Water fluoridation
Health and dental organizations worldwide have endorsed its safety and effectiveness. Its use began in 1945, following studies of children in a region where higher levels of fluoride occur naturally in the water. Further research showed that moderate fluoridation prevents tooth decay.
2000 Flushes
In October 1993, toilet fixture manufacturers reported rapid degradation of flush valve flappers; some new, water-saving toilets (introduced to meet a 1994 US federal water conservation deadline) were leaking within months of installation. The growing popularity of in-tank drop-in cleaning tablets quickly drew suspicion as many contain chlorine bleach; if a toilet is flushed infrequently, the amount of chlorine in the tank may build to problematic levels. The Metropolitan Water District of Southern California (MWD) began tests of flapper materials in 1994-1997. By 1998, flappers had been redesigned to withstand continuous immersion in 2000 Flushes or Clorox bowl cleaners, then the most popular products. A rival in-tank cleaner introduced by Vanish in 2000 caused problems until new durability and marking requirements for flappers were added to the ASME A112.19.5 standard in 2005.