Can you define safe water?

[music fades in]

Welcome to CoreFacts, where we're always short on time and big on science. I'm Jessica Robertson. Today's question is about your safety.

Can you define safe water?

Safe water means water that will not harm you if you come in contact with it. The most common use of this term applies to drinking water, but it could also apply to water for swimming or other uses. To be safe, the water must have sufficiently low concentrations of harmful contaminants. The list of harmful contaminants includes bacteria, viruses, pesticides, petroleum products, some metals and metalloids, strong acids, and many more substances.

In comparison to such other activities, drinking U.S. public tap water, or any of the bottled waters, or water from most domestic wells, is safe. These waters might come from wells or springs that tap shallow or deep aquifers, from rivers or lakes, or glaciers, fog collectors, or even from rain-water collectors. Most of these waters are filtered and treated to kill microbes and keep contaminants at safe levels.

It is important to keep in mind that water can be safe for one person and may be unsafe for another. If your immune system is weak, you are a young child or an elderly person, or you are pregnant or a nursing mother, you are more susceptible to contaminants in drinking water than the rest of the population.

And now you know. Join us every week for a new CoreFact. If you have questions you think we should answer on the air, email it to us at corefacts@usgs.gov or leave us a voicemail at 703-648-5600. Remember, long distance fees do apply.

CoreFacts is a product of the U.S. Geological Survey, Department of the Interior.

[music fades out]