethylene oxide into the liquid phase. The ethylene oxide is recovered from the liquid in a desorber and distilled to remove water. In the air process, no CO2 scrubbing is used because the gas purge of inerts (mostly N2) is sufficient to remove the CO2. The reactor operates at a low conversion, however, so unreacted ethylene is fed to a secondary fixed bed reactor, then separated. Ethylene oxide purity is typically greater than 99.5%.  15

Figure 1 is a process flow diagram (PFD) showing combined pure oxygen- and air-based systems. 15

Figure 1. Simplified process plow of ethylene oxidation15

Catalyst pellets are designed to favor selective oxidation (epoxidation) over total oxidation (combustion) by limiting the availability of active sites. Silver is supported on pure aluminum oxide with pore diameters ranging 0.5-50 micrometers and specific surface area less than 2 m2/g. The motivation for designing this catalyst is that a less active catalyst will promote the partial oxidation of ethylene to ethylene oxide, but it will promote neither the total oxidation of ethylene nor the subsequent oxidation of ethylene oxide. Catalyst is operated with alkali metal promoters, usually cesium, and chlorine-containing inhibitors. Alkali metal promoters are dissolved in the catalyst by adding an alkali metal salt to the catalyst mixture during manufacture. Chlorine inhibitors are adsorbed onto the catalyst in the reactor by adding a small amount of a chlorine-containing gas, such as dichloromethane, to the reactor.16

The amount of chlorine added must be tightly controller, however, since high coverage of chlorine will deactivate the catalyst. The main drawback to using silver catalyst is that, although its initial selectivity ranges 79-83%, as it ages its selectivity deteriorates, and there are no generally applicable methods of regeneration. Silver catalyst may age due to abrasion, deposition of carbon-containing compounds, and recrystallization of the silver.

The life span of the catalyst is 2-5 years, and due to this limitation, new technologies are being investigated. One of the most important uses of ethylene oxide is the production of ethylene glycol. So, although no new technology is available for the production of ethylene oxide, new processes are being investigated that can produce ethylene glycol directly from ethylene. Increases in the cost of the ethylene could mean that only significant increases in catalyst selectivity and life span could maintain an economically viable ethylene oxide process.

Silver is an effective catalyst for the epoxidation of ethylene due to its good ability to adsorb oxygen. The form of adsorbed oxygen, however, is different in two possible reaction mechanisms. One mechanism proposes that silver adsorbs oxygen molecularly, while the other mechanism proposes that an oxygen molecule dissociates into atoms on adsorption. The roles of chlorine-containing inhibitors and alkali-metal promoters are also explained differently in each mechanism.

In the molecular (or dioxygen) adsorption model, one molecule of oxygen adsorbs on the silver surface and reacts with one adsorbed ethylene molecule, producing one ethylene oxide molecule and one adsorbed oxygen atom. This remaining oxygen atom participates in a combustion reaction with ethylene. Chlorine inhibitors serve to block active sites from adsorbing atomic oxygen, thereby increasing selectivity. The role of alkali-metal promoters is not fully understood.

Since six oxygen atoms are required for the total oxidation of one ethylene molecule, six ethylene oxide molecules are produced for every molecule of ethylene that is combusted. Thus, the selectivity to ethylene oxide is 6/7, or 85.7% (assuming that neither ethylene nor ethylene oxide are combusted by any other pathways). This mechanism seems to be supported by industrial operations, since the maximum selectivity obtained in an industrial setting is approximately 80% 15. Mechanistic research has shown, however, that the epoxidation of ethylene performed in the presence of atomic oxygen is not affected by the concentration of adsorbed molecular oxygen.

The epoxidation can also be performed with N2O, which is a source of atomic oxygen only 16.  Figure 2 shows mass spectra obtained from a temperature-programmed reactor (TPR) during ethylene epoxidation performed under two sets of circumstances.  The epoxidation was performed with both molecular oxygen and atomic oxygen present and with only atomic oxygen present.  The short, broad peak of the O+2 signal represents molecular oxygen, and the tall, sharp peak represents atomic oxygen.  Ethylene oxide production, represented by the CHO+ signal, is independent of molecular oxygen concentration. 16

Figure 2. Multimass TPR spectra with molecular oxygen present in the left-hand sample and absent in the right hand sample. 3

