PHNOM PENH (The Phnom Penh Post/Asia News Network) - When Mr Va Savorn was around 10 years old, he stepped outside of his home and watched three planes swoop low over the flatlands of Svay Rieng province, leaving behind a trail of white dust.

"The land around my house was very flat so I could see very far and very clearly," Mr Savorn recalled recently, adding that the planes were about 20km away.

"Our village elders did not tell us it was a chemical; they thought it was just gasoline or water," said Mr Savorn, now an elder himself in the village of Svay Ta Plauk, in Svay Chrum district's Bassac commune.

Only years later would Mr Savorn come to realise he was likely witnessing an American defoliant spraying mission, similar to the thousands of flights that crisscrossed Vietnam and Laos over the course of a decade - the effects of which, more than 40 years later, are still being felt.

During America's war in Vietnam, millions of gallons of the defoliant Dioxin, also known as Agent Orange, were dumped across the Vietnamese countryside. The chemical, and others like it, were sprayed as part of Operation Ranch Hand, which took place between 1962 and 1971. The official purpose of the operation was to kill trees and crops, depriving guerrilla Viet Cong soldiers of forest cover and food sources.

The unintended consequence, however, was the exposure of four million Vietnamese citizens to a chemical nobody fully understood, and one which has now been linked to severe birth defects in the children and grandchildren of those exposed.

Official US government records from Operation Ranch Hand show that the herbicide spraying missions crossed over the border into Cambodia's Svay Rieng province, although very little research has been done on the effects.

Mr Pov Soun, the village chief in Svay Ta Plauk, was a soldier in his 20s at the time, stationed in the neighbouring district of Svay Tiep.

"Three airplanes swerved overhead, dipping down, and we saw some white powder pour of out of the airplanes," Mr Soun recalled."We were hiding in dug-out trenches. Around 500 metres from us, we saw the spray. It was so white," he said. "We didn't know what exactly it was, but based on our assumptions, no one ever dumped water, just chemicals."

Mr Soun said the chemical had no smell, but the airplanes sounded like tearing clothes.Immediately after spraying the area, bombs were dropped.

"The trees burned," Mr Soun said, explaining that the village had been evacuated before the spraying, and no people were allowed to return for over a month.

In Svay Tiep district, an uncharacteristically well-paved road leading to the Vietnamese border gives way to familiarly bumpy side streets. One of these narrow lanes ushers visitors to the home of Mr Kim Khen, the 68-year-old chief of Koki Som commune.

As a pair of surly dogs stalked up and down the driveway, surrounded by the green of banana trees, Mr Khen sat with his wife and other villagers and described the day Koki Som took a direct hit from a mysterious substance during what he called the "American war".

"I saw it myself, the spraying. In the morning, when we got up, we saw it on the leaves like dewdrops. It irritated our eyes and the leaves fell off the trees," Mr Khen remembered. "We drank water from the well; we didn't really think about hygiene at that time. The leaves fell off after three or five days. I think it was in 1970," he continued.

Ms Susan Hammond, founder and director of the War Legacies Project (WLP) research organisation, described the spraying of Agent Orange in similar terms the day before Post Weekend visited Svay Rieng.

"If the area itself was sprayed, you would hear stories from the population about planes that came in low and sprayed chemicals (often 3 or 4 planes at a time)," she said via e-mail. "They may have been accompanied by a spotter plane that was armed to hit ground fire. Then several days later the leaves would drop," she said via e-mail.

Ms Hammond also supplied Post Weekend with photographs of deformities typically associated with Agent Orange.

When shown Ms Hammond's photographs of common deformities, the gathered villagers began nodding excitedly and talking over each other.

Mr Khen instantly pointed to the photo of a child suffering from hydrocephaly - an abnormal buildup of fluid in the brain. Within moments, Noy Saroeun, a bubbly, giggling 4-year-old boy with a head deformity, was carried over.

"My grandson, I had no idea what happened to him. I don't know what the reason is, whether it's natural or a previous life," Mr Khen said, referring to a common Buddhist belief that birth defects are a karmic punishment for transgressions in a past life.

While young Saroeun revelled in being the centre of attention, climbing on tables and posing for photos, phone calls were made inviting others to the gathering.

