New method for destroying potentially deadly toxins in drinking water

Microcystins are produced by blue-green algae, which can grow in reservoirs, lakes and other bodies of water that are used for municipal drinking water. Blue-green algae, often referred to as pond scum but known scientifically as cyanobacteria, can be found in all areas of the world.

The detoxification method uses titanium dioxide and light to destroy the toxins. When titanium dioxide, a white powder commonly used in sun creams and paints, is added to water and exposed to light, it becomes active and destroys the toxins.

Known specifically as microcystin-LR (cyanobacterial hepatotoxins), the toxins are “very difficult to destroy” with normal water purification methods, says the article’s lead author, Linda Lawton, Ph.D., of the Robert Gordon University in Aberdeen, Scotland. Acute exposure to the toxic microcystins produced by the algae can cause liver damage and is fatal in extreme cases, according to the article. Approximately 50 dialysis patients in Brazil died in 1996 “due to the use of microcystin-contaminated water in their treatment,” notes Lawton. Long-term exposure is thought to contribute to liver cancer.

In the U.S., the risk of humans getting ill or dying from microcystins in drinking water is relatively low, says Wayne Carmichael, Ph.D., a professor of aquatic biology and toxicology at Wright State University in Dayton, Ohio, and a leading expert on the subject of toxic cyanobacteria. However, he adds, “a recent study of municipal water supplies in the U.S. and Canada found a few cases where microcystin levels were higher than guidelines established by the World Health Organization.” One part per billion, or one microgram per litre, is the WHO standard.

The detoxification method developed by the Scottish researchers is quicker and more effective than currently used methods, claims Lawton. “Costs are comparable with other methods,” she adds, “but if sunlight could be used, it would greatly reduce costs.” The laboratory research was done using a xenon UV lamp.

Further testing needs to be done, according to the article, to evaluate the performance of the new method in the field and to confirm that water treated with titanium dioxide is safe to drink.

The detoxification method is described in the Jan. 26 web edition of the journal Environmental Science & Technology, a peer-reviewed publication of the American Chemical Society, the world’s largest scientific society. The research article is scheduled to appear in the March 1 print issue of the semi-monthly journal.