On arsenic and groundwater in West Bengal

9 Oct

I make a lot of presentations in India and elsewhere, explaining my work on groundwater in West Bengal. And almost always, the first question I get is: ‘but what about arsenic?’ And it is a very important question, something I want to answer carefully.

To be able to do so, my colleague, Nari Senanayake, now a graduate student at University of California at Davis and I decided to sift through evidence to understand what we know about entry of arsenic into human food chain through irrigation with arsenic rich water on the one hand and ways of mitigating the same on the other hand. To me, mitigation always seemed important. This is because, farmers in this part of the world, often don’t have any other viable livelihood alternative than irrigating with groundwater and in some places, this groundwater contains arsenic. I have noticed how easily one recommends that irrigation with groundwater be banned in such places, without providing any other alternatives. That, to me does not sound like a good public policy due to two reasons. First, such a ban can never be implemented in reality given that farmers depend on this resource for their livelihoods. Second, assuming it was possible to actually implement this ban, it will only make farmers poorer than they already are, and in the process, make them even more nutritionally insecure. There is a lot of literature to show that people with poor nutritional status are more prone to arsenic poisoning than others. Thus, in some sense, such a policy will end up victimizing the same people it was purportedly designed to serve!

Now coming back to our paper. This paper, titled ‘Irrigating with arsenic contaminated groundwater in West Bengal and Bangladesh: A review of interventions for mitigating adverse health and crop outcomes’ is now under review process of an ISI journal. But a few months ago, we published a working paper version of the same paper for a more policy oriented audience. Here is the paper.  

We looked at two distinct, but related aspects. First, we looked at consequences of irrigating with arsenic rich groundwater. Here, we reviewed 27 high quality studies that had credible counter factual and found that irrigating with arsenic rich water leads to accumulation of the same in soil, but not necessarily accumulation in crop parts in equal severity and that such accumulation depends on crop types and water management practices. But what was evident was that irrigating with arsenic rich water for long periods almost always led to decline in yields. 

Second, we looked at ways of mitigating the negative impacts of irrigating with arsenic rich water. Here, we reviewed 29 high quality studies with experimental design and found that there are at least 6 categories of interventions that have been tried and tested in the field or in the laboratories. And the good news is that most of these work, but work with varying degrees of success. These six categories of interventions are:

1. Improved water management practices like deficit irrigation

2. Correct doses of artificial fertilization and bio-remediation of soil

3. Switching to alternative field crops with low water requirement

4. Breeding arsenic tolerant rice varieties

5. Cooking rice with clean water and in traditional ways

6. Providing nutritional supplements to those most at risk

We explain the pros and cons of each of these interventions in our paper. To me, the most important take home message is that we have to move beyond scare mongering and find solutions to managing arsenic in agriculture. And that those solutions are already being tried and tested by scientists. What then is needed is to link this science with extension activities. Agricultural extension in India, has literally gone to the dogs. But, good extension services are now needed like never before. Therefore, for me, the greatest concern is not that some farmers are irrigating with arsenic rich groundwater. The greatest concern is that they are not aware that they are doing so in the first place and second, they are not aware of how they could potentially avoid the negative impacts of doing so by adopting some best practices. It is here that there is a huge role for innovative extension services — something that is conspicuous by its absence. 

And this, my friends, is my answer to: ‘But what do we do about arsenic?’



2 Responses to “On arsenic and groundwater in West Bengal”

  1. Bharaty Sharma October 14, 2013 at 4:33 pm #

    Nice to read your good piece on a very technical issue and you are mostly correct in your observations. Some of the additional things one need to keep a note , are the following:

    1. Farmers must be made aware of the fact that continuous use of arsenic rich water leads to decline in yields and contamination of the soil. The resource degradation process is more serious and the process is generally more or less irreversible.

    2. Just the way, the drinking water sources/pumps with arsenic-rich water are marked in red colour and some sort of a caution; the irrigation water tubewells may also be marked in the same fashion to warn populations ( and their livestock) not to make use of this source for drinking / other consumptive needs.

    3. As a matter of general guideline; grains accumulate lesser amounts of arsenic as compared to the fresh and dry biomass. Avoid irrigation/ cultivation of fodder crops, leafy vegetables and root crops.

    • aditimukherji October 19, 2013 at 7:29 pm #

      Dear Dr. Sharma,
      Yes, you are right. Thanks for your very good comments. To me, extension seems to be the key here and I am concerned about the very poor extension services we have in India these days…

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