Arsenic Contamination in Groundwater is Becoming a Threat Towards Human Health
Written by Shubhra Biswas Kolkata, January 18, 2019
Arsenic contamination in groundwater is becoming a threat towards human health. Arsenic with the chemical formula ‘As’ is tasteless, odourless metalloid that is widespread in the earth’s crust. According to WHO, the groundwater may contain a maximum of value of 10 ppb (parts per billion) of this element to render it safe for drinking. Over the years, developing countries including India, Pakistan, and Bangladesh follow 50 ppb of arsenic as the accepted value for safe drinking water. About a few decades ago, common men rarely heard about the Arsenic pollution and the adverse effects caused by it. However, currently, it has become a significant health hazard in many countries in Asia and South America. A study conducted in 2007 revealed that approximately 137 million people across 70 countries are now affected by the consequences of arsenic poisoning of drinking water.
Most Toxic form of Arsenic
Arsenic may be present in the earth crust as organic (arsenobetaine, arsenocholine, arsenosugar) as well as inorganic (arsenite and arsenate) forms. This metalloid is the 26th abundant element present in the earth crust. While the organic forms are non-toxic and commonly present in many kinds of seafood, the inorganic forms cause a significant health hazard. Specifically, Arsenite or [As (III)] leads to acute toxicity in human beings.
Areas Impacted by Arsenic
As already stated many countries in Asia, North and South America are facing the crisis of arsenic poisoning of groundwater. Detailed below are the major areas where this chemical pollution is a primary health concern.
India
Arsenic contamination in the Gangetic Delta in India has caused severe health concerns in the last few decades. West Bengal, Bihar, Jharkhand, Chhattisgarh, Uttar Pradesh, Assam, and Manipur are the leading states in India which are bearing the brunt of arsenic poisoning. In the Gangetic Delta, wells within the depth of 20 metres to 100 metres are particularly affected. 7 out of 24 districts in West Bengal and 13 districts in Bihar have a groundwater arsenic concentration of more than 50 ppb.
Bangladesh
The arsenic contamination of groundwater in Bangladesh is most profound in the world. A study conducted by the British Geological Survey in 1998 earmarked 61 out of 64 districts where 46 per cent of the samples showed an arsenic concentration above 10 ppb, while 27 per cent showed it above 50 ppb. About 28 to 35 million people in 1999 got exposed to arsenic poisoning in Bangladesh.
Pakistan
WHO conducted an arsenic test on 1200 samples out of which 66 per cent had the metalloid above the permissible limit. 50-60 million citizens of Pakistan consume water having more than 50 ppb of arsenic.
Chile and Argentina
These South American countries also have arsenic above the permissible value. La Pampa region in Argentina has an arsenic level in the range of 4-5300 microgram per litre.
United States
In the United States, individual states have their own regulation regarding the permissible concentration of arsenic in groundwater. In Arizona, 35 per cent of water supply wells have arsenic beyond allowable value. The percentage of arsenic poisoning in California is 38.
What happens when Arsenic enters the human body?
Arsenic present in the drinking water gets absorbed by the intestine and enters the circulation through the bloodstream. It reaches various organs and leads to an adverse health effect. Arsenicosis is the medical condition resulting from a high amount of arsenic deposit in the body. The immediate effect is vomiting, abdominal pain and diarrhoea. Long term effects result in various ailments including keratosis, lung and bladder cancer, skin cancer, malfunctioning of the vascular system, and adverse effect on reproductive organs. It also leads to the inhibition of functioning of numerous vital enzymes and ultimately causes death through multi-system organ failure. The doctors determine the extent of arsenic poisoning in human bodies by investigating the hair and nails.
Prevention of Arsenic Poisoning
Detailed below are some of the preventive and control measures of groundwater arsenic poisoning.
· Substitution of high-arsenic drinking water sources with microbiologically safe low arsenic potable water like rainwater and treated surface water.
· Painting the tube wells and hand pumps with red colour if the water is found unsafe for drinking. It is a cost-effective measure of reducing arsenic exposure.
· Installation of centralised and domestic arsenic removal system incorporating arsenic removal through the different chemical process including oxidation, coagulation-precipitation, absorption, ion exchange, and membrane techniques.
Finally, we can say that millions of people in the Indian sub-continent are currently facing the adverse effects of arsenic poisoning. However, the good news is WHO and UNICEF have taken up joint monitoring programmes for providing safe arsenic-free drinking water under their 2030 Agenda for Sustainable Development.
Image source: Model illustration of Space-filling model of part of the crystal structure of arsenic triiodide, AsI3. Structural data from Z. Kristallogr.1965, 121, 81-86. Credited to CCoil (talk) CC-BY-3.0
References: who.int, en.wikipedia.org, indiawaterportal.org
