Water quality fact sheet: Iodine

Most trace elements in drinking water are of concern from a public health point of view because of potential for excess above recommended limits. However, some trace elements are essential to health and so are required to be present at certain concentrations in drinking water or food. Iodine is one such essential element. Deficiency in dietary iodine can lead to a number of iodine-deficiency disorders (IDDs) in humans. No regulations or recommendations are placed on concentrations of iodine in drinking water because such standards are imposed to regulate upper rather than lower limits. Iodine may also be potentially detrimental to health at high concentrations, but the element usually behaves in a similar way to chlorine in nature and hence iodine-rich waters are likely to be rendered unfit for potable use due to high salinity before iodine becomes a significant problem

Groundwater quality: Bangladesh

Bangladesh has a total area of around 144,000 square kilometres and lies within the Bengal Basin of South Asia. It is bordered on most sides by India, and by Burma in the south-east. Bangladesh has a tropical monsoon climate with a high annual rainfall of 1000–2000 mm or more, falling mainly during June–September. The wettest place in the world, Cherrapunji, lies just to the north of Bangladesh in the Meghalaya Hills of India. Around a third of the country floods annually during the monsoon season, a factor which hinders economic development considerably. Bangladesh has a large area of surface water in the form of the major Padma (Ganges), Jamuna (Brahmaputra) and Meghna Rivers and their tributaries. These originate in the highlands (including the Himalaya) of northern India and beyond. The land is mainly a flat-lying alluvial plain with hill country in the south- east (Chittagong Hill Tracts). Elevation varies from 1230 m in Keokradong (south-east) to sea level. Much of the land is within 5 m of mean sea level

Groundwater quality: Mali

Mali is located in the Sahel region of West Africa, to the south-west of Algeria and north of Burkina Faso and Niger (Figure 1). It has a large area of some 1.24 million square kilometres. The terrain is dominated by flat or rolling sand-capped plains in the north and savannah in the south, although rugged hills occur in the north-east. Elevation varies from the highest point at Hombori Tondo (1,155 m) to the lowest on the Senegal River (23 m)

Groundwater quality: Nigeria

Nigeria is situated in West Africa, bordered by Benin in the west, Cameroon in the east and the Gulf of Guinea in the south (Figure 1). It has a land area of some 911,000 square kilometres. The terrain is very variable, with mountains in the south-east, hills and plateaux including the Jos Plateau in the centre, lowlands in the south and plains in the north. The highest point is Chappal Waddi (2419 m) in eastern Nigeri a and the lowest is sea level

Water quality fact sheet: Manganese

Manganes e is an esse nti al trace el eme nt for human heal th. The daily nutri tional requirement is 30– 50 μg/kg of body weight (WHO, 1993). Manganese is readily a bsorbed in hu man me taboli sm but t he degree of absorption depends on dos e, chemic al form and effects of ot her metals. Manga nese dissolved in water is lik ely to be more bioavailable than solid forms

Groundwater quality: Mozambique

Mo zamb ique lies in so uth -eastern Africa between South A frica and Tan zania, with the Mo zam bique Channel forming its easter n border (Figur e 1). Lake Nyas a forms par t of t he n orth- west ern b order wit h Malawi and Ta nzani a. Th e count ry has an area of 801,600 square kilometres and s ome 2500 kilometres of coas tline

Water quality fact sheet: Arsenic

Arsenic is a trace element found at variable concentrations in the atmosphere, soils and rocks, natural waters and organisms. It is mobilised in the environment through a combination of natural processes such as weathering reactions, biological activity and volcanic emissions as well as through a range of human activities, including mining, industry and agricultural use of arsenical pesticides. Of the various sources of arsenic in the environment, drinking water poses potentially the greatest threat to human health

Groundwater quality: Nepal

Nepal is a landlocked co untry in southern Asia, between China and India, with a total land area of 140,800 square kilometres . Topographic variations are extreme and the terrain has a general southward slope. The topography ranges from rugged high Himalaya in the north, to the central hill region, to the lower-lying Siwalik Range (south-central) and down to the ‘terai’ or flat river plain in the south. Elevations range from gr eater than 8000 m (Mount Everest range) on the north border with China (Tibet; Figure 1) to 70 m (Kanchan Kalan, terai region) in the south. Nepal has eight of the ten highest mountains in the world

Groundwater quality: Zambia

Zambia is a landlocked country in southern Africa, lying to the south of Congo and north of Zimbabwe, with a total land area of around 752,600 square kilometres (Figure 1). Terrain consists mainly of high plateau with some mountains and hills. Elevation varies from greater than 2300 m in the Mafinga Hills on the north-east national border, to 329 m in the valley of the Zambezi River (Figure 1). The western part of the country consists mainly of plateau, typically at 1000–1300 m above sea level. The terrain is more variable in the east. The Muchinga Mountains form a north-east to south-west ridge (up to 1788 m) in the Central and Northern Provinces. Deep valleys occur along the Luangwa and Zambezi Rivers in south-eastern Zambia . Topographic depressions also occur in parts of Northern and Luapala Provinces, where many of the low-lying areas are occupied by swamps, of which the largest is the Bangweulu swam

Groundwater quality: Pakistan

Pakistan lies in southern Asia, bordered to the east by India, the west by Iran and Afghanistan and to the north by China (Figure 1). The total area is 803,940 square kilometres. Terrain consists of the flat-lying Indus Plain in the east, mountains of the Himalaya, Karakoram and Hi ndukush ranges in the north, hill regions (up to 4761 m) in the north-west, and the upland Baluchistan plateau in the west. Elevation ranges are extrem e, from K2 (8611 m) to the Indian Ocean (0 m)