The Water Quality and Health Council is an independent,
multidisciplinary group sponsored by the Chlorine Chemistry Council. Its mission is to promote science based practices and policies to enhance water quality and health by advising industry, health professionals, policy makers and the public.

Drinking Water & Health Newsletter
March 1, 1995

Table of Contents

Cryptosporidium And Public Health
by Kathleen Blair, MS

Cryptosporidium Q&A

New Research on Chlorine and Cryptosporidium

New Congress = New Approaches

The Future of Water

Cryptosporidium And Public Health
by Kathleen Blair, MS
Epidemiologist, City of Milwaukee Health Department

In the spring of 1993, the largest documented waterborne disease outbreak in U.S. history occurred in Milwaukee, Wisconsin. Cryptosporidium was identified as the cause, and more than 400,000 residents were infected with the parasite. Cost estimates of the outbreak exceeded $54 million and will probably go higher.

Cryptosporidium was first identified in humans in 1976, and for most of the following decade it was seen almost exclusively among AIDS patients. The species responsible for most infections in both domestic and wild animals and humans is Cryptosporidium parvum Isolates from animals are able to cause illness in humans and vice versa. Like many other waterborne pathogens, Cryptosporidium completes its life cycle in the gastrointestinal (GI) tract. The cycle begins with ingestion of the oocyst, which breaks open and releases sporozoites. The sporozoites invade and feed off the epithelial cells of the GI tract. The most common clinical characteristic of the resulting infection in both healthy and immunocompromised individuals is watery diarrhea. In immunocompetent persons, the illness is self-limited. In immunocompromised persons, however, infection can be unrelenting and fatal. Over 100 persons in the Milwaukee area with compromised immune systems are believed to have died prematurely after being infected with Cryptosporidium.

Milwaukee has always prided itself in the quality of its water. But on the morning of Monday, April 5, 1993, the Milwaukee Health Department became aware of widespread gastrointestinal illness in the community through phone calls from citizens and the media. There was increased absenteeism from schools and businesses, and groceries and pharmacies reported depletion of anti-diarrheal medications.

The Suspect: Water

Due to the widespread distribution of illness, water became an early suspect. Milwaukee receives its water supply from Lake Michigan and is served by two water treatment plants, located in the north and south sides of the city. Telephone logs from the Water Department indicated widespread consumer complaints from the area served by the south treatment plant, and increased turbidity readings at the plant in recent weeks. Increases in plant effluent turbidity can indicate microbial contamination and have been associated with other documented waterborne disease outbreaks. (All applicable water quality standards were met by the city's treatment plants throughout the outbreak.)

By Wednesday, April 7, Cryptosporidium had been isolated in eight stool specimens, enough evidence for Mayor John 0. Norquist to issue a boil-water advisory to all 880,000 customers served by the Milwaukee Water Works. The next day the south water treatment plant was shut down. The boil advisory was effective in stemming the outbreak. After a week (the average incubation period for Cryptosporidium), the incidence of illness dropped precipitously as indicated by active disease surveillance among nursing home residents and the daily review of hospital emergency room logs and stool specimen data from clinical laboratories.

Within two weeks, a team of water industry professionals had completed an engineering review of both water treatment plants, focusing on modifications to improve plant performance, and cleaning and disinfection procedures to safely bring the south treatment plant back into operation.

Since chlorine in concentrations practical for drinking water treatment is ineffective in eradicating Cryptosporidium optimizing the filtration process becomes critical. Both treatment plants have installed continuous on-line turbidimeters and particle counters to monitor the effluent of each of the 40 filter beds. In addition, monitoring occurs on raw water and in the clearwell. The new equipment enables staff to receive significantly more information with which to rapidly respond to changing lake conditions and monitor finished water quality.

