Hierarchy of contamination control in the fire service: Review of exposure control options to reduce cancer risk

Figures & data

Table 1. Overview of recent meta-analysis of epidemiology studies that have been conducted to assess the risk of cancer in the fire service.

Author, year	# studies	Associated cancers
LeMasters et al. 2006	26	Testes, prostate, non-Hodgkin’s lymphoma, multiple myeloma
IARC, 2010b	44	Testes, prostate, non-Hodgkin’s lymphoma
Soteriades et al. 2019	49	Testes, prostate, non-Hodgkin’s lymphoma, bladder, colorectal, melanoma, central nervous system
Jalilian et al. 2019	48	Testes, prostate, non-Hodgkin’s lymphoma, bladder, colorectal, melanoma, thyroid, mesothelioma
Casjens et al. 2020	25	Testes, prostate, bladder, colorectal, pancreas, melanoma, mesothelioma
Laroche and L'Esperance 2021	104 (from 11 systematic reviews)	Testes, prostate, non-Hodgkin’s lymphoma, bladder, colorectal, melanoma, mesothelioma

Table 2. Types of contaminants commonly studied in the fire service and associated cancer risk.

Contaminant	Description/definition	Cancer risk^a
Products of combustion
PAHs	Polycyclic aromatic hydrocarbons (PAHs), containing two or more benzene rings. PAHs with four or more rings have low volatility, while shorter chain PAHs are semi-volatile. Naphthalene (two rings) is the most volatile.	IARC known and probable carcinogens include benzo[a]pyrene, cyclopenta[cd]pyrene, dibenz[a,h] anthracene, and dibenzo[a,l] pyrene
VOCs	Volatile organic compounds (VOCs), typically containing hydrocarbon chains or a single benzene ring with branching organic or inorganic elements. As the name suggest, they are volatile and typically present as gas or vapor. Examples include benzene, toluene, and styrene.	IARC known and probable carcinogens include benzene, formaldehyde, 1,3-butadiene, styrene, and acrolein.
PM	Particulate matter (PM) that may be composed of organic or inorganic elements. Combustion particulate is typically in the fine (<2.5 um) or ultrafine (<0.1 um) size range. Combustion PM will have high surface area and is likely to contain other adsorbed chemicals.	Although PM is not classified as a carcinogen, a variety of carcinogens may be adsorbed to PM.
Released from materials during combustion
FRs	Chemical flame retardants (FRs), including polybrominated diphenyl ethers (PBDEs), other brominated FRs, organophosphate FRs, and chlorinated FRs. Examples include deca-BDE (BDE-209) and chlorinated tris (TDCPP).	According to the National Toxicology Program (NTP), certain types of PBDEs have been shown in animal studies to cause liver and thyroid tumors (deca-BDE). Chlorinated tris is labeled as a carcinogen in California.
PFAS	Per- and polyfluoroalkyl substances (PFAS) are a class of synthetic chemicals that have been used in various consumer products for their stain and water repellant properties, including carpeting, furniture, and fabric. PFAS have also been used in Aqueous Film-Forming Foams (AFFF). Examples of long-chain PFAS include perfluorooctane sulfonic acid (PFOS) and perfluorooctanoic acid (PFOA).	IARC classifies PFOS and PFOA as probable carcinogens.
Other occupational exposures
Diesel exhaust	Diesel exhaust is composed of PM, PAHs, and oxides of carbon, nitrogen, and sulfur. It is usually characterized by measuring airborne elemental carbon. Exposure is possible at the fire station or fire incident where diesel apparatus or other vehicles or equipment are operated.	IARC classifies diesel exhaust as a known human carcinogen.

^a Associated cancer risk according to the International Association for Research on Cancer (IARC 2010a, 2012a, 2012b, 2019, 2021), the National Toxicology Program (National Toxicology Program (NTP) 1986), and California Office of Environmental Health Hazard Assessment (OEHHA 2016).

Table 3. Control options for the fire service based on the hierarchy of controls approach.

