Dr. Annette Johnson interview about the geogenic contamination of groundwater
Dr. Annette Johnson is a senior scientist at EAWAG. She was the coordinator of the Water Resource Quality ( WRQ ) project. This was an integrated project aimed at developing a generally applicable framework for the mitigation of geogenic contamination in groundwater used for drinking, in particular concerning arsenicand fluoride. They combined natural and social scientific expertise for the solution of a health problem that affects the 100s of millions of people worldwide. The mitigation framework developed by the WRQ team from Eawag will help decision-makers and water resource managers to identify contaminated regions and to provide feasible options to help reduce the effects of contamination. The global probability risk maps for arsenic, fluoride contamination can be found here http://bit.ly/1tFCKmv
Our Water network research team met her at EAWAG and interviewed her about the problem of geogenic contamination, the WRQ project and about some of the major products developed through this interdisciplinary research project.
Dr. Annette Johnson
Q1. Water quality related health hazards are often related to bacteria or the presence of fecal coliform in the water and geogenic contaminants are often neglected. Could you give us a brief introduction of some of the common geogenic contaminants and the health hazards caused by them?
Microbes are the number one contaminants affecting the lives of billions of people worldwide.
Ranked second to these are the natural contaminants in groundwater used for drinking.
They are substances dissolved from rocks.
It is thought that about 140 million are exposed to elevated arsenic concentrations in their drinking water. Arsenic can be a killer – the cause of severe skin problems, heart disease and cancers.
About 200 million people are exposed to high fluoride concentrations in their drinking water. High fluoride intake can lead to dental and skeletal fluorosis and is also known to affect the endocrine system.
Both arsenic and fluoride affect people with poor diets in low-income countries the most.
Many of these countries have difficulties providing safe water free of microbes–providing water free of arsenic and fluoride is a greater problem
Q2. What was the main focus of the Water Resource Quality (WRQ) project at EAWAG? How many people were involved in the project that is coordinated by you?
The goal of the WRQ project was to provide a framework for the mitigation of drinking water contaminated by arsenic and fluoride in low-income countries and different types of users
In total there were 18 people with backgrounds in geochemistry, engineering and social sciences.
Q3. Could you explain to us some of the major deliverables of the project?
There were 2 deliverables
1. Global and regional maps of predicted arsenic and fluoride contamination FOR planners and donor agencies
2. A handbook for practitioners on how to monitor for contamination, water alternatives or treatment options.
The handbook handles both technical and social issues.
The handbook is interactive, with tools. An electronic version will be available by the end of the year.
Q4. The global risk maps look very informative. How reliable are these maps? Are they supported with ground data?
The hazard maps show the probability of elevated contaminant levels within a given pixel. The pixel resolution of the global maps is 10 km x 10 km at the equator.
The maps have been statistically calibrated and verified with measured data.
They indicate where conditions are similar to places where contamination has been found
They are very useful but NEVER a substitute for monitoring.
Because of small-scale changes in geology, neighboring wells can have very different contaminant concentrations.
Q5. Which were the critical regions affected by geogenic contamination in the world that are the particular focus of this project?
For arsenic, the largest affected populations are in river basins and deltas in South and SE Asia
For fluoride, it is the arid regions in China, India, the African Rift Valley, Central America
Q6. Focusing now on fluoride, how come the people in some countries are affected more by fluoride problem than the others?
Fluoride is present in most rocks in concentrations ranging between 0 and 1 g/kg.
It is the chemistry of the groundwater that will influence whether or not it is released.
As a rough guide, it is possible to say that if calcium is present the solubility of fluoride will be limited by fluorite – a calcium fluoride mineral.
So, elevated fluoride concentrations are generally found where the dissolved calcium concentration in groundwater is low, for example in association with:
Volcanic or metamorphic ultramafic rocks
Arid climates where groundwater chemistry is dominated by sodium bicarbonate and alkaline pH.
High rock/sediment fluoride concentration exasperate the problem – e.g. in the Rift Valley
Q7. What is the guideline value for human intake of Fluoride? Is the tolerable intake different for adults and children?
The WHO guideline value is 1.5 mg/L. Elevated concentrations are often in the 2-5 mg/L range but can reach as high as 34 mg/L.
The maximum tolerable intake for adults is around 8 mg/day. It is lower for children and it is the children that are most at risk.
Q8. What is the best way to manage the fluoride problem in developing countries? Can it be achieved by better management of water resources or through changes in lifestyle?
The first option is always the use of alternatives – because water treatment for fluoride is expensive and difficult to organize.
However, if the alternative is surface water, water for drinking and food preparation will still need to be treated.
There is no one technology – it all depends on the situation: the fluoride content in the water, the amount of water available, the population that needs to be served etc.
Institutional aspects are of prime importance:
The government agencies need to be involved – because financial support will be necessary
The water users have to be involved from the beginning and there has to be a sense of ownership – enough for them to make affordable financial contributions.
An organization that supports monitoring and maintenance
It is important to also prepare food with treated water
Food supplements can sign of skeletal fluorosis in children
Changes in diet may suffice in situations where:
fluoride contamination in drinking water is relatively low.
Where it is easy to eliminate specialty foods For eg. Himalayan rock salt in India (which is found to contain fluoride).
Q9. What are you planning for the future?
We think awareness creation is very important
The maps are a good aid to this
We have also noticed that though information on water quality may be available it is often not shared
We have therefore initiated the Groundwater Quality Assessment Platform (GAP) in association with the Swiss Agency for Development and Cooperation and the WHO for users, national or regional government agencies to :
View and download information
Do their own mapping and modeling
Obtain information on water alternatives and treatment