Crypto Lab

The Milwaukee Health Department has opened a new "Crypto Lab," and regular testing for Cryptosporidium and Giardia is done on raw, backwash and finished water. These tests will provide valuable information over the long term about the presence of this organism in our environment and are used in conjunction with particle and turbidity readings to monitor plant efficiency. Regular testing for Cryptosporidium will not prevent contaminated water from reaching the consumer. Even in the best of situations the sampled water has long been in the distribution system by the time testing is completed. Milwaukee has placed its emphasis on using particle and turbidity readings, thereby reducing the number of Cryptosporidium-sized particles that pass through the plant. These monitoring tools are a true reflection of current water quality and allow immediate plant operation decisions to be made before water moves into the distribution system. Should turbidity or particle counts rise, there are written protocols for assembling a team of Water and Public Health officials at the plant to provide guidance and recommendations.

Milwaukee discovered that passive, laboratory-based surveillance for Cryptosporidium was inadequate for detecting the outbreak. Few people sought medical care for their illness, and those who did were not tested for Cryptosporidium. Since the outbreak, the city has put in place alternative surveillance systems that are more sensitive in detecting diarrheal disease in the community. Pharmacies now report over-the-counter anti-diarrheal sales, and diarrheal disease among nursing home residents is routinely monitored. Many of the clinical laboratories in Milwaukee report weekly the number of stool specimens submitted for Cryptosporidium testing and report any positives. One hospital has tested every stool specimen received in the facility for Cryptosporidium as part of a yearlong surveillance project.

Two studies are under way to elucidate the possible sources of Cryptosporidium in the Milwaukee watershed. In a coordinated effort between the City of Milwaukee and the Department of Natural Resources, multiple sites throughout the entire watershed are being tested for Giardia and Cryptosporidium. Testing sites include both urban and rural locations. Information obtained will help determine whether the presence of Cryptosporidium is related to land use, season, weather conditions or geographic locations.

The University of Wisconsin recently completed an analysis of the southern plant intake, and has recommended relocation of the intake crib to reduce the effect of pollutants from the rivers and the sewage treatment plant that feed into the lake.

At this point there is no single, clear source of contamination of the Milwaukee watershed, and we may never know exactly what happened in April 1993. Possible sources include cattle along the two rivers that flow into the Milwaukee harbor above the southern treatment plant, local slaughterhouses and human sewage. Rivers swelled by significant rain and snow runoff may have transported oocysts great distances into the lake and from there to the intake of the southern plant.

A High Price Tag

In August the City of Milwaukee received a final report from CH2M Hill, an environmental and engineering consulting firm hired to study Milwaukee's water system. Their recommendations, which could easily apply to hundreds of utilities across the country, point to the need for long-term investment in the infrastructure and technology that supply the city's and the nation's water. In November, the Milwaukee Common Council voted in support of Mayor Norquist' s budget proposal to upgrade the water treatment system. The price tag is high. In Milwaukee, the cost of moving the southern plant intake crib alone is estimated to be $11 million; it will cost $27 million to upgrade both treatment plants and replace filter beds, and another $51 million to provide an enhanced disinfection system using ozone as a primary disinfectant. Chlorine is still used in reduced amounts so that residual levels are maintained.

Milwaukee's outbreak was a wake-up call to the nation, pointing out the inadequacies in watershed protection programs, public health surveillance and drinking water standards. It has prompted the formation of new partnerships between water utilities and public health agencies. Communities throughout the country have begun to question the safety of their water supplies and have put pressure on federal and state governments to develop more stringent water quality standards and to increase the resources currently allocated for water quality monitoring and plant modernization.

The outbreak clearly points out the need for a strong and flexible public health infrastructure, and for testing for Cryptosporidium in patients with diarrhea so that the prevalence of this illness can be assessed. This can be accomplished in part by making it a reportable condition.

Milwaukee's experience has also made clear the need to utilize timely surrogate markers, such as particle counts and turbidity, until such time as a rapid and sensitive means of detecting and quantifying Cryptosporidium in treated water are available.

Additionally, we must develop a national, enforceable and adequately funded watershed protection program so that the mw water is never again as contaminated as it was in Milwaukee in April 1993 when even one glass of water consumed at the airport while passing through the city was enough to cause illness.

Given our experience, we urge other communities and the federal government to take the proactive steps necessary to prevent similar outbreaks of Cryptosporidium or other emerging pathogens.

