Flame retardants, known as polybrominated diphenyl ethers (PBDEs), are found in a multitude of products including televisions, computers, textiles and furniture upholstery.
These PBDEs are not chemically bound to the material and are susceptible to leaching into the environment. The presence of PBDEs in sediments is of concern since they can accumulate, transfer up the food web and, once ingested by humans, cause thyroid hormone disruption, alter neurodevelopment and interfere with reproductive systems. Several restrictions have been placed on the use of flame retardants and some have been banned altogether.
The accumulation of PBDEs in estuarine and river sediments is not entirely unexpected as they are easily water soluble and resistant to biodegrading.
BGS scientists have carried out a study in the Inner Clyde Estuary to look at how flame retardants accumulate in sediment and to see if concentrations are increasing or declining.
Six short cores were collected at different sites in the estuary. Each sediment core was refrigerated on the day of collection in order to minimise microbial decay before being analysed in the laboratory
Results showed that flame retardants are accumulating in the uppermost (0–10cm) sediment in the Clyde Estuary. In our study, the presence of flame retardants, known as BDE-209, found close to the surface in Clyde sediments correspond with the greater historical production of 'Deca-mix PBDE' flame retardant and the European ban of octa- and penta-mix flame retardants in 2004.
The predominance of BDE-209 over other flame retardants in Clyde sediments is entirely consistent with recent environmental health studies of UK domestic indoor dusts which contained BDE-209 at concentrations as high as 45 000 µg/kg.
Although the deca-BDE flame retardants are now banned in electrical goods sold in Europe, it is unlikely that their accumulation in sediment in the Clyde Estuary will decline rapidly given their resistance to biodegradation and widespread usage in industrial and consumer products.
This idea is supported in part by the fact that structurally similar compounds (PCBs) are still found in estuarine sediments despite manufacture being prohibited in the United Kingdom in 1977 and is no longer used at all in closed low volume equipment since 2000.
Flame retardants reduce fire hazards in materials by releasing bromine atoms which capture OH and H radicals formed during combustion at a temperature ~50°C below ignition temperature of the material. Many of these have now been banned from use.
Vane, C H, Yun-Juan, Ma, She-Jun, Chen, and Bi-Xian, Mai. 2010. Inventory of Polybrominated diphenyl ethers (PBDEs) in sediments of the Clyde Estuary, UK. Environmental Geochemistry and Health, 32(1), 13-21.
Contact Dr Christopher Vane for more information.