[Industrialized countries] Tap water is one of the best examined foodstuffs, and one of the most strictly regulated. Each day in any average city in the developed world, hundreds of laboratory tests are carried out. European legislation, for example, contains no less than 61 paragraphs that have to be observed by water distributors. Home filters and purification systems are not only superfluous and expensive, some of them can be even dangerous. No filter is free of microbes when is not properly rinsed and maintained. Bottled water may contain undesirable levels of salts or may come from a source equipped with less stringent quality controls.