Although, photocatalytic cement contains nanosized TiO ₂ , a possibly carcinogen, no exposure assessments exist for construction workers. We characterized airborne nanoparticle exposures during construction activities simulated in an exposure chamber. We collected some construction site samples for regular cement in Switzerland and Thailand for comparison. Airborne nanoparticles were characterized using scanning mobility particle sizer (SMPS), portable aerosol spectrometer (PAS), diffusion size classifier (DiSCmini), transmission electron microscopy (TEM), scanning electron microscope energy dispersive X-ray spectroscopy (SEM-EDX), and X-ray diffraction. Bagged photocatalytic cement had 2.0 wt% (GSD ± 0.55) TiO ₂ , while TiO ₂ in aerosols reached 16.5 wt% (GSD ± 1.72) during bag emptying and 9.7 wt% (GSD ± 1.36) after sweeping. The airborne photocatalytic cement particles were far smaller (approximately 50 nm) compared to regular cement. Cutting blocks made from photocatalytic cement or concrete, resulted in similar amounts of airborne nano TiO ₂ (2.0 wt% GSD ± 0.57) particles as in bagged material. Both photocatalytic and regular cement had a geometric mean diameter (GMD) < 3.5 μm. Main exposures for Thai workers were during sweeping and Swiss workers during drilling and polishing cement blocks. Targeted nanoparticle exposure assessments are needed as a significantly greater exposure to nano TiO ₂ were observed than what would have been predicted from the material's nano- TiO ₂ contents.