A study in Vietnam has revealed that massive over-pumping of groundwater sources to meet surging demand is drawing arsenic into the country’s village wells.
The research, published in the journal Nature, shows that a clean aquifer can become contaminated when water suppliers accelerate their flows of groundwater which contains naturally high levels of the deadly poison arsenic.
And while the decade-long study concentrated on Van Phuc, a small village on the outskirts of Hanoi, it has frightening implications for the entire region.
Study co-auther Pham Hung Viet of the Hanoi University of Science says arsenic contamination is elevated because people are using arsenic-laden water for their daily cooking and drinking needs.
“The phenomena we observe in Van Phuc village can be considered as a typical natural phenomena of arsenic contamination in the whole of the Red River Delta,” he said.
“As you know it can be considered one of the most densely populated areas in the world, with about 17 to 20 million people living in these area.
“So we cannot say exactly, but we think at least half of this population area can be affected.”
The World Health Organisation guidelines for arsenic in drinking water are 10 micrograms per litre. Concentrations in Van Phuc have been found to be 10 to 300 times higher than that.
Michael Berg, an environmental scientist currently visiting Curtin University in Western Australia, says arsenic contamination is a very slow disease that is difficult to diagnose.
Even in low concentrations, arsenic poisoning over a long period of time causes cancers of the skin, lungs, bladder and kidneys. The most visible symptoms are disfiguring skin lesions.
“If you are exposed the first year you feel nothing, and then later you are a little bit fatigued and then the first visible symptoms are skin problems, then various forms of internal cancer,” Dr Berg said.
Arsenic poisoning emerged as a public health crisis in India and Bangladesh in the 1990s. Wells installed for drinking water by well-meaning NGOs were in fact poisoning large sections of the population.
Only later did the problem gain attention in Cambodia, Laos, Vietnam, and China. A United Nations study in 2008 revealed that as many as 1.7 million people living along the Mekong could be at risk of arsenic poisoning.
Higher levels in the aquifer in the past meant that water from village wells were generally safe.
But as more groundwater is being pumped, water from arsenic-rich sediments is increasingly intruding into the previously uncontaminated water. Pumping for municipal water supplies has doubled between 2000 and 2010.
The movement of dangerous arsenic levels is much slower than the migration of groundwater itself.
Water from the contaminated aquifer has migrated more than two kilometres towards the city centre over the past 40-60 years, while arsenic contamination has only advanced around 120 metres.
But while the movement may be slow, it is also unpredictable.
“We found that in Van Phuc, there is a natural border between the low arsenic contaminated wells and the higher arsenic contaminated wells,” Pham Hung Viet said.
“But we’ve found this border moves from time to time, depending on the exploitation of the pumping of the groundwater by the water company in Hanoi.”
Scientist Michael Berg says water suppliers are pumping around one million cubic metres per day for drinking water purposes.
“Of course this is very large-scale pumping and the groundwater table is drawn down significantly and then water is flowing towards these production wells,” Dr Berg said.
‘We have no other choice’
Hanoi’s population of six and a half million is growing by more than 400,000 every year.
And with rapid urbanisation across the region, the study’s authors say it is critical that water infrastructure keeps pace with the city’s booming population.
“Currently we have the exploitation of groundwater by the private people from the tubewell so we can not control how fast they exploit the groundwater,” Pham Hung Viet said.
“So our recommendation is that the government pays attention by supplying the drinking water by the centralised water supply.”
Authorities in Hanoi have moved to filter arsenic from the city’s water supply, but many people on the city’s outskirts remain off the water grid.
The villagers of Van Phuc say they continue to have little choice but to drink from their poisoned wells.
Tran Thi Bay says her family has been using water from the village well for over 20 years.
“Everyone in the village uses it because we don’t have other option,” she said.
Nguyen Van Thi says he knows the water is contaminated and tries to filter the water as much as possible.
“We live far from the centre so the city water pipe system has not been installed in our village,” villager Nguyen Van Tin said.
“We really hope that the authority will soon provide us clean water for our daily needs.
“The city promised that 80 per cent of the population would have access to clean water in 2010, but it is 2013 now and we are still waiting.”