This month our example is Phosphine
which has a chemical formula of PH3.
Phosphine has a United Nations # of 2199 and a Chemical
Abstract Service # of 7803-51-2. Phosphine is a
colorless, flammable, and toxic gas with an odor of
garlic or decaying fish. It can ignite spontaneously on
contact with air. The gas is shipped as a liquefied,
compressed gas. Aluminum phosphide (Celphos, Phostoxin,
Quick Phos, UN# 1397 and CAS# 20859-73-8) and zinc
phosphide (UN# 1714 and CAS# 1314-84-7) are solids used
as grain fumigants and as a rodenticide, respectively.
Zinc phosphide is often mixed with bait food such as
cornmeal, which can be a danger to pets and children.
When phosphides are ingested or exposed to moisture,
they release Phosphine gas. Phosphine gas may also be
released when acetylene is made by the action of water
on calcium carbide which is contaminated with calcium
phosphide as is commonly the case.
For those readers familiar with the
US DOT Emergency Response Guide (ERG), at the end of the
“green pages” in the back of the ERG are several pages
of materials that react with water to form toxic gases.
If you notice, Phosphine is one of the toxic gas species
listed for a number of phosphide substances in that
list. They may not be a toxic hazard by themselves, but
on contact with water (or moisture in the air) they can
become a concern.
Persons exposed only to Phosphine gas
do not pose substantial risks of secondary
contamination; however, persons exposed to solid
phosphides may present such risks. Metallic phosphides
on clothes, skin, or hair can react with water or
moisture to generate Phosphine gas. Vomitus containing
phosphides can also off-gas Phosphine. Phosphine is
extremely flammable and explosive; it may ignite
spontaneously on contact, with air. Phosphine has a
fish- or garlic-like odor, but may not provide adequate
warning of hazardous concentrations. When Phosphine
burns it produces a dense white cloud of phosphorus
Pentoxide, P2O5 fume. This fume is
a severe respiratory tract irritant due to the rapid
formation of Orthophosphoric acid,
H3PO4, on contact with water.
Phosphine is a respiratory tract
irritant that attacks primarily the cardiovascular and
respiratory systems causing peripheral vascular
collapse, cardiac arrest and failure, and pulmonary
Most Phosphine exposures occur by
inhalation of the gas or ingestion of metallic
phosphides, but dermal exposure to phosphides can also
cause systemic effects.
Phosphine is produced when metallic
phosphides (e.g., aluminum, calcium, or zinc phosphides)
react with water or acid. Both aluminum and zinc
phosphides are used as rodenticides. Phosphine may be
produced during the generation of acetylene gas.
Phosphine is used in the semiconductor industry to
introduce phosphorus into silicon crystals as an
intentional impurity. Phosphine is also used as a
fumigant and a polymerization initiator.
of Phosphine include hydrogen phosphide, phosphorus
hydride, phosphorus trihydride, and phosphoretted
Routes of Exposure:
Inhalation is the major route of Phosphine toxicity.
Odor is not an adequate indicator of Phosphine’s
presence and may not provide reliable warning of
hazardous concentrations. The OSHA PEL of 0.3 ppm is
within the range of reported odor thresholds. Phosphine
is heavier than air and may cause asphyxiation in
enclosed, poorly ventilated, or low-lying areas.
Children exposed to the same levels of Phosphine as
adults may receive a larger dose because they have
greater lung surface area:body weight ratios and
increased minute volumes: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 Phosphine found nearer to the ground.
Contact Phosphides may be absorbed dermally,
especially through broken skin, and can cause systemic
toxicity by this route. Phosphine gas produces no
adverse effects on the skin or eyes, and contact does
not result in systemic toxicity. Contact with liquefied
or compressed Phosphine gas may cause frostbite.
Ingestion of Phosphine is unlikely because it is a
gas at room temperature. Ingestion of metallic
phosphides can produce Phosphine intoxication when the
solid phosphide contacts gastric acid.
Colorless gas; odor of garlic or decaying fish
properties: Inadequate; nonirritating and
garlic-like or fishy odor at 1 to 3 ppm.
weight: 34.0 daltons
point: -209°F (-134°C)
point (760 mm Hg): = -126°F (- 87.7°C)
pressure: >31,300 mm Hg at 68°F (20°C)
density: 1.17 (air = 1)
solubility: Slightly water soluble (0.3% at 68°F)
Extremely flammable and explosive; may ignite
spontaneously on contact with air. Lower explosive limit
(LEL)=1.8% and upper explosive limit (UEL)=98%.
Standards and Guidelines
(permissible exposure limit) = 0.3 ppm (averaged over an
(immediately dangerous to life or health) = 50 ppm
reacts with air, oxidizers, chlorine, acids, moisture,
halogenated hydrocarbons, and copper.
Symptoms of Phosphine intoxication
are primarily related to the cardiovascular and
pulmonary systems and may include restlessness,
irritability, drowsiness, tremors, vertigo, diplopia,
ataxia, cough, dyspnea, retrosternal discomfort,
abdominal pain, and vomiting.
The same symptoms may occur after
ingestion of phosphide salts. Multiple signs may be seen
representing various stages of cardiovascular collapse.
Phosphine interferes with enzymes and
protein synthesis, primarily in the mitochondria of
heart and lung cells. As a result, effects may include
hypotension, reduction in cardiac output, tachycardia,
oliguria, anuria, cyanosis, pulmonary edema, tachypnea,
jaundice, hepatosplenomegaly, ileus, seizures, and
Exposure: Phosphine interferes with enzymes and
protein synthesis, primarily in the mitochondria of
heart and lung cells. Metabolic changes in heart muscle
cause cation disturbances that alter transmembrane
potentials. Ultimately, cardiac arrest, peripheral
vascular collapse and pulmonary edema can occur.
