Microbes in Drinking Water (The Thirst for Safe Water Series, Part 1)
Air Date: Week of April 3, 1998
The United States has one of the best water supplies in the world, and some of the worst waterborne diseases like typhoid and cholera are just about unknown here. But, research now shows that new risks to drinking water can resist even chemical treatment, slip through most filters and make people sick. This week we begin our six part series: The Thirst for Safe Water. The series will examine the health of the nation's water supply. We start in Philadelphia where despite meeting all federal clean water standards, Living on Earth has learned there is evidence that certain disease-causing microbes are getting through the city's treatment system. Daniel Grossman has our story.
CURWOOD: This is Living on Earth. I'm Steve Curwood. Clean water is a basic requirement for public health. And compared to the epidemics of typhoid, dysentery, and cholera that plague many poor nations, here in the US we've pretty much done away with these ancient diseases. But even in affluent America, we still can't turn on our taps without some worry about what comes out. Toxic chemicals from industry, agriculture, and households lace some water supplies, changing the chemical balance in our bodies and increasing our risk of cancer. Newly-discovered microbes from animal and human waste infect perhaps millions of people each year. And even the chemicals used to kill germs can cause problems of their own. This week, we kick off a 6-part series: The Thirst for Safe Water, which will examine the health of the nation's water supply. We begin in Philadelphia. Even though Philadelphia meets all Federal clean water standards, there is evidence that certain disease-causing microbes are getting through the city's treatment system. Daniel Grossman has our story.
GROSSMAN: Chris Crocket of the Philadelphia Water Department spends a lot of his time here: an industrial area on the banks of Wissahickon Creek. Behind a chainlink fence surrounded by weeds is a sewage treatment plant.
CROCKET: We could go around to the other side of the creek, to a place that's actually below the sewage discharge, but you can't see the effluent.
GROSSMAN: The Wissahicken is polluted. Along its 23 miles, animal waste from farms, woods, and neighborhoods, runs off into the creek. And there's effluent from factories, sinks, and toilets, at least from this and four other sewage plants on the creek, which flows into the Schuykill River, a source of Philadelphia's drinking water.
CROCKET: There are periods or times when wastewater does make up a significant portion of the flow in the stream, especially when there hasn't been rain for a long time. That does present a concern for us, since our drinking water intakes are below areas where this tributary discharges into our rivers, which are our source water supplies.
GROSSMAN: Mr. Crocket is surveying the Wissahickon watershed for sources of disease-causing microbes, especially cryptosporidium, a protozoa that can cause everything from minor stomach aches and diarrhea to severe dehydration and even death.
CROCKET: From our preliminary work, we have been able to detect cryptosporidium in raw sewage and in wastewater effluent in our watershed.
GROSSMAN: Fortunately, the microbe has not yet been found in Philadelphia's treated water. But no one can say for sure it's not there. Cryptosporidium is notoriously difficult to detect.
GROSSMAN: Philadelphia gets its drinking water from rivers. The Schuykill and Delaware and their tributaries, including the Wissahickon. When they arrive at the intakes, these rivers are a murky mixture of untreated and treated fecal matter, agricultural chemicals, and industrial effluents. And Philadelphia's situation is by no means unique. Many Americans get their water from lakes and rivers that are polluted. And like most of these other communities, Philadelphia has had to resort to costly treatment plants to try to make its water safe to drink.
MULDOWNEY: The water is pumped up Belmont Avenue to two raw water reservoirs located at City Line Avenue. Now, these reservoirs, they look like big lakes.
GROSSMAN: John Muldowney oversees one of Philadelphia's three water treatment stations. At the turn of the century, Philadelphia had thousands of cases of typhoid and other waterborne illnesses every year, with hundreds of deaths. But in 1913 the city built one of the nation's first large-scale treatment plants using chlorine. The outbreaks fell off dramatically.
MULDOWNEY: The water flow then splits. And 58% of the water goes to the south side of the plant...
GROSSMAN: The process here is typical of water treatment plants across the country. Chemicals are added to the dark river water to make particles of silt clump together and settle out. Then chlorine is added to kill disease agents, and the water is then filtered through sand and crushed coal.
MULDOWNEY: And the remaining particulate matter that leaves the settling basin is filtered out of the water.
GROSSMAN: Finally, ammonia is mixed in, which helps disinfection after the water leaves the plant. By this point, says Gary Burlingame, who supervises water quality for the department, Philadelphia's water is as good as any in the country.
BURLINGAME: By all standards that have been set, whether by the Federal regulators or the state regulators, or internal goals set by us, or knowledge from research across the world, we meet all the standards and requirements that anyone has set.
GROSSMAN: But this may not be good enough. Research suggests that even drinking water that meets the current government safety standards could be causing widespread gastrointestinal illness, which can bring on diarrhea, vomiting, and fever. In November of 1997, Professor Joel Schwartz at Harvard's School of Public Health published a controversial study comparing water quality records with hospital records in Philadelphia from 1989 to 1993.
SCHWARTZ: Now, what we did in Philadelphia is, we took a measure of how much stuff is getting through the treatment plant. And we asked the question, well, if that goes up, is that followed by an increase in the number of people who have gastrointestinal illness?
GROSSMAN: The measure of stuff Professor Schwartz used was the cloudiness of the treated water. Water authorities use a cloudiness index to see how well their filters are working, because many kinds of microbes, including cryptosporidium, are hard to detect directly.
SCHWARTZ: And what we found was that indeed, when this sort of measure of water contamination increased, that was followed by two blips in the admissions and the emergency room visits for gastrointestinal illness of children.
