Which of the following statements about DDT is NOT correct?

The correct answer is Option (4) → DDT has a low toxicity towards fish.

DDT (p,p’-dichlorodiphenyltrichloroethane) was used widely because it killed disease-carrying insects. Its extensive use soon caused problems, both with insects and with other animals.

Option (1) DDT was the first chlorinated organic insecticide. — Correct about DDT. It was first prepared in 1873; its insecticidal effect was discovered later, in 1939.

Option (2) The use of DDT increased greatly after World War II because it was effective against the mosquito that spreads malaria. — Correct about DDT. It was effective against the malaria mosquito and against lice that carry typhus.

Option (3) Many species of insects developed resistance to DDT. — Correct about DDT. This resistance was one of the problems that appeared in the late 1940s.

Option (4) DDT has a low toxicity towards fish. — Not correct about DDT. DDT was found to have a high toxicity towards fish, the second problem of its wide use.

NCERT (2026-27 edition):
6.8.6 p,p’-Dichlorodiphenyltrichloroethane (DDT) – “DDT, the first chlorinated organic insecticides, was originally prepared in 1873, but it was not until 1939 that Paul Muller … discovered the effectiveness of DDT as an insecticide. … The use of DDT increased enormously on a worldwide basis after World War II, primarily because of its effectiveness against the mosquito that spreads malaria and lice that carry typhus. However, problems related to extensive use of DDT began to appear in the late 1940s. Many species of insects developed resistance to DDT, and it was also discovered to have a high toxicity towards fish.”