Naturally Poisoned: Geogenic Contamination of India’s Water

Entry #5: September 26-30, 2011

Naturally Poisoned: Geogenic Contamination of India’s Water

Water is one of the most important natural resources on the earth. Without water, life would not be able to exist. This liquid is responsible for supporting and sustaining the health and well being of living organisms all across the globe. However, in some areas of India, human consumption of this life-enabling liquid results in physical ailments and severe health impacts. This is due in large part to the fact that the water in various regions of India has been contaminated, not necessarily from anthropogenic inputs, but from geogenic sources. Nature is poisoning the water.

One of the major geogenic contaminants of India’s water supply is fluoride (Dissanayake et al, 2010). Although low concentrations of fluoride are helpful in preventing dental carries, the consumption of high concentrations of fluoride can lead to serious health issues. This ion is found in fluoride-bearing minerals, including hornblende, mica, topaz, apatite, phosphorite, and fluorite (184). Fluorite is the primary supplier of fluoride in the environment. This mineral is typically found in rocks such as gneiss, pegmatite, and quartz. Interestingly, regional climate has a large impact on the degree to which fluoride is released into the environment. The higher amount of rainfall in wet regions promotes the leaching of fluoride, which results in low groundwater concentrations of fluoride. Drier regions have less rain, less leaching, and greater fluoride concentration in the groundwater (183). Fluoride contamination is a widespread issue in India, but the states most severely impacted by unhealthy concentrations of fluoride in drinking water include Andhra Pradesh, Tamil Nadu, Uttar Pradesh, Gujarat, and Rajasthan. In these states, 50-100% of districts have drinking water containing unhealthy levels of fluoride. The major health issue associated with the consumption of unsafe concentrations of fluoride is fluorosis. This disease damages the enamel of teeth and causes the deterioration of bones and ligaments (187).  Tooth damage can inhibit one’s ability to consume necessary nutrients and decreased limb function leads to difficulty in locomotion, which decreases one’s ability to work (Sarkar, 2009).

Arsenic is another key geogenic contaminant. This element is the 47^th most abundant of the naturally occurring elements. Arsenic is typically found in sedimentary rocks, including shale, slate, and mudstone (Vaughn, 2006). In India, the tectonic uplift of the Himalayan Mountains resulted in increasing the accessibility of arsenic-containing rocks to chemical and physical weathering, which increased the amount of arsenic in the environment (Dissanayake et al, 2010). Arsenic weathered from the rocks of the Himalayas is transported by water down gradient, where it is then deposited in the sediments of areas of lower elevation. These areas are known as arsenic sinks since large amounts of arsenic are dumped and accumulate there. The northeast corner of India is one of these sinks, and large concentrations of arsenic have been found to accumulate in the sediments of West Bengal (177). Increased reliance on ground water for irrigation and drinking water has resulted in an increase in the number of bore wells in northeast India. Overdrafting of the water table has increased the concentration of arsenic in the water by preventing suspended arsenic to settle and precipitate (Dissanayake et al, 2010). Because arsenic exists at typical terrestrial pH values (6.5-7.5) and can be transported in both oxidative and reductive conditions, it is fairly ubiquitous in the environment. This is bad news for the inhabitants of northeastern India, since ingestion of arsenic contaminated water can cause several types of cancer as well as lead to the onset of cardiac, vascular, and pulmonary disease (Vaughn, 2006).

Currently, there are several methods that can be employed to help mitigate the health effects of geogenic contamination. The magnesium silicate serpentine can be used to absorb large amounts of fluoride ions in aqueous solution. Humans suffering from fluorosis can also be directly treated via intravenous administration of magnesium hydroxide. Magnesium hydroxide has been shown to complex with free fluoride ions, which reduces the impact of fluorosis. The long-term solution to the problem of fluoride contamination involves the widespread practice of the Nalgonda technique, which involves increasing pH and adding chlorine and aluminum salts. Increased public participation and governmental support are needed to implement this technique on a broad scale (Dissanayake et al, 2010).

            The mitigation strategies for dealing with arsenic contamination include the use of filters, rainwater harvesting, and regulating bore well distribution and utilization. Although filters are effective in removing arsenic from water, these complex filtration systems often breakdown due to a lack of quality control and an absence of maintenance in rural areas. Additionally, the arsenic removed from the water accumulates in the filtration system in the form of arsenic sludge, which presents another set of health risks.

            Rainwater harvesting is another possible method of reducing arsenic-related health problems. Collecting and saving rainwater reduces one’s reliance on groundwater, which means that overdrafting of the water table is reduced. Arsenic concentration will drop as a result of less groundwater pumping since it will be allowed to settle and precipitate. However, rainwater harvesting is not always a practical solution since many houses in India are constructed with thatched roofs, which are not conducive to the collection of rainwater (Sarkar, 2009).

            The most effective way of ameliorating the health impacts of arsenic contamination is to regulate groundwater access. Currently, the government is too lax in its restrictions on groundwater pumping. As a result, private individuals are free to tap the ground water, even to the point of exploitation. Already high levels of arsenic in the water are exacerbated by constant groundwater withdrawal. Regulating access to groundwater will allow the water table to properly recharge and reduce the concentration of arsenic in the water.

            With all the concern over anthropogenic contamination of the environment, it is easy to forget that there are other sources of environmental contamination. Geogenic materials like fluoride and arsenic occur naturally in the environment, but high concentrations of these substances can result in human health problems. The combination of natural process and human practices can influence the temporal distribution, and thus the health effects presented by geogenic contaminants.   

References

Dissanayake, C. B., Rao, C. R. M., and Chandrajith, R., (2010). Some Aspects of the Medical Geology of the Indian Subcontinent and Neighboring Regions. In Selinus, O., Finkelman, R. B., and Centeno J. A., (Eds.). Medical Geology: A Regional Synthesis.  Springer.

Sarkar, A. (2009) Sustainable solutions to Arsenic contamination of groundwater: The Ganga-Meghna Brahmaputra Basin (Ch 3), In Water, Agriculture, and Sustainable Well-Being. Oxford University Press.

Vaughan, D. J., (2006). Arsenic, Elements, 2:71-75.