I work with polyurethane resin, and up until now was doing so at
school which took care of the disposal.
In my prior career, before becoming a wax carver, I had some
dealings with polyurethane in the work place at the factory I worked
at in Toronto.
First of all, don't know how much polyurethane you are using, but if
this is a 2 component foam or resin, there is a high possibility
that during the curing process it releases trace amounts of
isocyanates, which is a designated substance in Ontario and most
other provinces and states. Check out this link to Ontario's
Occupational Health & Safety Act dealing with products containing
If you don't have them, get the MSDS sheets from the manufacturer to
determine if the product you are using contains isocyanates. As for
disposal, my understanding is (and if others can confirm or correct),
once the 2 components have been mixed and cured, it is no more
hazardous than any other plastic resin. The best place to check would
be Ontario's Ministry of the Environment, but before you call, get
the MSDS sheet so that you can describe the product to them.
DUBIEL DESIGN STUDIO