The survey revealed that the amount of substances polluting water sources such as rivers and lakes located at, near, or passing by numerous villages, are tens of times, hundreds of times or even thousands of times higher than tolerable levels.

Tests conducted in villages specialising in metal production or recycling in northern Bac Ninh Province showed that the levels of biological oxygen demand (BOD) and chemical oxygen demand (COD) in their water exceeded tolerable levels by 20 to 35 times.

BOD and COD tests are analytical methods for measuring the amount of oxygen consumed during microbial or chemical breakdown of oxygen-depleting substances in water such as sewage and farm slurry. High levels of BOD and COD indicate heavily polluted water.

In northern Nam Dinh Province, environmentalists found out that the level of chromium-6, identified as dangerous to human health, was 3,200 times higher than tolerable levels in metal and plastic recycling villages.

The Viet Nam Craft Village Association estimates the number of craft villages nationwide to be 2,800, of which up to 90 per cent often violate environmental protection regulations. An estimated 47 craft villages were found to be facing the nation's most serious environmental pollution problems following the Prime Minister's decision from 2012 to 2015.

Households in craft villages discharge more than 15,000cu m of waste water and hundreds of tonnes of solid waste per day.

Although pollution has become more serious in numerous craft villages, waste treatment facilities at these villages were largely ineffective.

Deputy Natural Resources and Environment Minister Bui Cach Tuyen told Tien Phong (Vanguard) newspaper that he had visited numerous craft villages to inspect their waste treatment facilities and found that most of them were not sustainable and effective and many of them ceased operations after a short period of time.

A lack of operational management and maintenance were among the key reasons leading to the failure of waste treatment facilities, Tuyen said, adding that limited investment in waste treatment, backward technology and low public awareness were also blamed for the worsening problem.