Chris Miller
The Division of Oral Health at the Centers for Disease Control and Prevention (CDC) recently issued suggested procedures for dental offices to follow during boil-water advisories.
Waterborne disease outbreaks
The most recent data describing waterborne disease outbreaks is for 1995-1996 (CDC. Surveillance for waterborne disease outbreaks - United States 1995-1996. Morbidity Mortality Weekly Report 1998; 47[No SS-5]; 1-34). During this two-year period, 13 states reported a total of 22 outbreaks associated with drinking water. These outbreaks made 2,567 persons ill, but no deaths were reported. Microbes caused, or were suspected of causing, 15 of the 22 outbreaks. Two were caused by the protozoan Giardia lamblia and involved 1,459 people. Four others were caused by the bacteria Shigella sonnei, E. coli O157;H7, and Plesiomonas shigelloides, and one was caused by a virus. Unidentified microbes caused eight others. Chemicals (chlorine, nitrite, copper, sodium hydroxide, and liquid soap) caused seven of the 22 outbreaks. Ten of the 22 outbreaks involved community water systems - three of these involved the water-treatment plant and the other seven involved individual facilities (e.g., offices, buildings, homes).
The largest waterborne disease outbreak involving drinking water ever reported in the U.S. occurred in 1993 in Milwaukee (CDC. Surveillance for waterborne disease outbreaks - United States 1993-1994. Morbidity Mortality Weekly Report 1996; 45 [No SS-1]: 1-35). The protozoan Cryptosporidium parnum found to be present in drinking water that had been filtered and chlorinated after it was obtained from Lake Michigan caused this outbreak. Apparently, a decreased effectiveness in the treatment-plant filtration process allowed the organism to survive and end up in the drinking water supply. An estimated 403,000 persons became ill with this diarrheal disease during this outbreak, and 4,400 were hospitalized!
Causes of disease outbreaks
CDC indicates that waterborne disease outbreaks involving drinking water have occurred because:
* untreated surface water gets into the system
* untreated ground water gets into the system
* the water is not adequately treated (e.g., interruption of disinfection or filtration due to electrical, mechanical, or other failures at the treatment facilities)
* the water-distribution system becomes deficient (e.g., contamination of water mains during construction, repair, or earthquakes; contamination of water-storage facilities).
A boil-water advisory issued by local health departments is a statement to the public advising persons to boil tap water before drinking it. An advisory is issued when there is a possibility that the drinking-water supply has become contaminated with potential microbial pathogens.
The Division of Oral Health, which is part of the National Center for Chronic Disease Prevention and Health Promotion at the CDC, suggests that the following procedures may be appropriate for dental offices during boil-water advisories. These procedures should be observed in addition to specific instructions issued by state or local health departments during these advisories.
While a boil-water advisory is in effect:
- Water from the public-water system should not be delivered to the patient through the dental unit (the device at each dental chair that provides water and compressed air), ultrasonic scaler, or other dental equipment that uses the public-water system until the boil-water advisory is canceled.
- Patients should not use water from the public-water system for rinsing; water from alternative sources, such as bottled or distilled water, should be used.
- Dental workers should not use water from the public-water supply for hand washing. Instead, antimicrobial-containing products that do not require water, such as alcohol-based hand rubs, can be used until the boil-water notice is canceled. These products have been reviewed and cleared for marketing by the U.S. Food and Drug Administration (FDA).
When the boil-water advisory is canceled:
- First, incoming public-water-system lines in the dental office should be flushed (i.e., cleared of contaminated water). All faucets in the dental setting should be turned on completely for at least 30 minutes, including water lines to dental equipment that uses the public-water system.
- After the incoming public-water-system lines are flushed, dental-unit water lines should be disinfected. The dental-unit manufacturer should be consulted to determine the appropriate procedures for disinfecting the lines.
Because water from the affected public system should not be delivered to the patient during a boil-water advisory, many dental procedures cannot be performed. Alternative water sources, such as separate water reservoirs that have been cleared for marketing by the FDA, can be used. However, if the alternative source flowed through a dental unit previously connected to the public-water supply, the dental unit lines should be flushed and disinfected according to the manufacturer`s instruction.
Boil-water advisories are particularly troublesome to dental offices that rely upon the public-water system. Patient care needs to be suspended in these situations unless water is not used during patient care or an alternative source of water and water delivery is available. The CDC-suggested procedures are important and useful both during and after a boil-water advisory. Procedures for each office should be determined in advance so that they can be instituted immediately and "down time" kept to a minimum.
Chris Miller is director of Infection Control Research and Services and professor of oral biology at Indiana University.
