"Copy machines, as it turns out, have one of the strongest magnetic fields, and they increase as you get closer," says the NIOSH's W. Gregory Lotz. "I've seen some measurements taken a foot away from the machine. The lowest field measured was 2 milligauss. The highest was 40 milligauss. Electric pencil sharpeners are even worse -- I've seen measurements of up to 90 milligauss."