Hair-raising effects of electrostatic trick

Walter Margulis raises an interesting point (Physics Today, March 2010, page 10 ) about whether any ill effects might result from applying an electrostatic charge to a human body. I agree that high-energy electron bombardment would indeed be dangerous were the demonstration performed in a vacuum with lots of free electrons floating around, but then the electrons would be the least of our brave volunteer’s worries. I am assuming, however, that we do the demonstration in normal air at 1 atmosphere. Under those conditions, the mean free path of an electron is about 7 × 10⁻⁵ mm. The maximum electric field without breakdown is on the order of 1 kV/mm. Thus any stray electrons would accelerate through less than 0.1 V before striking an air molecule. But air contains almost no free electrons, or it would not be the near-perfect dielectric that it is. So, go ahead, climb on that wooden stool, crank up the Van de Graaff, and watch your hair stand up as long as you like.