This month our example is
Crotonaldehyde, which has a chemical formula of
(C4H6O). Crotonaldehyde is listed
under the UN # (United Nations Number) by the US
Department of Transportation: UN 1143. Crotonaldehyde
exists as one of two isomers; the trans isomer is
listed as CAS# (Chemical Abstract Service Number)
4170-30-3 and CAS 123-73-9, while the cis isomer
is listed as CAS# 15798-64-8.
Persons exposed only to
Crotonaldehyde vapor do not pose secondary contamination
risks. Persons whose clothing or skin is contaminated
with liquid Crotonaldehyde can secondarily contaminate
others by direct contact or off-gassing vapor.
At room temperature, Crotonaldehyde
is a clear, colorless to straw-colored liquid with a
pungent, suffocating odor. It is highly flammable and
burns to produce carbon dioxide and some toxic gas
carbon monoxide. It is volatile, producing toxic
concentrations at room temperature. Vapors may travel to
a source of ignition and flash back. The odor of
Crotonaldehyde provides adequate warning of hazardous
Crotonaldehyde is highly toxic by all
routes. Exposure causes inflammation and irritation of
the skin, respiratory tract, and mucous membranes.
Delayed pulmonary edema may occur after inhalation.
Systemic effects occur in animals after oral exposure,
but have not been reported in humans.
Crotonaldehyde exists in two isomeric forms (cis
and trans) that have similar properties and
effects. Crotonaldehyde is produced commercially as a
mixture of the two isomers (>95% trans and
<5% cis). At room temperature, the mixture is
a clear, colorless liquid that turns yellow upon contact
with air or exposure to light. It has a pungent,
suffocating odor. Crotonaldehyde should be stored in a
cool, dry, well-ventilated area in tightly sealed
containers. It is very flammable and may polymerize
violently. Crotonaldehyde should be stored separately
from alkaline materials such as caustics, ammonia,
organic amines, or mineral acids, strong oxidizers, and
oxygen. Crotonaldehyde is soluble in water, alcohol,
ether, acetone, and benzene.
Crotonaldehyde is generally produced by aldol
condensation of acetaldehyde, followed by dehydration. A
process involving direct oxidation of 1,3-butadiene to
Crotonaldehyde with palladium catalysis has also been
reported. Crotonaldehyde is produced during the
combustion of paper, cotton, and plastics, and is a
component of cigarette smoke.
Crotonaldehyde was formerly
used in the manufacture of n-butanol, but currently, the
most extensive use of Crotonaldehyde is in the
manufacture of sorbic acid. Crotonaldehyde has also been
used as a warning agent in fuel gases, in the
preparation of rubber accelerators, in leather tanning,
as an alcohol denaturant, and as a stabilizer for
colorless liquid that becomes yellow with exposure to
light or air.
properties: Sharp, pungent odor at 0.035 to 0.12
ppm; adequate warning of acute or chronic exposures.
point (760 mm Hg): 215.6 °F (102 °C)
Freezing point: -105.7
°F (-76.5 °C)
pressure: 19 mm Hg at 68 °F (20 °C)
density: 2.41 (air = 1)
Specific gravity: 0.85
(water = 1)
solubility: 181 g/L at 20 °C
Flammability: 55 °F
Flammable range: 2.1%
to 15.5% (concentration in air)
beta-methylacrolein; propylene aldehyde; ethylene
propionate; crotonic aldehyde; but-2-enal; 2-butenal;
crotonal; topanel; methyl acrolein; butenal;
crotonaldehyde inhibited; (E)-crotonaldehyde;
Standards and Guidelines:
(permissible exposure limit) = 2 ppm.
(immediately dangerous to life or health) = 50 ppm.
ERPG-2 (maximum airborne concentration below which it is
believed that nearly all persons could be exposed for up
to 1 hour without experiencing or developing
irreversible or other serious health effects or symptoms
that could impair their abilities to take protective
action) = 10 ppm.
reacts with caustics, ammonia, organic amines, or
mineral acids, strong oxidizers, and oxygen.
