For those worried about radiation, I used to fly with a captain who was a fanatic. He carried a radiation detector when he flew. He found that on pur 757s the worst offender was the window heat controllers located above the center of each forward window so he turned the heats off above 10,000 ft since there was no restriction against flying without them there. He turned them back on below 10 because there was a restriction. Takes all kinds I guess. I always just followed the book. Simpler that way.