Minutes later a young woman with a similar head deformity and an underdeveloped left hand pulled up to the house on a motorbike. Ms Dauk Paris, 22, introduced herself, but left almost immediately, returning with 16-year-old Ms Soun Chantrea, who also suffered from a head deformity.

In total, Post Weekend spoke to seven villagers born after the spraying with deformities commonly associated with Agent Orange. Ms Soun Sopheak was born without a right arm. Ms Sor Leakhena had an underdeveloped right foot, and her son had only three fingers. Another young boy had a cleft lip.

Ms Chantrea and Mr Saroeun both had surgery to relieve swelling in their heads. Ms Chantrea's forehead had swelled so large when she was young that her eyes were almost entirely obscured.

Ms Sopheak wears a prosthetic, which she keeps covered with long sleeves.

Ms Leakhena's clubbed foot ends with a single toe in the centre. Her mother was born just months after the spraying, and her grandparents all remembered the white chemicals.

Ms Leakhena's son was born with three fingers on the left hand, raising questions of a genetic mutation, although the members of her family vehemently denied any previous conditions.

In an e-mail, Ms Hammond explained that the way dioxin works in humans is still debated, and it is virtually impossible to prove that a defect is a result of Agent Orange without a complete family history and medical testing. Even tests, she said, can be inconclusive.

Many of the deformities could be attributed to another source. Hydrocephaly, for example, can be caused by the Zika virus. Cleft lips are common regardless of the presence of Agent Orange. Ms Chantrea's father is cousins with Paris' mother, and so their deformity could be genetic too.

However, all of the families insisted there was no presence of deformities within their lineage prior to 1970. All of the subjects with birth defects were born after Koki Som was sprayed, and all of them had either parents or grandparents exposed to the chemicals.

It is worth noting, too, that researchers sometimes find inconsistencies in anecdotal evidence of spraying from villagers. There were no such variations in Koki Som. Three different groups of five or more villagers separately interviewed all reported 1970 as the year the village was sprayed. Nobody reported any other year.

Ms Hammond also explained how defects caused by Agent Orange can affect future generations of offspring. "In animal studies, it does cause epigenetic changes that cause birth defects especially neural-tube defects. We suspect it is doing the same in humans," Ms Hammond said.

"Epigenetic changes" are changes in the way genes express themselves. While these changes do not affect DNA directly, they can still become hereditary.

Ms Hammond said to "keep an eye out for clusters of birth defects in one village where spraying is reported", which was certainly true of Koki Som, where seven deformities were found in a village with only 172 families. Khen claimed at least two other deformed villagers had already died.

"Most definitely they could be related to Agent Orange/Dioxin," Ms Hammond said of the deformities in Koki Som after reviewing photographs of Saroeun and the others. "And the stories the villagers are telling about the spraying is spot on."

Official US military records show that herbicide spraying crossed the border into Svay Rieng. And while none of the recorded routes match up with the year reported by the villagers, Ms Hammond said it was likely the military didn't document some runs because of their illegality.

There was a mission flown in March, 1970, just across the border that was noted to be aimed at an "alternate target". The official records do not show the planes crossing into Cambodian territory.

While there is no debate that Svay Rieng was sprayed by herbicides, the effects of the chemicals used remain shrouded in uncertainty.

Vietnam-based researcher Andrew Wells-Dang, who studied Agent Orange in the early 2000s before going on to join the WLP as a board member, repeated Ms Hammond's warnings that he could give no definitive answer, but said the circumstantial evidence was certainly there.

"As there is evidence (Koki Som) was sprayed, the villagers were exposed," said Mr Wells-Dang in an e-mail, after also reviewing the photos of villagers. "The disabilities your pictures show look like some that the Vietnamese who were exposed also think are linked to Agent Orange... There is a circumstantial case that (Koki Som) villagers' disabilities could be linked to their exposure to herbicides, but there's no way to be sure."

The United States government has long toed the line of this uncertainty in regards to potential victims. America has continued to deny that birth defects - except for spina bifida - in the Vietnam theatre are related to Agent Orange exposure, all while offering benefits to female veterans who have children with specific deformities.

Under the "Agent Orange" section of the US Department of Veterans Affairs website, there is a link to another page on birth defects. The page confirms that birth defects are grounds for compensation, but insists the defects are "not related to herbicide exposure".

Despite American protestations, Mrs Dam Morn, the grandmother of little Mr Saroeun, has already made up her mind. Mrs Morn, who was exposed in the 1970 spraying, has long held American chemicals responsible for her grandson's disability.

