By Tim Ford
Summary: Everyone in the international water community understands that waterborne diseases are of utmost concern. The emphasis takes on a greater impetus when the subject involves developing countries where resources aren’t nearly as available. Where do we start and what diseases do we target? Some suggestions are provided here.
While the United States is concerned about health risks from exposure to disinfection by-products (DBPs) and ingestion of disinfectant resistant protozoa, the developing world still struggles with an enormous burden of microbial waterborne disease. Annual morbidity rates are consistently estimated in the billions by the World Health Organization (WHO) and mortality from diarrheal disease still runs into the millions.
The reasons for these discrepancies are partially obvious, reflecting a basic lack of hygiene and sanitation. There are, however, other factors that should be considered and they relate to the issue of population susceptibility. In the developing world, populations are exposed to a multitude of challenges to their health:
- A high burden of infectious diseases such as HIV, malaria and tuberculosis,
- Poor nutritional status from vitamin deficiencies to starvation,
- Exposure to chemical pollutants in food, air and water (from poorly or uncontrolled industrial, agricultural and municipal discharges of wastes), and
- Harsh working environments (“sweatshops,” child labor, exposure to industrial toxins, other environmental extremes, etc.).
Placement of burden
In the developed world, we must take some responsibility for each of these “challenges”—our pharmaceutical companies (and governments) have been unwilling to provide affordable drugs; the developing world provides a market for many agricultural chemicals that are banned in developed countries due to their toxicity; our multinationals move manufacturing to developing countries, specifically to avoid high labor costs and environmental regulations; and our economic policies and market forces stimulate a “sweat shop” industry. We have also effectively created an unregulated market for antibiotics in developing countries. Misuse of multiple antibiotics in human population, animal husbandry and aquaculture has created what has rapidly become, next to HIV/AIDS, the most serious health threat from infectious disease to date, the emergence of multiple antibiotic resistance in most identifiable bacterial pathogens.
Our responsibilities aside, waterborne diseases such as cholera and typhoid (together with other infectious diseases such as smallpox and the plague) have been part of our societies throughout human history. Our ability to understand those diseases, the causative organisms and their potential control has only occurred over the past 100 years or so. The major waterborne diseases will continue to be endemic to many developing countries and epidemic within certain regions. The major changes that have occurred over the past 100 years that cause most concern are increases in population, the rapid urbanization that has accompanied these increases, rapid migration rates and burgeoning refugee populations.
Despite the economists’ models that devalue human life in developing countries based on earnings potential, people in those countries have as much right to safe drinking water as citizens of the developed world. As in the United States, watershed protection, water treatment and effective distribution networks are important in providing safe drinking water along with wastewater collection and treatment. “Integrated water management” has become a catch phrase of the international community and non-governmental organizations (NGOs), but is an elusive goal. In many developing nations’ cities where infrastructure exists, there’s little effective watershed protection, water treatment is generally inadequate and water supply is intermittent through deteriorating distribution networks. In many cases, untreated waste is discharged directly to receiving waters or accumulates around homes.
Area of emphasis
Should we, therefore, be concerned about Cryptosporidium or about DBPs in developing countries? The question presents both a public health and an ethical dilemma. Most of the infectious agents transmitted by water that raise concerns in developed countries—Cryptosporidium parvum, Legionella pneumophila, E. coli O157, the potentially vast number of waterborne viruses, and others—are seldom if ever diagnosed. Plus, in certain cities I have visited, many opportunistic pathogens have yet to be recognized by public health authorities.
A global rate of morbidity caused by one of the most common agents of waterborne disease, Giardia lamblia, has been consistently underreported by the WHO as 500,000. Yet, the 1995 WHO world health reports suggest there are 200 million people with symptoms consistent with giardiasis in just Asia, Africa and Latin America. In other words, it’s almost impossible to estimate the total burden of these diseases. An increasing number of seroprevalence studies (analyzing presence of antibodies in blood samples) are indicating high rates of infection by Cryptosporidium parvum, although cryptosporidiosis is seldom, if ever, diagnosed.
