Average concentration (ng/m3) of heavy metals in the different orthopaedic sections: (OOT) orthopaedic operation theatre; (OW) orthopaedic ward; (OER) orthopaedic emergency room and (OD) uutdoor (a) lead (Pb); (b) cadmium (Cd); (c) nickel (Ni) and (d) arsenic (As).