Poisoned Irish blubber

A team led by Dutch researcher Jan Boon from the Royal Netherlands Institute for Sea Research (Royal NIOZ) has discovered that one isomer of the toxin HBCD accumulates in dolphins and porpoises.

HBCD, hexabromocyclododecane, is a much-used flame retardant in insulating foam and furniture upholstery. It disrupts the thyroid function and the functioning of the nervous system in mammals.

The porpoises and dolphins investigated were stranded on the coasts of Scotland, Ireland, the Netherlands, Belgium, France and northwest Spain. By far the most HBCD was found in the blubber of animals from the Irish Sea and the West Coast of Scotland.

Using a new analytical technique that can distinguish between the three different isomers that comprise HBCD, Boon and his colleagues discovered that the beta and gamma isomers were metabolised by the animals.

The enzyme complex cytochrome P450 in the liver played an important role in the process, adding oxygen to the HBCD.

It could not, however, react with the alpha isomer due to subtle differences between the spatial structure of the molecule and its beta and gamma cousins. Problematic, because the alpha isomer itself accounts for 15% or less of the HBCD used in commercial flame retardants.

Since it was not metabolised, the alpha isomer accumulated in the fat-rich tissues of the sea mammals, such as the blubber.