Routes of Exposure:
Inhaled Crotonaldeyhyde is highly toxic.
Crotonaldehyde is irritating to the upper respiratory
tract even at low concentrations. Its odor threshold of
0.035 to 0.12 ppm is lower than the OSHA permissible
exposure limit (2 ppm); thus, odor may provide an
adequate warning of potentially hazardous
concentrations. Crotonaldehyde vapor is heavier than
air, but asphyxiation in enclosed, poorly ventilated, or
low-lying areas is unlikely due to its strong odor.
exposed to the same levels of Crotonaldehyde vapor as
adults may receive a larger dose because they have
greater lung surface area:body weight ratios and higher
minute volume:weight ratios. In addition, they may be
exposed to higher levels than adults in the same
location because of their short stature and the higher
levels of Crotonaldehyde vapor found nearer to the
Contact Crotonaldehyde is highly toxic by the dermal
route. Direct contact with liquid Crotonaldehyde causes
rapid and severe eye and skin irritation or burns.
Exposure to vapor produces inflammation of mucous
membranes and it is a potent lacrimator. Because of
their relatively larger surface area:body weight ratio,
children are more vulnerable to toxicants affecting the
No information was located pertaining to ingestion
of Crotonaldehyde by humans. Crotonaldehyde is very
irritating; thus, ingestion would probably produce
chemical burns of the lips, mouth, throat, esophagus,
and stomach. In animal studies, ingestion has led to
Crotonaldehyde is severely
irritating to skin, eyes, and mucous membranes.
Inhalation of Crotonaldehyde may result in respiratory
distress and delayed pulmonary edema. Contact with the
skin or eyes produces irritation and lacrimation, and
can result in chemical burns.
mechanism by which Crotonaldehyde produces toxic
symptoms is not known, but the compound is highly
reactive. No information was found as to whether the
health effects of Crotonaldehyde in children are
different than in adults. Exposure to Crotonaldehyde
produces severe respiratory problems and individuals
with pre-existing breathing difficulties or skin disease
may be more susceptible to its effects.
Exposure The mechanism by which Crotonaldehyde
produces toxic symptoms is not known, but the compound
is highly reactive, cross-links DNA, and inhibits the
activities of some enzymes in vitro, including
cytochrome P450 and aldehyde dehydrogenase. In vitro
treatment of human polymorphonuclear leukocytes with
Crotonaldehyde produced a dose-related decrease in
surface sulfhydryl and soluble sulfhydryl groups and
inhibition of superoxide production. Onset of irritation
is immediate, but pulmonary edema may be delayed.
do not always respond to chemicals in the same way that
adults do. Different protocols for managing their care
may be needed.
Crotonaldehyde produces irritation of the
respiratory-tract. Relatively high-concentration
inhalation can lead to pulmonary edema. Clinical cases
of sensitization have been reported.
be more vulnerable because of higher minute ventilation
per kg and failure to evacuate an area promptly when
Crotonaldehyde is a skin irritant. Contact with the
liquid may cause second- and third-degree skin burns.
Skin contact may also result in allergic contact
their relatively larger surface area:body weight ratio,
children are more vulnerable to toxicants affecting the
Crotonaldehyde liquid or vapor can cause eye
irritation and damage to the cornea.
No cases involving ingestion were located. Because
Crotonaldehyde is a known irritant, it is likely to
cause burns of the lips, mouth, throat, esophagus, and
Sequelae After an acute, relatively
high-concentration exposure, persons may become
sensitized to Crotonaldehyde.
Exposure Apart from rare cases of sensitization, no
adverse effects in humans chronically exposed to
relatively low concentrations of Crotonaldehyde have
exposure may be more serious for children because of
their potential for a longer latency period.
The Department of Health and Human Services has
determined that Crotonaldehyde may possibly be a human
carcinogen. The International Agency for Research on
Cancer has determined that Crotonaldehyde is not
classifiable as to its carcinogenicity to humans.
Developmental Effects No studies were located that
address reproductive or developmental effects of
Crotonaldehyde in humans. Crotonaldehyde can cause
degeneration of spermatocytes in mice. No information
was found as to whether Crotonaldehyde crosses the
placenta, but it has been measured in breast milk.
