Does anyone know the voltage rating of the four 2.2 uF capacitors on the stereo inputs/outputs of the Audio Board?

Also, are they polarized? They don't have a + symbol in the schematic I see, but on the other hand, they do have the curved plate, which could indicate the cathode (-). So, polarized... but then, I see that all of the capacitor symbols on the schematic have the curved plate... are they all polarized? I wouldn't have thought the 0.1 uF caps were polarized.

https://www.pjrc.com/store/schematic_audio4.png

Reason: I am incorporating a Teensy 3.2 + Audio Board as a DSP unit in a ham radio transceiver. The radio's audio input has +8V or so DC bias for an electret mic. So, (a) I want to make sure the blocking caps have a high enough rating, but also (b) I want to make sure the polarity is correct.

Thanks!