Saturday, August 30, 2014

Death by Overhaul

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


Smoke is a complex and dangerous by-product of combustion presenting multiple 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 acute respiratory problems. These threats 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. I would like my comrades to consider a fuller disclosure about the dangers of post fire exposure.There are other asphyxiants, irritants, chemicals and particulates that are also present during overhaul, investigation and recovery stages, that we do not routinely monitor, but are injuring and killing us due to our complacency. 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 based on a low level of carbon monoxide alone. What other agents may be present that have not been tested for, and what are the compounded effects of multiple agents’ short term and long term? If a firefighter or citizen has detectable levels of CO and/or cyanide in their blood, what other agents have they 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 materials, 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” that is injuring and killing us.

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 which affect the nervous system, the heart and other organs.
·       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                           
None of the sources of these materials are unusual, therefore nearly all of these agents can be found in varying concentrations during and after any 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. With this information we can no longer be passive and complacent with respiratory protection. We know the environment during and after a fire is dangerous, we have been given the best possible equipment to protect ourselves, now we must be accountable for our part in preserving our health for our own sake as well as those we love and work with. It's not just the PPE, we have to acknowledge that how we use it, clean it, store it, inspect and maintain it is not someone else's problem, it will surely be ours if we fail to recognize and address the risk.

Something to think about before you pull your face piece off next time.


References:
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