Reprinted with permission from Health & Environment De a publication of the Freshwater Foundation For subscription information, contact Health & Environment Digest 725 Country Road 6, Wayzeta, Minnesota 55391 Copyright 1995.

Cryptosporidium Q&A

Cryptosporidium, a waterborne pathogen, has been identified as the cause of a major outbreak of gastrointestinal disease that struck Milwaukee in 1993, infecting 400,000 and causing the death of more than 100. Other cities also have experienced problems with Cryptosporidium in their drinking water supplies.

How Does Cryptosporidium Affect Public Health?

  • Cryptosporidium is a microscopic parasite contained in an oocyst that breaks open and releases sporozoites once it enters the gastrointestinal tract. These sporozoites invade the GI tract lining, causing a disease known as Cryptosporidiosis, the chief symptom of which is acute watery diarrhea. There is no known cure other than treatment of the symptoms.
  • One of the primary sources of Cryptosporidium is drinking water or contact with recreational waters contaminated by domestic and wild animal feces or human wastewater. Contact with infected animals or individuals is another possible pathway. It can infiltrate drinking water systems from source water contaminated by sewer overflows, wastewater plants and agricultural operations, as well as treatment plant breakdowns.

  • Cryptosporidiosis more severely affects those with depressed immune systems, such as AIDS and cancer patients, the very young or the elderly. However, in instances where drinking water supplies become contaminated, widespread effects may occur in the general population.

How Are Water Systems Kept Free of Cryptosporidium?

  • Because of its ubiquity in animals, the presence of Cryptosporidium oocysts is widespread in surface water sources as well as in some groundwater sources.
  • Unfortunately, this parasite is resistant to the traditional disinfection methods alone. Filtration in conjunction with ozonation and chlorine, plus chloramines, is generally effective in removing or destroying it if such treatment occurs before the water is released for distribution.

  • Testing in watershed areas can detect the presence of Cryptosporidium and alert water treatment authorities to take necessary preventive measures. Particle and turbidity readings can be used to evaluate filtration.

  • If the water supply becomes contaminated, boil-water advisories are required to prevent or minimize infection among the population.

How Is the Public Being Protected from Cryptosporidium Infection?

  • Current approaches in monitoring do not guarantee protection from Cryptosporidium in drinking water. Health professional s, water treatment specialists, environmental experts and government regulators have been examining methods to improve the prevention, detection and treatment of Cryptosporidium in water sources. Cooperative efforts among these entities will enhance their ability to contain future outbreaks of Cryptosporidium related illness.
  • Additional research is proceeding on the health effects of Cryptosporidium, which are still incompletely understood.

  • The Environmental Protection Agency has proposed new regulations for water disinfectants and disinfectant by-products as well as for surface water treatment, in an attempt to improve monitoring, testing and treatment for both chemical and microbial contaminants. More research and regulatory flexibility is being sought to balance the relative risks between these two threats to drinking water supplies.

  • Drinking water suppliers are attempting to develop and implement the most effective detection and treatment methods for dealing with Cryptosporidium. Multi-barrier techniques, including source water protection, followed by filtration and disinfection in the treatment plant, plus a distribution system disinfectant residual, are considered the best approach.


New research results indicate that chlorine and chlorine-based disinfectants may be more effective against Cryptosporidium than previously recognized. Dr. Gordon Finch at the University of Alberta reported his preliminary findings at the November 1994 American Water Works Association Water Quality Technology Conference.

It appears that combinations of disinfectants, including chlorine followed by chloramine, inactivate Cryptosporidium oocysts more effectively than demonstrated by past studies with single disinfectants. In particular, chlorine followed by chloramine, at concentrations and contact times typical of those used in practice (chlorine (1 mg/ L, 60 min.), monochloramine (2 mg/L, 240 min.), achieved substantial inactivations of this troublesome parasitic organism. Assuming continuing studies confirm these results, then water utilities would be able to adopt this inexpensive method for both waterborne disease protection and reduction of disinfection byproducts.

