I don’t know all the answers to that question, but many of them lie in the chasm that has opened between public health and drinking-water treatment since the epidemics of cholera and typhoid gave birth to them as twin sciences in the nineteenth century. The engineers, chemists, and microbiologists who now dominate the province of drinking water dwell in the land of physics and chemistry, a realm ruled by unwavering principles that obey finely honed equations. Laboratory science makes good sense to them, but the squishy conclusions of epidemiology do not sit well, especially when they imply the need for substantial and expensive changes in the tried and true methods for treating water.
Three lines of evidence, primarily from epidemiologists, were driving the move to tighten regulations on drinking water. Research had continued to suggest that chemicals formed during the chlorination of drinking water increased the risk of cancer (the Poole study notwithstanding). A new front had opened when a series of studies raised the possibility that these chemicals might also cause miscarriages, retard the growth of the fetus, and induce birth defects. None of this research gave clear, irrefutable evidence, but there was enough smoke in the air to encourage a prudent observer to pull the alarm or at least make sure nothing was burning. Just as the industry and its regulators were trying to digest this information, cryptosporidium hit. Like the massive chest pain that finally gets us to the doctor, the events in Milwaukee had forced a more thorough examination of our drinking water. That closer look had begun to reveal evidence of more widespread disease.
When I began to look at the data that emerged from the Milwaukee outbreak, the fact that the water had not violated any federal drinking water standard during the period leading up to the outbreak stopped me in my tracks. How could the largest recorded outbreak in U.S. history have been caused by water that was, according to the federal government, safe to drink? When I attended meetings related to drinking water, people in the industry were always quick to describe the Milwaukee outbreak as an isolated episode caused by a rare convergence of conditions, but I remained unconvinced. If standards were not violated, how could we be sure that this was such an unusual event?
To begin to answer this question, I first requested records of routine tests for water quality from Milwaukee’s two treatment plants. The waterworks, more forthcoming in the wake of the outbreak, sent me data for a period of two years, which included the fifteen months leading up to the outbreak. From it I could see that elevated turbidity had not been a rare event in Milwaukee. It had been routine.
If the turbidity of Milwaukee’s water had often been elevated in the months and years leading up to the outbreak, it seemed possible, even likely, that many cases of waterborne disease had occurred that were not recognized as such. But could I prove it? There was no way to know if the water had contained cryptosporidium. Water suppliers do not routinely test for specific pathogens. Instead they use surrogates like turbidity and the presence of certain common types of bacteria to test the water. I could not prove that Milwaukee’s drinking water had caused cryptosporidiosis before the 1993 outbreak. But I had an idea that might shed some light on the question.
Through the billing office at the Medical College of Wisconsin, I was able to determine the number of adults and children treated for gastrointestinal illness by Medical College physicians on each day of the two-year period. With the help of a talented Russian statistician, I pulled the two data sets together. As we worked, a disturbing picture began to emerge.
Our analyses showed that each time the turbidity of Milwaukee’s drinking water rose the number of serious cases of gastrointestinal illness tended to rise about one week later. This time lag is critical. In clinical studies, volunteers exposed to cryptosporidium usually developed symptoms after six to ten days, a time delay known as the incubation period. No other common waterborne agent that causes gastrointestinal infections has such a long incubation period. In other words, the evidence available suggested that Milwaukee’s water had been causing cryptosporidiosis for months if not years before the outbreak.
This was not the first evidence to suggest that human pathogens could penetrate the barriers erected by conventional water treatment plants to cause disease without it being recognized as waterborne. Two years before the outbreak in Milwaukee, Pierre Payment, a Canadian microbiologist, studied two groups of randomly selected homes in Montreal. One group received an in-home water filter. The other group served as a control. Both groups received water from the city’s state-of-the-art water treatment plant. He followed the health of both groups for twelve months, paying particular attention to any gastrointestinal illness. He found that the water filters reduced the rate of significant gastrointestinal illness by about one-third despite the fact that the city had a water treatment plant that was as good or better than most other cities in North America.
The results of the Milwaukee study and the Canadian study suggested that our water supply was not as safe as we have long assumed and waterborne disease was far more common than anyone had imagined. How much waterborne disease occurs every year in the United States? The CDC routinely publishes reports of all the known outbreaks of waterborne disease in the United States, but these usually list only a few thousand cases. However even those who collect these data concede they are a gross underestimation of the scope of the problem.
These numbers rely on a method known as passive surveillance or what one might call coffee cup epidemiology. Grab a cup, sit down, and wait for a phone call. Nothing happens until a state or local health official concerned that he or she is seeing a waterborne outbreak contacts the CDC. Someone, somewhere, has to start thinking a group of cases is waterborne. Then that person must take the initiative to contact someone in an agency with enough epidemiological firepower to conduct a thorough study of the event. Only if that agency conducts a proper study and can uncover compelling evidence to show that the outbreak is waterborne will the cases find their way into the CDC report on waterborne disease.
