A new system for treating harmful persistent organic pollutants has been developed by researchers based in Birmingham, UK.

Stuart Harrad and co-workers treated polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) with a biomass-supported palladium catalyst, successfully removing halogen atoms and significantly reducing their toxic effects.

PCBs have found widespread use in a diverse range of applications, with around 1.2 million tonnes produced worldwide. PBDEs are widely used as flame retardants in carpets, vehicle interiors and furniture. The production of PCBs ceased in the 1970s as these were shown to have adverse effects on wildlife and human health, and recent evidence of similar harmful effects of PBDEs has sparked many jurisdictions to ban their marketing and use. Despite these efforts, there is still a significant level of human consumption of these compounds through diet and exposure to air and dust.

Harrad said that 'this "reservoir" requires very careful management and treatment if we are to limit future impact by human exposure'.

This view was echoed by Andrew Hursthouse, a professor of analytical and physical chemistry at the University of Paisley, UK: 'Rapid dehalogenation provides a chance to engineer effective remedial solutions for an issue which remains of potential health concern long after regulatory attempts to reduce human exposure'.

Harrad's work exploits the catalysed reducing power of biomass materials for dehalogenation, a much less problematic system than the commonly used zero-valent metal catalysts, which produce harmful metal ions. Frank Chang, an environmental chemist at the University of Idaho, US, is 'optimistic that the system will be implemented into a pilot-scale operation that is able to effect complete dechlorination of halocarbons in the near future'.

Ian Gray