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.