By Maggie Fox, Health and Science Correspondent
WASHINGTON - Americans have been busy protecting their waters from chemical pollution, but microbes such as viruses and bacteria pose a much greater threat, a report issued early this week said.
Such dangerous organisms include E. coli O157, cryptosporidium, giardia, hepatitis A and pfiesteria, the report, from the American Society for Microbiology, said.
"Control of water pollution in the United States over the past two decades has focused on chemical risks, overshadowing the significant risks associated with microbial pollutants," the report said.
"However, current evidence indicates that microbial pollutants in water, when compared to chemicals, pose far greater risks to communities."
According to the Centres for Disease Control and Prevention (CDC), as many as 900,000 people get sick and 900 die every year in the United States because of waterborne microbial infections.
E. coli bacteria can kill, as can legionella, which causes Legionnaire's disease, a respiratory illness. Cholera, salmonella and shigella are all bacteria that cause diarrhoea and sometimes death.
Parasites such as Giardia cause diarrhoea and can lead to lactose intolerance and severe joint pain, while cryptosporidium, which also causes diarrhoea, can kill weak victims.
Viruses range from hepatitis A, which can cause liver failure, to coxsackieviruses, which can cause a deadly heart inflammation and sometimes even diabetes, while echoviruses cause meningitis.
People whose immune systems are weakened, such as cancer and AIDS patients, as well as the elderly and young children, are at special risk from such microbes.
Much of the contamination comes from the practice of pumping human waste into rivers or oceans, or letting them filter into groundwater. "A small drop of fecal matter can contain millions of these microorganisms," the report said.
"There are approximately 25 million septic tanks in the United States, receiving 175 billion gallons of wastewater that could contaminate ground and surface waters with viruses and other pathogens," it added.
It said viruses had been found in 20 percent of groundwaters tested nationwide.
Farming also pollutes waters. "Cattle can excrete millions of E. coli O157, cryptosporidium, giardia and other microbes," the report said. "Chicken wastes carry the pathogenic bacteria salmonella and campylobacter."
The report points out that the Environmental Protection Agency's (EPA) standards for drinking water name at least 70 chemicals, but only one microbe - coliform bacteria, which include the E. coli family.
Sewage treatment plants are supposed to filter out or destroy microorganisms, but do not always succeed, the report adds. "Thus the wastewaters released could still contain enough pathogenic microorganisms to threaten human health," it says.
Joan Rose, a marine biologist at the University of South Florida who helped write the report, said she found nasty bugs sometimes present in feces wind up right offshore within 12 to 24 hours of being flushed.
The report called for coordinated national action by the EPA, the Food and Drug Administration and other agencies.
"There is a critical need for an integrated national initiative on the microbial quality of water and on risk assessment as related to public health," it concluded.
(C) Reuters Limited 1999.