Potential effectiveness	Types of controls	Options that are being researched
Least	PPE
	Inhalation	Consistent use of respiratory protection during all phases of a response
	Dermal	Tightening the interfaces of turnout gear, use of particulate-blocking hoods
	Administrative controls	Use of specific fire attack tactics, crew rotation, PPE donning and doffing practices, PPE decontamination, PPE retirement/removal from service, skin cleaning, fire apparatus cleaning, fire station cleaning
	Engineering controls	Fire station design, diesel exhaust capture, training prop design
	Substitution	Training fuel selection, use of simulated smoke and flame, replacing hazardous chemicals in products with less hazardous chemicals (e.g., fluorine-free foams), replacing diesel apparatus with electric or hybrid-electric apparatus
Most	Elimination	Public education programs (increased installation of smoke alarms and sprinklers), fuel reduction efforts to prevent exterior fires transitioning to structure fires

Table 4. Summary of PPE control options and considerations.

PPE control options	Important considerations or need for additional research
Turnout gear manufactured with tighter interfaces around the neck, wrists, waist, and boots	May impact thermal strain and ability to quickly don and doff protective equipment.
Station gear made of long-sleeves and pants vs. short-sleeves and/or shorts	May impact thermal strain, comfort, and mobility; although, encapsulating gear is expected to be the dominant factor for heat stress.
Turnout gear that incorporates a zipper vs. hook & dee closure	Zippers may not be as durable as hook & dee closures, but they are actually more common in the marketplace today.
Particulate-blocking hoods	Like all hoods, must seal properly around respiratory facepiece to provide most protection. Particulate barrier could make hearing difficult.
Wearing SCBA during all phases of the fire response, including in the fireground, especially in smoky conditions.	Need adequate resources to provide SCBA and air-packs for all impacted personnel. Wearing SCBA is heavy and contributes to physical strain. The SCBA facepiece can impact incident command’s ability to communicate.

Table 5. Summary of administrative control options and considerations.

Administrative control options	Important considerations or need for additional research
Utilizing exterior attack or transitional attack vs. interior attack at structure fires	Choice of attack will depend on a variety of factors, including life-safety and preservation of property.
Rotating crews of firefighters through positions to lessen their exposure and physiological burden	Need enough personnel available to rotate through positions. Rotating crews may also provide staggered times for managing decontamination efforts.
Rotating trainers through live-fire exercises to lessen their exposure time	Need enough qualified trainers available to rotate through live-fire training exercises.
Careful doffing of turnout gear, especially hoods and gloves, to minimize the transfer of contaminants to the skin	Doffing procedures are ingrained in the firefighting workforce. Changing doffing procedures will require training and reinforcement from leadership.
Cleaning skin immediately after firefighting	Effectiveness is likely to vary depending on how and when skin is cleaned. Several options available for cleaning skin at the fireground, including various types of skin wipes and traditional soap and water. Infrared saunas have been proposed as a way of excreting contaminants from skin, but more research is needed, including studies that examine heat stress and dehydration.
Gross decontamination of PPE	Studies indicate that using detergent along with water and scrubbing will increase the efficacy of decontamination. Setting up a decon line requires adequate resources, training, and personnel, although the materials can be as simple as a garden hose, bucket, dish soap, and scrub brush. Firefighters should ideally breathe through their SCBA while going through decon. All PPE (helmets, boots, SCBA packs, radios, and tools) should also be decontaminated.
Laundering of turnout gear (jacket, pants) and hoods after firefighting	Laundering will remove many contaminants, but the efficacy for specific types of contamination continues to be studied. Cross-contamination during the laundry cycle is possible. Research is needed to determine the optimal parameters and conditions to more fully clean turnout gear.
Routine cleaning of the fire apparatus interior	Several contaminants have been found inside the cabins of fire apparatus. Routine cleaning of apparatus interior surfaces and upholstery will reduce surface contamination.
Routine cleaning of the fire station	Several studies have documented higher levels of certain types of contaminants (including PBDEs, OPFRs, and metals) in dust collected from fire stations. Routine cleaning of surfaces should lower firefighters' potential exposure to those contaminants.

