Dioxins: The most hazardous substance in structure fire environments

What firefighters must understand about their exposure risks and decontamination efforts


By Sean M. Scott & Briana C. Scott

Hazardous and potentially cancer-causing chemicals can be found in post-structure fire settings, especially those where plastics, synthetic materials, electronics or household products made with polyvinyl chloride (PVC) have burned. One of those chemicals – dioxin – is considered second only to radioactive waste as the most toxic chemical known to man. Not only is dioxin toxic to all life, but the World Health Organization also includes it as a member of the so-called “dirty dozen” – a group of dangerous chemicals known as persistent organic pollutants (POPs).

Dioxin origins

Dioxins can enter your body if you inhale contaminated particulate, have skin or eye contact with contaminated soot, ash or other materials, or eat contaminated food.
Dioxins can enter your body if you inhale contaminated particulate, have skin or eye contact with contaminated soot, ash or other materials, or eat contaminated food. (Photo courtesy of Mark Doyle)

POPs are chemicals of global concern due to their potential for long-range transport, persistence in the environment and atmosphere, ability to biomagnify and bioaccumulate in ecosystems, and significant negative effects on human health and the environment. (Note: Bioaccumulation is the accumulation of chemicals in organisms from the surrounding environment through skin absorption by contact with contaminated surfaces, clothing, and equipment; ingestion; and inhalation.)

The most encountered POPs – chlorinated dibenzo-p-dioxins (CDDs) and dibenzofurans – are unintentional byproducts of many industrial processes. CDDs are toxic compounds created during combustion processes, including structure fires where PVC, plastics, paper and other chlorinated materials burn. The most toxic form of CDD is 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), better known as dioxin.

There are 75 different dioxins, including the related polychlorinated dibenzodioxins (PCDDs) and 209 different polychlorinated biphenyls (PCBs). Certain dioxin-like polychlorinated biphenyls (PCBs) with similar toxic properties are also included under the dioxins umbrella.

Dioxins are formed when burning products containing carbon and chlorine, especially plastic, paper, pesticides, herbicides or other products where chlorine is used in the manufacturing process. Dioxins don’t typically exist in materials before they are burned. They are also prevalent in wildfires.

Depending on the ambient temperature in a fire, dioxins can be adsorbed or chemically bound to smoke particles or remain in a vapor phase. (Note: Adsorption is when particles bond with one another, similar to how a magnet bonds with iron, rather than being absorbed like a sponge absorbs liquids.)

Dioxins can enter your body if you inhale contaminated particulate, have skin or eye contact with contaminated soot, ash or other materials, or eat contaminated food. Since ultra-fine smoke particulate matter generated in fires is often less than 3 microns in size (half the size of a red blood cell), inhalation of dioxin-laden particulate can easily bypass the lungs and enter the bloodstream.

Health risks of exposure to TCDD

Adverse health effects of dioxin have been well documented in scientific literature. According to the EPA, as reported in “Dioxins and human toxicity,” “TCDD is considered the most toxic manmade substance and the fifth most toxic naturally occurring compound known to man. 2,3,7,8-TCDD is a potent toxicant in animals and has the potential to produce a wide spectrum of toxic effects in humans” (1997c). Sources:

Further, scientists say the toxicity of TCDD is exceeded only by radioactive waste. Short-term exposure to high levels of dioxin may result in skin lesions, such as chloracne. Other adverse health effects may include cardiovascular disease, diabetes, cancer, porphyria, endometriosis, early menopause, reduced testosterone and thyroid hormones, altered immunologic response and altered metabolism.

The list of diseases linked to dioxin seem endless. Ingesting dioxin can result in congenital malformations, spontaneous miscarriages, and a fatal, slow wasting syndrome similar to AIDS. Dioxin is strongly suspected of contributing to pathology of the urinary and hematological systems, growths in the colon, gallbladder complications, multiple myeloma, and lung, larynx and prostate cancer.