This approach might have worked when we were worried about the lingering remnants of typhoid fever, dysentery, and cholera in a country still upgrading its water supply. These diseases rarely go undiagnosed and when found immediately raise suspicions about drinking water. Modern water treatment has done an excellent job of driving these diseases into obscurity in the developed world. But passive surveillance was never intended to catch outbreaks with less obvious links to the water supply. According to Dennis Juarnek, a drinking-water epidemiologist at the CDC, “we came within a whisker” of failing to recognize that the outbreak in Milwaukee was waterborne. Not only were the holes in this system big enough to drive a truck through, they were almost big enough to accommodate the biggest truck in American history.
So how much waterborne disease is there in the United States? The truth is that we don’t know, but several lines of evidence suggest that millions of cases of waterborne disease, perhaps more than ten million, may be occurring every year in the United States. How is this possible? How could water treatment plants that rely on methods refined over the past century allow pathogens to reach our taps?
Water treatment seems simple. Filter, disinfect, drink. The devil, invisible and relentless, lurks in the details. As I prepared to write this book, I tried to identify a water supply that faces the range of challenges confronting water supplies around the world. I picked a city and made plans to visit on August 22, 2005. I didn’t give it a second thought when I had to cancel the trip at the last minute. I assumed that I could reschedule for a few weeks later. One week later hurricane Katrina arrived and much of New Orleans, the city I had intended to visit, had disappeared beneath her floodwaters.
Lake Itasca appears unremarkable among the hundreds of lakes that dot the pockmarked flatlands of northern Minnesota. At its north end, it gives rise to a river that appears equally unremarkable except for one thing—its name. There, just south of Bemidji, Lake Itasca officially gives birth to the Mississippi. Headwaters, however, are a fiction of mapmakers and explor
ers. In reality the Mississippi begins on a thousand hillsides as a thousand streams take form.
Altogether, 65 million people live along the baroque filigree of rivers and streams that form the Mississippi watershed. All of them drink from those streams or the aquifers that feed them. All of them discharge their sewage into that same watershed. Those people along with the industries and farms in the watershed use 135 billion gallons of water each day, the majority for irrigation and agriculture. Sixteen billion of those gallons return directly to the streams and rivers of the watershed as treated and untreated wastewater. The remainder runs off the land, seeps into groundwater, is drawn into crops, or evaporates.
In the northeast corner of that watershed, the upper Allegheny flows out of western New York, swells in the valleys of the Appalachian mountains, and marries the Monangahela in the hills of western Pennsylvania. Pittsburgh presides over the joining of the rivers and marks the birthplace of that new waterway, the Ohio River. Just three miles downstream, when the weather is dry, a steady stream of Pittsburgh’s filtered sewage pours into the newly formed Ohio River.
A heavy rain, however, sends Pittsburgh back in time. Like many of the world’s largest cities, Pittsburgh’s sewage flows into the sewers that drain its streets. When a rush of rainwater overwhelms the treatment plant, the sewers overflow and send a vile soup of raw sewage and runoff from the city streets into the rivers around Pittsburgh at a rate of 16 billion gallons each year.
Pittsburgh is not alone. Since Edwin Chadwick first made the decision to send human waste into the London sewers, cities around the world have followed suit. In the United States, 752 cities have combined sewers (i.e., sewers that carry both street drainage and domestic and industrial wastewater), including 152 in Pennsylvania alone. Sewage treatment plants were an afterthought in the design of these systems. None of them can handle the gushing torrent that fills these sewer pipes during a heavy rainfall. Together they dump 861 billion gallons of untreated sewage into American rivers and streams every year, roughly half of it into the Mississippi watershed.
Wastewater treatment does not remove all hazards from sewage. Pathogens, particularly those that are resistant to chlorine, can and do survive the process. Also the process is not designed to remove chemical contaminants. Some chemicals are trapped in the sludge removed from the wastewater, but others pass into the river. Household chemicals, the chemicals from industries that send their waste to the treatment plant, and even the drugs that we consume and excrete find their way into treated wastewater. Treatment plants send everything from hormones to antidepressants into our waterways. The chemical stew emerging from treatment plants can be potent enough to change the sex of fish swimming in the river.
Laden with the effluent from Pittsburgh’s sewers and factories, the Ohio leaves Pennsylvania and lumbers westward. It flows past Cincinnati, Louisville, and hundreds of smaller towns and cities. The liquid boundary between north and south, it accumulates water and waste on its path to the Mississippi.
Three thousand miles from the roots of the Ohio, in the mountains of southwestern Montana, three trout streams merge to form the Missouri River, at the northwest corner of the Mississippi River watershed. Near its origin, coursing through the eastern slopes of the Montana Rockies, the Missouri is a clear, swift mountain stream. As the land flattens, the river slows and grows into the Big Muddy, waddling across the Great Plains toward St. Louis.
The Missouri and the upper Mississippi pass through some of the richest farmland in the world. As they pass, the chemicals of modern agriculture flow downhill and into their tributaries. From a watershed that includes 65 percent of America’s cropland, more than one million pounds of pesticides and the runoff from 6 billion pounds of fertilizer find their way into the Mississippi River and its tributaries each year.
