Editor_s note: The following content is supplemental information to ˙Everyday Hazmat Risks: The top 10 hazardous chemicals every provider needs to understandÓ by David Hostler, PhD, NREMT-P, & Steve McConachie, BS, in April 2006 JEMS. In some cases, antidotes may be available in the prehospital setting and are indicated in this story with the symbol *. Chemicals presenting special hazards to the patient or provider are marked with the symbol *.
All prehospital providers will respond to a hazardous materials incident at some point in their careers. For most EMS personnel, this response won_t be for a large spill of ˙liquid deathÓ or radioactive explosion. Instead, you_ll be called upon to render care to people exposed to chemicals you might find in your workplace or in your own home.
Less-than-lethal irritants are a common class of chemicals encountered by EMS personnel. Many irritants are used as self-defense weapons by both civilians and by law enforcement. These irritants are often described as ˙less than lethalÓ because they_re intended to cause pain, burning and irritation of exposed membranes but not intended to kill or cause permanent injury. Such irritants include oleoresin capsicum (OC), 2-chloroacetophenone (CN) and the more modern o-chlorobenzylidene malononitrile (CS).
PHOTO DALE STOCKTON
Less-than-lethal irritants, including pepper spray,
is common class of hazardous chemicals
encountered by EMS personnel.
OC has become the tool of choice for many law enforcement agencies to apply less-than-lethal force when faced with violent individuals. A derivative of hot peppers, OC is the active ingredient in pepper spray. Most EMS providers have responded to incidents involving OC pepper spray. Within the general public, many incidents involving OC pepper spray have been justified, while others have resulted from the malicious use of the product, causing panic and injury. The safety profile of OC is high, and it_s not known to cause permanent damage or chronic pulmonary disease. However, when individuals suffering lung disease are exposed, they may suffer severe or lethal reactions.
The symptoms of OC pepper spray include a severe burning sensation in the eyes, nose and mouth, along with labored breathing and significant lacrimation. Symptoms are usually self-limiting and do not require treatment beyond decontamination. However, patients with a history of lung disease or demonstrating persistent or worsening respiratory symptoms should be given 100 percentoxygen and transported to the ED for evaluation.
Patients should be decontaminated by removing contaminated clothing and flushing the exposed areas with plain water.* It_s important to note that placing water on OC-contaminated clothing does not remove the substance but causes it to be held in the fibers, creating a secondary exposure risk. This is especially important to remember when rehabilitating law enforcement personnel who may need to immediately return to duty. These officers should change clothes or have contaminated clothing blotted with a dry rag to absorb the OC from the uniform.
On first glance, the signs of OC exposure are practically indistinguishable from those of nerve agents. However, closer examination will reveal an important difference. OC exposure will cause bronchospastic signs, such as wheezing, but nerve agents produce copious amounts of pulmonary mucous.
[Editor_s note: For information on cyanide poisoning, review Smoke Inhalation & Hydrogen Cyanide Poisoning, a supplement to August 2004 JEMS.www.jems.com/resources/supplements.]
Pesticides include a wide range of chemicals designed to kill or control pests. The major categories of pesticides include insecticides, herbicides and fungicides.
Some pesticides are particularly harmful to humans. We will focus on the most common class of insecticides, the organophosphates. This class includes such pesticides as malathion, parathion and diazinon. Although organophosphates are used primarily in commercial settings, such as farms, these same chemicals are often stored and used in small quantities by the general public.
*Organophosphates inhibit the enzyme acetylcholinesterase, which is found throughout the body. The most noticeable signs will be those associated with muscle control and the parasympathetic nervous system (PNS). The full array of PNS symptoms are associated with various glands being over-stimulated and are often described as ˙oozing from every orificeÓ or SLUDGE (salivation, lacrimation, urination, defecation, GI pain and emesis). Inhibition of acetylcholinesterase at the nerve-muscle junction results in muscle contraction being constantly ˙turned on,Ó resulting in tremors and tachycardia.
These insecticides are very similar to nerve agents, such as sarin and VX, and the medical treatment of organophosphate exposure is similar to that of exposure to nerve agents. These agents are easily absorbed through the skin, making rapid decontamination essential. Manage the patient_s airway aggressively and provide artificial ventilation if needed. Patients should be placed on the monitor and have IV access established.
*Once hypoxia has been corrected, atropine should be administered. Copious lung secretions are produced after organophosphate poisoning, causing bronchial secretions and pulmonary edema. The initial dose of atropine should be 2 mg IVP, repeated every three to five minutes until lung sounds are clear. Severe cases of organophosphate poisoning may require more atropine than is carried on a typical ambulance, requiring you to take atropine from other EMS vehicles or rapidly transport to the nearest ED for stabilization. Patients with this level of exposure may have seizures. These should not be treated with diazepam or lorazepam until adequate atropine and oxygen have been administered.
An understanding of vapor pressure is helpful when dealing with hazardous chemicals and gases. The vapor pressure of a chemical indicates its tendency to evaporate. Think of vapor pressure as an indicator of how quickly a chemical will come out of its container to bite you. This value is usually indicated in the physical properties section of a Material Safety Data Sheet (MSDS).
Vapor pressure is very temperature-dependent; the higher the temperature, the higher the vapor pressure.
Vapor pressure is measured in one of several units. Low vapor pressures are measured in millimeters of mercury (mmHg). High vapor pressures are measured in atmospheres (atms). Other units of measure for vapor pressure include pounds per square inch (psi) and kilopascals (kPa).
1 atm = 14.7 psi = 101.3 kPa = 760 mmHg
Below are some approximate vapor pressures at room temperature (68_ F).
Anhydrous Ammoniaƒ6460 mmHg (8.5 atm)
Chlorineƒ5170 mmHg (6.8 atm)
For more information on the appropriate EMS response to common hazardous materials, read ˙Everyday Hazmat Risks: The top 10 hazardous chemicals every provider needs to understandÓ in April 2006JEMS.