Jack, Its a #2.
#2 is ok , it’s HDPE , also used for milk jugs.
not sure I’d use film canisters as some of the chemicals from the film might not be good (just a thought). No science behind this. Though I know some of the chemicals in older film are not healthy in larger enough amounts over a prolonged period…
I did wash them out before use! 
Well i guess the chemicals can be bad. However if you have no alternative i suggest using only canisters that held the new film (which is in an aluminium thingy). Not ones that held open rolls of film. And if washing , do it properly like so: -fill with cooking oil and let it sit for an hour -wash with detergent -fill with alcohol -wash and fill with water -let it dry. The reason for this is that different chemicals need different solvents. Some go away with fat , some with water , etc.
I don’t think it would be super horrible but some film chemicals can do strange things after long exposure. There isn’t much info on getting in your nose.
Well, these film canisters haven’t had film in them in 10 years or longer. I wasn’t too worried on that. Some have had salt and spices in them from time to time for camping trips. Others have had coins. paper clips, thumb tacks or whatever odds and ends I have the need for. I just keep them around as they are so handy. When I needed something to put some spare snuff in, they were the first thing I thought of. As yet, I have not tried the snuff that is in them, so I’ll report back if it smells or tastes tainted. They have been washed in the past with just soap and water.