Prof. Dr. Shyam P Lohani

About 200 million people worldwide are exposed to high concentration of arsenic in drinking water beyond the recommended limit of 10 ppb (part per billion) by World Health Organisation. The majority of those exposed population live in South Asian countries, including Nepal (WHO, 2014). The United Nation General Assembly in 2010 has explicitly recognised that clean drinking water and sanitation are essential for the realisation of all human rights. Although a large majority of Nepali population has access to drinking water but it is not safe. Around 50 per cent of the country’s population lives in the Terai region and above 90 per cent of people rely on groundwater as their major source of drinking water. To extract water, most often shallow tube wells are used in those areas. Despite being bacteriologically safe to drink, the water from many of those shallow tube wells are contaminated with arsenic which was first reported in Nepal in 1999.

Situation
Arsenic is found in the earth’s crust and gets distributed in the air, water and soil. It is usually found in both organic and inorganic forms. The inorganic form of arsenic is most toxic to humans. This is found naturally in high levels in the groundwater of many countries in the world from Argentina to Bangladesh, Chile, China, India and Mexico to the United States of America (WHO, 2018). The issue of arsenic toxicity mainly arises due to its presence in groundwater, crops irrigated and food prepared with contaminated water. It is also used in industrial processes and still used as pesticides in many developing countries.
The arsenic contamination of groundwater in Nepal was found in all Terai districts but at different concentrations. A blanket testing of all tube wells in the Terai region was started in 2004. As of June 2008, testing of 11, 39, 891 tube wells was completed. The testing showed that about 1.77 per cent (20,243) tube wells have exceeded the national standards of Nepal for drinking water (50 ppb) and 5.62 per cent (64,168) have exceeded the WHO Guideline Value (10ppb) (NHRC, 2009). The above report showed there is a problem of arsenic contamination of groundwater.
Whatever the source of exposure, arsenic is very dangerous in the sense that it has no odor or taste and we get exposed to it without knowing about it. The symptoms of arsenic poisoning can be acute, severe and intermediate or chronic depending on the exposure. The acute effects include drowsiness, headaches, confusion and severe diarrhea. The severe and intermediate effects include a metallic taste in the mouth and garlicky breath, excess saliva, problems swallowing, blood in the urine, cramping muscles, hair loss, stomach cramps, and convulsions, excessive sweating, vomiting and diarrhea. The chronic exposure to arsenic causes cancer, liver diseases, diabetes, nervous system complications, such as loss of sensation in the limbs and hearing problems, and digestive difficulties. Besides skin cancer, chronic exposure to arsenic also causes cancers of bladder and lungs.
It is important to monitor arsenic level among the people residing in the areas where water source is contaminated with arsenic above the guideline level. The level of arsenic can be tested in blood, urine, hair and fingernail samples. The urine and blood sample is useful in case of acute toxicity for those occupationally exposed and hair and fingernail samples for people who have undergone arsenic exposure over the long period of time especially in areas where water source is contaminated. The treatment of arsenic poisoning depends on type and stage of exposure including removal from the source of exposure, symptomatic treatment and chelation therapy.
The most important step in the prevention for the affected people are to remove them from further exposure by providing safe water for drinking, food preparation and also for crop irrigation. The decontamination of arsenic at the source is another way of dealing arsenic poisoning. Installing RO water purifiers can reduce the arsenic contamination at source. Other water purification techniques based on oxidation, coagulation precipitation, absorption and ion exchange can also reduce arsenic contamination but should be considered only as a short term solution till the permanent solution at the source is available.

Awareness
The depth of the wells determine the concentration of arsenic in water, therefore, deep tube wells can be considered in areas of heavy arsenic contamination provided arsenic level falls below the set standard with depth. Rainwater harvesting and treating surface water for microbial contamination can be the acceptable ways of reducing arsenic contamination. The large scale awareness programmes targeting people most at risk of arsenic poisoning should be developed and conducted in order to make them able to distinguish between levels of contamination of arsenic and identify initial symptoms caused by the exposure of arsenic contaminated drinking water. The symptoms caused by arsenic poisoning are often misdiagnosed; therefore healthcare providers at those areas should be trained in diagnosing and treating arsenic poisoning. The continuous monitoring of the arsenic contamination at the groundwater should be carried out in order to develop mitigating measures at the policy level.

(Prof. Lohani is Clinical Director of the Nepal Drug and Poison Information Centre and can be reached at lohanis@gmail.com)