This month our example is Ethylene
Oxide, which has a chemical formula of
C2H4O. Ethylene Oxide is a
colorless gas or liquid with ether odor. It is a health
hazard because of its toxicity and it is extremely
flammable forming mixtures with air that are flammable
or explosive. It is shipped as a liquefied, compressed
gas. Both the gas and liquid are potential fire and
explosion hazards. Ethylene oxide has a sweet,
ether-like odor at air concentrations above 500 ppm.
Ethylene oxide is soluble in water and organic solvents.
It is highly flammable and, in vapor form, is subject to
explosive decomposition. The liquid is stable to common
detonating agents, but polymerization may be violent
after initiation by acids, bases, or heat.
Polymerization is catalyzed by certain metal chlorides
and hydroxides. Both liquid and gaseous ethylene oxide
are very reactive. It is relatively stable in aqueous
solution, or when diluted with carbon dioxide or
Ethylene oxide reacts with water,
strong acids, alkalies, and oxidizers; chlorides of
iron, tin, and aluminum; and oxides of iron and
Ethylene oxide is produced by
catalytically reacting ethylene and oxygen. Ethylene
oxide ranks 26th in volume among the major industrial
chemicals produced in the United States. About 65% of
ethylene oxide is used for synthesis of ethylene glycol,
an antifreeze product. A mixture of 88% Freon and 12%
ethylene oxide is used as a cold sterilizing agent for
foods and medical equipment and supplies. Ethylene oxide
is also used as a fumigant and fungicide in the
manufacture of medical products and spices, and as a
(permissible exposure limit) = 1 ppm (averaged over an
STEL (short-term exposure limit) = 5 ppm (15 minute
IDLH (immediately dangerous to life or health) = 800 ppm
AIHA ERPG-2 (emergency
response planning guideline) (maximum airborne
concentration below which it is believed that nearly all
individuals could be exposed for up to 1 hour without
experiencing or developing irreversible or other serious
health effects or symptoms which could impair an
individual’s ability to take protective action) = 50
Ethylene oxide is a highly reactive
alkylating agent that reacts with many constituents of
tissue resulting in cellular and tissue dysfunction and
destruction. Evidence for human exposure to this
chemical is the presence of ethylene oxide adducts of
DNA and hemoglobin. Direct contact with liquid ethylene
oxide or solutions of ethylene oxide produces immediate
local irritation of skin and mucous membranes.
Inhalation of high concentrations of ethylene oxide can
cause CNS depression or pulmonary edema. The onset of
symptoms may be delayed for up to 72 hours.
Ethylene Oxide has a melting point of
-171°F and a boiling point of 51°F. Its molecular weight
is 44.1, and has a relative vapor density is 1.49
(compared to air), so it will seek low areas. It has a
vapor pressure of 1,110 mm Hg at 68°F (1.46 atmosphere).
The lower Explosive Limit (LEL) is 3%; the Upper
Explosive Limit (UEL) is 100%.
The important thing to remember when
dealing with Ethylene Oxide is that it is both a very
flammable substance and its vapors are toxic. Therefore
if the material is released from its container, every
effort should be made to eliminate ignition sources and
appropriate PPE must be worn to protect from exposure or
- Store in a cool, dry place. Keep container closed
when not in use.
- Wash thoroughly after handling. Remove
contaminated clothing and wash before reuse. Avoid
contact with eyes, skin, and clothing. Avoid ingestion
- Wear appropriate protective gloves, clothing and
goggles -- as recommended by the manufacturer. Always
wear thermal protective clothing when handling
- A respiratory protection program that meets OSHA's
29 CFR 1910.134 and ANSI Z88.2 requirements or European
Standard EN 149 must be followed whenever workplace
conditions warrant a respirator's use.
spills or leaks - Clean up spills immediately, using
the appropriate protective equipment.
- Reacts violently with many compounds. Avoid metal
fittings containing copper, silver, mercury or
magnesium; ammonia, oxidizing agents; acids, organic
bases; amines; certain salts; alcohols; mercaptans,
ferric chloride; magnesium perchlorate; m-nitroaniline;
trimethylamine, potassium, tin chlorides; alkanethiols;
bromoethane; aluminum chloride; aluminum oxide; iron
chlorides; and iron oxides. Avoid air, heat, acids and
bases, metal or metal chloride catalysts. Hazardous
polymerization may occur. Avoid acids; covalent halides
such as chlorides of aluminum, iron (III), tin (IV);
basic materials like alkali hydrides, ammonia, amines,
and potassium; catalytically active solids such as
aluminum or iron oxides or rust, chlorides of boron,
aluminum, tin, and iron; some carbonates; and metals
such as copper and copper alloys.
Decomposition - Irritating and toxic fumes and
hazards - The gas is heavier than air and may travel
along the ground; distant ignition possible.
Pulmonary irritation is
likely after inhalation; dyspnea may occur. Convulsive
movements, twitching, malaise, lethargy, headache,
seizures and dizziness have been reported. Serious
exposure may result in coma. Chronic exposure may result
in peripheral and central nervous system effects,
including neuropsychiatric symptoms, cognitive
dysfunction and polyneuropathies. Ethylene oxide has
been fetotoxic and teratogenic in experimental animals.
- Nausea, vomiting and diarrhea may occur.
- Pulmonary irritation is a common symptom after
inhalation. Pulmonary edema may be seen with acute
exposures. Pneumonia may be a complication of ethylene
oxide exposure. A rare report of asthma has also been
- May be toxic/fatal if absorbed through skin.
Contact may cause burns, severe injury and/or frostbite.
- Contact may cause burns, severe injury and/or
- If victim is conscious and alert, give 2-4 cupfuls
of milk or water. Get medical aid immediately.
