Why is my left foot getting wet when I apply the brake?

It appears to be water.

This is an odd one. Without seeing the car it's very difficult. My thought is condensation in the heater vent system, but this would have to occur when the A/C (or defroster) has been used, or an external water leak after it has rained. If you take it to a shop, they should check all Volvo service bulletins, and look on iATN. If the shop doesn't have access to this info, then try to find a better shop, e.g. Volvo dealer or European specialty shop.