"I have always been angry with the war and the Americans. I was always angry: 'Why are the other sons fine; why just my grandson?' I really hate the war - they destroyed us; they destroyed our house," Ms Morn said."The sky was very black, not from rain clouds, but from gas falling. It made our eyes water."

Repeated attempts to reach Cambodia's Ministry of Foreign Affairs were unsuccessful, but government spokesman Phay Siphan said he was aware of "unofficial rumours" of Agent Orange in Svay Rieng.

He called America's presence in Cambodia during the Vietnam War a "lesson learned", and turned the conversation to America's recent criticisms of Cambodia's current political climate.

"They pushed and violated our neutrality," Mr Siphan said, claiming Cambodia became a pawn in a Cold War geopolitical conflict."This is why my prime minister and my government decided we don't want the third hand or US agents to intervene in our internal issues, especially during an election," Mr Siphan added, referring to Prime Minister Hun Sen's recent accusations that the US was behind a conspiracy to topple his government.

The US Embassy in Cambodia, meanwhile, expressed its concerns about the deformities without addressing the question of American responsibility directly.

"The Embassy empathises with the medical challenges of the Cambodians you have described. However without more specific information, we can't comment further. As we have said before, the US remains committed to addressing our war-time legacy, and over the past two decades has spent more than US$120 million here removing the remnants of war," deputy spokesman David Josar said in an e-mail.

Ms Paris's family lives just down the road from Saroeun's, and her grandfather too remembered the day when white powder fell from the sky. Mr Khen Sarun sat shirtless in the shade, a broad traditional tattoo stretching across his chest.

"It happened in 1970," he said, repeating a sentence that echoed around Koki Som that day."The spraying was at the forest. The leaves fell down. It was so irritating in our eyes that we mixed water with onion to wash them out."

Ms Paris explained that she dropped out of school in grade 10 because she found riding a bicycle to class too difficult and exhausting. Eventually she was able to learn how to drive a motorbike.

"I feel very sad because I am not like the other kids. And I am pretty sad that I cannot work or do the jobs that other people can do," she said.

Ms Paris' mother, mrs Khoun Chanthy, told Post Weekend about the difficulties she had raising a child with disabilities.

"During my pregnancy I just wanted to have my daughter born healthy and complete. I never killed anyone or ate anything weird, so why is my daughter strange like that?" Mrs Chanthy asked."My daughter has a very high temper, she is easily angered. Raising a disabled kid is not easy, we need to raise her and take care of her mental state . . . She is very different from my other four daughters."

Ms Chanthy also asked why neither the American nor the Cambodian government has offered her any assistance.

"Apologies do not make any difference; I want help raising my daughter as she cannot go to school or work... an official from the Ministry (of Health) came to document the disabled. They wrote her name down, but after two years we have not seen anything," she said.

Officials at the Ministry of Health said they were not aware of the possibility that Cambodians had been affected by Agent Orange during the Vietnam War.

Mr Tung Rathavy, the director of the National Maternal and Child Health Centre, did not even know what the chemical was, and refused to answer questions about it.

Mr Ly Sovann, spokesman for the Ministry of Health, said he wasn't aware of any health problems in Cambodia caused by Agent Orange, but vowed to investigate if there was credible evidence of a problem.

"I do not have any data for that yet in my department," said Mr Sovann, who is also the head of the Communicable Disease Control Department."If there is any evidence of abnormalities, we will send an expert to investigate it... Please report that if any people have any abnormal health, please send information to 115 so we can investigate," he added, referring to the ministry's free public hotline.

Mrs Chanthy, however, is tired of waiting, but knows she has no other choice. She told Post Weekend a story, recounting that when Ms Paris was first born, a Thai factory worker offered to adopt her.

Fearing that she would be used as a beggar, Mrs Chanthy refused."I would be full of remorse if my daughter became a beggar. No matter how hard it is I want to raise my daughter myself," she said fiercely.

"When I was delivering her, the doctor told me my daughter's hand was disabled, but what can we do? She is our daughter. She was very sick often. She has many headaches. When she was 2 months old, she had to stay at the Kantha Bopha hospital for two weeks," Mrs Chanthy added, before admitting to being plagued by an ongoing worry.

"People with these problems in the village very often die," she said.