Editor’s note: This is part three of a four-part series on Agent Orange.

In 1991, Congress enacted the Agent Orange Act, giving the Department of Veterans Affairs the authority to declare certain conditions “presumptive” to exposure to Agent Orange/dioxin, making these veterans who served in Vietnam eligible to receive treatment and compensation for these conditions. The same law required the National Academy of Sciences to periodically review the science on dioxin and herbicides used in Vietnam to inform the secretary of Veterans Affairs about the strength of the scientific evidence showing association between exposure to Agent Orange/dioxin and certain conditions.

The list of “presumptive” conditions has grown since 1991, and currently the U.S. Department of Veterans Affairs has listed prostate cancer, respiratory cancers, multiple myeloma, type II diabetes mellitus, Hodgkin’s disease, non-Hodgkin’s lymphoma, soft tissue sarcoma, chloracne, porphyria cutanea tarda, peripheral neuropathy, chronic lymphocytic leukemia, and spina bifida in children of veterans exposed to Agent Orange as conditions associated with exposure to the herbicide. This list now includes B cell leukemias, such as hairy cell leukemia, Parkinson’s disease and ischemic heart disease. These three were added on Aug. 31, 2010.

Since 2017, the VA has added to the presumptive list. The Navy Blue Water Act that went into effect in 2019 has caused the VA to add more to the list. Several highly placed individuals in government are voicing concerns about whether some of the diseases on the list should, in fact, actually have been included.

In 2011, an appraisal of the 20-year-long Air Force Health Study that began in 1982 indicates that the results of the AFHS as they pertain to Agent Orange do not provide evidence of disease in the Operation Ranch Hand veterans caused by “their elevated levels of exposure to Agent Orange.”

The VA initially denied the applications of post-Vietnam C-123 aircrew veterans because as veterans without “boots on the ground” service in Vietnam, they were not covered under VA’s interpretation of “exposed.” In June 2015, the secretary of Veterans Affairs issued an interim final rule providing presumptive service connection for post-Vietnam C-123 aircrews, maintenance staff and aeromedical evacuation crews. The VA now provides medical care and disability compensation for the recognized list of Agent Orange illnesses.

The University of Hawaii has acknowledged extensive testing of Agent Orange on behalf of the United States Department of Defense in Hawaii, along with mixtures of Agent Orange on Kaua’i Island in 1967-68 and on Hawaii Island in 1966; testing and storage in other U.S. locations has been documented by the United States Department of Veterans Affairs.

In 1971, the C-123 aircraft used for spraying Agent Orange were returned to the United States and assigned various East Coast USAF Reserve squadrons, and then employed in traditional airlift missions between 1972 and 1982. In 1994, testing by the Air Force identified some former spray aircraft as “heavily contaminated” with dioxin residue. Inquiries by aircrew veterans in 2011 brought a decision by the U.S. Department of Veterans Affairs opining that not enough dioxin residue remained to injure these post-Vietnam War veterans. On Jan. 26, 2012, the U.S. Center for Disease Control’s Agency for Toxic Substances and Disease Registry challenged this with its finding that former spray aircraft were indeed contaminated and the aircrews were exposed to harmful levels of dioxin. In response to veterans’ concerns, the VA, in February 2014, referred the C-123 issue to the Institute of Medicine for a special study, with results released on Jan. 9, 2015.

In 1978, the EPA suspended spraying of Agent Orange in national forests. Agent Orange was sprayed on thousands of acres of brush in the Tennessee Valley for 15 years before scientists discovered the herbicide was dangerous. Monroe County, Tennessee, is one of the locations known to have been sprayed according to the Tennessee Valley Authority. Forty-four remote acres were doused with Agent Orange along power lines throughout the national forest.

In 1983, New Jersey declared a Passaic River production site to be a state of emergency. The dioxin pollution in the Passaic River dates back to the Vietnam era when Diamond Alkali manufactured it in a factory along the river. The tidal river carried dioxin upstream and down, tainting a 17-mile stretch of riverbed in one of New Jersey’s most populous areas.

A December 2006 Department of Defense report listed Agent Orange testing, storage, and disposal sites at 32 locations throughout the United States, as well as in Canada, Thailand, Puerto Rico, Korea, and in the Pacific Ocean. The Veteran Administration has also acknowledged that Agent Orange was used domestically by U.S. forces in test sites throughout the United States. Eglin Air Force Base in Florida was one of the primary testing sites throughout the 1960s.

In February 2012, Monsanto agreed to settle a case covering dioxin contamination around a plant in Nitro, West Virginia, that had manufactured Agent Orange. Monsanto agreed to pay up to $9 million for cleanup of affected homes, $84 million for medical monitoring of people affected, and the community’s legal fees.

On Aug. 9, 2012, the United States and Vietnam began a cooperative cleaning up of the toxic chemical on part of Da Nang International Airport, marking the first time the U.S. government has been involved in cleaning up Agent Orange in Vietnam. Da Nang was the primary storage site of the chemical. Two other cleanup sites the United States and Vietnam are looking at is Biên Hòa, in the southern province of Đồng Nai (a “hotspot” for dioxin) and Phù Cát airport in the central province of Bình Định, says U.S. Ambassador to Vietnam David Shear. According to the Vietnamese newspaper Nhân Dân, the U.S. government provided $41 million to the project. As of 2017, some 110,000 cubic meters of soil have been “cleaned.”

The Seabee’s Naval Construction Battalion Center at Gulfport, Mississippi, was the largest storage site in the United States for Agent Orange. It was 30 odd acres in size and was still being cleaned up in 2013.

In 2016, the EPA laid out its plan for cleaning up an 8-mile stretch of the Passaic River in New Jersey, with an estimated cost of $1.4 billion. The contaminants reached to Newark Bay and other waterways, according to the EPA, which has designated the area a Superfund site. Since destruction of the dioxin requires high temperatures over 1,000 degrees Celsius, the destruction process is energy intensive.