Agent Blue: When the US Poisoned Vietnam’s Rice Fields

By Joe Marzo

In the vast catalog of chemical warfare, few names are as notorious as Agent Orange. Its association with dioxin contamination, cancer, and birth defects has rightfully earned it infamy. But buried beneath the headlines and public outrage lies a quieter, deadlier legacy—one less talked about, but arguably just as devastating. This is the story of Agent Blue: the rice killer, the arsenic-laced herbicide that salted the earth of Vietnam and left behind a toxic shadow that lingers to this day.

A Different Kind of Weapon

While Agent Orange was designed to strip trees and jungle foliage bare—denying enemy forces concealment in the thick canopies of Southeast Asia—Agent Blue had a simpler and more sinister purpose: starvation.

The United States military, frustrated by its inability to isolate and defeat the Viet Cong in

the dense rural countryside, came to a chilling conclusion: if they couldn't locate the enemy, they could destroy what the enemy lived on.

And in Vietnam, that meant rice.

Agent Blue was composed primarily of cacodylic acid and sodium cacodylate—both organic arsenic compounds. These ingredients were chosen not because they were the most effective at defoliating jungle, but because of their potency in killing narrow-leaf plants—especially rice. Sprayed in concentrated doses, Agent Blue dried out rice stalks from the inside out, rendering entire fields unusable within days.

This wasn’t just a side effect of war. It was the goal.

From the Sky: Chemical War on Food

Between 1962 and 1971, over 4.6 million liters of Agent Blue were sprayed by U.S. aircraft as part of Operation Ranch Hand, the Air Force’s herbicidal warfare campaign. Another estimated 3 million liters were used by the South Vietnamese Army in tandem with the CIA.

These chemicals were dumped over the most fertile areas of South Vietnam, especially in the Mekong Delta, where lush rice paddies once fed not only the Viet Cong but also millions of civilians.

Low-flying UC-123 planes painted silver streaks across the sky, dispensing fine chemical mists over waterlogged paddies. These missions, conducted in clusters, were methodical and relentless. Sometimes rice fields were sprayed just weeks before harvest. The message was clear: starve the fighters—and starve their families too.

What made Agent Blue particularly insidious was that it didn’t just kill plants. It stayed behind, seeping into the water table, poisoning the soil, and infiltrating the very infrastructure of Vietnam’s agricultural system. It was not a bomb with a blast radius. It was a slow, silent decay—a poison with a long memory.

Toxic by Design

Unlike Agent Orange, whose dioxin content caused deformities and cancers due to its persistence in fatty tissues, Agent Blue’s danger lay in its arsenic base—a known carcinogen and toxic metal.

The U.S. military insisted that the compound was safe when used as directed. But the conditions in which Agent Blue was deployed couldn’t have been further from a laboratory setting. Vietnamese farmers were never warned. Children played in puddles. Water buffalo drank from ditches. People lived, ate, and bathed in areas that had been saturated with the chemical.

And unlike the thick jungle areas targeted by other agents, Agent Blue was deployed directly onto food crops, into the lifeblood of rural Vietnamese society.

The impact? Immediate food shortages. Starvation. Livestock deaths. And over time—diseases that could not be easily traced, because arsenic poisoning is rarely dramatic. It mimics other illnesses. It accumulates slowly. It kills quietly.

The Lingering Legacy

Fifty years later, many of the areas most heavily sprayed with Agent Blue are still struggling. Arsenic remains in the soil and water, especially in the delta regions, where high water tables and porous soil make contamination difficult to contain.

A study published in the 2000s found elevated levels of arsenic in well water in regions like An Giang and Dong Thap provinces, where Agent Blue was used most heavily. Prolonged exposure to arsenic has been linked to skin lesions, diabetes, neurological problems, cardiovascular diseases, and a range of cancers—including lung, bladder, and kidney.

Children born decades after the war still suffer the consequences. Families who rely on subsistence farming in contaminated areas unknowingly ingest trace amounts of arsenic with each meal. The soil refuses to forget.

Meanwhile, cleanup efforts have lagged far behind those focused on Agent Orange. Much of the international attention and funding has targeted dioxin contamination near former U.S. bases like Bien Hoa and Da Nang. But arsenic? It's harder to isolate. Harder to track. And, some might argue, easier to ignore.

The Unspoken Crime

What makes Agent Blue particularly troubling from an ethical standpoint is that it was never really about the jungle. It wasn’t about revealing enemy hideouts or cutting supply routes. It was about targeting food—weaponizing hunger.

While military leaders argued that such tactics were necessary to defeat a guerilla force embedded in the civilian population, humanitarian observers saw it differently. In the eyes of many, Agent Blue constituted a violation of international norms—even if those norms had not yet been codified in treaties. Destroying civilian food sources en masse is a war crime in principle, if not always in name.

It is no stretch to call Agent Blue’s deployment a form of ecocide. It represents the use of science and military strategy to not just kill an enemy—but to poison the land itself. To destroy not just the fighter, but the field he came from. And in doing so, it blurred the lines between soldier and civilian in horrifying ways.

A Legacy That Demands Acknowledgment

Despite its scale and impact, Agent Blue remains largely forgotten in the popular memory of the Vietnam War. Few outside the military or chemical industries know its name. Even among veterans, Agent Orange dominates discussions of herbicide exposure.

But that silence must be broken.

For the people of Vietnam, for the families still drinking tainted water and tilling poisoned fields, and for the U.S. veterans who handled those barrels or flew those missions without understanding the long-term risks, the story of Agent Blue must be told.

It was a weapon engineered not for firepower or explosion, but for famine and fallout.

And its damage, while often invisible, may last longer than any battlefield scar.

Sources

Stellman, Jeanne Mager, et al.“The Extent and Patterns of Usage of Agent Orange and Other Herbicides in Vietnam.” Nature, vol. 422, no. 6933, 2003, pp. 681–687.https://www.nature.com/articles/nature01537

Vietnam Red Cross EstimatesOfficial estimates regarding health impacts from herbicide exposure.https://www.un.org/press/en/2006/sgsm10341.doc.htm

National Museum of the U.S. Air Force – Operation Ranch Handhttps://www.nationalmuseum.af.mil/Visit/Museum-Exhibits/Fact-Sheets/Display/Article/195955/down-in-the-weeds-ranch-hand/

U.S. Department of Veterans Affairs – Agent Orange and Other Herbicideshttps://www.publichealth.va.gov/exposures/agentorange/locations/vietnam.asp

Koppe, Janna G., et al.“Environmental Pollution and Human Birth Defects.” Environmental Health Perspectives, vol. 104, suppl. 4, 1996, pp. 653–658.https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1469343/

Schecter, Arnold, et al.“Agent Orange and the Vietnamese: The Persistence of Toxicity.” American Journal of Public Health, vol. 81, no. 5, 1991, pp. 611–615.https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1405177/

SCIRP Journal: Open Journal of Soil Science“Arsenic Legacy in the Soils of the Mekong Delta Due to Agent Blue Herbicide Use.”https://www.scirp.org/journal/paperinformation.aspx?paperid=123596

Asia Times – “Vietnam’s Other Chemical Legacy: Agent Blue”https://asiatimes.com/2024/10/vietnam-chemical-warfares-secret-toxic-legacies-agent-blue/

CounterPunch – “The Quiet Agent: Revisiting Agent Blue in Vietnam”https://www.counterpunch.org/2024/10/28/vietnam-chemical-warfares-secret-toxic-legacies-agent-blue/