If you limit yourself to new build only you WILL find yourself out of work regularly. Also you'll find that you get yourself a reputation for being difficult, this will also make you less employable.
There are thousands of things which are hazardous to your health which you will come across or into contact with during your career either knowingly or unwittingly. Sites (even new build ones) usually have a rodent problem, their urine can cause Weil's Disease, Bird droppings can cause respiratory ailments, power tools can have your fingers off, scaffolding can collapse, cranes can drop things. The list goes on and on.
Life isn't about arriving at the pearly gates in a beautifully preserved body, it's about screaming up on a Harley with a bottle in one hand and a smoke in the other shouting "Woohoo what a ride"
Take the courses as suggested, get the risks in perspective and enjoy your work.