Crotonaldehyde is not included in Reproductive and
Developmental Toxicants, a 1991 report published by
the U.S. General Accounting Office (GAO) that lists 30
chemicals of concern because of widely acknowledged
reproductive and developmental consequences. No
teratogenic effects from acute exposure have been
In using the PEAC application we
access information for the chemical by first locating
Crotonaldehyde in the database. The following figures
show the screens displayed for chemical properties,
Figure 1 for the PEAC-WMD for Windows application
and Figure 2-4 for the PEAC‑WMD for the Pocket PC
Figure 1 - Using the Lookup By: Name for
Crotonaldehyde using the PEAC-WMD for Windows
Review of the information displayed
in the chemical properties screen whether in Figure 1
(above) or Figures 2-4 (below), show chemical properties
values discussed earlier at the top of this discussion.
As you can see below, the published toxicity values,
e.g., IDLH, ERPGs, and the TEELs (Temporary Emergency
Exposure Limits) published by Department of Energy are
provided. We will use the IDLH as the Level of Concern
when we develop the Protective Action Distance (PAD) a
Figure 2 – Selecting
Crotonaldehyde using the PEAC-WMD for Pocket PC
Figure 3 – The top portion of the
Chemical Properties Data Display Screen
Figure 4– The bottom 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. As
with most 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
For our hypothetical scenario using
Crotonaldehyde as the involved chemical we’ll set the
location to be plastics manufacturing facility located
just outside Houston, TX. The date is March 11, 2004,
about 10:00 AM with a temperature of 75°F, wind speed of 2 mph and a clear
sky. The hypothetical release involves a storage tank
(15’ in diameter and 50’ high) that contains
Crotonaldehyde and a valve has been knocked off the
bottom of the tank. The contents have created a liquid
pool that is about 200’ in diameter. The PEAC tool can
provide guidance with regards to toxic vapor cloud that
If you decide to follow along as we
proceed through these examples, remember to set the
location to Houston and set the date and time to the
proper values, otherwise you’ll compute different
values. We’ll use a terrain type of urban/forest since
this is a manufacturing facility and has buildings and
processing equipment in the immediate area.
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 5. Following through the screens, we
provide information on the Meteorology, Container Size,
and Type of Release (Source). The following figures
demonstrate how we would work through our scenario to
see what our Protective Action Distance should
It’s Houston in March and the
temperature about 75°, wind is set for 2 mph,
clear skies and the terrain is Urban/Forest
since it’s a processing facility setting.
We have selected from our list
of container sizes the Large Storage
selection with a 15’ diameter and a 50’ tall.
This gets us a quick estimate of how much material
might be involved.
We have selected a Hole or
Pipe Release, and since the liquid boils at
219°F it will form a liquid pool. So the
application asks for a pool depth and diameter.
Figure 5 – Calculating a PAD using the
PEAC‑WMD System for March 11th
By pressing the right arrow at the
top of the screen, the PEAC system will display a screen
as shown in Figure 6. This calculates a PAD
(Protective Action Distance) based on the default
Level of Concern the IDLH of 50 ppm. This
evacuation or standoff distance is based on the toxicity
of Crotonaldehyde, not the flammability.
Figure 6 – Default PAD for
Crotonaldehyde using the IDLH of 50 ppm
If we want to calculate a PAD based
on a toxicity level other than the IDLH, we can enter a
value in the field for Level of Concern or we can
select a value from our list of toxicity values shown in
Figure 7. In this figure we select the ERPG-2 value or
Figure 7 – Selecting another Level of
The calculated PAD will be displayed,
see Figure 8.
Figure 8 –Calculated PAD using the
EPRG-2 Level of Concern
In addition to the toxicity of the
released material, the user should also remember the
flammability issue with Crotonaldehyde and eliminate all
Substantial portions of this
discussion were adapted from the Agency for Toxic
Substances and Disease Registry (ATSDR) Web site for
Medical Management Guidelines at: http://www.atsdr.cdc.gov/.