Date: Started in 1962 based on a book, Rachel Carson’s Silent Spring

Forecast of impending disaster: DDT was claimed to be a dangerous cancer-causing chemical. Publication of the book was followed by what some called a national hysteria. The alarm over forecasts of DDT’s harmful effects combined concerns about the health and wellbeing of people with concerns about other species. Papers by scientists purported to demonstrate harmful effects on people from DDT exposure.

Forecasting method: A scenario based on the author’s speculations from various pieces of information about the effects of DDT. There was no direct evidence that DDT harmed people.

Actions called for: Governments were asked to ban exports of DDT and World Bank loans would be banned to countries that used DDT.

Endorsements of and challenges to the forecast: Leading scientists from institutions (such as Stanford University), politicians (such as Senator Al Gore,) and a report by a commission appointed by President Carter. The reports of the dangers were widely covered by the mass media.

Outcomes of the conflict: The U.S. Environmental Protection Agency (EPA) banned the use of DDT following an 80-day hearing in 1972. Europe and Africa, under pressure from international agencies, did too. No actual harmful effects on humans have been found to result from DDT. Millions of people have died from mosquito-born diseases such as malaria. The EPA decision was based on two studies of animals: the first could not be replicated and the second used a flawed experimental design.

Source: Edwards (2004); Waite (1994)

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