If you think issues of uncleanness are limited to the ancient world, consider this cover story headline last year from an issue of U.S. News & World Report: "The Future of Water: Costly - Dirty - Scarce."

The article began with an account of dirty water in Atlanta, where in some neighborhoods it had been flowing brown from the tap. From time to time, "boil water" advisories had been issues to let residents know the water was not safe to drink. The situation may grow worse as 700,000 miles of aging pipes and mains throughout America decay and reach the end of their life spans. One federal official called clean water "the biggest environmental issue that we face in the 21st century."

-Today in the Word, p.20