Once seen as threatening little more than a stomachache, microscopic waterborne bugs are increasingly turning deadly  forcing health officials to shift priorities as they try to make drinking water safe for a changing population.

For years, the Environmental Protection Agency has focused on potential cancer-causing chemicals as the main drinking water threat. But now water agencies and federal health officials concede the more immediate concern is waterborne bacteria, parasites and viruses  with names like cryptosporidium and girardia  some of which were largely ignored, or even unknown, until a few years ago.

For the past week, people in the nation's capital have been reluctant to drink their water. Boiling orders were issued, then canceled. Finally, officials poured more chlorine into the system. The reason: signs that the city's aging water pipes are full of bacteria. The urgency surrounding waterborne pathogens comes because more and more Americans are susceptible to the illnesses they cause, health experts say. "Most of these organisms have been around for eons, but we're just now beginning to detect them," said Dennis Juranek, an expert in parasitic diseases at the Centers for Disease Control and Prevention in Atlanta. Only when people began reporting severe illnesses and even dying from such bugs did they emerge on health officials' radar screens as important, he said.

In most healthy people, the damage is limited to a brief bout of intestinal discomfort, sometimes even mistaken for the flu. But for those suffering from AIDS or HIV infection, cancer patients and the elderly  whose immune systems cannot ward off bacterial attack  drinking water can become deadly, say health officials.

Some of the emerging pathogens are still mostly a mystery to health experts. Some, like cryptosporidium, aren't stymied by chlorine, the most successful and widely used disinfectant in drinking water. According to CDC estimates, between 900 and 1,000 people a year die and another million people become sick from microbial illnesses from drinking water. Other estimates have put deaths as high as 1,200 and estimated illnesses at more than 7 million, many never reported to doctors.

Nevertheless, at federal agencies and in Congress, microbial problems were "put on the back shelf" until just the last few years, said Diane VanDe Hei, Executive Director of the Association of Metropolitan Water Agencies. The health threat crystallized in 1993 when 100 people  most of them elderly or otherwise susceptible to illness  died in Milwaukee in an outbreak of cryptosporidium in the city's drinking water. More than 400 others got sick.

"It is a serious issue, an emerging threat. We think it needs significant focus," said EPA Administrator Carol Browner. Her agency already has shifted some of its focus in dealing with pollutants and plans a five-year, $50 million effort to learn more about microbial pollution. But the problem is likely to become more severe before it gets better as susceptible populations grow and scientists discover yet more pathogens. "Waterborne disease outbreaks caused by protozoan parasites appear to be on the
rise," concludes C.R. Sterling, a researcher at the University of Arizona. "One can't help but wonder how many more organisms with the potential for waterborne transmission await discovery."

Immune to chlorine, parasites such as cryptosporidium must be trapped by filtration, but they often pass through existing filtration systems. If they are detected, about the only answer is to warn vulnerable users to boil their water. There are no easy, or inexpensive answers, say health and water industry experts. The real solution is to reduce the bacteria and parasites in the lakes and rivers that supply drinking water, say many water treatment officials and environmentalists.
 
 

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