Thursday, February 4, 2016

Respiratory and inhalation hazards on fire scenes

Respiratory and inhalation hazards on fire scenes
By Alan Perry
August 30, 2014

Smoke is a complex and dangerous by-product of combustion presenting many dangers to firefighters and building occupants during and after a fire event. The most obvious concern is during the fire where super-heated gases loaded with toxins and asphyxiants can enter the airway & lungs causing immediate acute respiratory problems. These are well understood as are the dangers of post-fire exposure to carbon monoxide and cyanide, but this is only the tip of the iceberg so-to-speak. I would like my comrades to consider a fuller disclosure about the dangers of post fire exposure to the other asphyxiants, irritants, chemicals and particulates that are also present during overhaul, investigation and recovery stages that we do not routinely monitor. I believe many are lulled into a false sense of security by the lack of information about the harm caused by, and technology for measuring these harmful agents. Consider the typical fire where the scene is declared safe for removal of SCBA because of a low level of carbon monoxide. What other agents may be present? What are the compounded effects of multiple agents’ short term and long term? If a firefighter or citizen has detectable levels of CO in their bloodstream and/or evidence of cyanide exposure, what other agents have they also been exposed to? The by-products of combustion are not always present in a recognizable form such as smoke; they can linger for hours or days in the debris and residue at a fire scene and on tools and turnout gear. Just because you can’t see it does not mean it is not there.

The compounds present in the post-fire environment include asphyxiants, irritants, complex compounds and particulates. Most of these are present in all fires; the exact composition will depend on what is burned and how it burns. The transition in home construction and furnishings, as well as items kept in storage areas such as garages and sheds can yield a very wide variety of harmful agents when burned. This makes it virtually impossible to predict exactly what, or how much, is present in any given fire event. As I stated earlier, most every firefighter is aware of the dangers associated with CO and cyanide, we talk about these a lot, and we have tools to measure and treat the effects of these. Now let’s look at the “other stuff”
Asphyxiants- these compounds interfere with transport of oxygen in the blood stream and use of oxygen by target tissues or displace oxygen, causing hypoxia.
            Substance                                            Source                                                 effects begin
·         Carbon Monoxide (CO)                     incomplete oxidation of organic fuels
·         Hydrogen Cyanide (HCN)                 organic fuels containing carbon & nitrogen                                       <130ppm
·         Carbon Dioxide (CO2)                       organic fuels
·         Oxygen deficient atmospheres

Irritant gases- these compounds irritate and in many cases damage the airways and lung tissues reducing their ability to function and causing pulmonary edema and introducing toxins.
·         Hydrogen chloride (HCL)                  plastics, polymers, PVC                                                                           35 ppm
·         Hydrogen bromide (HBr)                   synthetic polymers, flame retardants                                                      5   ppm
·         Hydrogen fluoride (HF)                      fluorinated synthetic polymers                                                              0.5 ppm
·         Sulfur dioxide (SO2)                            fossil fuels, rubber, tires                                                                          0.4 ppm
·         Nitrogen Oxides (NOx)                        any combustion in ambient air                                                            20  ppm
·         Phosphorous pentoxide (P2O5)          electrical components, flame retardants                                                 n/a
·         Acrolein                                                 wood, cotton, paper                                                                               0.5 ppm
·         Formaldehyde                                      wood, cotton, polymers, plastics                                                          0.1 ppm
·         Ammonia (NH3)                                  wood, coal, paper, household waste                                                    50 ppm
·         Chlorine                                                 plastics, polymers, synthetic rubber                                                     1 ppm
·         Phosgene (COCL2)                              chlorinated compounds, plastics, polymers                                       3 ppm

Complex molecules- long carbon-chain and carbon ring compounds. These compounds can have acute effects and are known carcinogens & mutagens, in addition to their irritant and toxic effects. Several have delayed onset of symptoms.
·         Polycyclic aromatic hydrocarbons (PAHs)  organic materials                                                                              n/a
·         Dioxins/Dibenzofurans                      PVC, PCB, plastics                                                                                       n/a
·         Isocyanates                                          polyurethane foam & plastics                                                                   1 ppm
·         Perfluoroisobutylene (PFIB)              PTFE, fluorine containing polymers                                                        n/a
·         Particulate matter                               
The sources of these materials are not unusual, therefore nearly all of these agents can be found in varying concentrations during and after a fire event. The interactions and effects on the human body are still largely unexplored but clearly are likely to affect the health of those exposed. The effects may be delayed for hours, weeks or years and the cumulative effects will be even harder to predict.

Firefighting causes a great deal of stress on the body from the combined effects of hyperthermia and physical stress causing profound changes in physiological function, particularly with the circulatory system. Firefighters experience coagulopathy for up to two hours after a fire event, in this state the blood does not clot properly even when properly hydrated. When you are exposed to smoke, injuring lung tissue and poisoning the circulatory system with toxins, it is easy to see why we suffer cardiovascular problems and death.
Something to think about before you pull your face piece off next time.

Wakefield, J.C., A Toxicological Review of the Products of Combustion, Health Protection Agency, 2010

Demling, Robert H., Smoke Inhalation Lung Injury: An Update, Harvard Medical School, Burn Trauma Center, 2008