- Get medical aid immediately. Remove from exposure
to fresh air immediately. If not breathing, give
artificial respiration. If breathing is difficult, give
- Get medical aid. Flush skin with plenty of soap
and water for at least 15 minutes while removing
contaminated clothing and shoes. Remove contaminated
clothing and shoes.
- Irrigate exposed eyes with copious amounts of
tepid water for at least 15 minutes. If irritation,
pain, swelling, lacrimation, or photophobia (light
sensitivity) persist, the patient should be seen in a
health care facility.
In using the PEAC application we
access information for the chemical by first locating
Ethylene Oxide in the database. The following figures
show the screens displayed for chemical properties,
Figure 2 for the PEAC-WMD for Windows application
and Figure 3-6 for the PEAC‑WMD for the Pocket PC
Figure 2-Using the Lookup
By: Name for Ethylene Oxide using the PEAC-WMD for
Review of the information displayed
in the chemical properties screen whether in Figure 2
(above) or Figures 3-5 (below), show chemical properties
values discussed earlier at the top of this discussion.
As you can see, the published toxicity values, e.g.,
IDLH, and ERPGs (Emergency Response Protection
Guidelines) published by American Industrial Hygiene
Association are provided. We will use the IDLH as the
Level of Concern when we develop the PAD a little later.
Figure 3 – Selecting Ethylene
Oxide using the PEAC-WMD for Pocket PC application
Figure 4 – The top portion of
the Chemical Properties Data Display Screen
Figure 5 – The middle portion
of the Chemical Properties Data Display Screen
Figure 6 – The middle portion
of the Chemical Properties Data Display Screen
A benefit of using the PEAC tool is
assistance in the development of an evacuation zone for
those chemicals that produce a toxic vapor cloud.
Ethylene Oxide has a very high vapor pressure (1,110 mm
Hg) at room temperature, so if the chemical is released
from a container it will exit as a gas. As with all of
our examples, AristaTek creates a scenario for a spill
or release of the specific chemical, and then we work
through the development of a PAD (Protective Action
Distance) to demonstrate how the PEAC system works. For
our scenario using Ethylene Oxide as the spilled
chemical we’ll set the location to be Ft. Lauderdale, FL
and the time as 11:00 PM on April 15th. A railcar of
Ethylene Oxide has been involved in an accident just off
US Highway 1. There is a 2-3” hole in the railcar,
venting vapor very rapidly. The temperature is about
80°F, the winds are about 2 mph, and it’s a clear night
As seen at the top of the data
display screens, there is a yellow icon displayed; this
is the PEAC icon for notifying the user that a
Protective Action Distance can be calculated. Clicking
or tapping on the PAD icon will display a screen as
shown in Figure 7. Following through the screens, we
provide information on the Meteorology, Container Size,
and Type of Release (Source). The last screen displays
the PAD based on the provided information. If you decide
to follow along on this example, remember to change the
location to Ft. Lauderdale and the time to 11:00 PM,
It’s Ft. Lauderdale in April
and the temperature about 80°, light wind is set
for 2 mph, clear sky so we’ll set cloud cover to
0%, and the terrain is Urban/Forest since it’s an
We have selected from our list
of container sizes the Railcar selection.
This provides us with a default size that should
get us pretty close to the actual size.
Since the scenario has a 2-3”
hole so we’ve assumed a worst-case scenario and
used a 3” hole, we’ve selected a Hole or Pipe
Release as the Source type of
Figure 7– Calculating a PAD using
the PEAC System
By pressing the right arrow at the
top of the screen, the PEAC system will display a screen
as shown in Figure 8. This calculates a PAD
(Protective Action Distance) based on the default
Level of Concern the IDLH of 800 ppm. This
evacuation or standoff distance is based on the toxicity
of Ethylene Oxide, not its flammability. Since it is so
flammable, extreme care needs to be given to ignition
sources in the immediate vicinity of the release.
Clicking or tapping on the pop up
list for the Level of Concern a list of published
toxicity values for Ethylene Oxide is displayed.
Clicking or tapping on the ERPG-2 value of 50 ppm
(Figure 9) and will allow the PEAC tool to recalculate a
PAD for the 50 ppm concentration Level of
Concern. In our example a warning screen appears as
shown in Figure 10, that the calculated PAD is greater
than 7 miles and conditions can change substantially
over long distances. After acknowledging the warning
message, the PAD for the 50 ppm concentration is
displayed (Figure 11).
Figure 8– Default PAD for Ethylene
Using the IDLH of 800 ppm
Figure 9– Selecting another
Level of Concern
Figure 10– Warning that
calculations for PAD exceed 7 miles
Figure 11– PAD for ERPG-2 (50 ppm)
Portions of this discussion were
adapted from the WEB site supported by the Hardy
Research Group, Department of Chemistry, The University
of Akron: http://ull.chemistry.uakron.edu/. Additional
information was adapted from the web site provided by
International Programme on Chemical Safety (IPCS) INCHEM
site located at: http://www.inchem.org/.
Additional information was also adapted from the
National Occupational Health & Safety Commission web
provided by the Commonwealth of Australia. Additional
information was also adapted from the Agency for Toxic
Substances and Disease Registry (ATSDR) Web site for
Medical Management Guidelines at: http://www.atsdr.cdc.gov/.
Additional information was adapted from the Ethylene
Oxide User’s Guide developed by a collaborative effort
of Hoechst Celanese Polyester Intermediates, Occidental
Chemical Corporation, Shell Chemical Company and
SunCompany, Inc. (1999, August) found at: http://www.ethyleneoxide.com/html/introduction.html.