A few years ago there were lots of concerns about pesticides and chemicals getting into wax. Particularly in the USA as they were hunting for the cause of CCD. However that worry seems to have died down (not CCD of course but nasty wax).
With regard to pesticides, there can be toxic mixes when fungicides are mixed with other treatments - the separate treatments are apparently "OK" in themselves but the manufacturers of them didin't test the mixes that can occur.
May your bees read the same books as you do.