acid rain

“At that time, people were concerned about acid rain.”

Part of the reason for concern is that when sulfur dioxide leaves the stratosphere and sinks into the lower atmosphere, it can potentially fall as acid rain.

He was also passionate about environmental causes, leading a global treaty to protect the ozone layer and signing a pact with the U.S. to reduce the pollution that causes acid rain.

Internationally, he pushed for Reagan to sign a treaty to curb acid rain and an agreement to modernise Canada's air defence systems.

For example, the U.S. regulated industrial sulfur and nitrogen dioxide emissions in 1990, but only after we had determined that they caused acid rain and acidified many water bodies in the Northeast.