56 years after the U.S. began spraying Agent Orange over Vietnam, its victims still face skepticism from both governments.

As a teenage soldier during the Vietnam War, Pham Van Tieu walked through countless jungles covered in dioxin. He and his comrades knew it was a herbicide, but they had no idea that its effects would last for generations.

Tieu’s family of 12 live in a house of around 20 square meters (215 square feet) in Ung Hoa District on the outskirts of Hanoi. He and his wife managed to find wives for both of their sons through marriage brokers, despite their medical problems.

They both have epilepsy that causes convulsions once in a while. “Even at their best they are slow,” a family member said. One of them, now 35, married a woman nearly 10 years his senior after meeting her just twice.

The other son’s wife had never met him and had no idea about his condition before becoming part of the family.

The couples have had six children. Two of them are sitting first grade for the second and third times because they are still unable to write. Another four-year-old child still soils himself.

Pham Van Tieu's family in their house on the outskirts of Hanoi.

Many neighbors believe the dioxin effect has spread to the third generation of the family, but the Vietnamese government disagrees. Only Tieu and his sons have been identified as victims of Agent Orange, which entitles them to monthly support of up to around VND1.7 million ($74).

Vietnamese officials say they face technical challenges identifying the impacts of dioxin on third generation children. Minister of Labor, Invalids and Social Affairs Dao Ngoc Dung admits there is a chance that there could be long-term impacts and wants to put them all on the benefits register.

But that depends on when and whether the health ministry will be able to establish a link between their conditions and dioxin, which has been difficult even for the first generation. In 2008, the health ministry issued a list of 17 diseases and disabilities it had linked to dioxin, but that list has never been updated.

On the other side of the Pacific, the U.S. government has maintained that there is no clear link between Agent Orange and the myriad health problems. It has instead provided assistance to Vietnamese people with disabilities regardless of the cause.

Between 1961 and 1971, the U.S. Army sprayed some 80 million liters of Agent Orange over 30,000 square miles of southern Vietnam.

Dioxin, a highly toxic chemical in the defoliant, stays in the soil and at the bottom of lakes and rivers for generations. It can enter the food supply through the meat of fish and other animals, and has been found at alarmingly high levels in breast milk.

Between 2.1 to 4.8 million Vietnamese citizens were directly exposed to Agent Orange and other chemicals that have been linked to cancers, birth defects and other chronic diseases during the Vietnam War that ended in April 1975, according to the Vietnam Red Cross.

The Vietnamese Association of Victims of Agent Orange believes there are tens of thousands of third-generation victims of dioxin in Vietnam, but none of them have been officially recognized, and thus are not entitled to support.

The U.S. and Vietnam have yet to conduct a joint study on the health effects of Agent Orange on human beings. In 2003, the two countries attempted to conduct a study of birth defects in children whose mothers were exposed to Agent Orange.

But with Vietnamese and American scientists at odds on how to conduct the $1 million project, the deadline for funding from the U.S. National Institute on Environmental and Health Sciences expired before the work could get started.

A leaked unclassified U.S. embassy memo written in 2003 exhibited the skepticism that has perpetuated America's position on the issue.

"The Embassy advocates taking a straightforward approach to counter the Vietnamese propaganda campaign that hinges on non-scientific, but visually effective and emotionally charged, methodology aimed at laying blame on the [US government]," said the memo, posted on a number of credible Agent Orange-related websites including the War Legacies Project, a Vermont-based nonprofit whose main focus is to address the long term health and environmental consequences of Agent Orange.

"Allegations of adverse impacts of Agent Orange/dioxin on health are grossly exaggerated and unsupported by any objective measure," the memo said.

The U.S. has thus blamed Vietnam for stalling progress on conducting across-the-board studies on the true extent of the health effects of Agent Orange.

"We believe the [Vietnamese government] will never permit research that in any way might discredit the main theme of its two-decade long propaganda campaign, i.e., Agent Orange/dioxin is to blame for a huge range of serious health problems, especially birth defects and mental retardation," the memo said.

But David Carpenter, who received the U.S. grant to conduct the ill-fated 2003 study, offered a different view.

"The U.S. has never acknowledged that the birth defects seen in Vietnam are due to Agent Orange exposure," said Carpenter, the director of the University at Albany's Institute for Health and the Environment.

"I thought at the time and still think that it really was that our government did not want to know the long term effects of Agent Orange exposure," Carpenter said.

"This is, in my judgment, why they cancelled my grant to study the relationship between Agent Orange exposure and birth defects seen in new births, not just those 30 or more years ago."

Pham Van Tieu's daughter-in-law and his grandchildren in their house on the outskirts of Hanoi.

Meanwhile, the U.S. has come to acknowledge a number of conditions and diseases associated with Agent Orange exposure in its own veterans and has thus compensated them accordingly. It refuses to do so for the Vietnamese who were on the receiving end of the toxic rain.

Some American veterans have expressed sympathy toward their Vietnamese counterparts, and bitterness toward their own government for the perceived injustice. To them, it is "hypocritical" for the U.S. to place this unnecessary burden of proof on the Vietnamese while it does not do so for its own veterans.

"The U.S. government refuses to compensate Vietnamese victims of chemical warfare because to do so would mean admitting that the US committed war crimes in Vietnam," said Fred Wilcox, author of Scorched Earth: Legacies of Chemical Warfare in Vietnam, the first book of testimonies from Vietnamese victims of Agent Orange.

"This would open the door to lawsuits that would cost the government billions of dollars," Wilcox said.

Trinh Tran Nam Dat with his mother in their house on the outskirts of Hanoi.

Trinh Tran Nam Dat, whose grandfather fought in the war and died of cancer in 1998, lies all day in a room filled with the smell of his own urine.

The 17-year-old was born with cerebral palsy, something the family was completely unprepared for.

He cannot speak or sign. His only form of communication is smiling when he’s happy and tensing up his muscles when he feels uncomfortable.

His family believes that Agent Orange is the culprit, but officials in the neighborhood have advised them not to waste time looking for an answer.

They have listed him as a disabled person, a title that affords him VND800,000 ($35) in monthly support.

Tan, another veteran who did not want to reveal his full name, does not blame the U.S. or the Vietnamese government, even though his son is blind and his granddaughter is also losing her sight.

He carries the burden himself.

“I blame myself for giving birth to them and making them suffer,” he said.