Could Drinking Floodwater Save Your Life?

Dehydration vs. contamination.

Water, water everywhere, but not a drop to drink

With emergency supplies slow to arrive, some New Orleans residents have died of dehydration in the past few days. Though the city is covered with water, one Louisiana public-health expert has called it a “toxic gumbo” of sewage, gasoline, and other contaminants. Could you drink the floodwater if you were dying of thirst?

Yes, if it’s not too briny. The run-off may be a bit like seawater—so loaded with salts that drinking it would only make you more dehydrated. But if that’s not the case, a few gulps of floodwater could save your life. Any illness you got from the contaminated water wouldn’t start to affect you for a day or more, perhaps giving you enough time to find clean water or medical care.

It’s not yet clear how much salt is in the New Orleans floodwater, but we do know that most of it spilled into the city from Lake Pontchartrain, a brackish reservoir linked to the Gulf of Mexico. Brackish water—which is saltier than freshwater but not as bad as seawater—could actually help save you from dying of thirst. Your body needs salt to absorb water, which is why rehydrating drinks like Gatorade and Pedialyte contain so much sodium. If you were drinking floodwater, you’d want it to have a fair amount of salt—enough to help your body hang on to the fluid you’re ingesting, but not so much that it kills you. (For a discussion of how salty the floodwater might be, click here.)

If the floodwater isn’t too salty, the microorganisms will likely provide the most immediate danger to those desperate enough to drink it. Illnesses caused by salmonella, shigella, E. coli, and vibrio bacteria can cause severe diarrhea and vomiting, both of which would lead to further dehydration. Water-borne parasites like giardia and viruses like Norwalk virus could cause similar problems. But exposure doesn’t guarantee infection—a strong immune system and high levels of stomach acid might head off a possible problem. Even if you did get a nasty bug, the symptoms that can cause dehydration probably wouldn’t kick in for several days.

It’s possible that the floodwaters are contaminated with toxic industrial chemicals, but these are less likely to cause major problems in the short term. The effects of dioxins, for example, can be quite nasty, but they take some time to emerge. Chemicals used in pesticides and solvents could be carcinogenic without causing acute harm.

What about the fuel products that have seeped into the water? They’re not worth avoiding, if you’re dying of thirst. Gasoline can be toxic in high doses, but a little bit in the water is unlikely to cause significant damage. Some components of gasoline don’t dissolve in water and could conceivably be skimmed before drinking. Other chemicals, like benzene, are known carcinogens. The additive MBTE would give water a foul taste, but any health problems it caused would unfold over the long term. Though a little gasoline in the water wouldn’t be much of a problem, larger doses could induce vomiting—which would hasten the process of dehydration.

Next question?

Explainer thanks Ellen Glickman of Kent State University, Hassan Mashriqui of Louisiana State University, Don Powell of the American Gastroenterological Association Mark Sobsey of the University of North Carolina, and Larry Zinn of LL Zinn and Associates, Inc.

Correction, Sept. 7, 2005: This article originally failed to note that Lake Pontchartrain is a brackish lake, meaning that it has more salt than freshwater, but less than the ocean. The article said “Yes—you could and you should” drink the floodwater if you were dying of thirst. This statement is incorrect. The correct answer, now noted in the piece, is “Yes, if it’s not too briny.” Whether or not floodwater actually can save your life depends on its salinity. In order to clarify the answer, the author has added the following new information:

1. It is possible that the run-off from the lake contains so much salt (more than 8 parts per thousand) that drinking it would cause further dehydration rather than rehydration.

2. It is also possible that the floodwater could contain salt at a concentration (around 5 parts per thousand) that actually makes it more helpful than freshwater would be in staving off dehydration. (Some salt in fluid helps the body absorb water.)

3. The article can’t determine whether the floodwater would cause dehydration or rehydration because it is difficult to ascertain the exact salt content of the floodwater. A sidebar explains how various factors could have increased or decreased its salinity. The water that flooded New Orleans may have come from the top of the lake, which is less salty than the bottom. The storm may also have diluted the floodwater. Either of these occurrences would have helped to lower the salinity of the floodwater. On the other hand, water from the Gulf of Mexico could have been blown in by Katrina, increasing the salinity of the floodwater. And Katrina could have churned the water in Lake Pontchartrain such that saltier water on the bottom of the lake got into the floodwater. Either of these occurrences would have made the floodwater more salty.