| Alar is the Uniroyal company's trade name for daminozide, a chemical used to keep apples from dropping off the tree too early or rotting while still on the tree. The U.S. Food and Drug Administration approved it as safe in 1968. Over the next two decades, studies were done that gave mice something like 8 times the "maximum tolerated dose" of the chemical; the mice developed tumors. (Rats given similar doses did not get tumors.) Because of the massive doses, the study results were not necessarily applicable to the amount a human eating apples would ingest; as drkoop.com points out, "For any substance, no matter how benign, a maximum tolerated dose exists above which the substance will damage tissues merely from its high concentration."
However, the Environmental Protection Agency required that Alar be phased out of use by July 1990. Other organization, such as Ralph Nader's National Resources Defense Council, had been calling for such a ban for a while, and their campaigns had already prompted some chains of grocery stores to stop selling Alar-treated produce.
But on February 26, 1989, however, 60 Minutes did a segment called "A is for Apple," which cast Alar as a potent carcinogen, a major scare began. People assumed all appples and apple products were tainted; supposedly a woman called an apple growers' association to ask whether she should take bottles of apple juice to a hazardous waste collection site.
Apple growers lost sales and money whether or not they used Alar; their organizations sued the National Resources Defense Council and 60 Minutes. The show did a second broadcast on the subject; critics of the earlier program were on it, but Ed Bradley did a lot to suggest that the chemical manufacturers were pressuring these people into saying that Alar was not a risk. The apple-growers' lawsuits were eventually dismissed.
Alar was voluntarily withdrawn from the market a year before the ban went into effect in the U.S. However, many countries did not ban Alar, so apples with the chemical are still available and are sometimes imported to countries which do not use the chemical in their own apple-growing. It is still up in the air whether the use of Alar is actually harmful to humans; there are an equal number of sources that cite studies to say it has and hasn't been shown to be a carcinogen. The 1989 publicity is often referred to in retrospect as an unfounded "scare," but that all depends on who you believe.
Sources:
Carlson, Laurie Wynn. Cattle: An Informal Social History. Chicago: Ivan R. Dee, 2001.
http://www.ewg.org/pub/home/reports/alar/alar.html
http://www.prwatch.org/prwissues/1997Q2/alar.html
http://www.fumento.com/lancetsiege.html
http://www.drkoop.com/news/focus/june/alar.html | 
