at least in Aus, about 50V AC, or above 70V DC is where the line in the sand has been drawn saying this is potentially life threatening and you need an electrical or disconnect-reconnect license to continue.
measure the resistance between your thumbs at random points in the day and you will see it change quite varyingly, i myself tend to lie somewhere within 10K and 370K depending on the day of the week, from this divide the voltage by the resistance (in ohms) and if you exceed 6mA, your in potentially life threatening territory, (6mA because your supply may be continuous)