Table 6. Summary of engineering control options and considerations.

Engineering control options	Important considerations or need for additional research
Isolating contaminated PPE from personnel and passenger cabins	VOCs are expected to volatilize quickly in open air, but semi-volatiles will off-gas slower. Transporting contaminated PPE in enclosed containers or unoccupied compartments in vehicles will help reduce air concentrations of off-gassing contaminants and the transfer of particulate to other surfaces.
Fire station design (e.g., delineation of clean and dirty areas, maintaining positive pressure in living quarters relative to the engine bay, and other designs for contamination control).	Some design elements may be implemented without incurring substantial costs, but others may require significant investments. How these design elements relate to biological exposure is largely unknown.
Diesel exhaust capture systems	Installation of local exhaust ventilation systems in engine bays will help control diesel exhaust emissions, however, it is critical that these systems are maintained and function properly. It is also important that the vehicles are maintained so that they run optimally.
Vehicle-mounted diesel exhaust filtration systems	These systems are designed to provide filtration of diesel particulate before being emitted from the tailpipe into the environment and would likely reduce exposures for personnel at an incident.
Training prop design at fire academies	Instructors and firefighters can be exposed during live-fire training. Training props may be designed to reduce exposure. For example, some training structures include exhaust ventilation systems to quickly remove smoke.

Table 7. Summary of substitution control options and considerations.

Substitution options	Important considerations or need for additional research
Using training fuels for live-fire training that can achieve training objectives but lessen exposures	Studies indicate that burning different types of wood products at different orientations and different amounts with different ventilation parameters can impact the concentrations of hazardous substances produced. The training fire environment should balance risk of exposure with the intended benefit of the training objective.
Using simulated smoke and fire vs. live fire to achieve training objectives.	Simulated smoke (e.g., glycol-based aerosols) and digital flame can produce conditions for certain types of training without combustion. This type of training would not eliminate other hazards (e.g., slips, trips, falls, and thermal and physiological strain). These systems can range in cost and sophistication.
Supplementing live fire training with virtual/augmented reality training	This type of training would eliminate many hazards, including exposure to combustion byproducts. However, more research is needed to determine how to effectively achieve desired learning objectives.
Replacing chemical flame retardants (FRs) with nontoxic alternatives	Many chemical FRs (e.g., PBDEs) have been phased out of production and use in furniture. Barrier layers, including natural materials, have been incorporated in some products for fire retardancy. Other products have switched to new or other FR formulations (e.g., organophosphate FRs). Research to understand performance characteristics, exposure and toxicity of these new FRs is ongoing.
Replacing long-chain PFAS with other compounds, including non-fluorinated compounds	Class B foams are being manufactured that do not contain any fluorinated compounds, however, PFAS-containing foams are still being used in some settings. Turnout gear manufacturers may use long-chain PFAS in the manufacture of textiles and to achieve certain properties. However, some manufacturers are moving away from the use of PFAS.
Replacing aging diesel apparatus with electric or hybrid-electric apparatus	Just like the rest of the automotive industry, manufacturers are starting to develop apparatus that are powered by rechargeable batteries. Although the initial investment may be much higher than a diesel apparatus, exposure to diesel exhaust could be eliminated, or in the case of a hybrid, dramatically reduced.

Table 8. Summary of elimination control options and considerations.

Elimination options	Important considerations or need for additional research
Community Risk Reduction	How effective are fire safety messaging strategies at reducing the number of fire starts? What impact does early notification of fires through smoke detectors have on helping to eliminate large fires and the need for occupant rescue?
Installation of residential sprinklers	What impact does early control of fires through automatic sprinklers have on eliminating large fires and the subsequent smoke production and contamination risk?
Exterior fuel treatments	Careful removal/elimination of unnecessary and/or easily ignitable exterior fuels near homes and communities can reduce the risk of exterior fires transitioning into the structure. Implementation of the Home Ignition Zone concept has been shown to improve fire safety which can eliminate smoke production from household items.

Figure 1. Firefighter exposure risks and protection.

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