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Chemicals Undergo Toxic Inversion

By Stephen Luntz

Pharmaceuticals in wastewater can become converted to toxic forms.

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Even non-toxic pharmaceuticals escaping into the water supply may be unsafe, Dr Stuart Khan of the University of NSW Water Research Centre has revealed in the journal Water Research.

Many chemicals exist in two forms known as enantiomers, mirror images that cannot be superimposed on each other. The transformation from one enantiomer to another is known as a chiral inversion and can be triggered by bacteria. While some enantiomers have identical effects on the human body, some are harmless or beneficial while their reflection is toxic.

Consequently some drugs, such as the anti-inflammatory naproxen, have to be carefully manufactured to only contain a particular enantiomer, in naproxen’s case the S-form. However, when Khan examined the output of a water treatment plant he found quantities of the liver toxin R-naproxen.

Khan says he has long been interested in what happens to pharmaceuticals in the wastewater system. “I saw a paper that monitored the change of ibuprofen through a plant, using quantities in and out as a measure of effectiveness. They found higher levels of one form afterwards. However, because ibuprofen is dispensed in both forms it could have been that bacteria selectively take up more of one than the other,” Khan says.

Khan’s measurements in the sewerage system revealed only S-naproxen, making it clear that the transformation is...

The full text of this article can be purchased from Informit.