CAMBODIA: Arsenic in Mekong putting 1.7 million at risk

Photo: Tharum Bun/IRIN

A child dives into the Mekong River in Cambodia, where millions of nearby residents are at risk of dangerous ailments due to arsenic poisoning

PHNOM PENH, 17 November 2008 (IRIN) - Arsenic contamination of the Mekong River and groundwater is putting millions of residents at risk of severe illness due to arsenic poisoning, the UN and NGOs warned.

After surveying wells along the Mekong, which flows through Lao PDR, Cambodia and Vietnam, the UN Children's Fund (UNICEF) and governments concluded that as many as 1.7 million people were at risk of arsenic poisoning, whose long-term symptoms include skin lesions and cancer.

Twenty-one percent of the Vietnamese population is exposed to arsenic above the World Health Organization's acceptable level of 10ppb (parts per billion). It is found not just in groundwater but in bottled water, tap water, even fish, according to the Vietnam Ministry of Health.

In Cambodia and Laos, the precise numbers of people exposed to arsenic contamination is not yet known, though UNICEF and government agencies are compiling a report to be released later this year.

In some provinces along the Mekong River in Vietnam and Cambodia, residents are exposed to 30 times the acceptable level of arsenic, according to data from the Vietnam Ministry of Health.

Water containing arsenic above 300ppb could cause cancer within three to four years, the Health Ministry said.

Arsenic has no taste or smell, and can take years of slow build-up before symptoms are revealed, making it especially hazardous and hard to detect.

Contamination caused by sedimentation

"Arsenic contamination in the Mekong is understood to have been caused by recent sedimentation," Thowai Sha Zai, chief of UNICEF's water, environment, and sanitation (WES) division in Vietnam, told IRIN.

Sedimentation refers to the process whereby sediment accumulates, often with the side-effect of accumulating naturally occurring arsenic through chemical interactions.

In the 1990s, a lot of poorly planned NGOs built wells for villages and did not fully understand the long-term situation after they left.

"It is not known if this has been caused by other reasons as well, such as industrial pollution, since there has been no scientific study or evidence on that," he added.

Clearing arsenic from water supplies is costly, so authorities in Cambodia instead paint contaminated wells red and instruct residents to use them only for washing clothes and dishes.

In Vietnam, UNICEF and the government have provided rural residents with special filters to strain the water to reduce their exposure.

Yet some villagers remain scared of poisoning, even if only using the water for washing clothes. "We have abandoned many wells," Le Giau, a Vietnamese Mekong resident at the Vietnam-Cambodia border, told IRIN, adding that they were afraid of what could happen to them if they wore clothes with arsenic residue.

Since clean drinking water is hard to come by, some residents collect rainwater.

"In the 1990s, a lot of poorly planned NGOs built wells for villages and did not fully understand the long-term situation after they left," said one Cambodian NGO employee in Phnom Penh, who asked not to be named. "Many were short-term volunteer programmes that didn't teach people about the dangers of arsenic from their wells."

Arsenic poisoning became a public health crisis in India and Bangladesh at the time, and later gained more attention in Cambodia, Laos, Vietnam, and China, which all depend on the Mekong.

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