The world’s top producer of natural mineral water is struggling to keep its sources clean of contaminants, from pesticides to bacteria to animal fecal matter. If it filters its water it loses its designation as “natural” and most likely a lot of its business. Perrier is not alone; over 15% of Europe’s aquifers are dangerously polluted or over-exploited and things are getting worse. The World’s Gerry Hadden reports from Vergèze, France.