A city sanitation worker was busted on weapons possession charges when he took a gun to his urinalysis test in Lower Manhattan, police sources said.

Anthony Greico, 43, was caught with a .22 caliber handgun when he went through security at the Beaver Street sanitation facility about 11:30 a.m. Friday.

Greico had the gun in his backpack, cops said.

He told police he hadn’t used the bag in a while, and was unaware of its contents, said a police source.

Greico is a former Florida resident, where he had a legal carry permit for the gun, police sources said.