Tackling arsenic and fluoride in drinking water

One third of the world's population obtains water for daily needs and agriculture from groundwater supplies. In developing countries in particular, groundwater is often less contaminated than water from lakes and rivers, or even the only source available. However, about 10 percent of wells and boreholes are contaminated with arsenic or fluoride. These trace substances are mostly of natural origin and are washed out of rocks and sediments by the water.

Taken in high doses or over a long period of time, arsenic and fluoride have fatal effects on health. Too much fluoride causes tooth damage, growth disorders and bone deformities. Chronic exposure to arsenic discolors the skin and causes it to become very calloused. Cardiovascular diseases and cancer are also among the possible consequences

A new method to locate the danger

In 2008, a research group at Eawag presented a newly developed method for producing hazard maps for geogenic contaminants in groundwater without the need to review all wells and groundwater supplies in a region (Amini et al, 2008a, 2008 b). Such maps were a first in the field of groundwater research.

The researchers were able to demonstrate in various countries that their model calculations are accurate. These include Bangladesh, Vietnam and Sumatra (Winkel, Nature Geosci. 1, 2008), but especially China, where Eawag, in collaboration with the China Medical University Shenyang, was able to show that some 20 million people live in areas at risk. In addition, several new risk areas were discovered as part of this research (Rodriguez-Lado, Science 23, 2013).

Michael Berg, Head of the Water Resources & Drinking Water department at Eawag, explains the principle of the method: "We have developed a statistical model based on data from geology, topography and soil properties. These are supplemented by other data sets - for example, climate or satellite data - and combined and calibrated with the available arsenic and fluoride measurements of an area."

Facilitate local research

The compilation of arsenic and fluoride hazard maps is complex and often almost impossible for the responsible authorities in developing countries, where technical and financial resources are scarce. With the financial support of the Swiss Agency for Development and Cooperation (SDC), the Eawag team, in collaboration with Ernst Basler + Partner and Hydrosolutions, has now developed an online solution that is available free of charge to all interested parties: The Groundwater Assessment Platform GAP (www.gapmaps.org). "This gives experts from all over the world the opportunity to visualize their own data with relatively little effort and to create their own risk maps," explains Michael Berg. "This makes it easier to determine which wells should be investigated as a priority. This means that the available funds and forces can be used in a more targeted way."

Rick Johnston, a staff member at the World Health Organization (WHO), also sees a significant role for the new platform: "For countries with an arsenic or fluoride problem, GAP can become an important monitoring tool in the implementation of the 2030 Agenda for Sustainable Development." GAP is also an exciting tool for the WHO and Unicef, the UN Children's Fund, because both organizations are very intensively involved in the fight against arsenic and fluoride in drinking water.

Knowledge exchange for the elimination of toxic substances

GAP is more than a web-based risk mapping database. "The new platform enables faster and simplified location of geogenic contaminants. This is a milestone in protecting the public," says Michael Berg. "However, just as important as early detection is the development of practical methods to remove toxins from the water."

Some such procedures are listed in the "Geogenic Contamination Handbook", which was also prepared by Eawag and is available at www.gapmaps.org (as a PDF and as a wiki that can be expanded by all users). Water researcher Michael Berg comments: "Despite numerous advances, there is still a great need for research. Especially in the development of purification technologies that are easy and safe to use." For this reason, he says, the GAP platform was also designed from the outset as a forum for knowledge exchange. "The faster and the better the existing knowledge is disseminated, the better," says Berg. The new Internet portal now enables networking on a global scale.

(eawag)