(New York) - Vietnam is the world’s largest exporter of cashews. But in the south, where cashew production is common, some of that production occurs in so-called drug “treatment” centers. Forty thousand drug users are detained at any one time in Vietnam, and forced labor is their main “treatment.”

Last month, Vietnam took part in Asia-Pacific trade negotiations in Chicago, but the labor conditions in Vietnam aren’t going unnoticed. Ben and Jerry, of ice cream fame, presented 10,000 postcards demanding that the negotiations address labor, environment and human rights concerns.

Fairfood International also opened a petition drive demanding that U.S. snack companies reveal the source of their cashews. The deadline for signatures is Nov. 20, two days shy of National Cashew Day .

Over the course of two years of research for a new report , Human Rights Watch talked to men and women who had been locked inside these drug “treatment” centers, some when they were children. They got no help in the centers. They told of grueling work, being shocked with electrical batons, beaten by staff and held for months in locked “punishment rooms.”

A month’s work might net them between 75 cents and $7.50, after deductions for food, lodging and “management fees.” Some even left the centers owing center officials for these “expenses.” Many returned home battered, in broken health. And many were forced to process cashews.

In Vietnam drug use is not a criminal offense, and even after the release of our report Vietnamese government officials claimed that drug users are “patients,” not “criminals.”

But typical “patients” are not made to shell cashews six days a week for up to four years. Nor are they normally rounded up by the police and detained without any thorough medical assessment. Vietnam's drug users are.

These “patients” — without access to a lawyer, a hearing in front of a judge or a formal sentence — are subject to long hours of monotonous labor, physical abuse and torture. There is no drug “treatment” or “rehabilitation” in any meaningful sense of the words, and very little health care of any kind.

Our research focused on centers run by Ho Chi Minh City authorities, and in these centers we found that staff set a quota, usually 5 to 8 kilograms of cashews per person per day. Meeting a 5-kg quota requires husking about 4,800 nuts.

The work is hazardous: cashew resins can cause itching and burning, and dust from the cashew skins can irritate the lungs. Provision of protective gear to safeguard “the patients'” health was not the norm. On the contrary detainees were charged for gloves and masks, when they were available.

The nuts are packaged, weighed and collected by cashew wholesalers, who come to the center, monitor production and pay the detention center administration. Identifying which wholesalers is not easy. There is no publicly accessible source that lists the entities that use the center's forced labor for processing their goods, and companies named by detainees or staff at the centers refused to answer or acknowledge our inquiries about their relationship with the centers.

Vinacas — Vietnam’s cashew association — estimates that $1.4 billion worth of cashews will be exported in 2011, 30 percent more than in 2010.

Certainly only a part of that production is occurring in detention centers, but it is difficult to determine how much. The government denies that commercial products are processed in detention centers, and Vinacas does not seem to be interested in doing its own investigation.

Nguyen Thai Hoc, the chairman of Vinacas, said that 2011 has been a tough year for Vietnamese cashew processors, with a shortage of capital and laborers, and poor quality raw cashews imported from Africa and Cambodia. Cashew thefts could affect the country’s prestige, Vinacas said .

But if it has been a tough year for Vietnam’s cashew companies, it’s always tough for drug users who are shelling cashews, and often punished for not working fast enough.

If Vinacas is concerned about the country’s prestige, you would think they would be concerned that some of its companies process their cashews in detention centers that engage in torture and forced labor.

In its response to our report, the Vietnamese government claimed that work in the centers was “therapeutic” and helped detainees “enhance their health, life skills, vocational skills and to develop their awareness of the value of labor, and responsibility toward one’s self and the society.”

The Vietnamese government also claimed that Vietnam’s drug treatment was “in line with” treatment principles espoused by the U.S. National Institute for Drug Abuse, as well as the United Nations Office of Drugs and Crime and the World Health Organization.

That claim is false: forced labor is both illegitimate as drug treatment and illegal under Vietnamese law. These organizations should set the record straight, clearly and unequivocally.

Vietnam advertises itself as a tourist paradise and low-cost hub for manufacturing. But unless the government ends the torture and forced labor of drug users in the name of “treatment,” it may be equally well known as well as the source of “blood cashews.”

Joe Amon is the director of the health and human rights division at Human Rights Watch.