Perchlorate, a chemical used in rocket fuel, is turning up in the nation's food -- in vegetables like lettuce and spinach -- and water supply.

You've never heard of it? Most Americans haven't, but millions have been exposed to it. This week Congress held hearings to determine just how dangerous it is to humans' health.

"A study from the Centers for Disease Control last year tested almost 3,000 people who are representative of the U.S. population. They found perchlorate in every single person," said Dr. Anila Jacob of the Environmental Working Group.

so how did something used to launch inter-continental missiles and the space shuttle find its way into our homes?

At a hearing of the House Committee on Energy and Commerce this week, a government report was made public for the first time revealing that at sites in more than 25 states, perchlorate had leaked into the drinking water and soil. About 65 percent of that contamination was attributed to the Department of Defense and to NASA.

The Pentagon said it has invested "over $114 million in research related to perchlorate toxicity," and that they are "developing substitute chemicals."

Doctors agree that large amounts of the chemical can lead to thyroid problems in adults and abnormal brain development in children, but it is still unknown how much damage smaller amounts can inflict.

"The developing fetus can have severe inhibition of brain development as a result of perchlorate intake by the mother through drinking water or through breast milk," Rep. Albert Wynn, D-Md. said.

Democrats on Capitol Hill are working on a bill that would require the EPA for the first time to set strict guidelines limiting the amount of perchlorate in the nation's drinking water.

For now, more research is being done to determine if the amounts present today can cause any serious damage to people's health.