I don't have numbers to back this up, but I have medium doubts that most solder used in electronics is lead based these days. There are plenty of lead free options available, and electronics as a whole are moving that way. Anything with an RoHS label will be lead free for example. If products in these categories are sold in the EU they have to meet the standard.

Edit: This is not an argument against ventilation though! You should still have some kind of air handling on account of the flux fumes, and also any other metal fumes that may not be good. Better than lead doesn't always mean completely harmless.