EPA revises guidelines on perchlorate in drinking water; says it's safe to drink rocket fuel

• Adults can tolerate nearly 25 times more of the potentially toxic chemical perchlorate in their drinking water than previously thought, the U.S. Environmental Protection Agency said on Friday.
• The announcement marks the first time the EPA has issued an official guideline on how much perchlorate humans can safely ingest.
• Environmental groups have been pushing for such guidelines since 1997, when the chemical -- commonly used in rocket fuels and explosives -- was found to contaminate water sources nationwide.
• More recently, perchlorate has been detected in the majority of the nation's milk and lettuce supply.
• Based on the assumption that a 70-kilogram (154-pound) adult drinks 2 liters of water each day, the EPA estimates that 24.5 parts of perchlorate to 1 billion parts of water is a safe limit for water quality.
• The figures are based on a report by the National Academy of Sciences, which examined several studies on the effects of perchlorate in humans and rats.
• The EPA said it will use the first figure -- 0.7 micrograms per kilogram per day -- to help determine the level of cleanup necessary at contaminated Superfund sites.
• The second figure -- 24.5 parts per billion -- will be used to guide further discussions about an official standard for water quality.
• This worries many environmental groups that have been pushing for a standard as low as 1 ppb, which they say would protect those who are most likely to be affected by perchlorate.
• The aerospace and defense industries argue that an unnecessarily low limit could cost them billions of dollars in excess cleanup costs.
• Most of the perchlorate contamination in the United States has come from leaks or dumps at aerospace and defense sites, according to the National Academy of Sciences.