New evidence on chlor-alkali, aluminium pollutant

Canadian scientists have detected a new potentially endocrine-disrupting compound in polar bears which appears to come from industrial sources. 1

4-Hydroxyheptachlorostyrene was "a major component" of the chlorinated phenolic fraction of bears' blood plasma, accounting for up to 25% of total chlorinated phenolics, they report.

The researchers suggest that the most likely source of the chemical is from the breakdown of octachlorostyrene - a pollutant from industrial processes also present in trace quantities in bears and seals, the bears' main food. Octachlorostyrene is believed to be generated by chlor-alkali processes using carbon electrodes and from the purification of aluminium using chlorine in graphite vessels.

Octachlorostyrene has not been regarded as a major contaminant in Arctic food chains. But the researchers suggest that the discovery of high levels of the breakdown product in polar bears may mean that its importance has been underestimated. The breakdown compound showed a strong affinity for binding with the thyroid hormone transport protein, transthyretin, suggesting it has the potential to interfere with thyroid hormone systems.

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