Your Vancouver Province

No rules on what's going down the drain
Water from slaughterhouses, rendering plants worries microbiologist
Margaret Munro, CanWest News Service
Published: Tuesday, July 10, 2007

Brains, eyes, tonsils and other select tissues from older cattle -- even bone dust generated when their spines are split open -- will be diverted out of the food chain to meet new federal rules that go into effect Thursday in an effort to eradicate mad-cow disease.

But the water that pours down the drains at slaughterhouses and rendering plants continues to be considered risk-free.

"It's not contaminated," says Freeman Libby, an official with the Canadian Food Inspection Agency, who likens it to "normal waste water going down your sink drain."

Mike Belosevic, a University of Alberta microbiologist, however, is not convinced.

"They are making a huge assumption," Belosevic says, noting there are "zero data" to back up claims that water from slaughterhouses and rendering plants is free of infectious prions that cause bovine spongiform encephalopathy, or mad-cow disease. "The point is no one has even looked."

He stresses the risk is "infinitesimally small," given that only 10 cases of the mad-cow disease have turned up so far in Canada. But the possibility of prions entering and persisting in waste water cannot be discounted, says Belosevic, who is leading a $2-million project to learn more about the water used in cattle-processing facilities.

Saws, knives and other equipment are now washed or hosed off after use to remove tissues that will be diverted into a special waste stream as part of a multimillion-dollar effort to eradicate mad-cow disease in Canada.

The tissues, called "specified risk material," or SRM, are where infectious prions can concentrate. Prions are rogue proteins that induce abnormal folding of other proteins, leading to fatal brain-wasting diseases such as mad cow, scrapie in sheep and Creutzfeldt-Jakob disease in humans.

More than 100,000 tonnes of such SRM is generated in Canada every year, the bulk of it in Alberta. Until now it has been processed like other cattle waste, most of it ending up in pet food and chicken feed, and as fertilizer and bone meal.

Once the new ban comes into effect, most of Canada's SRM will be taken to rendering plants in Calgary and reduced to dry meal. It will then be hauled to a Coronation, Alta., landfill and buried.

During rendering, the wastes are compressed and "dewatered."

"Along with that squeeze of water you may release prions," says Belosevic, who explains the proteins can persist for years and may be "bioaccumulating" in waste-water ponds.

"Say you had a rendering plant and two or three infectious animals came through in a year," he says. "You may find it in leachates from that rendering plant."

Over the next two years, researchers will look for prions in waste water from rendering plants and slaughterhouses.

The only proven ways of destroying prions are with high-temperature incineration, or a combination of heat, chemicals and high pressure.

Composting is another option, but it's problematic.

"We don't anticipate composting is going to be so effective that it will totally destroy the prions, but it could decrease the infectivity," says Belosevic.

Even so, several small slaughterhouses in northwestern Ontario are proposing to pool their waste at one compost site. However, any compost made with SRM will not be allowed on grazing land or gardens, although it might be permitted on Christmas-tree farms and golf courses.

Belosevic, meanwhile, sees more promise in a chemical process that may deform the proteins and render them non-infectious.

© The Vancouver Province 2007