Consider the following statements about the effects of some polyhalogen compounds.
(A) Methylene chloride harms the human central nervous system.
(B) Chronic exposure to chloroform may cause damage to the liver, where chloroform is metabolised to phosgene.
(C) There is some evidence that exposure to carbon tetrachloride causes lung cancer in humans.
(D) Carbon tetrachloride released into the air rises to the atmosphere and depletes the ozone layer.
Which of the statements given above are correct? Choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → (A), (B) and (D) only
Many polyhalogen compounds are useful solvents, but they harm human health, and some of them harm the environment.
(A) Methylene chloride harms the human central nervous system. — True. Even low levels in air can slightly impair hearing and vision.
(B) Chronic exposure to chloroform may cause damage to the liver, where chloroform is metabolised to phosgene. — True. Long exposure can damage the liver and the kidneys.
(C) There is some evidence that exposure to carbon tetrachloride causes lung cancer in humans. — False. The evidence links carbon tetrachloride to liver cancer, not lung cancer.
(D) Carbon tetrachloride released into the air rises to the atmosphere and depletes the ozone layer. — True. So carbon tetrachloride harms the environment as well as human health.
NCERT (2026-27 edition):
6.8.1 Dichloromethane (Methylene chloride) – “…Methylene chloride harms the human central nervous system. Exposure to lower levels of methylene chloride in air can lead to slightly impaired hearing and vision.”
6.8.2 Trichloromethane (Chloroform) – “…Chronic chloroform exposure may cause damage to the liver (where chloroform is metabolised to phosgene) and to the kidneys, and some people develop sores when the skin is immersed in chloroform.”
6.8.4 Tetrachloromethane (Carbon tetrachloride) – “…There is some evidence that exposure to carbon tetrachloride causes liver cancer in humans.” … “When carbon tetrachloride is released into the air, it rises to the atmosphere and depletes the ozone layer.”