The Percy Amendment
In August 1978, Senator Charles Percy (R-Ill.) introduced
an amendment to Section 481 of the Foreign Assistance
Act of 1961, prohibiting US support for programs
involving spraying of herbicide to eradicate marijuana, if the
use of herbicide "is likely to cause serious harm to the health
Under the Percy Amendment, the Secretary of State
was required to inform the Secretary of Health, Education,
and Welfare of the use or intended use of any herbicide in a
US-funded program. The Secretary of HEW was then required
to determine potential health hazards. On October 13,
1978 the Department of State notified HEW that the United
States was providing assistance to the Mexican program.
In response to that notification, then HEW Secretary
Joseph Califano directed CDC to conduct a systematic
sampling program to determine the extent and severity of
paraquat contamination of marijuana. At the same time, he
directed NIEHS to undertake additional combustion testing
of paraquat-contaminated marijuana.24 HEW legal staff reviewed
the legislative history of the Percy Amendment to
define the phrase "serious harm". They determined that no
documentation of persons who had been damaged by exposure
to paraquat was required, and that "actual harm need
not be shown if it is reasonable to predict that it will
occur. "25