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Biosensor analyses arsenic in water

Up to 80 million people could be affected by tainted underground water supplies in Bangladesh (EAWAG)

Scientists in Switzerland have developed a cheap, fast and accurate biosensor for measuring arsenic in drinking water.

They believe it could have significant applications in a country like Bangladesh where millions are at risk from groundwater contaminated by arsenic.

In laboratory testing, the sensor has proved reliable and sensitive to small concentrations of arsenic.

Researchers from the Federal Institute for Environmental Science and Technology (EAWAG) in Dübendorf are preparing to conduct field trials and have filed for a patent. They are also looking for industrial partners.

Source of danger

Arsenic is a semi-metallic toxic chemical, which occurs naturally in the water below ground in Bangladesh.

This poison is being pumped out of the ground in wells, many of them paid for by the international community.

The World Health Organization (WHO) estimates that as many as 80 million people could be affected by naturally occurring arsenic in underground water supplies across the country.

Prolonged exposure to arsenic can cause serious skin conditions, tumours and often fatal breathing difficulties.

Colour change

"The bacterial biosensor is a very simple device that can measure arsenic very sensitively," said microbiologist, Jan-Roelof van der Meer, who has led the development team.

The sensor cells on a paper strip change colour in response to arsenic levels.

A number of chemical kits already in use can lack sensitivity and be difficult to interpret at low levels, while some of the current biosensors require expensive laboratory equipment to measure the response.

"Our biosensor produces a colour at very low concentrations of arsenic of around two to five micrograms per litre," Van der Meer told swissinfo.

The WHO recommends arsenic level limits of ten micrograms per litre of drinking water.

Detection

Van der Meer admits that the sensors will not actually treat the problem of contamination, but says that just detecting the presence of arsenic is already a significant step.

He says the arsenic content of water in wells even within short distances of each other can vary widely.

"It might even be that one well in a village is contaminated whereas a well 100 metres away is not contaminated so severely, so you could just use the other well."

"Also, with simple technologies, it can be very useful to know how effective your treatment is."

Van der Meer adds that the successful prototype now needs to be tested outside the laboratory.

One hurdle they face is that the sensor is based on a genetically modified bacterium and the light it generates in the presence of arsenic.

Since it is a genetically modified organism, strict conditions may be attached to its use in the field.

Arsenic pollution

Estimates suggest there over 11 million wells in Bangladesh - all of which need to be screened.

Other developing countries, particularly in Southeast Asia, have significant problems with arsenic pollution in groundwater.

However, the situation is particularly acute in Bangladesh because the water supply is very locally organised in the form of groundwater wells.

The team at Dübendorf is hoping to train up local researchers from Bangladesh and Vietnam.

swissinfo, Vincent Landon

In brief

Scientists at the Federal Institute for Environmental Science and Technology in Dübendorf have developed a biosensor for measuring arsenic in drinking water.

Those in charge of its development say the sensor is cheap to make, fast and accurate.

The World Health Organization (WHO) estimates that as many as 80 million people could be affected by arsenic in underground water supplies in Bangladesh.

The WHO recommends arsenic level limits of ten micrograms per litre of drinking water.

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