Biosensors Race to Catch Flame Retardants Lurking in Air, Water and Food

Brominated flame retardants were supposed to be a quiet success story of fire safety. For decades, these chemicals have been blended into plastics, textiles, electronics, foams and building materials to slow the spread of flames, and they did their job well. But the same chemical stubbornness that makes them effective flame suppressants also makes them an environmental nightmare. A new review published in Frontiers in Analytical Science by researchers at the University of Florence examines how biosensor technologies are stepping up to detect these persistent pollutants, and the findings reveal both remarkable progress and troubling blind spots.

The review focuses on two of the most notorious groups of brominated flame retardants: polybrominated diphenyl ethers, or PBDEs, and tetrabromobisphenol A, known as TBBPA. PBDEs consist of 209 individual organobromine compounds that were once sold in three major commercial mixtures called Penta-BDE, Octa-BDE and Deca-BDE. Demand for Deca-BDE alone reached 54,800 tons in 1999, accounting for nearly 80 percent of the PBDE market by 2001. Although regulatory bans have since been implemented worldwide, these compounds resist degradation and bioaccumulate in the food chain, meaning they continue to circulate through air, water, soil, sediments and living organisms long after their manufacture ceased.

The health implications are serious. PBDEs have been detected in human blood, breast milk and brain tissue, and exposure occurs primarily through inhalation, dermal absorption and ingestion of contaminated food. Studies cited in the review link these compounds to endocrine disruption, particularly interference with thyroid hormone regulation, as well as adverse effects on neurodevelopment and behavior. Because PBDEs undergo long-range atmospheric transport, they have even been found in remote regions like the Arctic and Antarctic, where they threaten fragile ecosystems that had no role in producing them. The European Union classified PBDEs as persistent organic pollutants under the Stockholm Convention, banning Penta-BDE and Octa-BDE in 2004 and restricting Deca-BDE in 2017 due to concerns about its degradation into lower-brominated congeners.

TBBPA presents a different but equally concerning picture. Unlike PBDEs, TBBPA forms covalent bonds with polymers, which theoretically reduces its tendency to leach into the environment. Nevertheless, contamination still occurs, particularly through improper disposal of electronic waste. TBBPA has been detected in surface water, sediment, soil and human tissues, and it remains one of the most widely used brominated flame retardants on the market today. Concerns about its potential health effects continue to grow, as the compound has been linked to endocrine disruption and possible carcinogenicity. Meanwhile, as older flame retardants face restrictions, manufacturers have introduced new brominated flame retardants such as hexabromocyclododecane and bis(2-ethylhexyl) tetrabromophthalate as replacements, but many of these substitutes share similar persistence, bioaccumulation and toxicity concerns.

Traditionally, detecting these compounds has relied on sophisticated analytical techniques like gas chromatography and liquid chromatography coupled with mass spectrometry. These methods are highly accurate and sensitive, capable of measuring trace-level concentrations in complex environmental matrices. However, they come with significant drawbacks: high instrumentation costs, the need for skilled personnel, labor-intensive sample preparation and long analysis times. The review notes that the most reliable spectrometric method, high-resolution gas chromatography coupled with electron capture ionization mass spectrometry, is often limited by expensive equipment, complicated pre-treatment procedures and lengthy data processing. These constraints make conventional methods poorly suited for rapid, real-time monitoring or for screening large numbers of samples in the field.

Biosensors offer a compelling alternative. These compact analytical devices combine a selective recognition element, such as an enzyme, antibody, nucleic acid, whole cell or molecularly imprinted polymer, with a transducer that converts the biological interaction into a detectable signal. The result is a technology that can provide rapid, sensitive and cost-effective detection of flame retardant contamination at trace levels, often without extensive sample preparation. The Florence review systematically catalogs the progress made in biosensing PBDEs and TBBPA, classifying devices by transducer type and documenting their detection limits, linear ranges and applications in real environmental samples.

