News release

From: University of Sharjah

By Leon Barkho, University of Sharjah

A new study has found that regulatory restrictions introduced more than half a century ago have failed to eliminate contamination from banned chemicals across Europe.

Researchers say they detected the banned chemical substances in air, water, sediments, soils, snow, and sludge, demonstrating their remarkable environmental persistence.

They add that they were surprised to find concentrations of polybrominated diphenyl ethers (PBDEs) in the ecosystems of the 25 European countries included in the study.

For decades, PBDEs played a vital role in reducing fire risks in electronics, textiles, plastics, vehicles, furniture, and building materials. While their purpose was to enhance safety, their legacy has proven far more complex.

“One of the most important findings is the dominance of BDE-209 in particle-rich matrices, including sediments, sludge, wastewater-related systems, and deposition,” said the study’s lead author, Prof. Khaled Abass from the College of Health Sciences at the University of Sharjah. “This matters because sediments and sludge are not passive storage sites.”

According to the researchers, sediments can serve as long-term environmental reservoirs, gradually releasing contaminants into waterways, soils, waste-management systems, and food chains. The study also found that lower-brominated congeners such as BDE-47 and BDE-99 were more prevalent in air and soil samples, indicating that PBDE behavior and distribution vary considerably across environmental compartments.

The results are published in the journal Environmental Research.

“PBDEs were widely detected across Europe in both impacted and remote environments, with distributions strongly dependent on matrix type,” the authors noted. “Water generally showed lower, more transient concentrations, whereas sediments, sludge, and some soils acted as major reservoirs.”

Legacy pollutants lingering on

The team led by Prof. Abass brought together researchers from the University of Oulu in Finland, the Technical University of Ostrava in the Czech Republic, and the University of Belgrade, Serbia.  Their study presents a comprehensive systematic review in which they assessed the occurrence, distribution, and congener-specific patterns of PBDEs across European environmental compartments, while assessing the implications of legacy contamination and existing regulatory frameworks.

The review followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines and was registered with PROSPERO (CRD420251207298). Peer-reviewed studies were retrieved from Ovid, Scopus, and Web of Science up to November 2025. Of the studies identified, 181 met the inclusion criteria for analysis. Evidence was synthesized across multiple environmental matrices, including air, water, sediments, soils, snow/firn, and sludge. Study quality and risk of bias were assessed using the SURE checklist.

“This systematic review assessed the occurrence, distribution, and congener-specific patterns of PBDEs across European environmental compartments and examined the implications of legacy sources and regulatory frameworks,” the authors write. “Data were synthesized across air, water, sediments, soils, snow/firn, and sludge. Study quality and risk of bias were assessed using the SURE checklist.”

PBDEs were found to remain widespread across Europe, occurring in both heavily impacted and remote environments, with their distributions strongly dependent on matrix type. Water generally showed lower, more transient concentrations, whereas sediments, sewage sludge, and certain soils served as long-term reservoirs, accumulating and retaining these pollutants.

The researchers found that PBDEs remain widely detectable across the continent because they persist in legacy consumer products, recycled materials, waste streams, contaminated reservoirs, sediments, soils, and indoor environments.

The findings challenge the common assumption that hazardous chemicals simply disappear once regulatory bans are introduced. Instead, the evidence suggests legacy pollutants can circulate among environmental compartments for decades after their original production and use have ceased.

“The European evidence also highlights a difficult policy tension,” Prof. Abass explains. “Europe is moving toward more ambitious circular-economy models, but circularity without chemical safety can unintentionally recirculate legacy pollutants. Materials once manufactured for fire safety may re-enter modern product chains through recycling if old chemical burdens are not carefully monitored.”

Ongoing risks

The study points to an uncomfortable scientific reality: environmental contamination does not conform to the neat boundaries of regulatory frameworks. PBDEs were detected not only in industrial and urban hotspots but also in remote alpine, Arctic, and background locations across Europe. This reflects their persistence, capacity for long-range transport, and the enduring environmental legacy of past chemical use.

For this reason, the study calls for comprehensive monitoring strategies. The findings underscore the need for harmonized, multi-matrix monitoring programs, improved quality assurance and quality control (QA/QC) reporting, greater attention to BDE-209, its transformation products, and replacement flame retardants.

“Monitoring only one matrix, one country, or one group of congeners is no longer sufficient,” Prof. Abass emphasized. “PBDEs move across connected systems: from products to dust, from dust to wastewater, from wastewater to sludge, from sludge to soils, and from sediments to aquatic food webs.”

The researchers highlight an important public-health dimension that policymakers should not overlook. Indoor air and household dust remain significant exposure pathways, particularly in environments with high densities of electronic devices.

The study urges governments and regulatory agencies to pay greater attention to legacy pollutants in homes, offices, schools, and workplaces since people spend most of their time indoors. The authors’ broader message is that chemical regulation must be paired with long-term environmental surveillance.

“Europe has made major progress in controlling PBDEs,” Prof. Abass concludes. “However, the contamination record shows that past chemical decisions continue to shape present and future exposure. PBDEs are therefore not simply pollutants of the past. They are legacy chemicals with an active environmental presence.”