My plants are exposed outdoors, near a pine tree that has dropped its pollen on my little plants on a windy day, as seen in the photo. Could this pose a problem for my harvest?
It really shouldn't - I can't imagine a pine tree pollinating a weed! :-D I guess what I would do if I were you would be to hose the pollen off at dusk (don't do it in the mid-day sun or your burn your leaves!) ... and relax... they'll be ok...
Good luck outdoors!