The Evolving Landscape of Firefighting with Fluorine-Free Foams

An Update on the Journey Beyond PFAS

May 13, 2025

A couple of years ago, my colleagues and I published a perspective piece, "Sunrise of PFAS Replacements: A Perspective on Fluorine-Free Foams". In it, we explored the critical shift away from PFAS-containing Aqueous Film-Forming Foams (AFFF) due to mounting concerns about the environmental persistence and health impacts of these "forever chemicals." Today, the world of fluorine-free foams (F3) is advancing at a remarkable pace, bringing forth both promising innovations and new considerations that warrant careful examination. This is more than a technical update; it's an ongoing story about environmental stewardship and safety that affects us all.

A Significant Step Forward: DoD Qualifies Fluorine-Free Foams

One of the most pivotal developments has been the U.S. Department of Defense (DoD) officially listing several F3 products on its Qualified Products List (QPL) for the MIL-PRF-32725 specification. This is a landmark achievement. The military's historical reliance on AFFF, driven by its demanding performance standards, was a significant factor in the broader adoption timeline for F3. The new MILSPEC, released in January 2023, established the framework for this change, notably requiring that F3 contain no more than 1 part per billion (ppb) of PFAS.

As of early 2024, several F3 products have successfully met these stringent requirements and are now on the QPL. For instance, Perimeter Solutions' SOLBERG 3% MIL-SPEC SFFF was among the first, achieving this in September 2023, followed by others such as BIOEX ECOPOL A3+ and National Foam's Avio Green Mil 3%. This qualification allows military branches, airports, and other entities adhering to DoD standards to transition to these fluorine-free alternatives.

The transition, however, is a complex undertaking. The initial target for phasing out AFFF by October 2024 may see extensions, possibly to 2026, to address challenges related to training, equipment compatibility and retrofitting, and the potentially higher costs associated with some F3 products. The DoD has also noted that while current MILSPEC F3s are effective, ongoing work is needed to ensure they meet all performance criteria across the full range of existing firefighting systems and scenarios.

The Ongoing Innovation in F3 Chemistries

While the currently approved F3s represent substantial progress, the pursuit of even more effective and environmentally sound chemistries continues. Researchers and manufacturers are deeply engaged in developing and testing new formulations. The objective is to create F3s that can serve as "drop-in" replacements, mirroring the exceptional firefighting capabilities of AFFF without the associated environmental concerns. This involves exploring novel surfactant systems and additives, which might include silicone-based compounds or other innovative chemical approaches. Any new chemistry, of course, must navigate the rigorous MILSPEC approval process to validate its performance in challenging fire scenarios. This continuous research and development is backed by significant investment, including efforts supported by programs like SERDP and ESTCP, which fund projects aimed at developing new F3 formulations and improving fire suppression performance.

Understanding the Environmental Profile of F3s

A central theme in the transition to F3 is their environmental and health impact. The primary driver for moving away from PFAS-based AFFF was to mitigate harm. However, emerging research indicates that while F3s are free of PFAS, their overall environmental profile requires thorough evaluation. Studies have shown that certain F3 formulations can exhibit acute and chronic toxicity to aquatic and soil organisms. Some research has found that certain F3s can show toxicity levels comparable to, or in some specific assays, greater than the C6 AFFF they aim to replace, especially concerning aquatic life. For example, studies have pointed to potential reproductive impacts in soil invertebrates and varying levels of phytotoxicity in plants exposed to different F3 formulations.

These findings highlight the necessity of comprehensive toxicological assessments for F3s, extending beyond the mere absence of fluorine. It's crucial to understand the complete toxicological characteristics of these complex mixtures and their individual components, including their potential for endocrine disruption and the effects of their degradation products. Programs like SERDP and ESTCP are actively funding research to assess the relative toxicity of F3 alternatives, focusing on chronic exposures and ecologically relevant endpoints such as reproduction, growth, and development in various species. This research is vital to prevent "regrettable substitutions," where one problematic substance is inadvertently replaced by another with different, but still significant, negative impacts.

Verification is Key: Ensuring "Fluorine-Free" is Truly Fluorine-Free

Confirming that F3 products meet the stringent PFAS limits—whether the 1 ppb DoD MILSPEC requirement or the 1 ppm for certifications like GreenScreen—presents a considerable analytical challenge. The potential for cross-contamination during manufacturing or from residual PFAS in equipment previously used with AFFF is a genuine concern. Studies have indicated that PFAS can adhere to equipment surfaces and subsequently leach into newly introduced F3 foams, a phenomenon sometimes referred to as "PFAS rebound".

To address this, robust and sensitive analytical methods are indispensable. Techniques such as the Total Oxidisable Precursor (TOP) assay and Total Organic Fluorine (TOF) analysis are being utilized to detect not only specific PFAS compounds but also their precursors, which can transform into problematic PFAS over time. Combustion ion chromatography (CIC) is another method employed for measuring total organic fluorine. These analytical advancements, some also supported by SERDP-ESTCP initiatives, are crucial for validating "fluorine-free" claims and for ensuring that decontamination procedures for firefighting equipment are effective.

The Nuances of Biodegradation: A Complex Picture

A significant advantage attributed to F3s is their improved biodegradability compared to the highly persistent PFAS found in AFFF. While many F3s are classified as readily biodegradable under aerobic conditions, the complete picture is more intricate. My research team and I will soon be sharing findings that delve into the complexities of standard biodegradation testing protocols and the actual biodegradation outcomes for F3s under diverse environmental conditions. A key insight is that complete biodegradation is not always achieved under typical test parameters.

This is an important consideration. Incomplete biodegradation can result in the formation of intermediate metabolites whose environmental fate and toxicity are often not fully understood. While F3s are generally less persistent than PFAS, a thorough understanding of their degradation pathways and the potential impacts of any resulting byproducts is essential for a comprehensive environmental risk assessment. There remains a notable research gap concerning the fate, transport, potential for bioaccumulation, and toxicity of F3 degradation products.

Navigating the Path Forward

As I discussed in the follow-up Science article, the transition from PFAS-containing AFFF to safer, effective fluorine-free alternatives is an evolving and multifaceted process. The progress, especially with the DoD's qualification of MILSPEC-compliant F3s, is commendable. However, ongoing work is needed to optimize firefighting performance across all applications, fully characterize environmental compatibility, and manage the logistical and economic aspects of this global shift.

Continued research, rigorous and transparent testing, and open communication are vital as we move forward. The lessons learned from the legacy of PFAS underscore the importance of approaching F3s with a scientifically informed and precautionary perspective. By thoroughly evaluating their entire lifecycle, we can better ensure that we are genuinely progressing towards a safer and more sustainable future for both firefighting operations and environmental health. The "sunrise" of PFAS replacements we discussed a few years ago is indeed here, and it’s illuminating a path that requires our continued diligence and scientific rigor.

Some good and relevant references are listed here:

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