GROSSMAN: Children 3 years and older were 10% more likely to make emergency room visits for stomach bugs when cloudiness increased. Professor Schwartz found a similar pattern for hospital admissions for children and for the elderly. He admits these correlations don't prove that drinking water caused the illnesses, but they are a cause for concern, especially since the water during this study period met Federal standards. And Professor Schwartz says his results may underestimate the problem.
SCHWARTZ: Very few cases of gastrointestinal illness drive people to the hospital, so we are looking at just the tip of the iceberg.
GROSSMAN: The Philadelphia Water Department's Gary Burlingame says since the time covered by the Schwartz study, the Department has significantly improved the quality of its water. And he says there's no clear evidence today Philadelphians get sick from it. The Department and the EPA are raising doubts about Professor Schwartz's research, saying poor quality data and errors in his methods invalidate the conclusions. But Professor Schwartz stands by it, and says his results are supported by a growing body of scientific research. One critical piece of evidence came out after a public health tragedy.
NEWSCASTER: Authorities in Milwaukee are trying to find out how a rare parasite, usually found in farm animals, apparently contaminated that city's drinking water system....
GROSSMAN: Until 1993, most water experts believed that waterborne disease had been pretty much wiped out in the US. Then, Milwaukee made national headlines.
NEWSCASTER: Milwaukee residents have been advised to boil their tap water, or drink bottled water. More from Beth Graham, of member station WUWM.
GRAHAM: Health officials know what has caused...
GROSSMAN: The parasite which caused the outbreak was cryptosporidium, which probably came from animal manure, slaughterhouse waste, or human sewage flowing into Lake Michigan, the city's water supply. Four hundred thousand people became ill, 4,000 were hospitalized, and more than 70 died. It was the largest outbreak of waterborne disease in modern American history.
OLSON: Milwaukee is looked to by many experts as an alarm bell.
GROSSMAN: Eric Olson runs the Drinking Water Program at the Natural Resources Defense Council.
OLSON: What that suggests to many of us in the field is that you could see a similar outbreak in other cities.
GROSSMAN: When Mr. Olson looked, he found that similar outbreaks had already occurred. Centers for Disease Control records showed more than 100 incidents in 32 states from 1986 through 1994. One episode in Georgia made 13,000 people ill. For Dr. Robert Morris, a leading expert on waterborne pathogens and health at Tufts University Medical School in Boston, the events in Milwaukee raised an even more troubling question.
MORRIS: I knew that the drinking water in Milwaukee was meeting the Federal standards throughout the outbreak. And so, I became interested in the question of whether this was an isolated event, or whether this was just an extreme manifestation of a problem that may have been there for some time.
GROSSMAN: What he found shocked him. In the 15 months leading up to the outbreak, Milwaukee children were nearly three times as likely to visit the hospital for gastrointestinal illness when cloudiness levels were high. These results are similar to what Joel Schwartz would later find in Philadelphia. This and other research suggests to Dr. Morris that gastrointestinal illness from microbes in drinking water is widespread in the US.
MORRIS: If you look at the range of studies that are out there and the estimates in terms of how many cases of diarrhea and gastrointestinal disease are related to drinking water, or what percentage, it's -- it ranges from 10 to as high as 30% of all cases are related to drinking water. We're probably talking about millions of cases per year of disease.
GROSSMAN: Dr. Morris says a number of different microbes could be causing the illnesses, although cryptosporidium, which researchers say is in water from about half the nation's public water supplies, is a leading suspect. Dr. Morris thinks it was at least partly responsible for the problems he found in Milwaukee, and that worries him, because conventional treatment doesn't get rid of the tiny parasite.
MORRIS: Cryptosporidium is an organism that wasn't recognized as a waterborne pathogen as recently as 10 or 20 years ago, and it's now emerged as a major concern. It's as if you designed something that can get through a drinking water treatment system. It's very small, and it's resistant to chlorine. And those are the ways we treat drinking water.
GROSSMAN: So far, drinking water suppliers are resisting the idea that conventional treatment is not good enough. Jack Sullivan is a top official at the American Water Works Association, the country's biggest water utility group.
SULLIVAN: You're talking about a fraction of one percent of the total microbial illness that occurs in the United States as attributable to drinking water. There are many, many thousands and approaching millions of people who are exposed to microbial contamination on a routine basis. By the simple measure of not properly washing our hands in contact with contamination, we transmit just an exorbitant amount of microbial disease.
GROSSMAN: One top water official privately discounted gastrointestinal illness as mere tummy aches, especially when compared to the scourges of the past. Often, a case of the runs is over in a day. But many public health experts say people with weak immune systems are in danger of more severe symptoms or even death. Young children, pregnant women, the elderly, people with AIDS, and people undergoing chemotherapy, about 20% of the population, are included.
GROSSMAN: If researchers like Joel Schwartz and Robert Morris are right, rivers like Philadelphia's Wissahickon Creek are washing virulent and visible germs right into the nation's kitchen and bathroom sinks. So far the EPA has responded primarily by proposing rules, expected this fall, that would cinch down the cloudiness and hopefully the microbial contamination of tap water. But Eric Olson of the Natural Resources Defense Council says tweaking the old technologies simply can't get rid of the most recalcitrant organisms like cryptosporidium.
OLSON: The real difficult bullet that EPA has not yet bitten is forcing a change in the way water is treated in the United States. It would really require a fairly substantial revolution in the way we treat water in the US to shift from these World War I era technologies and into advanced water treatment.
GROSSMAN: Advanced technologies already in use like countries like France and Germany include ozonation, which attacks microorganisms with ozone gas, and filters made of fine synthetic membranes, which take out small microbes better than sand and coal. Eric Olson says water suppliers could update their systems at an annual cost of about $30 per customer. A bargain for public health. For Living on Earth, this is Daniel Grossman.
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