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Letters from the March 22, 2008, issue of Science News

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1:45pm, March 17, 2008
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The price of water

In reference to the article "Going Down: Climate change, water use threaten Lake Mead" (SN: 2/23/08, p. 115), scarcity requires society to allocate. Usually markets do a better job than law at allocating efficiently and fairly. Lake Mead could remain full to the brim regardless of pending climate change. The quoted "demand" for 16.6 km3 of Lake Mead water in Southern California and Arizona is not some fixed biological imperative but an artifact of absurdly low water prices. At these low prices, people take 20-minute showers, hose off their driveways, use 5 or more gallons of water to flush their toilets, top off their swimming pools, flood or sprinkler irrigate their lawns, etc. Raise the price, and these uses disappear voluntarily. At the right price, Lake Mead remains full.

Kendrick Miller
Aptos, Calif.

Beneficial bacteria

The article "Swell, a Pain Lesson: Gut microbes needed for immune development" (SN: 2/16/08, p. 101), by Tina Hesman Saey, offers a mechanism to explain the hygiene hypothesis featured prominently in past issues of Science News. If exposure to microbes has a beneficial effect on the immune response of mice, it may also help humans as well. The relatively antiseptic environments that many Western children experience today as compared to the past may explain the skyrocketing incidence of diseases like asthma.

Simcha Pollack
Queens, N.Y.

It is true that the hygiene hypothesis—that modern cleanliness throws our immune systems out of balance because of less exposure to microbes early in life—has been used to explain rising asthma and allergy rates. However, it doesn't apply to the recent study, which focused on intestinal bacteria. There is little reason to think that people have fewer bacteria in their intestines now than they did in the past.—Tina Hesman Saey

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