2.4.2  Chemical tests

Although the great majority of health-related water quality problems are the result of biological contamination, chemical contamination of water sources can also cause serious health problems.

Fluoride in low concentrations (less than 1.5 mg l–1) in drinking water has beneficial effects on teeth, but exposure to excessive fluoride can give rise to a number of adverse effects (WHO, 2004). Fluorosis (an abnormal condition caused by excessive intake of fluorides) is a common problem in children living in the Rift Valley region of Ethiopia where the level of fluoride, especially in groundwater, can be high. Levels of fluoride above 1.5 mg l–1 can lead to mottling of children’s teeth (the appearance of spots or blotches of different shades of colour – Figure 2.9). Higher levels can lead to severe skeletal fluorosis, where fluoride accumulates in the bones over many years causing stiffness and pain in the joints and bones (WHO, 2004). Consuming water that has levels in excess of 10 mg l–1 leads to crippling skeletal fluorosis where the extremities become weak and moving the joints is difficult. The vertebrae partially fuse together, crippling the patient (WHO, 2004).

Figure 2.9  Fluorosis causes mottling of children’s teeth.

Alternatively, some health effects occur as a result of specific chemical deficiencies in the diet, of which water forms a part. Examples include goitre, caused by iodine deficiency, and dental caries resulting from low fluoride intake.

2.4.1  Microbiological tests

2.4.3  Physical tests