Dr. Finch has received additional funding to continue his work from the U.S. Environmental Protection Agency, the American Water Works Association and the Chlorine Chemistry Division of the American Chemistry Council.


The new Republican majority in Congress promises changes in the regulation of water quality and other environmental issues, which raises many questions about the future of the Clean Water and Safe Drinking Water Acts that did not get through the reauthorization process last year.

The shift in leadership and members of jurisdictional committees, along with the Republican commitment to reexamine many regulations, suggests a new approach to the federal government's role in the protection of public health and the environment. Drinking water issues will be at the top of the agenda to be addressed in four major legislative vehicles: Risk Assessment, Safe Drinking Water Act, Clean Water Act and the Farm Bill. Other topics for review include unfunded mandates and property takings.

Reauthorization Clouded by Regulatory Reform Fever.

While both Chairmen Bliley and Chafee sponsored compromise legislation reauthorizing the Safe Drinking Water Act in the last Congress and have promised to bring up similar bills this year, the current focus is on limiting further regulation. Those governing the environment - the Clean Air Act, Clean Water Act, Safe Drinking Water Act, Superfund - will be closely examined. Efforts to incorporate risk assessment and cost-benefit analysis into environmental protection measures can be expected. Intense opposition from advocacy groups to any perceived weakening of air and water quality standards also can be anticipated.

The Committee Picture

Realignment of House committees presents the most changes: Rep. Thomas Bliley (R-VA) takes over as chairman of the Committee on Energy and Commerce and Rep. Michael Bilirikis (R-FL) chairs the Health and Environment Subcommittee, replacing Rep. John Dingell (D-MI) and Rep. Henry Waxman (D-CA), respectively. Rep. Bud Shuster (RPA) now chairs the Transportation and Infrastructure Committee, formerly Public Works, replacing Rep. Norman Mineta (D-CA).

Sen. John Chafee (R-RI) moves into the chair of the Senate Environment and Public Works Committee.

The Legislative Calendar

Following is a rundown of the major bills affecting drinking water programs:

  • Risk Assessment
    Title III of HR 9, the Job Creation and Wage Enhancement Act, is the principal vehicle of the Republican "Contract with America" that mandates risk assessment and cost-benefit analysis of new regulations. Principles of risk assessments, risk characterization and risk communication would apply prospectively to "major rules," defined as those having a total economic impact of more than $25 million a year. The bill would also require an analysis of risk reduction costs and benefits, and require peer review for rules with an annual economic impact of$l00 million. Before a new rule could go into effect, agencies would have to go through a 23-step process, including possible judicial review, to perform the required analyses.
  • In March, the House passed HR 1022, which incorporated the central features of HR 9. The Senate Energy and Natural Resources Committee, chaired by Sen. Frank Murkowski (R-AK), is considering a number of risk reform bills at the subcommittee level. Senate floor action is anticipated in May.

    The Clinton Administration and environmental advocacy groups spent some time defining their positions, but now have joined the debate in an effort to maintain present environmental protections while still streamlining the regulatory process.

  • Safe Drinking Water Act
    Reauthorization of the Act is expected to be a priority this spring, with Senate hearings to be held by the new Drinking Water, Fisheries and Wildlife subcommittee, chaired by Sen. Dirk Kempthorne (R-ID).

    On the House side, Rep. John Dingell (D-MI) has reintroduced a reauthorization bill (HR 226) identical to the one that passed the House last year. However, with Republicans in control of the Commerce Committee, this bill cannot be considered the main legislative vehicle in the House. Instead, the committee has indicated it will have a different perspective that reorders priorities on drinking water regulation. The approach is likely to include a new standard setting process, based on scientific risk assessment and cost-benefit analysis. Chairman Bliley sponsored similar legislation in the 103rd Congress, although he has commented that he does not intend to submit a bill that is too far to the right.

    Not surprisingly, environmental groups find this new approach to safe drinking water quite controversial, although their ability now to significantly affect the outcome is probably limited.