Sorting out the facts
The diseases of the developed world are present in developing countries, but no active surveillance exists. The obvious question is whether we need to care if they present a relatively low mortality risk relative to typhoid and cholera, for example. We must remember that the highest mortality rates are in children succumbing to diarrheal diseases. Although some may be diagnosed as cholera or shigellosis, most are of unknown etiology and are likely caused by opportunistic pathogens—protozoa, viruses and bacteria—that present mortality risks to susceptible individuals. A better understanding of the effects on individuals weakened by poor nutrition, chemical exposures, multiple infections, etc., could assist in future intervention. Linking these mortality risks to contaminated water can help provide impetus to local governments and the international community to invest in “integrated water management.”
It’s harder to argue that exposure to DBPs formed by the presence of organics in chlorinated waters presents a cancer risk to populations in places where an individual’s life expectancy is dramatically reduced by infectious diseases and other environmental concerns. The ethical issue is also difficult. Developing countries see the United States and other developed nations spend vast resources on investigating cancer risks. The trend in the United States is to reduce DBP formation by changes in treatment design, which is often extremely costly and may employ inappropriate technologies for developing country environments. Although it’s understood that we should never compromise disinfection for the poorly defined risks of cancer from DBPs, we’ve created a double standard. We dismiss the relevance of a health issue for developing countries that we take seriously in the United States.
It’s arguable that technology is available to address most of the world’s water problems. Even in water-scarce nations, desalination and water reuse technologies could be employed to provide safe drinking water; however, until there’s greater equity between nations, the key for most developing countries is to provide technology/treatment options that are low-cost, easy to maintain, can be easily repaired with readily available parts and don’t require high levels of training to operate. This cannot only apply to providing safe drinking water, but must be integrated with some form of waste collection and treatment, and with basic education on hygiene and sanitation. The above sounds obvious, yet can be remarkably difficult to achieve. The problems in achieving the most basic hygiene and sanitation are partly economic, partly cultural and primarily political.
Many reports highlight the need for better surveillance, development of low-cost treatment systems and education. For any improvements to occur, education at all levels is critical—from the community level to government leaders.
If we, in the United States, are to take a share in the responsibility for the global burden of waterborne disease, we must not only facilitate transfer of education and technologies, but also educate and better regulate our own industries. The United States continues to profit from the political and environmental conditions—including poverty, national debt and austerity programs imposed by international finance institutions—that prevail in developing nations, while those same conditions contribute to both endemic disease risk and emergence of new diseases.
- Ford, T.E., and R. Colwell, A Global Decline in Microbiological Quality of Water: a Call for Action, American Academy of Microbiology, Washington, pp 40, 1996.
- Ford, T.E., “Microbiological Safety of Drinking Water: United States and Global Perspectives,” Environmental Health Perspectives, 107(Suppl 1):191‑206, 1999.
- Ford, T.E., and W. MacKenzie, “How Safe is Our Drinking Water.” Guest Editorial, Postgraduate Medicine, 108:11-14, 2000.
- World Health Organization, World Health Report 1996, “Fighting Disease—Fostering Development,” Geneva: WHO 1996.
- WHO, Global Water Supply and Sanitation Assessment 2000 Report, website: www.who.int/water_sanitation_health/Globassessment/GlobalTOC.htm
- WHO, “ Environmental toxic exposures and poisoning in children,” website: www.who.int/peh/CEH/topics_toxic.htm
About the author
Tim Ford is director of the Program in Water and Health at the Harvard School of Public Health, as well as an associate professor of environmental microbiology. He’s currently working on measurement of waterborne disease risks in cities in India and Russia, and seeking support to develop further programs in Vietnam and China. Dr. Ford has published more than 100 articles on water-related topics and has lectured extensively, both in the United States and internationally. Further information on his program can be found at www.hsph.harvard.edu/water