According to researcher Joe Thornton, "Dioxin's health effects include endocrine disruption, reproductive impairment, infertility, birth defects, lowered sperm counts, impaired neurological development, damage to the kidneys, and metabolic dysfunction. There is no evidence that there is a safe level of dioxin exposure below which none of these effects will occur.”

Additionally, the U.S. National Toxicology Program and the EPA have determined that TCDD is a proven human carcinogen. In July 2009, the U.S. Institute of Medicine published a report that showed evidence of an association between exposure to TCDD and soft-tissue sarcoma, non-Hodgkin’s lymphoma, chronic lymphocytic leukemia, Hodgkin’s disease, prostate cancer, multiple myeloma, as well as cancers of the larynx, lungs, bronchi and trachea.

The International Joint Commission, composed of the United States and Canadian governments, has publicly stated that zero exposure to dioxin is the only safe level. There is no permissible exposure limit set by NIOSH.

There is no antidote for dioxin toxicity. Symptomatic and supportive care is the only known therapy.

Courtesy of the Central Fire Protection District – Santa Cruz County

The risk to firefighters and investigators

Thirty years ago, firefighters were most frequently diagnosed with asbestos-related cancers. Today, the cancers are more often leukemia, lymphoma, myeloma, oral, digestive, respiratory and urinary cancers. It is no coincidence that these are the same types of cancers known to be caused by exposure to TCDD. 

Although firefighters wear state-of-the- art PPE, toxic chemicals often find their way through it and are inhaled, ingested, or absorbed by the skin. Exposure to TCDD is likely to be one of the primary causes or at least a contributing factor for the high number of cancers, diseases and fatalities to firefighters.

Additionally, fire investigators typically spend hours, sometimes days, inside fire damaged structures. They sift through smoldering debris and ash searching for the cause and origin of fires. PPE is sometimes regarded as cumbersome and not worn. Investigators are exposed to TCDD and a myriad of other toxins in the ash as well as in the airborne particulate matter.

Turnout and textile contamination

Currently, there are no scientifically proven methods to clean textiles contaminated with TCDD. In fact, the only known way to destroy TCDD is by incinerating it at temperatures over 1,500 degrees F. TCDD is not water-soluble nor does it decompose when exposed to ozone or hydroxyl in the atmosphere.

Although some fire departments use industrial-grade washing machines and detergents to clean their gear, periodic testing should be performed to verify these cleaning methods are effective or if hazardous substances remain embedded in the fabric after cleaning. In fact, if an attempt is made to clean smoke-damaged textiles that are contaminated with TCDD, samples of the articles should be analyzed after the cleaning by a qualified independent third-party laboratory to see if the cleaning was truly successful. This is particularly important for clothing where TCDD and other toxic-combustion byproducts can come in contact with the skin and be absorbed.

Final thoughts

There are literally thousands of toxic chemicals found in combustion byproducts other than dioxins that are present in post-structure fire environments. Firefighters should take every precaution possible to protect themselves from exposure and health risks. This may include wearing additional protective undergarments, applying protective ointments or salves on exposed skin to create a barrier (prior to entering a fire scene), replacing contaminated clothing or gear, and getting regular blood tests and physical exams.  

Additional resources are available on the Red Guide to Recovery website.

About the Authors

Sean Scott is a licensed general contractor in the State of California who has spent over 43 years in the construction and fire restoration industry. In 2009, Scott wrote the award-winning book “The Red Guide to Recovery-Resource Handbook for Disaster Survivors,” which has been adopted by fire departments, emergency management agencies, and disaster relief organizations across the U.S.

Briana Scott is the co-author and editor for Heritage Publishing & Communications. She has been instrumental in providing and interpreting information regarding the ecological effects of disasters. Scott also adds invaluable knowledge and understanding of scientific processes, and her research has helped raise awareness of a wide range of post-disaster health and environmental hazards.

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