Polypropylene and polyethylene are inert plastics - just straight chain hydrocarbon polymers. No nasty functional groups.
If there were plasticisers like phthalates added to soften the plastic then that could be a problem. I must admit, am not particularly familiar with the mechanical properties of said products plastic, so I dont know if plasticisers are added.
You have to consider the relative danger of the alternatives. People you find in bars might have all manner of horrible bugs. Flashing in the mall can get you arrested. And cucumbers have traces of insecticide on them. Nah, don’t sweat the polypropylene.
If you’re looking for disease factors in your sex toys, just make sure you clean them regularly–my guess would be that disease from poor hygeine is more of a danger than carcinogens .