Electrochemical biosensors have emerged as particularly promising for field applications. One early study developed an amperometric biosensor using horseradish peroxidase immobilized on a polyaniline-modified platinum electrode, achieving a detection limit of 0.014 micrograms per liter for PBDE-100 in landfill leachate. More recently, researchers have created devices based on the blocking effect of PBDEs on glucose oxidase activity, using gold nanoparticles and reduced graphene oxide to enhance sensitivity. Other electrochemical approaches include chronoamperometric detection using iridium oxide nanoparticles on screen-printed carbon electrodes, impedimetric sensors employing camelid-derived single-domain antibodies, and photoelectrochemical immunosensors with sensitized zinc oxide nanosheets that achieved a detection limit of 3.98 picomolar for BDE-121. For TBBPA, competitive amperometric immunosensors using bimetallic gold-palladium nanoparticles on manganese oxide nanoflowers reached detection limits of 0.10 nanograms per milliliter in real water samples.

Optical biosensors, which convert biological recognition into light-based signals, have pushed sensitivity to extraordinary levels. Fluorescence-based immuno-polymerase chain reaction assays have achieved detection limits as low as 1.32 picograms per liter for BDE-47 in indoor airborne particles and 0.62 picograms per liter for TBBPA in PM2.5 samples, comparable to the sensitivity of advanced chromatographic methods. Colorimetric approaches using plasmonic enzyme-linked immunosorbent assays with gold nanoparticles allow naked-eye detection of TBBPA derivatives at concentrations of 10 to the power of negative 3 micrograms per liter, while surface plasmon resonance biosensors using thyroid transport proteins offer label-free, real-time screening of thyroid-disrupting chemicals. Whole-cell luminescent biosensors based on genetically engineered bacteria have even been applied to detect BDE-209 in sediment samples, demonstrating the potential of living systems for in situ environmental monitoring.

Despite these advances, the review identifies critical gaps that must be addressed before biosensors can fulfill their promise. Fluorescence-based biosensors coupled with antibody receptors showed the lowest detection limits for both PBDEs and TBBPA, but their specificity may limit the ability to detect multiple congeners simultaneously, whereas chromatographic techniques excel at multi-target analysis. Miniaturization and portability are essential trends for real-time field monitoring, yet long-term stability of biological recognition elements like enzymes and antibodies remains a persistent challenge, particularly in complex environmental matrices that can compromise sensor performance. The review also highlights a notable absence of research on new brominated flame retardants, meaning that as industry shifts toward these alternative compounds, biosensor development has not kept pace with the emerging contamination landscape.

The authors conclude that biosensors will not fully replace established methods like gas chromatography-mass spectrometry, but they can serve as invaluable screening tools before costly instrumental analysis, particularly in food quality control, identification of contamination hotspots and customs enforcement of import regulations. Rigorous field validation in real large-scale conditions, standardized validation protocols and scalable manufacturing while maintaining cost-effectiveness and reproducibility are essential next steps. As brominated flame retardants continue to persist in the environment despite decades of regulatory action, the race to develop faster, cheaper and more versatile detection technologies has never been more urgent, and biosensors are positioning themselves at the front of that race.

Subject of Research: Environmental monitoring of brominated flame retardants using biosensor technologies

Article Title: Status and trends of biosensor technologies for environmental monitoring of brominated flame retardants

Article References: Sarti, C., Sforzi, L., Martellini, T., & Cincinelli, A. (2025). Status and trends of biosensor technologies for environmental monitoring of brominated flame retardants. Frontiers in Analytical Science, 5, Article 1527655. https://doi.org/10.3389/frans.2025.1527655

Image Credits: AI Generated

DOI: 10.3389/frans.2025.1527655

Keywords: brominated flame retardants, biosensors, PBDEs, TBBPA, environmental monitoring, nanotechnology, Status, trends, biosensor, technologies, environmental, monitoring