The atomic oxygen adsorption mechanism explains the epoxidation of ethylene in terms of the electronic properties of the reactants. Atomic oxygen is the reactive species in both epoxidation and combustion; molecularly adsorbed oxygen is inactive. Epoxidation occurs when one oxygen atom reacts with the double bond of one adsorbed molecule of ethylene. Combustion occurs when one oxygen atom abstracts the slightly acidic hydrogen atom of one adsorbed molecule of ethylene, which results in complete oxidation. Similarly, one oxygen atom can react with and completely oxidize a newly produced ethylene oxide molecule. 17

The presence of inhibitors can increase selectivity by altering the electronic properties of the adsorbed oxygen atom and activating it for epoxidation. Electron-withdrawing species, such as adsorbed chlorine, act to decrease the electron density of the oxygen atom. The electron-deficient oxygen favors an attack on the electron-rich double bond of ethylene. Annealing in the presence of oxygen has activated clean silver catalyst samples, and this procedure dissolves atomic oxygen in the bulk of the silver 16.

This bulk-dissolved oxygen also acts as an electron-withdrawing species, further activating the surface atomic oxygen.  Figure 3 is a representation of how electron-withdrawing species affect reaction selectivity.  The top reaction takes place without electron-withdrawing species and produces combustion products; the bottom reaction takes place with electron-withdrawing species (in this figure, dissolved oxygen) and produces epoxidation products. 15

Figure 3. Surface structures active in combustion (top) and epoxidation (bottom)15

Although alkali-metal promoters are electron-donating species, their presence also increases the selectivity of the epoxidation. Electron donors, such as cesium, might be thought to increase oxygen electron density, thereby favoring combustion. However, research has found that cesium promoters do not affect the electronic properties of the oxygen, but they instead affect the electronic properties of the ethylene 16. Cesium prevents both ethylene and ethylene oxide from isomerizing to an isomer that is more active to combustion.

Raw materials

Ethylene oxide is produced when ethylene and oxygen react on a silver catalyst at 200–300 °C. Pressures used are in the region of 1-2MPa. The chemical equation for this reaction isCH2=CH2 + ½ O2 ? C2H4O The typical yield for this reaction is 70-80%, the major side reaction being combustion of ethylene to produce carbon dioxide. Several methods to produce ethylene oxide more selectively have been proposed, but none have achieved industrial importance. 1

Ethylene oxide is the simplest of the cyclic ethers, which is colorless gas at a room temperature and within normal pressure. Its odor is ether-like which is soluble in water, ethanol, acetone, benzene, diethyl ether, and most organic solvents. It is relatively stable in aqueous solutions or when diluted with carbon dioxide or halocarbons, but it may undergo slow polymerization during storage.

Ethylene oxide is highly reactive and potentially explosive when heated or in the presence of alkali metal hydroxides and highly active catalytic surfaces. It reacts readily with acids resulting in ring opening. Vapors may be flammable or explosive if there is inadequate heat dissipation. Incomplete combustion releases carbon monoxide. 13

Ethylene Oxide is available commercially in the United States as a high-purity chemical that contains a maximum of 0.03 percent water, 0.003 percent aldehydes as acetaldehyde, and 0.002 percent acidity as acetic acid. It has been sold as a mixture with either carbon dioxide or fluorocarbon 12 to reduce its fire hazard. 20

Ethylene oxide was first produce in the US in 1921. Before, ethylene oxide was produced by the chlorohydrin process, in which ethylene was treated with hypochlorous acid to produce ethylene chlorohydrin. Calcium hydroxide or sodium hydroxide was used to convert ethylene chlorohydrin to ethylene oxide. Currently in the US, essentially all production of ethylene oxide uses the direct vapor phase oxidation process. This process oxidizes ethylene with air or oxygen in the presence of a silver catalyst to produce ethylene oxide. In addition, ethylene oxide is produced naturally as a metabolite of ethylene and has been identified in automobile and diesel exhaust and in tobacco smoke. 13

Ethylene oxide is a major industrial chemical and is consistently ranked among the top 25 highest production volume chemicals produced in the US.

According to the equation stated, the raw materials used in the production of Ethylene Oxide are: Ethylene, Oxygen, and the presence of a silver coated Catalyst.


Ethylene (C2H4)


Ethylene is also known as Ethane and Ripening hormone. It plays a regular role in many phases of a plants life and their deaths. It is also the simplest alkene hydrocarbon, containing a double bond between the two carbons, which results in being called an olefin or an unsaturated hydrocarbon.

Ethylene in its gas phase is used in producing Ethylene Oxide. It has a boiling point at – 103.7°C and a melting point at – 169.1°C. It has a density of 577kg/m2 and a Molar mass of 28.05 g/mol[i]. Its Ethylene viscosity is 0.0000951 Poise at these conditions: (1.013 bar and 0 °C (32 °F))[ii].

