Rollins Edwards recalls the moment he was locked in a gas chamber and engulfed in a blister-forming chemical agent called mustard gas, but it wasn’t by the enemy. The 93-year-old World War II veteran, who is black, was part of the U.S. Department of Defense’s secret chemical weapons testing program – tests that were carried out based on soldiers’ race, according to a recent NPR investigation.

"They said we were being tested to see what effect these gases would have on black skins," Edwards, who lives in Summerville, South Carolina, told NPR. The defense department had previously admitted it conducted mustard gas experiments on U.S. soldiers, but this was the first time the Pentagon conceded that it grouped test subjects based on skin color. The investigation found that black, Japanese-American and Puerto Rican soldiers were often the subjects of tests involving mustard gas and lewisite, another chemical agent that caused blistering and lung irritation, while white soldiers were generally used as the control groups.

"You had no choice. You did not know where you were going. They didn't tell you anything," Edwards told the Independent. He added that his injuries were “still causing me problems even now. It's very itchy. I doubt it will ever go away."

African-Americans have fought in every war in U.S. history, but they haven't always  been treated equally. Black soldiers were typically separated from white soldiers, living in segregated units, including during World War II. About 125,000 African-Americans served overseas between 1939 and 1945.

Federal officials broke their silence on the military’s secret chemical testing in 1991, admitting that they tested chemical agents on soldiers. The experiments involved patch tests, in which liquid mustard gas was dropped directly onto a soldier’s skin, field tests and gas chamber tests, according to NPR.

In 2002, the defense department came clean about its testing nerve gas on Navy sailors in the 1960s. The gas was pumped into the ventilation system of the USS George Eastman, according to documents released by the Pentagon that year. Monkeys were also used as test subjects.