Regarding how safe is “Safe”?

To the Editor:

Dr. Brent's discussion of safety (Brent, 2012) reminds me of the time I was sent to Vietnam as part of a committee to investigate the biologic effects of agent orange. We were to fly in a helicopter over forests in which Viet Cong, armed with shoulder-launched guided missile, were known to lurk. At the briefing, we asked the pilot what height would be safe. He said 3500 feet. During the flight, I looked over the pilot's shoulder and noted that the altimeter read 3000 feet. I tapped the pilot on the shoulder and said “How come we are at 3000 feet when you said the safe height was 3500?” “Oh, 3000 feet is safe, but 3500 is safer.” Incidentally, we were fired on once, but they missed.

Clarke Fraser OC, FRSC*, * Professor Emeritus of Human Genetics, McGill University, Montreal, Canada,