In nature, plants, plant products like vegetables, and floral products are the largest producers of Ethylene. They produce it within their tissues and release it into the surrounding atmosphere. It can also be produced using a cretin procedure called steam cracking, where gaseous or light liquid hydrocarbons are briefly heated to 750-950ºC causing large hydrocarbons to breakdown in to smaller ones. Saturated hydrocarbons become unsaturated and it is a by-product of many man-made processes such as combustion.[iii]

The development of the industry nowadays has led to the abundance of ethylene worldwide and thus its manipulation is rather common. The average value of Ethylene is ¢29.00 per pound[iv] and the cost of building a new ethylene plant is estimated to be at about $540 million and the capacity of an ethylene plant is 1.27 million tones per year for that cost[v].

Hazards of Ethylene

 Ethylene is known as a very flammable gas and so it has many hazards associating it. It has to be refrigerated as a liquid in order to transport it.  As the case for any other gas, it has to be handled with care for any contact because it may cause severe cold burns or frostbites.

If inhaled or in contact with skin or eye, medical attention must be provided for the victim immediately.  In case of a spillage, there is a risk of a fire or even an explosion, in the presence of a catalyst and air.

If it has been heated or subjected to a fire, there is the risk of an explosion or a rupture of the container.  Ethylene will auto ignite if it reaches 425ºC. If fire occurs, there is the forming of carbon monoxide as a product of a not complete combustion as for its toxicity Ethylene is called a ripping hormone so the risk of pollution is minimized as the most damage it can cause to vegetation is to cause frost, which can ruin vegetation[vi].

The Environmental impacts of Ethylene gas and its health risks

Inhalation of high levels of ethylene may cause asphyxiation, which can cause death if not attended carefully. Most victims are not aware of asphyxiation because Ethylene has a sweetish smell[vii].

Ethylene contains two elements; the first element is carbon (C), which has the atomic number 6. Carbon has many forms, from the softest (graphite) to the hardest (diamond) substance known to humans.

In general, raw carbon has an atomic number of 6; its density varies from 2.267 g/cm3 in the graphite phase, and a density of 3.513 g/cm3 in the diamond phase.  This relatively wide range of density is due to the existence of isotopes.  Carbon exhibits a boiling point of 3726.85°C, and melts at -3550 º C.

Indeed, carbon is the most abundant element in the universe.  In fact, it could be found in wide range of compounds (nearly 10 million known), which are referred to as organics, not only on the earth, but other planets, as well.  This unique characteristic of carbon is due to the “interesting chemical property” that is the ability to bond with itself and a wide variety of other elements.

Carbon is mainly known in the formation of hydrocarbons, which are essential to industry in the form of fossil fuels.  Organics are also vital for humanity as it forms carbon dioxide when combining with oxygen; this is what plant absolutely depends on it in its growth.  Another importance of carbon use nowadays is the use of isotope carbon-14 that which plays a major role in the nuclear sector in terms of radioactive dating. 8

Hydrogen is a light colorless gas, which exists in air, water, and organic compounds. It has an atomic number 1, and has a density of 0.0898g/l. Its melting point is -259.14 °C (14.01 K), and its boiling point is -252.87°C (20.28 K).[viii]

Hydrogen is produced by many different methods; one method is by electrolysis of water, which splits it into hydrogen and oxygen. The other method is by steam-methane reformation, which is mixing methane with water at 1100 °C by:

CH4 + H2O à 4H2 + CO2

This method is efficient and inexpensive.10

Hydrogen is transported, as a compressed gas from the point of production, therefore, there is a risk of explosion. During storage, hydrogen is stored in compressed gas storage tanks. Hydrogen is highly flammable. However, it is generally safe, but there are fears that having excess hydrogen in the air will be harmful to the ozone layer.11

Hydrogen is available in many countries, for example: United Kingdom, United States, India, Japan, and almost all the industrialized countries in the world.12 Moreover, hydrogen can be available from water, air, and organic materials.

The final element that will be discussed is Oxygen (O2).

Oxygen is the most important gas for a human life. Oxygen is a chemical element, which has the symbol O in the periodic table and has the atomic number 8. This element is very popular as it can be found any where in the world and most of the time forming bounds with other elements.

Oxygen in the gas phase (state) has its boiling point at -182.95°C and its melting point at -218.79ºC and a density of 1.429 g/l and has an atomic mass of 15.9994 g/mol.12 Oxygen forms more than 21% of the earth’s atmosphere it is in the form of a colorless gas.

