ST. LOUIS — Three members of Congress are demanding answers after a St. Louis scholar's new book revealed details of secret Cold War-era U.S. government testing in which countless unsuspecting people, including many children, pregnant women and minorities, were fed, sprayed or injected with radiation and other dangerous materials.

The health ramifications of the tests are unknown. Lisa Martino-Taylor, an associate professor of sociology at St. Louis Community College who wrote "Behind the Fog: How the U.S. Cold War Radiological Weapons Program Exposed Innocent Americans," acknowledged that tracing diseases like cancer to specific causes is difficult.

But three House Democrats who represent areas where testing occurred — William Lacy Clay of Missouri, Brad Sherman of California and Jim Cooper of Tennessee — said they were outraged by the revelations.

Martino-Taylor used Freedom of Information Act requests to obtain previously unreleased documents, including Army records. She also reviewed already public records and published articles. She told The Associated Press that she found that a small group of researchers, aided by leading academic institutions, worked to develop radiological weapons and later "combination weapons" using radioactive materials along with chemical or biological weapons.

Her book, published in August, was a follow-up to her 2012 dissertation, which found that the government conducted secret testing of zinc cadmium sulfide in a poor area of St. Louis in the 1950s and 1960s. The book focuses on the mid-1940s to the mid-1960s.

An Army spokeswoman declined to comment, but Martino-Taylor's 2012 report on testing in St. Louis was troubling enough to trigger an Army investigation. The investigation found no evidence that the St. Louis testing posed a health threat.

Martino-Taylor said the offensive radiological weapons program was a top priority for the government. Unknowing people in places throughout the U.S., as well as parts of England and Canada, were subjected to potentially deadly material through open-air spraying, ingestion and injection, Martino-Taylor said.

"They targeted the most vulnerable in society in most cases," Martino-Taylor said. "They targeted children. They targeted pregnant women in Nashville. People who were ill in hospitals. They targeted wards of the state. And they targeted minority populations."

The tests in Nashville in the late 1940s involved giving 820 poor and pregnant white women a mixture during their first pre-natal visit that included radioactive iron, Martino-Taylor said. The women were chosen without their knowledge. Blood tests were performed to determine how much radioactive iron had been absorbed by the mother, and the babies' blood was tested at birth. Similar tests were performed in Chicago and San Francisco, Martino-Taylor said.

Cooper's office plans to seek more information from the Army Legislative Liaison, said spokesman Chris Carroll.

Among those who recall the testing is Mary Helen Brindell, 73. She was playing baseball in a St. Louis street in the mid-1950s when a squadron of green planes flew so low overhead that she could see the face of the lead pilot. Suddenly, the children were covered in a fine powdery substance that stuck to skin moistened by summer sweat.

Brindell has suffered from breast, thyroid, skin and uterine cancers. Her sister died of a rare form of esophageal cancer.

"I just want an explanation from the government," Brindell said. "Why would you do that to people?"

Clay said he was angered that Americans were used as "guinea pigs" for research.

"I join with my colleagues to demand the whole truth about this testing and I will reach out to my Missouri Delegation friends on the House Armed Services Committee for their help as well," Clay said in a statement.

St. Louis leaders were told at the time that the government was testing a smoke screen that could shield the city from aerial observation in case of Soviet attack. Evidence now shows radioactive material, not just zinc cadmium sulfide, was part of that spraying, Martino-Taylor said.