Pulmonary edema and pneumonitis are believed to result
from direct cytotoxicity to the pulmonary cells. In
fatal cases, centrilobular necrosis of the liver has
also been reported.
deaths occur within the first 12 to 24 hours after
exposure and are cardiovascular in origin. If the
patient survives the initial 24 hours, the ECG typically
returns to normal, indicating that heart damage is
reversible. Deaths after 24 hours are usually due to
do not always respond to chemicals in the same way that
adults do. Different protocols for managing their care
may be needed.
Phosphine is a CNS depressant. Initial effects may
include headache, restlessness, dizziness, loss of
feeling, impaired gait, trembling of the extremities
during movement, and double vision.
Toxicity that occurs after inhalation is
characterized by chest tightness, cough, and shortness
of breath. Severe exposure can cause accumulation of
fluid in the lungs, which may have a delayed onset of 72
hours or more after exposure. Pulmonary symptoms can
also result from ingestion of metallic phosphides (e.g.,
aluminum or zinc phosphide).
may be more vulnerable because of relatively increased
minute ventilation per kg and failure to evacuate an
area promptly when exposed.
Cardiovascular manifestations include hypotension,
reduction in cardiac output, tachycardia, irregular
heart beat, or cardiac arrest. Laboratory tests may
reveal abnormal myocardial enzymes. Phosphine affects
the small peripheral vessels, causing a profound
decrease in systemic vascular resistance. Vascular
changes may lead to marked low blood pressure that does
not respond well to pressor agents.
Gastrointestinal symptoms are usually the first to
occur after exposure. Symptoms may include nausea,
vomiting, abdominal pain, and diarrhea.
Typically, liver injury does not become evident
until 48 to 72 hours after exposure. Findings may
include jaundice, enlarged liver, elevated serum
transaminases, and increased bilirubin in the blood.
Blood and protein in the urine, and acute kidney
failure can occur.
Analysis of blood gases may reveal combined
respiratory and metabolic acidosis. Also, there have
been reports of significant hypomagnesemia and
hypermagnesemia associated with massive focal myocardial
Sequelae Although most survivors of acute Phosphine
exposure show no permanent disabilities, damage due to
insufficient blood supply to the heart and brain have
been reported. Subacute poisoning resulting from
exposure for a few days may cause reactive airways
dysfunction syndrome (RADS) months later.
Exposure Chronic exposure to very low concentrations
may result in anemia, bronchitis, gastrointestinal
disturbances, and visual, speech, and motor
disturbances. Chronic exposure may be more serious for
children because of their potential longer latency
The EPA has determined that Phosphine is not
classifiable as to its human carcinogenicity.
and Developmental Effects Phosphine is not contained
in the TERIS or Reprotext databases, nor is it mentioned
in Shepards Catalog of Teratogenic Agents.
Phosphine 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.
teratogenic effects from acute exposure are known.
In using the PEAC application we
access information for the chemical by first locating
Phosphine in the database. The following figures show
the screens displayed for chemical properties, Figure 1
for the PEAC-WMD for Windows application and
Figure 2-5 for the PEAC‑WMD for the Pocket PC
Figure 1 - Using the Lookup By:
Name for Phosphine using the PEAC-WMD for Windows
Review of the information displayed
in the chemical properties screen whether in Figure 1
(above) or Figures 2-5 (below), show chemical properties
values discussed earlier at the top of this discussion.
In addition, other values are provided such as the TEELs
(Temporary Emergency Exposure Limit) published by
Department of Energy.
Figure 2 – Selecting Phosphine
using the PEAC-WMD for Pocket PC application
Figure 3 – The top portion of the
Chemical Properties Data Display Screen
Figure 4 – The middle portion of
the Chemical Properties Data Display Screen
Figure 5 – The bottom portion of
the Chemical Properties Data Display Screen
An advantage of using the PEAC tool
is assistance in the development of an evacuation zone
for those chemicals that produce a toxic vapor cloud.
Phosphine has a very high vapor pressure (>40 atm),
and with a boiling point of –126°F it is usually shipped
as a liquefied gas under its own vapor pressure. When
such a container is breached or vented, the material is
going to be released as a vapor or aerosol and rapidly
form a vapor cloud.
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 PAD calculation portion of the PEAC
system works. For our scenario using Phosphine as the
spilled chemical we’ll use a computer chip manufacturing
facility in San Jose, CA that has a pressurized storage
tank containing Phosphine positioned next to a building
that has ½” feed line from the tank to the building
broken and releasing vapor. It’s 6:30 PM on July
2nd, the temperature is about 80°F, the winds
are 5 mph, and it’s a partly cloudy day.
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 6. 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.
It’s San Jose in July and the
temperature about 80°, wind is set for 5 mph,
partly cloudy so we’ll set cloud cover to 50%, and
the terrain is Urban/Forest since it’s an urban
setting (manufacturing facility).
We have selected from our list of
container sizes the Portable Tank
selection. This is smaller than a tanker
trailer but bigger than a drum or barrel.
Since the scenario has Phosphine
released from a broken transfer line Hole or
Pipe Release as the Source type.
Figure 6 – Calculating a PAD using the
After specifying the release or
source is a Hole or Pipe Release, the user taps
the right arrow at the top of the screen and the PAD
computation results are displayed, see Figure 7.
Figure 7 - The PEAC computation for PAD using
Portions of this discussion on
Phosphine were adapted from the ATSDR Medical Management
Guideline document, which can be downloaded from the
ADSTR web site at: http://www.atsdr.cdc.gov/mmg.html.