The U.S. Environmental Protection Agency plans to set a limit on the amount of the chemical perchlorate and other toxic contaminants in drinking water. This will reverse a 2008 decision made the George W. Bush administration.
Perchlorate is used in fireworks, road flares, and rocket fuel. It may be also present in bleach and some fertilizers. Research indicates that it can affect your thyroid and disrupt the development of fetuses and infants.
According to CNN:
"... [M]onitoring data shows more than 4 percent of public water systems have detected perchlorate and between 5 and 17 million people may be served drinking water containing it, the EPA said. The decision was made after considering input from nearly 39,000 public comments".