Let's get some data from the literature out to the sphere:
From Cornell:
http://www.cs.cornell.edu/~asaxena/papers/IEEEPD-shock.pdf
Contact currents occur when a person touches conductive surfaces at different potentials and completes a path for current flow through the body. Depending on the magnitude of the current flowing and its frequency, the current can be lethal. Detailed studies have been done on current flow in human body [7,8] and sophisticated models of current flow have been developed. From these investigations for 50/60 Hz currents on human body, current levels have been determined which cover the range of effects from the threshold of perception, let-go-current, ventricular fibrillation, and cardiac asystole [4].
It is generally agreed that it is the magnitude and time duration of the current passing through the body that causes a given effect. The touch voltage is only important insofar as it will produce a given current depending on the impedance in the circuit path. Death at voltages, like 120/220 V, can usually be attributed to ventricular fibrillation.
The threshold of perception for a finger-tapping contact is approximately 0.2 mA. The maximum allowed leakage current for appliances is 0.5 mA. Currents above 6 mA are considered as Let-Go current limit [9]. This level is important because for currents above this level, the victim can be involuntarily held by his or her own muscles to the energized conductor and cannot let go.
If a person is once frozen to a circuit, either he or she will get off and live; or he or she will not get offâ€â€the contact resistance may decrease and increase the current to a lethal level resulting in ultimately death.
By extrapolation from experiments on animals [4], the safe current limit for victim to survive is 500 mA for shock of 0.2 seconds.
[4] Theodore Bernstein, “Electrical Shock Hazards and Safety Standardsâ€Â, IEEE Transactions on Education, vol. 34, no. 3, August 1991.
[7] F.P. Dawalibi, R.D. Southey, and R.S. Baishiki, “Validity of Conventional Approaches for Calculating Body Currents Resulting from Electric Shocksâ€Â, IEEE Transactions on Power Delivery, vol. 5, no. 2, April 1990.
[8] Magda S. Hammam and Rod S. Baishiki, “A Range of Body Impedance values for Low Voltage, Low Source Impedance Systems of 60 Hzâ€Â, IEEE Transactions on Power Apparatus and Systems, vol. PAS-102, no. 5, May 1983.
[9] C. F. Dalziel and F. P. Massoglia, “Let-go currents and voltages,†AIEE Trans,, vol. 75, part II, pp. 49-56, 1956.
From the University of Missouri:
http://smarteng.mst.edu/sensors/electricshock.html
At values as low as 20 milliamperes,
breathing becomes labored, finally ceasing completely even at values below 75 milliamperes. As the current approaches
100 milliamperes, ventricular fibrillation of the heart occurs--an uncoordinated twitching of the walls of the heart's ventricles.
Above 200 milliamperes, the muscular contractions are so severe that the heart is forcibly clamped during the shock. This clamping protects the heart from going into ventricular fibrillation, and the victim's chances for survival are improved. However, there will certainly be other effects, depending upon the current level and duration of the shock.
Alternating current (AC) is four to five times more dangerous than direct current (DC). For one thing, AC causes more severe muscular contractions. For another, AC can lower skin resistance and thereby increase the shock-current. The skin resistance goes down rapidly with continued contact because sweating is stimulated and the skin oils and even the skin itself are burned away. Consequently, it is extremely important to free the victim from contact with the current as quickly as possible before the current increases to the fibrillation-inducing level. Also, the frequency of the AC influences the effects on the human body. Unfortunately, the standard electrical power frequency of 60 Hertz is in the most harmful range. At this frequency, as little as 25 volts can kill. On the other hand, people have withstood 40,000 volts at a frequency of a million Hertz or so without fatal effects.
So if you hands and feet are wet and salty and the voltage is high, it will be easy to drive the 6mA through you that will make you literally "toast". I believe as said before that the 42/48 volt so called low voltage limit is where "most folks" in "most circumstances" are statistically well below the 6mA Can't Let Go Threshold.