Final answer:
DDT's ban was prompted by its environmental impact and health concerns, including the thinning of bird eggshells and cancer risk in humans.
Step-by-step explanation:
The discontinuation of DDT usage was primarily due to its environmental and health impacts, as highlighted in Rachel Carson's book Silent Spring. DDT's persistence in the environment allowed it to bioaccumulate and biomagnify through food chains, leading to weakened eggshells in birds like eagles, and posing risks of cancer in humans.
Beyond its ecological damages, DDT also led to the development of resistance in pests like mosquitoes, reducing its effectiveness over time, detailed in Rachel Carson's Silent Spring. Despite earlier benefits in reducing malaria, drawbacks like resistance development and biomagnification led to its discontinued use.
The US government banned DDT in 1972 because of its environmental harm, specifically to birds of prey. After the ban, populations of affected species, including the bald eagle, showed recovery. However, the initial use of DDT had notable merits, such as significantly reducing malaria cases by controlling mosquito populations.