  • Clean Water Act
    House Transportation and Infrastructure Committee Chairman Bud Shuster has moved forward with hearings on reauthorization of the Clean Water Act. In the 103rd Congress, subcommittee action foundered on the unresolved issues of unfunded mandates, state flexibility, cost-benefit analysis and risk assessment, and compensation for property takings by the federal government. These issues, which form the basis of Republican regulatory reform initiatives described above, remain central to amending the Clean Water Act.

    How the Senate intends to proceed is unknown at this time.

  • Farm Bill
    Congress is due to consider reauthorization of agriculture programs, last enacted in 1990. Whenever such legislation is introduced, the primary focus will be on farm subsidy issues, particularly as they affect efforts to scale back the federal budget, a priority for both the Congress and the Administration. However, drinking water protection in relation to the run-off of pesticides and other crop protection chemicals also will be included.

Unfunded Mandates Targeted

A central feature of the current debate over the extent and cost of regulation concerns unfunded mandates, where federal requirements are imposed on the states without matching funds to pay the cost of their implementation. Long a target of the nation's governors and local governments, whose shrinking budgets must bear the brunt of these costs, banning unfunded mandates has been drawn into the bull's eye of congressional budget cutters as well. Legislation to help remedy the burden of federal regulation on states and localities has passed the Congress and been signed into law by the President.


With majorities in state houses and the Congress, Republicans are likely to accomplish much of their goal of replacing complicated, detailed federal requirements with block grants that will allow the states more flexibility in carrying out programs for public health and welfare and environmental protection, including water quality programs.

It is unclear, however, whether Republican goals can sustain a presidential veto.


Balancing burgeoning public needs for safe drinking water with dwindling supplies will be a major challenge for public works managers and regulators in the years to come. So asserts a draft report prepared by the EPA Science Advisory Board's Drinking Water Committee after a yearlong study.

The draft report, entitled Safe Drinking Water: Future Trends and Challenges, cites numerous trends that will affect the potable water supply over the next 10-20 years, and recommends steps EPA should take to ensure adequate safe water resources. The report is expected to be made final early this year.

Future Trends

In reviewing drinking water resources, the study evaluates population growth and its impact on groundwater and surface water availability and contamination. The continuing decline in groundwater tables, which account for half of the nation's residential consumption, is a major concern. The situation is further complicated by agricultural and industrial uses that both deplete water supplies and cause contamination from runoff and discharges.

Citing an increased demand for clean water, the committee addressed several areas of concern:

  • Increased public awareness of water environment issues and expectations for regulatory and management policies that protect water resources;
  • New scientific knowledge about health effects and lower detection levels for contaminants;

  • Increased demand for protection of virgin resources along with stricter standards; and

  • The changing profile of chemical and microbiological contaminants that endanger many water resource systems.


  • The Drinking Water Committee report includes several recommended steps that should be taken in response to the trends noted above. These trends indicate a need to fundamentally change the way drinking water is produced and managed. To that end, the Committee draft report recommends that EPA:
  • Improve source water protection and implement water recycling and conservation practices;

  • Support changes in treatment technologies to reduce disinfection byproducts while maintaining protection from microbial contaminants;

  • Greatly accelerate research to spur advances in risk assessment methodologies for both chemical and microbial contaminants of water;

  • Support the consolidation of small distribution systems as a means of upgrading aging infrastructure and assuring adequate supplies on a regional basis for less populated areas.

  • Establish a surveillance or alert system for emerging waterborne pathogens.

Drinking Water & Health Newsletter is a Publication of the Public Health Advisory Board to the Chlorine Chemistry Council


The Public Health Advisory Board

Sanford M. Brown, Jr.
School of Health and Social Work,
California State University, Fresno

Bruce K. Bernard, PH.D.
SRA International
Washington, DC

Linda Golodner
National Consumer League
Washington, DC

Jerod Loeb, PH.D
Joint Commission on Accreditation of Health Care
Oakbrook Terrace, Illinois

Ralph Morris
Galveston County (Texas)
Health District

Fred Reiff
Pan American Health Organization
Washington, DC

Chlorine Chemistry Division of the American Chemistry Council



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