A mouse in the house

soudal insulation foam to do this but the safety data sheet says the latter is carcinogenic - I can't determine if that's in it's liquid spray form or also once set.

I just took a quick look at the safety sheet and my interpretation is:

1) There isn't strong evidence that it is carcinogenic, more a supsicion.
2) The (theoretical) threat is from inhalation before it is set.
3) Data sheet says that you should wear an appropriate mask if you plan to breath the fumes for more than 8 hours.

In other words, sounds pretty safe to me.