Oxygen is produced by the electrolyses of water in labs. However, we cannot forget the fact that 21%of the earth’s atmosphere is oxygen so it is available in nature as well as produced. It costs 5 cents/ft3 for small quantities, and 15$/ton for large quantities. It is not toxic and most living beings need oxygen to survive. Transportation of oxygen can be done using compressed gas tanks and the same hazards applies as it must be liquefied under pressure as we discussed before with the hazards of transporting ethylene gas and must be kept away from any source of ignition and high temperatures and flammable gases.

Health and Safety

Ethylene oxide is toxic by inhalation. Symptoms of overexposure include headache and dizziness, progressing with increasing exposure to convulsions, seizure and coma. It is also an irritant to skin and the respiratory tract, and inhaling the vapors may cause the lungs to fill with fluid several hours after exposure.1

Ethylene oxide is usually stored as a pressurized or refrigerated liquid. At room temperature and pressure, it rapidly evaporates, potentially causing frostbite in cases of skin exposure. 1

Laboratory animals exposed to ethylene oxide for their entire lives have had a higher incidence of liver cancer. However, studies on human beings who have worked with ethylene oxide for extended periods and may have experienced low doses during that time have found no increase in cancer risk. Chronic ethylene oxide exposure may increase the risk of cataracts in humans. 1

In animals, ethylene oxide can cause numerous reproductive effects, including mutations and a higher rate of miscarriages. Its reproductive effects on humans have not been well studied, but it is considered probable that ethylene oxide exposure has similar effects on human reproduction. 1

Health is a major concern that faces human race. Hazards inherent in the process, the risk that these hazards poses and the hazards posed by the materials being processed will be discussed in this section. How to minimize the risks accumulated with the uses of ethylene oxide will also be tackled.

Ethylene is present in the environment. It is a result of evaporating or venting during the production and distribution of ethylene oxide or during its uses (sterilization and pesticides).  Ethylene oxide concentrations can be reduced in the atmosphere. This process is slow, however, it can be accelerated with rain, as ethylene oxide is highly soluble in water, although it would still evaporate to a great measure and return to the environment.

In the production stage of ethylene oxide, it is normally stored in special automated chemical process plants and is often located outdoors. All these masseurs are set due to its high explosive nature. Apart for its maintenance period, the exposure probability to ethylene oxide is minimum in factories or plants using or manufacturing ethylene oxide. However, Ethylene oxide has the highest in a working environment is endured in health instrument manufacture and in hospitals using ethylene oxide as a sterilizer.

Human exposure to ethylene oxide may occur through inhalation by the sterilization process in hospitals.  It is known that ethylene oxide can be used as a sterilizer in medical purposes. If left in air before it is used, it can travel into the human body, which can result in local effects, as ethylene oxide cannot be digested in the human body. It normally tends to dissolute in the body and evaporates or breaks up and reacts with food particles.[1]

 When ethylene oxide is inhaled, it is absorbed into the blood before it has passed into the human tissues and metabolized. Tests have shown that the half-life of ethylene oxide in the human body is around 10minutes and about 33 minutes in dogs.  Symptoms of intoxication from ethylene oxide are nausea and profuse vomiting.  It does not necessary occur from inhalation, since ethylene oxide can be absorbed through the skin.  Its excretion is mainly done through the urine marine life and is not affected in the same way as humans.

In animals, as the lethal dose is high and not endured in normal circumstances, a lethal dose of ethylene oxide is measured to be a single dose of 330mg/m3 and a vapor concentration of 2630mg/m3 for duration of 4 hours.  The ethylene oxide compound is moderately toxic in exposures in other assessment it is proved that exposure to ethylene oxide due to emissions and spillage in humans can be neglected and other reports show that life-threatening diseases caused by ethylene oxide is caused by long latency periods of several hours.13

In the production stage of ethylene oxide we use ethylene gas and oxygen and both are hazardous ethylene gas is known to be highly flammable and so is oxygen and ethylene is known

Minimizing the risks associated with the use of ethylene oxide is a task that has been considered more important than the actual production of ethylene oxide in this final section of the report the ways of minimizing the risks that can be faced in process and the use of ethylene oxide. Since ethylene oxide is a highly flammable gas, there is the risk of a fire or an explosion associated with the use of ethylene oxide.

It has been noted for 10 explosions between 1994 and 1998 in a repackaging plant where ethylene was just transferred from large to small containers to be used in hospitals and other uses to prevent further accidents.  Certain measures were introduced as written safety procedures to cover steps of ethylene oxide sterilization.  Interlocks safeguards and other safety measures should be present before a sterilization cycle begins.

