Key Concepts

The following information represents some contaminants to which certain patients may be particularly sensitive.

Cryptosporidium parvum. Cryptosporidium parvum is a pathogen found in human and animal fecal waste. It can enter rivers, lakes, and streams and, rarely, ground water that contribute to drinking water supplies. Because of its small size and composition, it is resistant to typical filtration and disinfection methods 00 though EPA has tightened its standards in recent years requiring public water systems specifically to address this contaminant.

• Exposure to Cryptosporidium parvum in drinking water may cause gastrointestinal problems, such as diarrhea, vomiting, and cramps. Patients whose immune systems are weakened by AIDS, chemotherapy, a recent transplant or other reasons are most vulnerable. Diarrhea and vomiting may cause infants and the frail elderly to become dehydrated more quickly. In most healthy adults and children, the problems are temporary. Other, more common routes of exposure to this pathogen are food, unsanitary diaper-changing practices, person-to-person contact, and swimming in contaminated water.
  
• Suggested interventions: Sample stools more frequently. Include questions on water sources for patients with diarrhea. Those with questionable water sources require further investigation. Most standard ova and parasite cultures do not automatically test for Cryptosporidium. Be sure to specifically request an acid-fast fluorescent test.

Escherichia coli or E. coli. E. coli is a type of fecal coliform bacteria commonly found in the intestines of animals or humans. The presence of E. coli in water is a strong indication of recent sewage or animal waste contamination. Sewage may contain many types of disease-causing organisms. Although most strains of E. coli are harmless and live in the intestines of healthy humans and animals, a particular strain, E. coli O157:H7, produces a powerful toxin and can cause severe illness.

• Most infections of E. coli O157:H7 are believed to have come from eating undercooked ground beef. However, some have been waterborne, and people have become sick after drinking contaminated water.
• Infection by E. coli O157:H7 is characterized by severe bloody diarrhea and abdominal cramps, although sometimes the infection causes non-bloody diarrhea, often with no fever. In some people, particularly children under 5 years of age and the elderly, the infection can also cause a life-threatening complication called hemolytic uremic syndrome, in which the red blood cells are destroyed and the kidneys fail. Hemolytic uremic syndrome is usually treated in an intensive care unit, and blood transfusions and kidney dialysis are often required.
• Suggested interventions: Encourage patients (or their parents) to have household well water tested annually for nitrates and bacteria by a state-certified laboratory. If a patient's well tests positive for E. coli, people in the household should not drink the water without boiling the water for at least one minute at a rolling boil - longer if they live at high altitudes. The well may also be disinfected according to procedures recommended by the local health department. Water must be monitored periodically after disinfection to make certain the problem does not recur. If contamination is a recurring problem, patients should investigate the feasibility of drilling a new well or installing a point-of-entry disinfection unit using chlorine, ultraviolet light, or ozone.

Disinfectants and Disinfection Byproducts (DBPs). Disinfectants, while effective in controlling many microorganisms, react with matter in water to form DBPs. Unchlorinated private well water is unlikely to contain any DBPs.

• While health effects from exposure to disinfectants and DBPs vary by contaminant, some epidemiological studies have shown a link between bladder, rectal, and colon cancers and DBP exposure. Additionally, human epidemiological studies report an association between chlorinated drinking water and reproductive and developmental endpoints such as spontaneous abortion, neural tube defects, pre-term delivery, intrauterine growth retardation, and low birth weight. In August 2003, EPA proposed measures beyond those already required for public water systems.
• Suggested interventions: Drinking plenty of water from a safe source during pregnancy is important. If your patients' public water system has notified customers of a DBP violation, follow instructions from the public water system. For example, your patients might want to consider alternatives to tap water during pregnancy.

Lead. Paint chips and dust from lead paint in old buildings are the primary routes of children's exposure to lead, but EPA estimates that up to 20 percent of a person's background exposure may be due to lead in drinking water - and the percentage is higher for infants drinking formula mixed with contaminated drinking water. Lead may be present in drinking water because of corrosion of household plumbing systems; erosion of natural deposits. In some communities, lead service lines can also contribute to high levels of lead in drinking water.

• In infants and young children, continuous exposure to high levels of lead may result in delays in physical or mental development, deficits in attention span, and learning disabilities.
• For adults, such exposure may result in kidney problems or high blood pressure.
• Suggested interventions: Look for symptoms of lead poisoning in children, and test infants' blood lead levels. If a child's blood lead level is high, consider lead in tap water as a possible factor, in addition to lead paint exposure. Encourage patients to have drinking water tested for lead in homes, schools, and day care centers by a state-certified laboratory. Encourage local schools and day care centers to test their drinking water outlets for lead.
• Use only cold water for drinking, cooking, and especially making baby formula. It's important to consider that foods that absorb all of the water in the pot, such as rice and dried beans, will also absorb all of the lead that is in the cooking water. Soups made or mixed with water will also contain any lead that's in the water. Foods cooked in water and then drained, such as pasta, meat, or vegetables, also absorb some lead from the water.
• If lead levels in drinking water are high, consider alternatives to using boiled tap water in baby formula.
• Information and brochures are available from the National Lead Information Center, (800) 424-LEAD [5323].

Nitrates and Nitrites. Nitrates may run off or percolate into water sources from excessive fertilizer use and animal waste; leaching from improperly constructed or maintained tanks, cesspools, sewage; or erosion of natural deposits.

• Exposure to nitrates in drinking water at levels above the drinking water standard may result in methemoglobinemia, or "blue baby syndrome," in infants under six months. Blue baby syndrome is life-threatening without immediate medical attention. Infants most likely to get methemoglobinemia are those who are already sick and consume food that is high in nitrates, such as spinach, broccoli and cured meats, and drink formula mixed with water that is high in nitrates.
• Possible interventions: Encourage patients to have household well water tested annually for nitrates and bacteria by a state-certified laboratory, especially those caring for infants and expectant parents and grandparents. If water has high nitrate levels, consider alternatives to using bottled tap water in baby formula. Boiling water only increases nitrate concentrations.

Drinking Water Security. Events of September 11, 2001, have brought into focus the possibility of intentional contamination of drinking water and wastewater infrastructure. Doctors, nurses, and others in primary care would likely be the first to observe unusual illness patterns or disease trends resulting from intentional biological or chemical contamination.

"Recognizing Waterborne Disease and the Health Effects of Water Pollution: A Physician On-line Reference Guide," by Patricia L. Meinhardt, MD, MPH, MA, includes a section, "Physician Preparedness for Acts of Water Terrorism." It is available at WaterHealthConnection.org.

Recognize, Report, and Prevent Waterborne Illness

• Report suspicion of waterborne illness to your local health department.
• Take an environmental health history that includes, "What is the source of drinking water?"
• Familiarize yourself with your patients' water supply. Annual water quality reports are a good first source of information on local public water systems. Household well owners are responsible for making sure their wells are tested regularly and maintained properly.