Final answer:
CFCs were manufactured in 1970 because they were widely used in various applications, but they were later found to have a harmful effect on the ozone layer. The Montreal Protocol agreement was established in 1987 to phase out CFC production.
Step-by-step explanation:
The dangerous CFCs were being manufactured in 1970 because at that time, they were commonly used in various applications such as refrigerators, air conditioning systems, foams, and aerosols. CFCs, or chlorofluorocarbons, were synthetized chemical compounds that had desirable properties for these applications, such as being stable and having low toxicity.
However, it was later discovered that CFCs have a detrimental effect on the ozone layer in the upper atmosphere. They react with ozone, damaging it and reducing the layer's ability to protect the Earth from harmful ultraviolet radiation.
As a response to this discovery and the international concern over the issue, the Montreal Protocol agreement was established in 1987 to phase out CFC production in most countries. This agreement aimed to prevent further harm to the ozone layer and promote the use of alternative chemicals and technologies.