Did a design project for running communication ducts up bridge legs and then attached to the underside of the old side of the Burlington Bay Skyway at Hamilton on the QEW about 15 years ago.
Pigeon shit was everywhere. And it is quite literally 'bad shit' to be near, and even worse if you breath any in.
Construction workers needed disposable suits like you wear around asbestos, and full face respirators.
Smokers could only light up after back on the ground and had walked through a disinfectant mister and then face and hands washed with soap and water then rinse.
A number of smokers quit the job, so used to lighting up whenever a nicotine urge surged in them they could not take the restrictions.