Jonathan Beard
28 January 2000

© CSIRO Land and Water, Australia

"Our research was intended to find out whether this toxin could get into dairy products, especially milk," said Phillip Orr, a senior experimental scientist at CSIRO's Land and Water division. "The good news is that it can't," he will announce at a meeting — Harmful Algal Blooms 2000 — to be held in Tasmania February 6-11.

Microcystin, explained Gary Jones, a colleague at CSIRO Land and Water, causes liver damage and cancer if consumed in sufficient amounts. "We know that it affects both cattle and humans, but no one had ever assayed milk to see if cattle exposed to the toxin secreted it into their milk. We gave cattle water contaminated with about 10 times the level of microcystin that WHO standards say is the maximum tolerable in human drinking water. We then used assays — both HPLC and ELISA kits — that would detect it. But even these sensitive methods could find no trace of the toxin in milk."

The cattle drinking this water showed no signs of ill effects from the water, but the challenge, Jones said, was finding assays that could find this hydrophilic chemical in milk. "The real problem was sample clean-up," Jones said. "Milk is a very complex mixture of water, lipids, proteins and other chemicals, and it was hard to isolate the right constituents so that the assays would unambiguously detect the toxin if it were present."

Although the news from these tests was reassuring for dairy products consumers and exporters, Jones said that he expects testing for microcystin and other algal toxins may soon become routine, at least in countries that already routinely check foodstuffs for pesticides and other harmful chemicals. "Now that kits to detect microcystin in milk can be made, fairly cheaply, it will probably become a routine measure at least in the developed world," he predicted.