Assertion: acid rain | /r/CapableOf | become recognized as regional environmental issue
Facets:
value: in early 1970s
type: TEMPORAL
value: in the 1960s
type: TEMPORAL
Source sentences:
text: In the 1950s, scientists in the United States started studying the phenomenon, and in the 1960s and early 1970s, acid rain became recognized as a regional environmental issue that affected Western Europe and eastern North America.