FOR Americans traveling to an undeveloped part of the world, conventional wisdom holds that drinking tap water is a ticket to trouble.
Those who ignore the advice sometimes suffer what's called "traveler's diarrhea," whose symptoms also include cramps, nausea and headaches. It affects as many as half of all travelers from developed countries who go to developing nations, according to travel health website www.travdoc.com, no matter how careful they are.
There's another potential water-related problem that can strike closer to home just as a vacation is getting off the ground. The running water in nearly 13% of 158 randomly selected passenger airplanes that the Environmental Protection Agency tested this summer was found to have a type of bacteria called coliform; 1.3% of the planes tested positive for E. coli bacteria.
The presence of coliform, which is commonly found in the intestinal tracts of mammals and is an indicator of water quality, does not necessarily indicate a health risk, according to the EPA. Coliform bacteria may not cause illness, but its presence in drinking water indicates that other disease-causing organisms (or pathogens) may be present in the water system.
Thus, some of the same bugs that can cause traveler's diarrhea might be in the water on your airplane. And because many aircraft circulate between domestic and international routes, you don't need to be on an aircraft returning directly from a foreign country to be concerned about water quality.
To understand the issue, it is helpful to take a look at how airlines acquire water, especially when they're in a foreign country.
"Safety is our No. 1 priority, and that is not limited to getting the plane in the air and on the ground," says Nancy Young, managing director of environmental programs and assistant general counsel for the Air Transport Assn., a Washington-based trade group representing many of the world's largest airlines.
"There are significant steps taken both internationally and domestically" to ensure that the water is safe, she says.
Water loaded on aircraft domestically is from local sources that meet the EPA's safe-water standards. In foreign countries, airlines contract with local suppliers that meet EPA standards.
Aircraft water tanks are cleaned and disinfected no less than twice and as often as four times a year, according to Food and Drug Administration and aircraft manufacturer guidelines.
The Air Transport Assn. conducted its own water-testing program, overseen by the EPA, at the end of last year. Of the 265 aircraft samples it tested, only 2.6% were positive for coliform, and none tested positive for E. coli. Why the difference from the EPA's results?
"We think that the problem is overstated," Young says.
The air transport group claims that at least some of the EPA samples may have been contaminated when they were collected in aircraft lavatories and that the EPA's sample size was not large enough.
The EPA disagrees with that assertion. "I am very confident in the quality of work that our folks have done," says Tom Skinner, head of the EPA's enforcement office. "The samples we took were properly taken, and we did more than twice the number of aircraft required to be statistically solid."
The EPA decided to release the results of its study even while the agency was planning a follow-up.
"We don't know what we have exactly at this point," Skinner says. "We felt better putting information out there early rather than keeping the information confidential while we did the work."
On one point all parties agree: There is no reason to panic. The EPA and 12 major airlines last week announced they have agreed to another round of tests for 169 randomly selected aircraft as well as annual testing of every aircraft in a carrier's fleet. If a plane fails to meet standards, a notice will be posted in the lavatories and galleys until the water tests safe.
Meanwhile, here are some precautions that can be taken:
* Travelers who have compromised immune systems or suffer other health problems may be at increased risk from airplane water. They and anyone else concerned about water quality should drink only bottled beverages.
* Adding alcohol to a drink is not an adequate precaution. It is a myth that alcohol will kill the bacteria in drinks, according to TravDoc.com. Alcohol will only kill bacteria after 24 hours of exposure.
* Coffee and tea are often prepared with water from the airplane's water system, so it's a good idea to ask a flight attendant whether bottled water was used in making those beverages. The EPA recommends boiling water that may have coliform for at least one minute to kill the bacteria. Coffee makers generally do not bring water to a boil, but Dr. Phyllis Kozarsky, an expert in travelers' health at the Centers for Disease Control and Prevention in Atlanta, thinks coffee and tea are probably OK; the beverages are "typically hot enough to ward off most organisms," she says.