New Journal Article Reports on PAH Ingress Through Firefighter Hoods and Base Layers
Firefighters face significant exposure to hazardous substances, including polycyclic aromatic hydrocarbons (PAHs), during routine firefighting operations. As awareness of these risks grows, innovations in personal protective equipment (PPE) aim to enhance protection without compromising performance. One such advancement is particulate-blocking hoods, which have been designed to reduce the ingress of harmful particles while maintaining comfort and functionality.
The Fire Safety Research Institute (FSRI), part of UL Research Institutes, recently published a paper with our collaborators at the National Institute for Occupational Safety and Health (NIOSH) on this topic, “Evaluating the ingress of total polycyclic aromatic hydrocarbons (PAHs) specifically naphthalene through firefighter hoods and base layers.”This paper examined the protection offered by different hood designs and cotton base layers against PAHs, specifically naphthalene. This journal article was published in the Journal of Occupational and Environmental Hygiene, as part of the PPE Interface Study.
Evaluating PAH Protection in Various PPE Configurations
This study used mannequins outfitted in one of four configurations of PPE:
| Knit Hood | Particulate-Blocking Hood | |||
| (1) Standard PPE | (2) Interface PPE | (3) Enhanced Interface PPE | (4) One-Piece Liner | |
| Hood attached to jacket and/or liner | ✔ | ✔ | ||
| Elastic cuffs at the waist and ankles to better seal open interfaces | ✔ | ✔ | ✔ | |
| Particulate-blocking material within jacket cuffs | ✔ | ✔ | ||
| Elevated collar at the boot-pant interface | ✔ | ✔ | ||
| Tighter zipper | ✔ | ✔ | ||
| One-piece integrated moisture barrier layer liner under the outer layer | ✔ | |||
All mannequins wore a 100% cotton turtleneck and pants under the turnout gear as a base layer. Researchers taped a filter under the base layers at the mannequin’s neck, which represented firefighters’ skin, to measure the amount of particulate-phase naphthalene.
The researchers exposed the mannequins to smoke by performing four burns in a fireground exposure simulator, where smoke was generated by burning a sofa. They collected and analyzed the mannequins’ base layers and hoods to evaluate PAH ingress. Finally, they measured PAH concentrations in the air at different body heights (i.e., breathing zone, abdomen, thigh). Of the 15 PAHs that were examined, only naphthalene was present in enough samples to allow for further analysis.
The Findings Demonstrated that Further Research into PAH Protection is Needed
The study determined that:
- Naphthalene was the most abundant airborne PAH (constituting 55% of the total PAH concentrations) in the fireground exposure simulator. It existed primarily in the vapor phase, accounting for 73% of total vapor-phase PAHs and 13% of total particulate-phase PAHs.
- Base layers may provide an additional protective layer to firefighters, as some naphthalene was collected in the base layer material. However, naphthalene also passed through the base layer and was collected on the filter that simulated firefighters’ skin. This finding suggests that base layers, while recommended, are not a complete solution to PAH exposure.
- No statistical differences in particulate-phase naphthalene were found in the base layers of the mannequins between those wearing traditional knit hoods compared to the particulate-blocking hoods. This finding differs from previous studies that sampled the air inside and outside of the hood for naphthalene vapor and sampled firefighters’ skin under their hoods for PAHs, both of which showed more protection with particulate blocking hoods. More research is needed to understand these differences.
This study highlights the complexity of mitigating PAH exposure for firefighters, particularly naphthalene, which primarily exists as a vapor and can bypass protective barriers. Prolonged and repeated exposure to PAHs is linked to serious health risks, including cancer. Therefore, understanding the limitations of current PPE designs is critical for developing solutions that better protect firefighters against PAHs.
“This research continues to build on our work to evaluate firefighting PPE. This information helps inform the development and future of PPE designs.“ —Richard Kesler, research engineer, FSRI
This study was supported by the U.S. Department of Homeland Security, Assistance to Firefighters Grant program (EMW-2017-FP-00635). The PPE Interface Study project is supported by the National Institute for Occupational Safety and Health, Skidmore College, and the Illinois Fire Service Institute.
About the Journal of Occupational and Environmental Hygiene
The Journal of Occupational and Environmental Hygiene (JOEH) is published to enhance the knowledge and practice of occupational and environmental hygiene and safety. The Journal provides a written medium for the communication of ideas, methods, processes, and research in the areas of occupational, industrial, and environmental hygiene; exposure assessment; engineering controls; occupational and environmental epidemiology, medicine, and toxicology; ergonomics; and other related disciplines.
