Read the passage and answer the questions:
Water Pollution
Indiscriminate use of water by increasing population and industrial expansion has led degradation of the quality of water considerably. Surface water available from rivers, canals, lakes, etc. is never pure. It contains small quantities of suspended particles, organic and inorganic substances. When concentration of these substances increases, the water becomes polluted, and hence becomes unfit for use. In such a situation, the self-purifying capacity of water is unable to purify the water. Though water pollutants are also created from natural sources (erosion, landslides, decay and decomposition of plants and animals, etc.) pollutants from human activities are the real causes of concern. Human beings pollute the water through industrial, agricultural and cultural activities. Among these activities, industry is the most significant contributor. Industries produce several undesirable products including industrial wastes, polluted waste water, poisonous gases, chemical residuals, numerous heavy metals, dust, smoke, etc. Most of the industrial wastes are disposed off in running water or lakes. Consequently, poisonous elements reach the reservoirs, rivers and other water bodies, which destroy the bio-system of these waters. Major water polluting industries are leather, pulp and paper, textiles and chemicals. Various types of chemicals used in modern agriculture such as inorganic fertilisers, pesticides and herbicides are also pollution generating components. These chemicals are washed down to rivers, lakes and tanks. These chemicals also infiltrate the soil to reach the ground water. Fertiliser induces an increase in the nitrate content of surface waters. Cultural activities such as pilgrimage, religious fairs, tourism, etc. also cause water pollution. In India, almost all surface water sources are contaminated and unfit for human consumption.
Which out of the following is correct about water pollution?
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → When concentration of substances increases, the water becomes polluted.
Option (1) Surface water available from river, canal, lakes etc. is pure. — Incorrect. Surface water is never pure; it always holds small quantities of suspended particles and other substances.
Option (2) When concentration of substances increases, the water becomes polluted. — Correct. Surface water always carries small quantities of suspended particles and organic and inorganic substances, which it can cope with by itself. When the concentration of these substances increases, the load becomes more than its self-purifying capacity can clean, so the water becomes polluted and unfit for use.
Option (3) When the concentration of substances increases self purifying capacity of water is increased. — Incorrect. A higher concentration overwhelms the self-purifying capacity; it does not raise it.
Option (4) Water pollution is caused by natural factors only. — Incorrect. Pollutants from human activities are the real causes of concern, not natural ones alone.
Note: A similar question was also asked in CUET (UG) 2026 on 31-05-2026 (Slot 1).
NCERT (2025-26): “Water Pollution Indiscriminate use of water by increasing population and industrial expansion has led degradation of the quality of water considerably. Surface water available from rivers, canals, lakes, etc. is never pure. It contains small quantities of suspended particles, organic and inorganic substances. When concentration of these substances increases, the water becomes polluted, and hence becomes unfit for use. In such a situation, the self-purifying capacity of water is unable to purify the water. Water Pollution … Though water pollutants are also created from natural sources (erosion, landslides, decay and decomposition of plants and animals, etc.) pollutants from human activities are the real causes of concern. Human beings pollute the water through industrial, agricultural and cultural activities. Among these activities, industry is the most significant contributor.” |