U.S. Air Force personnel who conducted aerial spray missions of the Agent Orange herbicide during the Vietnam War were twice as likely to have a disorder that can lead to a type of blood cancer, says a new study published in JAMA Oncology online Sept. 3.
This is the first study to uncover an association between exposure to Agent Orange and multiple myeloma among Vietnam veterans.
Previous research showing an association between similar herbicides and multiple myeloma examined agricultural workers in the United States and Canada.
“We have, for the first time, biological evidence of a connection between this particular cancer and exposure to Agent Orange and its dioxin contaminant,” said Joel Michalek, a professor of biostatistics at San Antonio’s University of Texas Health Science Center and an author on the paper.
Multiple myeloma is a relatively rare blood cancer that can damage the kidneys and other organs, weaken bones and cause high calcium levels in the blood, the National Cancer Institute says. Agent Orange has been linked to other cancers and diseases, including Type 2 diabetes.
U.S. Air Force personnel sprayed Agent Orange from aircraft to destroy forests and foliage that provided enemy cover in Vietnam from 1962 to 1971 as part of the Operation Ranch Hand program.
The study examined blood samples collected and stored in 2002 from 479 Ranch Hand veterans and compared them to blood samples from 479 veterans who served in Southeast Asia during the same time period but weren’t involved in the aerial spray missions.
Researchers found a 2.4-fold increased risk for a condition called monoclonal gammopathy of undetermined significance, a precursor disease for multiple myeloma, in the Ranch Hand veterans compared to the other veterans.
Of 479 Ranch Hand veterans, 34 of them, or 7.1 percent, had the precursor for the cancer, compared to 15 of 479, or 3.1 percent, in the other veterans.
The majority of people with the multiple myeloma precursor do not develop the cancer, but previous research has shown multiple myeloma is consistently preceded by that blood disorder, said Dr. Ola Landgren, a hematologic oncologist at Memorial Sloan Kettering Cancer Center in New York and the study’s lead author.
Agent Orange contains a contaminant called TCDD, which the Environmental Protection Agency classifies as a probable human carcinogen.
The study found the veterans who’d been exposed to Agent Orange and had developed the precursor had significantly higher levels of TCDD in their blood, making the results of the study “more meaningful,” Dr. Nikhil C. Munshi, a physician with the Dana-Farber Cancer Institute, wrote in an editorial accompanying the study. The risk increases as the concentration of TCDD in the blood increases.
Not all Air Force personnel involved in Operation Ranch Hand had the same level of exposure to Agent Orange, Michalek said.
“The pilots were probably the least exposed because they’re like the truck drivers,” Michalek explained. “The guys who got it the worst were the enlisted ground crew who had to fill the tanks, sit in the back of the plane, operate the spray equipment.”
Army ground troops in the jungles of Vietnam, crew members on boats and ships and other service members also may have been exposed.
“There’s a controversy going on even now as to who was exposed in Vietnam and who wasn’t and by how much,” Michalek said.
The research was conducted from 2013 to 2014 using specimens and exposure data collected by the Air Force Health Study. That 25-year study, headquartered at the now-closed Brooks AFB, examined the health effects of Agent Orange on Vietnam veterans and their children. Michalek headed the study for about 10 years before it ended in 2005.
More than 80,000 biological specimens from the study later were sent to Wright-Patterson AFB in Dayton, Ohio, where researchers continue to have access to the materials.
Jack McManus, an Operation Ranch Hand veteran who participated in the Air Force Health Study, wasn’t surprised to learn about the association between Agent Orange and multiple myeloma. He believes insufficient research has been conducted on the stored specimens.
“I think there are multiple more diseases that we’re going to find,” said McManus, 69, who lives in North Carolina and who works with the nonprofit Vietnam Veterans of America to advocate for veterans exposed to Agent Orange. “I think what we’re going to get is bits and pieces of information coming out for many, many years.”
Veterans exposed to Agent Orange during military service may be eligible to receive disability compensation from the Veterans Affairs Department for diseases associated with that exposure, including multiple myeloma.