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Guideline value of maximum arsenic contamination

Considering the widespread and verified negative health effects on humans, WHO recommended provisional health-based guideline value of total arsenic concentration of 10 pg L"1 in drinking water as ‘safe’ limit since 1993 (WHO 1993). Considering the difficulties in practical quantification and removal of arsenic in range of 1 to 10 pg L'1 and below from drinking water, especially from small supplies, the WHO guideline value of 10 pg L'1 is designated as provisional. However, there are evidences of arsenic related health hazards even from low concentration on long-term exposure. Many countries, viz. Japan, Jordan, Laos, Mongolia, Namibia, Syria, USA and the European Union have adopted this ‘safe limit’ as their national standard for dxinking water. However, several other counties like India and Bangladesh have accepted 50 pg arsenic L'1 in drinking water as National Standard based on 1971 WHO advice. Some other countries such as Bahrain, Bolivia, China, Egypt, Indonesia, Oman, Philippines, Saudi Arabia, Sri Lanka, Vietnam, Zimbabwe, etc. also did not update their drinking water standards as per recent WHO recommendation and retain the old WHO guideline of 50 pg L~‘ (Johnston et al. 2001). Australia has set most stringent national standard for acceptable arsenic concentration in drinking water (7 pg L-1). The joint Food and Agriculture Organization (FAO)-WHO Expert Committee on Food Additives has set 0.002 mg arsenic kg-1 of body weight as provisional maximum tolerable daily intake limit of inorganic arsenic in 1983.

Arsenic distribution in the world

Due to the worldwide distribution of arsenic contamination and its severe impact on health, arsenic problem is frequently illustrated by the term ‘mass poisoning’. United Nations considered arsenic poisoning as the second most important drinking water related health-threat (Johnston et al. 2001). The arsenic-induced health effects were first reported from Cordoba province of Argentina in 1917 and was popularly known as “Bell Ville Disease” (Chakraborti et al. 2018). Earlier (before 2000), only a few countries worldwide were considered as arsenic contaminated, viz. Bangladesh, China, India (West Bengal), Taiwan and Thailand. In the first decade of this century, arsenic related groundwater problems emerged in different countries across the globe. Currently, 107 countries in five continents are considered as affected with arsenic contamination in groundwater (Figure 2). In all these countries, around 296 million peoples are reported to be at potential risk of toxicity due to arsenic consumption through drinking water and also from food.

In India, arsenic contamination in groundwater in the range of 50 to 3700 pg L"1 has been reported from several states, namely Punjab, Haryana, Uttar Pradesh, Madhya Pradesh, Jharkhand, Chhattisgarh, Assam, Manipur, Tripura, Nagaland, Amtraclral Pradesh, Bihar and West Bengal (Figure 3). Among these, Bihar and West Bengal are the most severely affected. More than 40 percent of the people of Bihar and West Bengal are affected with arsenic contamination in groundwater and are suffering from seiious health hazards. The presence of arsenic in groundwater of West Bengal, exceeding the acceptable limit (50 pg L"1), was first detected in 1978 and the first cases of arsenicosis

Current global groundwater arsenic contamination situation and potentially exposed population (Source

Figure 2. Current global groundwater arsenic contamination situation and potentially exposed population (Source:

Chakraborti et al. 2018).

Arsenic affected stretches of Ganga-Meghna-Bralunaputra plains of North and North-Eastern India (source

Figure 3. Arsenic affected stretches of Ganga-Meghna-Bralunaputra plains of North and North-Eastern India (source:

Datta 2015).

were identified from one village of 24 Parganas district (Garai et al. 1984). In next few years, scientists identified arsenic contamination in several other adjoining districts. At present, approximately 111 blocks spreading over 12 districts along with the Kolkata city are considered as arsenic affected. In the northern states, high arsenic contamination has been reported from 17 districts of Punjab and 14 districts of Haryana. In North-Eastern part of the country, arsenic contamination in groundwater has been reported from several districts of Assam, Manipur, Nagaland, Tripura and Aranachal Pradesh (Muklieijee et al. 2006, Singh 2007, Chakraborti et al. 2008, Banerjee et al. 2011).

Arsenic contamination in groundwater of Bangladesh is considered as one of the greatest environmental disasters in the world. In Bangladesh, the groundwater of 61 out 64 districts is severely contaminated with arsenic. Over 35 million people are exposed to arsenic contamination in drinking water. In addition, around 57 million people are at the potential risk of arsenic exposure, especially in areas where groundwater is used for drinking, cooking and other household activities. In some parts of Bangladesh, arsenic in drinking water is considered as major cause of chronic health problem and at least 1 million people are feared to be affected with arsenicosis (Hasanuzzaman et al. 2015).

In Americas (North and South America), 21 countries are affected with arsenic. Among those, the problem is acute in Mexico, USA, Chile and Argentina. In Latin America, over 4 million people are affected with arsenic contamination in drinking water. In USA, 30 million peoples are in danger of arsenic poisoning through drinking water and food-chain. In USA, arsenic problem is mostly present in states like Alaska, Arizona, California, Hawaii, Idaho, New Hampshire, Nevada, Utah, Oregon and Washington.

As per the current status, 34 European countries are facing arsenic exposure, threatening over 8 million people. Portugal is the most severely affected country with 2.8 million people at potential risk followed by Serbia with 2 million affected people. The other alarming arsenic affected European countries are Hungary, Romania and Croatia. A study of groundwater quality repotted that drinking water of around 400 towns and villages situated in the Great Hungarian Plain have arsenic contamination several times higher than the WHO guidelines (Csalagovits 1999).

About 15 African countries are found to be affected with groundwater arsenic contamination with 24.3 million potentially exposed population. In Africa, high concentration of arsenic has been noticed predominantly in Nigeria, Ethiopia, Ghana, Morocco, Togo, Zimbabwe, and in some areas of Tanzania while the coastal countries are the least affected (Ahoule et al. 2015).

 
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