Hint: Black foot disease is a vascular disease and patients can suffer from severe systemic arteriosclerosis and dry foot gangrene. It is a severe disease of blood vessels.
A) Nitrates: Due to the consumption of nitrate containing water, one can suffer from serious diseases. It causes fatal disease methemoglobinemia i.e. “blue baby” disease. It may also lead to colon, thyroid, kidney, bladder and ovarian cancer too.
B) Fluoride: Too much fluoride can lead to dental fluorosis or skeletal fluorosis, which can damage bones and joints.
C) Arsenic: Due to consumption of Arsenic water black foot disease occurs. It affects the peripheral vascular system. Diagnostic criteria for this disease include objective signs of ischemia. Malnutrition can also contribute to the development of this disease.
Arsenicosis: Arsenic contamination in water may also be due to industrial processes, such as those involved in mining, metal refining etc. According to WHO the value for arsenic in drinking water is 0.0/mg/litre.
D) Sulphur – Sulphur contaminated water is harmful as it leads to Diarrhea and dehydration.
E) Mercury – It causes disease Minamoto. It is a neurological syndrome. It mainly affects. This disease was firstly discovered in Japan (in 1956). Symptoms include ataxia, numbness in hands and feet, muscle weakness, damage to hearing power and vision.
Hence the correct option is C. Arsenic.
Note: Arsenic is also related to heart disease, cancer, stroke, chronic lower respiratory disorders and diabetes. Arsenic is naturally present in groundwater in a number of countries and is highly toxic.