OK then, WHY are the threshold values always expressed in mA as opposed to volts or watts?
Is it because the authors of those values don't know what they are talking about? If you and Iwire's stance is indeed true, then why hasn't anyone else discovered this a long time ago and changed 'the books'?
The way that I see it, people always say "it's not the volts that is dangerous, it's the amps". And, while this is oversimplified, I understand that the intention of saying it this way, is to remind you that absolute voltage level itself isn't dangerous. It is only when the voltage can cause a current to flow, that it is dangerous.
In otherwords, think of the "bird on the wire". The bird is in contact with a high voltage relative to ground, but isn't in contact with anything other than that line of higher voltage. It is not absolute voltage at a particular location that does harm. It is a voltage difference causing current to flow. Volts still do directly determine the amps, but it is specifically Volts at point A minus Volts at point B.
An interesting question I thought of, is whether or not the ampere threasholds are valid no matter what the skin condition of resistance is. In otherwords, consider this example:
10 milliamps driven by 1000V through a 100 kOhm person with dry skin
10 milliamps driven by 10 Volts through the same person, but 1 kOhm after going swimming for a while (across the same two points on the body/through the same path in the body)
Are these two shock situations equivalent in danger?
I would expect that the first situation is much more dangerous. I would think that it is really cumulative Watt-seconds that would be a better metric of shock hazard.