Rampant use of highly toxic herbicides and pesticide in banana plantations established by Chinese investors in northern Laos has prompted a government ban on their expansion in at least one province.
After several years of heavy use of the chemicals - some of them banned - resentment is rising.
Media reports say locals in Bokeo province are now afraid to collect forest food like mushrooms, near plantations.
Banana plantations on land leased by foreign investors - almost all from China - are employing locals to spray chemicals over more than 10,000ha in Bokeo alone, the official Lao News Agency reported.
The agency on March 31 quoted Bokeo Governor Khamphanh Pheuyavong as saying chemicals banned in other countries were still being smuggled into the province.
"Impact on the environment and nearby communities partly results from the fact that relevant government authorities failed to carry out proper management and monitoring," he said.
"As a result, chemical fertilisers and harmful herbicides and pesticides have been used by foreign investors."
Bokeo is in northern Laos, on the border with Thailand and Myanmar, and close to China's border.
Laos' National Agriculture and Forestry Research Institute, at a workshop in the capital Vientiane on March 31, said studies showed more than 100 chemicals were regularly applied in banana plantations in several provinces, not just in Bokeo.
Separately last month, a discussion paper released by the Lao Upland Rural Advisory Service (Luras), a non-government organisation (NGO) under Swiss aid group Helvetas,revealed just two districts in Xieng Khuang province, north of Vientiane, had been sprayed with 19 million litres of herbicide last year.
Comparisons with other countries are hard to come by.
The amount sprayed is usually not tracked, and more important than the volume is the toxicity of chemicals used, says Bangkok-based Marut Jatiket, the director of Field Alliance, a group of NGOs working for sustainable agriculture in the region.
In the case of the Luras study, the crop was not bananas, but maize, which has spread during the past decade to become a dominant crop in a country where 75 per cent of the workforce is employed in the agricultural sector.
"The use of herbicides, such as paraquat, has brought about a transformation of the landscape in upland provinces such as Xieng Khuang," the report said.
"As an essential ingredient in the 'maize boom', these chemicals are a serious threat to human health and a contributing factor in the loss of biodiversity and declining soil fertility.
"This transformation started a decade ago, in 2004, when the first farmers started using toxic chemicals to clear their fields. Now, in districts like Kham and Nonghet, almost every rural household has a spray machine."
Laos' toxic chemical problem is linked to Thailand, where there is also heavy use of chemicals, which are also traded across the border.
In one Thai province - Maha Sarakham, near the Lao border - some two years ago, a village headman in his 50s "dropped dead while spraying chemicals in his own farm", former finance minister Korn Chatikavanij told The Straits Times.
Mr Korn, in a personal project in the past two years, has been focusing on turning the village into an organic farming community. "It was a wake-up call for the whole village," he said.
In one recent study, blood samples from primary schoolchildren in Thailand's Chiang Mai province showed over half had unsafe levels of pesticide in their blood.
And in Chiang Rai province, just across the Mekong from Bokeo in Laos, blood tests of 43 of a Chinese-owned banana plantation's 200 workers, showed 10 were in "risky condition" and 13 had "unsafe contamination levels", according to media reports last week.
Mr Marut told The Straits Times farmers in Laos, in particular, sometimes could not read labels on packaging because they were in other languages.
Mr Marut's data shows some persistent use of the deadly pesticide endosulfan and extensive use, especially in Laos, of paraquat, a weedkiller banned in many countries.
Farmers also typically mixed pesticide and herbicide "cocktails", he said.
"Paraquat is the most severe," said Penang-based Sarojini Rengam, executive director of Pesticide Action Network Asia and the Pacific, in a telephone interview.
"It is banned in Switzerland and the European Union... It is easily absorbed through the skin and has been linked with Parkinson's syndrome...
"Laos has also banned paraquat, but they can't enforce the ban. They don't have the resources."