Drinking Water and Arsenic

Arsenic is a toxic metal. Consumption of arsenic for a long period of time can cause serious health effects such as hyper pigmentation, depigmentation, keratosis, cardiovascular diseases, neurological diseases and skin cancer. Beside chronic effects, intake of excess amount of arsenic can also cause immediate health effects such as high blood pressure, muscular cramp, diarrhea etc.

Trace amount of arsenic is found naturally in soil and groundwater. In some soil and groundwater the metal is found at higher level depending upon the amount of arsenic in parent rock. Anthropogenic (human) activities also add the metal in soil and groundwater. The major anthropogenic sources that add arsenic in soil and groundwater are industrial effluents, mining wastes and pesticides used for agriculture.

In recent years, studies conducted by different government as well as non-government organizations in Nepal have revealed higher than World Health Organization (WHO) standard, United States Environmental Protection Agency (USEPA) standard and even Bangladesh standard level of arsenic in groundwater of the terai regions of Nepal. According to WHO and USEPA, amount of arsenic should not exceed 10 microgram in 1 liter of drinking water. Whereas, standard set by Bangladesh is 50 microgram per liter of drinking water (USGS, 2004; Edie Weekly, 2000; WHO, 2000). The concerned organizations in Nepal were alarmed only after the severe arsenic contamination found in groundwater of Bangladesh and India in last decade. It has been believed that the source of arsenic in groundwater in those countries is erosion of rocks containing higher concentration of arsenic in the Himalayas, and deposition of the metal in gangetic plains which subsequently moved into the groundwater through sub soil in thousands years. Since Nepal exists in the same geographical region, and we do not have heavy industrial activities in the terai region, the same natural process believed for groundwater contamination in Bangladesh and India is believed to be true for Nepal. Natural ways by which groundwater is contaminated is a slow process. That means arsenic contamination in our groundwater did not occur overnight. The notorious metal was in our groundwater since time immemorial. Let’s not talk about why Nepal is always behind other countries in everything. Otherwise we should have identified the arsenic problem in our country before the problem was identified in Bangladesh or in India.

Some solutions have already been put forward in arsenic affected countries to avoid arsenic poisoning. For example, scientists in Bangladesh have invented an arsenic filter. They have claimed that the filter will be very effective and cheaper. We can hope to see that filter in our market in near future. Another possible alternative, according to experts working in this field is to drink water from aquifer below 300 meter from the surface. It has been suggested that water from that depth not often contains unhealthy level of arsenic. Since most of the existing wells in the affected areas do not supply water from that suggested depth, we should think about how we can redesign and reinstall wells to get water from that depth. Another alternative we can practice to avoid arsenic poisoning is to drink water supplied from surface water sources such as rivers, springs, lakes etc. Currently majority of people in terai are drinking water from groundwater sources. In this context, question arises, whether the government of Nepal can immediately supply drinkable surface water to the affected population? There are also other expensive technologies available in developed countries to reduce toxic metals from groundwater. For example, soil contaminated by toxic metal can be treated chemically to keep the metal in soil from leaching into the groundwater. Metal can also be removed from groundwater that is pumped up from contaminated aquifer. Once the metal is removed, the water is released back to the aquifer through soil. These technologies are considered expensive even by developed countries such as the United States. Economically poor country like Nepal should keep these expensive options in mind but look for other economically feasible technologies. Let’s think one step forward. How about using trees to remove arsenic from soil and groundwater? Probably, this unique alternative has rarely been discussed or considered in arsenic affected countries, especially in Nepal. Plants naturally possess the ability to accumulate small amount of metals from soil and groundwater. But in nature there are some plants that accumulate significantly higher amount of metals in comparison to ordinary plants. Such extra-ordinary trees and shrubs are known as 'hyper-accumulators'. Recently, a new technology known as 'phytoremediation' has emerged in which such extra-ordinary trees and shrubs are utilized to extract toxic metals from soil and groundwater. Phytoremediation can not remove arsenic from groundwater instantly. It is a slow and steady process which in long term removes toxic metals from groundwater amazingly. Phytoremediation which is comparatively a cheaper technology is getting popularity in developed countries also because it is an environment friendly method. We can also practice this method in Nepal using our own indigenous trees, and exotic trees brought from other countries. However, we need to be clever when introducing new species because exotic species can sometimes cause adverse effect to our existing natural systems.

Groundwater is a major source of drinking water in the terai region. People know there is slow poison in their drinking water. Perhaps, they yet have no option other than drinking the slow poison knowingly. Testing arsenic level in tube wells of the affected areas, and writing a red notice ‘Do Not Drink Water from This Well’ will not alone solve the problem. Aren’t we getting late to discuss about the possible technologies and alternatives that we should introduce to save the public health? We all know the affected communities or the government or non-governmental organizations alone can not solve this severe environmental problem. What we need is a ‘Combined Effort’. Hopefully, we won’t be far behind other arsenic affected countries this time in solving the problem.

(From http://www.environmentnepal.com.np/)