The watershed is also home to the majority of the 60 million pigs, 99 million cows, and 1.3 billion chickens that live in the United States. These animals drink from the watershed, consume its crops, and produce vast quantities of waste. The watershed must absorb more than 120 billion gallons of animal waste every year, far more waste than is produced by the humans with whom they share the basin.
So too thousands of mills and factories ooze poison into the Mississippi River basin. Along its lower reaches in Louisiana, the great river encounters one of the densest concentrations of chemical plants and refineries on the planet. Together, the states that comprise the basin send 120 million pounds of toxic chemicals into their waterways including just under a million pounds of known or suspected carcinogens every year.
As an old professor of mine used to say, “The solution to pollution is dilution.” The Mississippi absorbs this immense quantity of pollutants into a far more immense volume of water. Every day 396 billion gallons of water surge through its final reaches.
By the time the Mississippi reaches Louisiana, it has become a massive muddy snake of mythic proportions. Then, in the land of the bayous, the river begins to break down. Two hundred miles from the Gulf of Mexico, it splits in two and would redefine its course each flood season were it not for human effort to tie it to the map with hundreds of miles of towering levees. At its south end, the river disintegrates into a twisting web of small rivers before disappearing into the Gulf of Mexico.
The Mississippi arrives at the Gulf of Mexico like an exhausted traveler dropping its luggage, some 440,000 tons of sediment each day, at the door. To say the Mississippi River ends in Louisiana is to mistake the map for reality once again. In truth the Mississippi invented southern Louisiana. The continental shelf ends at Baton Rouge. The rest is sediment left from a time when the Mississippi ran free. Today that sediment is trapped in a river that follows a course defined by man and rides out into the ocean.
Thick with organic matter and fertilizer, the river spills into the Gulf of Mexico so laden with nutrients that it creates an explosion of algae and bacteria. This microscopic frenzy of life and death is so intense that it sucks the oxygen from the water over an area the size of New Jersey. Within that area, known as the Hypoxic Zone, no plant or animal life can survive. No fish, no shrimp, no crabs, nothing.
One hundred miles upstream from the river’s mouth, on a crescent of sediment left as the river slows to turn a corner, the French built a city and called it La Nouvelle Orléans. The name has been anglicized and the city has grown, but the Mississippi remains its life force. Today when New Orleans is thirsty, it kneels down by the Mississippi, the drainage ditch for more than 40 percent of the United States, bends low to the water, and drinks.
The motives must have been convincing, indeed, which could induce colonization upon such an uninviting and insanitary waste. A low, flat, marshy area, subject to disastrous inundation at all seasons of the year, pest-ridden, infested with malaria in its most pernicious forms, without a feature to commend it and menaced on every side by seen and unseen enemies—such was the little crescent-shaped village named in honor of the Regent of France, when laid out in the midst of cypress swamps and willow jungles in the year of our Lord, 1690.
—Martin Behrman, mayor of New Orleans, speaking to the Convention of the League of American Municipalities, September 29, 1914
In the late nineteenth century, much of New Orleans drank rainwater captured in cypress cisterns. Like the swamps that surrounded the city, the cisterns gave mosquitoes a place to breed, which in turn advanced the spread of malaria and yellow fever. Those who did not have cisterns filled earthenware jugs with water from the Mississippi, allowed the mud to settle, and drank. The water seemed clear enough to drink, but was in reality dirty enough to kill. Typhoid fever and dysentery were endemic and, together with mosquito-borne illnesses, helped make New Orleans one of the most disease-ridden cities in the United States.
In 1891 Col. L. H. Gardner, superintendent of the New Orleans Water Company and a swashbuckling Civil War veteran who had served in the Orleans Light Cavalry, was searching for a source of pure water for the city. The Mississippi offered an endl
ess supply of water, but few people believed it could be purified, not because of bacterial contamination, but because of the vast amounts of sediment it contained, particularly during flood season. Lake Pontchartrain, to the north of the city, seemed a promising alternative, but New Orleans tilts to the north and at the time much of its runoff and sewage flowed into the lake. Efforts to find an adequate supply of clean groundwater beneath the bayous had not borne fruit.
Then Colonel Gardner received a proposal that seemed to give him a way out. The National Water Purifying Company would provide the city with 14 million gallons of drinking water each day. Furthermore, they guaranteed its purity, claiming the water would be “crystal clear water, free from opalescent hue,” a coloration apparently related to the oil that seeped from the bayous. To do so they proposed to build the largest mechanical filtration plant yet constructed. Gardner signed the contract sensing that the offer was too good to be true. It was.
Unbeknownst to Colonel Gardner, National Water Purifying had offered to install the plant over the vigorous objections of its largest stockholder, Albert R. Leeds. Leeds was a professor of chemistry at Stevens Institute who held not only several of the key patents for the filter that would be built in New Orleans, but also the first U.S. patent for the chlorination of drinking water. Despite his concerns, by 1893 the company had installed thirty filters, each thirty feet long and eight feet in diameter, in a water treatment plant along the banks of the Mississippi.
The Blue Death Page 23
