During the Vietnam war, the US military launched Operation Ranch Hand, in which it employed several herbicides to kill the dense tree canopies that concealed the North Vietnamese supply routes, nicknamed the Ho Chi Min trail. One of the most infamous chemicals used was Agent Orange, a potent defoliant which contains the harmful chemical dioxin.

Unbeknownst to the Soldiers, Sailors, and Airmen who handled the chemical or who were exposed to it, Agent Orange and dioxin are now known to cause “reproductive and developmental problems, cancer, as well as damage to the immune system, and can interfere with hormones,” according to a report from the World Health Organization (WHO). In total, 20 million gallons of the herbicide were dropped over 4.5 million acres of Vietnam between 1961 and 1971, according to a report from History.com.

Several Vietnam veterans have developed illnesses that are directly related to their exposure to Agent Orange. According to the Veterans Administration (VA) any service member who served in Vietnam “between January 9, 1962 and May 7, 1975” is automatically assumed by the federal government to have come into contact with either Agent Orange or other similarly harmful herbicides.

Although the chemical, manufactured by Monsanto, is no longer used by the military, many veterans are still fighting for compensation for illnesses they say are related to Agent Orange exposure.

According to Business Insider, more than 10,000 US Navy veterans who served aboard ships off the coast of Vietnam during the war are currently claiming that they were exposed to the chemical, and are asking for compensation. The VA, however, has thus far determined that their medical conditions are not related to Agent Orange, and that they were not exposed to the herbicide during their wartime deployments.

“Science does not support the presumption that blue water Navy veterans were exposed to Agent Orange,” said Robert Wilkie, the current Secretary of the Department of Veterans Affairs.

However, a new bill sponsored by David Valadao, a Republican Congressman from California, is hoping to bring Navy veterans who served off the coast of Vietnam under the protection of the VA. According to Business Insider, the bill, H.R.299 – Blue Water Navy Vietnam Veterans Act of 2017, has widespread support in the house, as well as support from former VA Secretary Dr. David Shulkin.

“As Secretary, I was faced with the dilemma of what to do when there was insufficient evidence to make a reasonable conclusion,” Shulkin stated in a letter addressed to Senate. “I stated then — and continue to believe — that in the absence of reliable data to guide a decision, the answer must not be to simply deny benefits. When there is a deadlock, my personal belief is that the tie should be broken in favor of the brave men and women that put their lives on the line for all of us.”

If the bill passes the Senate and eventually becomes law, it is expected to cost the VA around $5.5 billion to provide benefits to the affected veterans. The department as spent hundreds of millions of dollars over the last two decades on Agent Orange disability claims.