Mazur, AlanTrue Warnings and False Alarms: Evaluating Fears about Health Risks of Technology, 1948-1971. Washington: Resources for the Future, 2004. Pp. viii +191. Paperback, $18.95.

Thirty-One warnings about the health implications of various new technologies—water supply fluoridation, shoe fitting fluoroscopes, injuries on synthetic turf, to mention a few—were published in 1977.  (The actual warnings were made 1948-1971.)  Which of these warnings were valid?  How can the public decide if a warning is valid? Mazur argues successfully for four hypotheses: 1) True warnings are more likely to reach the news media through reputable scientific channels; 2) False alarms tend to have sponsors with biases against the producers of the alleged hazard; 3) Hyped media coverage is likely to indicate a false alarm; 4) A warning arising from a popular social issue is more likely to indicate a false alarm.  For example, a warning arising from a popular social issue is radiation from defective televisions, which derived from concerns about nuclear fallout and medical/dental x-rays.  Mazur rates whether a warning is true or false using two criteria, which generally agree.  The first criterion is empirical, based on a standard summary of empirical health effects.  The second criterion is regulatory, the presence or absences of pertinent government regulations.  Using these criteria, seventeen of the thirty one  warnings were true.  Mazur’s hypotheses more accurately distinguish the true warnings.  The case list, published in 1977, was complied by Edward Lawless. He made an assessment then about the validity of the warnings.  His assessment was correct in about 70% of the cases.  The book includes chapters about public attitudes concerning technology, beginning in 1900 and particularly in the 1948-1971 era. Also included is a convincing discussion of his methodology.   The case studies about warnings give a good picture of the political pressures present in regulating technology—a prominent argument against fluoridation involved concerns about communists in the government, which was feared would lead the country to socialized medicine.  A layperson or an engineering undergraduate would have no difficulty understanding the presentation. At a time when the president of General Motors calls global warming a “crock,” the issues of public decisions about technology seem entirely contemporary and not significantly closer to resolution than they were.