JEFFERSON CITY, Mo. (AP) – Missouri Sen. Claire McCaskill is pushing a bill she says is aimed at helping World War II veterans exposed to mustard gas.

McCaskill on Tuesday announced legislation to require federal agencies to reconsider disability claims denied to those veterans.

The Democrat says the military tested the effects of mustard gas and the blister agent lewisite on about 60,000 service members by the end of WWII.

Those veterans were sworn to secrecy until 1991. Since then, McCaskill says some have struggled to receive compensation for health issues caused by exposure.

McCaskill’s office says about 90 percent of applicants for benefits have been denied by the Veterans Affairs Department. They estimate a couple hundred veterans are still alive.

Requests for comment by The Associated Press to the federal agency weren’t immediately returned.