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(Fortune Magazine) -- Problem: Unclean drinking water can be deadly.

Solution: A portable filter.

For the world's poorest, water isn't just a life-sustaining resource: It's also a killer. According to the United Nations, about 1.8 million children worldwide die every year from diarrhea caused by polluted water. Fortunately, unlike other intractable world problems, the solution is clear: Water sources are plentiful, just not always drinkable. Enter LifeStraw--a simple plastic tube filled with carbon and other filters that remove deadly particles and 99% of bacteria like salmonella. It works, as you'd expect, like a straw: Just suck from the source, whether it's a swampy stream or aging lead pipes, and get clean water. Each LifeStraw can filter 700 liters before it needs to be replaced--enough for about a month of daily drinking water.

But the qualities that make LifeStraw a great humanitarian tool--like its cost of just $3 per unit--also make it a great consumer product. At least that's the hope of Switzerland's Vestergaard-Frandsen, a former textile maker that now sells lifesaving products like LifeStraw and mosquito nets. Right now LifeStraws are bought only by charitable agencies. But Vestergaard hopes to bring in small local businesses as distributors, which might then help turn the world's poor into consumers.

FOR MORE INFO Go to lifestraw.com.