Before Earth Day became a national holiday it was celebrated in Berkeley, CA, where I worked in the dormitories at California School for the Deaf.
We were having major problems with head lice. None of the staff had ever encountered those pesky creatures before, and we knew nothing about them, but they were driving us crazy. No matter what treatments the nurses gave the students, the lice spread, and spread. (Now I know that was partly because every week we washed all their combs and brushes in one bathtub.)
Finally one of the counselors got fed up and went downtown to the Public Health Department. They gave her something they said would certainly get rid of the infestation.
So we spent the very first Earth Day putting DDT on the heads of all the children.
Of course nobody knew back then how toxic that chemical was and it did work.