After sterilization is completed, the sterilized product is stored in a sterilization chamber or an aeration room, which should be periodically vented and monitored. This is to avoid unnecessary buildup of ethylene oxide. The concentration of ethylene oxide is to be monitored in the sterilization chamber before vents that router the excess or the escaping ethylene back to the main sterilizer chamber because this is essential to avoid exhausting high concentrations of ethylene oxide inadvertently.

In the event of power loss, sterilization chambers should be vented.  to the outside to prevent overfeeding of the emissions control device and regular preventive maintenance of the equipment should be performed in storage ethylene oxide is to be stored in tightly closed cylinders in a cool shaded highly ventilated and explosion proof area the use of any device that might cause a spark or any open flames is not to be done in areas with ethylene oxide is present in further more the containers should be earthed while liquid ethylene is poured or transferred in case a leak or a spill the area affected should be evacuated and in cases of large spills of ethylene oxide the whole plant needs to be evacuated and fire departments should be notified immediately and are not to be entered except by trained personal with personal protective equipment on including a full body breathing apparatus that has a full face piece and is pressure operated.14

In conclusion risks associated with the use and production of ethylene oxide is the same as in any other highly flammable gas in process care has to be taken and certain measures have to be set and not passed or ignored as the consequences can be fatal. Industrial and chemical companies have to develop the technology of using the Ethylene Oxide in order to get a safe environment.


Ethylene oxide is a colorless gas with a sweet odor. Ethylene oxide is very soluble in water and is flammable. Ethylene oxide is used mainly as a chemical intermediate in the manufacture of textiles, detergents, polyurethane foam, antifreeze, solvents, medicinals, adhesives, and other products. Relatively small amounts of ethylene oxide are used as a fumigant, a sterilant for food (spices) and cosmetics, and in hospital sterilization of surgical equipment and plastic devices that cannot be sterilized by steam.

Sources of ethylene oxide emissions into the air include uncontrolled emissions or venting with other gases in industrial settings.

The general population may be exposed to ethylene oxide through breathing contaminated air or from smoking tobacco or being in the proximity to someone who is smoking.  Certain occupational groups (e.g., workers in ethylene oxide manufacture or processing plants, sterilization technicians, and workers involved in fumigation) may be exposed in the workplace.

Acute inhalation exposure of workers to high levels of ethylene oxide has resulted in nausea, vomiting, neurological disorders, bronchitis, pulmonary edema, and emphysema at high concentrations. Major effects observed in workers exposed to ethylene oxide at low levels for several years are irritation of the eyes, skin, and mucous membranes and problems in the functioning of the brain and nerves.

Some evidence exists indicating that inhalation exposure to ethylene oxide can cause an increased rate of miscarriages in female workers.  These effects could be seen from acute, as well as chronic, exposure.  Ethylene oxide has an estimated half-life in air ranging from 69 to 149 days, while its half-life in water is about 50 years.


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       (Accessed at: 28 November 2005).

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(13) IARC. 1994. Some Industrial chemicals. IARC Monographs on the Evaluation of Carcinogenic Risk of Chemicals to Humans, vol. 60. Lyon, France: International Agency for Research on Cancer. 560pp.

(14) Ethylene Oxide “Health and Safety Guide” available online at: http://www.inchem.org/documents/hsg/hsg/hsg016.htm#PartNumber:2 (accessed at: 20 February 2006).

(15) Noish Update (2000) ” Industrial Ethylene Oxide Sterilization processes” available online at: http://www.cdc.gov/niosh/ethyster.html (accessed at: 21 February 2006).

(16) Bukhtiyarov, V.I., et.al.. “Stages in the Modification of a Silver Surface for Catalysis of the Partial Oxidation of Ethylene.” Journal of Catalysis, 150 (1994) 262-272.

(17) Grant, Robert M. and Richard M. Lambert. “A Single Crystal Study of the Silver-Catalysed Selective Oxidation and Total Oxidation of Ethylene.” Journal of Catalysis, 92 (1985) 364-375.

(18)Serafin, J.G., et.al.. “Surface Science and the Silver-Catalyzed Epoxidation of Ethylene: An Industrial Perspective.” Journal of Molecular Catalysis A: Chemical. 131 (1998) 157-168.

(19) Tan, S.A., et.al.. “Chlorine-Oxygen Interactions and the Role of Chlorine in Ethylene Oxidation of Ag(111).” Journal of Catalysis. 100 (1986) 383-391.     (20)”Ethylene Oxide.” Ullman’s Encyclopedia of Industrial Chemistry.


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